The ISL12026 device is a micro power real time clock with
timing and crystal compensation, clock/calender, power-fail
indicator, two periodic or polled alarms, intelligent battery
backup switching, and integrated 512 x 8 bit EEPROM
configured in 16 Byte per page.
The oscillator uses an external, low-cost 32.768kHz crystal.
The real time clock tracks time with separate registers for
hours, minutes, and seconds. The device has calendar
registers for date, month, year and day of the week. The
calendar is accurate through 2099, with automatic leap year
correction.
Ordering Information
TEMP
PART
NUMBER
ISL12026IBZ
(See Note)
ISL12026IVZ
(See Note)
NOTE: Intersil Pb-free plus anneal products employ special Pb-free
material sets; molding compounds/die attach materials and 100%
matte tin plate termination finish, which are RoHS compliant and
compatible with both SnPb and Pb-free soldering operations. Intersil
Pb-free products are MSL classified at Pb-free peak reflow
temperatures that meet or exceed the Pb-free requirements of IPC/
JEDEC J STD-020.
Add “-T” suffix for tape and reel.
PART
MARKING
12026 IBZ
2026 IVZ
RANGE
2.7V to
5.5V
2.7V to
5.5V
RANGE
VDD
(°C)PACKAGE
-40 to +85 8 Ld SOIC
-40 to +85 8 Ld TSSOP
(Pb-Free)
(Pb-Free)
PKG.
DWG . #
M8.15
M8.173
Pinouts
ISL12026
(8 LD SOIC)
TOP VIEW
8
7
6
5
SCL
SDA
GND
IRQ/F
V
DD
V
BAT
SCL
SDA
OUT
IRQ/F
V
OUT
GND
BAT
V
X1
X2
DD
X1
X2
1
2
3
4
ISL12026
(8 LD TSSOP)
TOP VIEW
1
2
3
4
8
7
6
5
Features
• Real Time Clock/Calendar
- Tracks Time in Hours, Minutes, and Seconds
- Day of the Week, Day, Month, and Year
- 3 Selectable Frequency Outputs
• Two Non-Volatile Alarms
- Settable on the Second, Minute, Hour, Day of the Week,
Day, or Month
- Repeat Mode (periodic interrupts)
• Automatic Backup to Battery or SuperCap
• On-Chip Oscillator Compensation
- Internal Feedback Resistor and Compensation
Capacitors
- 64 Position Digitally Controlled Trim Capacitor
- 6 Digital Frequency Adjustment Settings to ±30ppm
• 512 x 8 Bits of EEPROM
- 16-Byte Page Write Mode (32 total pages)
- 8 Modes of BlockLock™
Protection
- Single Byte Write Capability
• High Reliability
- Data Retention: 50 years
- Endurance: >2,000,000 Cycles Per Byte
2
C Interface
•I
- 400kHz Data Transfer Rate
• 800nA Battery Supply Current
• Package Options
- 8 Ld SOIC and 8 Ld TSSOP Packages
• Pb-Free Plus Anneal Available (RoHS Compliant)
Applications
• Utility Meters
• HVAC Equipment
• Audio/Video Components
• Set Top Box/Television
• Modems
• Network Routers, Hubs, Switches, Bridges
• Cellular Infrastructure Equipment
• Fixed Broadband Wireless Equipment
• Pagers/PDA
• POS Equipment
• Test Meters/Fixtures
• Office Automation (C opiers, Fax)
• Home Appliances
• Computer Products
• Other Industrial/Medical/ Automotive
1
CAUTION: These devices are sensitive to electrostatic discharge; follow proper IC Handling Procedures.
1-888-INTERSIL or 1-888-468-3774
BlockLock is a trademark of Intersil Americas Inc. Copyright Intersil Americas Inc. 2005, 2006. All Rights Reserved
| Intersil (and design) is a registered trademark of Intersil Americas Inc.
All other trademarks mentioned are the property of their respective owners.
Block Diagram
OSC
COMPENSATION
ISL12026
TIMER
CALENDAR
LOGIC
ALARM
KEEPING
REGISTERS
(SRAM)
COMPARE
ALARM REGS
(EEPROM)
MASK
EEPROM
ARRAY
TIME
4K
BATTERY
SWITCH
CIRCUITRY
IRQ/F
OUT
SCL
SDA
32.768kHz
INTERFACE
DECODER
SELECT
SERIAL
X1
X2
CONTROL
DECODE
LOGIC
8
OSCILLATOR
CONTROL/
REGISTERS
(EEPROM)
FREQUENCY
DIVIDER
STATUS
REGISTERS
(SRAM)
1Hz
Pin Descriptions
PIN NUMBER
SYMBOLDESCRIPTIONSOICTSSOP
13X1The X1 pin is the input of an inverting amplifier and is intended to be connected to one pin of an external
24X2The X2 pin is the output of an inverting amplifier and is intended to be connected to one pin of an external
35IRQ/
F
46GNDGround.
57SDAS erial Data (SDA) is a bidirectional pin used to transfer serial data into and out of the device. It has an open
68SCLThe Serial Clock (SCL) input is used to clock all serial data into and out of the device. The input buffer on
71V
82V
BAT
DD
32.768kHz quartz crystal. X1 can a l s o b e d ri v e n d i r e ct l y f r o m a 3 2 . 76 8 k H z s ou r c e . (S e e A p p li c a t i o n S e c t i o n)
32.768kHz quartz crystal. (See Application Section)
Interrupt Output/Frequency Output is a multi-functional pin that can be used as interrupt or frequency
OUT
output pin. The function is set via the control register. This output is an open drain configuration.
drain output and may be wire OR’ed with other open drain or open collector outputs.
this pin is always active (not gated).
This input provides a backup supply voltage to the device. V
that the V
supply fails. This pin should be tied to ground if not used.
CAUTION: Stresses above those listed in “Absolute Maximum Ratings” may cause permanent damage to the device. This is a stress only rating and operation of the
device at these or any other conditions above those indicated in the operational sections of this specification is not implied.
NOTES:
1. Jedec Class II pulse conditions and failure criterion used. Level B exceptions are: Using a max positive pulse of 8.35V on all pins except X1 and
X2, Using a max positive pulse of 2.75V on X1 and X2, and using a max negative pulse of -1V for all pins.
is measured with the component mounted on a high effective thermal conductivity test board in free air. See Tech Brief TB379 for details.
STOP Condition Hold Time for
Read, or Volatile Only Write
Output Data Hold TimeFrom SCL falling edge crossing
DH
From SDA rising edge to SCL
falling edge. Both crossing 70%
of V
.
DD
30% of V
30% to 70% of V
, until SDA enters the
DD
window.
DD
CbCapacitive Loading of SDA or SCL Total on-chip and off-chip.10400pF
CpinSDA, and SCL Pin Capacitance10pF
t
WC
Non-volatile Write Cycle Time1220ms10
NOTES:
3. IRQ/
F
Inactive.
OUT
= VDD x 0.1, V
4. V
IL
> V
5. V
DD
BAT +VBATHYS
6. Bit BSW = 0 (Standard Mode), V
= VDD x 0.9, f
IH
SCL
BAT
= 400kHz
>= 1.8V
7. Specified at +25°C.
8. In order to ensure proper timekeeping, the V
specification must be followed.
DD SR-
9. Para meter is not 100% tested.
10. t
is the minimum cycle time to be allowed for any non-volatile Write by the user, it is the time from valid STOP condition at the end of Write
WC
sequence of a serial interface Write operation, to the end of the self-timed internal non-volatile write cycle.
600ns
0ns
Timing Diagrams
Bus Timing
SCL
t
SU:STA
SCL
SDA
SDA
SDA
8TH BIT OF LAST BYTEACK
(INPUT TIMING)
(OUTPUT TIMING)
Write Cycle Timing
t
HD:STA
t
F
t
SU:DAT
t
HIGH
t
LOW
t
HD:DAT
t
R
t
DH
t
AA
t
BUF
t
HD:STO
t
SU:STO
t
WC
STOP
CONDITION
5
START
CONDITION
FN8231.5
October 23, 2006
ISL12026
Typical Performance Curves Temperature is +25°C unless otherwise specified
0.90
4.00
3.50
3.00
2.50
2.00
Ibat (uA)
1.50
1.00
0.50
0.00
1.82.32.83.33.84.34.85.3
FIGURE 1. I
BSW = 0 or 1
SCL,SDA pullups = 0V
SCL,SDA pullups = Vbat
BSW = 0 or 1
Vbat (V)
BAT
vs V
SBIB = 0FIGURE 2. I
BAT,
0.80
0.70
0.60
0.50
Ibat
0.40
0.30
0.20
0.10
0.00
1.802.302.803.303.804.304.805.30
SCL,SDA pullups = 0V
BSW = 0 or 1
Vbat(V)
vs V
BAT
BAT,
SBIB = 1
5.00
4.50
4.00
3.50
3.00
2.50
Idd (uA)
2.00
1.50
1.00
0.50
0.00
-45-35-25-15-5 5 1525354555657585
Vdd=5.5V
Vdd=3.3V
Temperature
FIGURE 3. I
4.50
4.00
3.50
3.00
2.50
2.00
Idd (uA)
1.50
1.00
0.50
0.00
1.82 .32.83.33.84.34.85.3
vs TEMPERATUREFIGURE 4. I
DD3
Vdd (V)
1.40
1.20
Vbat = 3.0V
1.00
0.80
0.60
Ibat (uA)
0.40
0.20
0.00
-45-35-25-15-5 5 1525354555657585
Temperature
vs TEMPERAT URE
BAT
80
60
40
20
0
PPM change from ATR=0
-20
-40
-32 -28 -24 -20 -16 -1 2 -8 -4 048 12 16 20 24 28
ATR setting
FIGURE 5. I
DD3
6
vs V
DD
FIGURE 6. ∆F
vs ATR SETTING
OUT
FN8231.5
October 23, 2006
Description
The ISL12026 device is a Real Time Clock with clock/
calendar, two polled alarms with integrated 512x8 EEPROM,
oscillator compensation, and battery backup switch.
The oscillator uses an external, low-cost 32.768kHz crystal.
All compensation and trim components are integrated on the
chip. This eliminates several external discrete components
and a trim capacitor, saving board area and component cost.
The Real Time Clock keeps track of time with separate
registers for Hours, Minutes, Seconds. The Calendar has
separate registers for Date, Month, Year and Day-of-week.
The calendar is correct through 2099, with automatic leap
year correction.
The Dual Alarms can be set to any Clock/Calendar value for
a match. For instance, every minute, every Tuesday, or 5:23
AM on March 21. The alarms can be polled in the Status
Register or can provide a hardware interrupt (IRQ
/F
OUT
Pin). There is a pulse mode for the alarms allowing for
repetitive alarm functionality.
The IRQ
/F
pin may be software selected to provide a
OUT
frequency output of 1Hz, 4096Hz, or 32,768Hz or inactive.
The device offers a backup power input pin. This V
BAT
pin
allows the device to be backed up by battery or SuperCap.
The entire ISL12026 device is fully operational from 2.7 to
5.5V and the clock/calendar portion of the ISL12026 device
remains fully operational down to 1.8V (Standby Mode).
The ISL12026 device provides 4K bits of EEPROM with 8
modes of BlockLock™ control. The BlockLock allows a safe,
secure memory for critical user and configuration data, while
allowing a large user storage area.
Pin Descriptions
Serial Clock (SCL)
The SCL input is used to clock all data into and out of the
device. The input buffer on this pin is always active (not
gated). The pull-up resistor on this pin must use the same
voltage source as V
Serial Data (SDA)
SDA is a bidirectional pin used to transfer data into and out
of the device. It has an open drain output and may be wire
ORed with other open drain or open collector outputs. The
input buffer is always active (not gated ).
This open drain output requires the use of a pull-up resistor.
The pull-up resistor on this pin must use the same voltage
source as V
the output signal with the use of a slope controlled pulldown. The circuit is designed to comply with 400kHz I
interface speed.
. The output circuitry controls the fall time of
DD
DD
.
2
C
ISL12026
V
BAT
This input provides a backup supply voltage to the device.
V
supplies power to the device in the event the VDD
BAT
supply fails. This pin can be connected to a battery, a
SuperCap or tied to ground if not used.
IRQ/F
(Interrupt Output/Frequency Output)
OUT
This dual function pin can be used as an interrupt or
frequency output pin. The IRQ
/F
mode is selected via
OUT
the frequency out control bits of th e IN T re gi ste r.
• Interrupt Mode. The pin provides an interrupt signal
output. This signal notifies a host processor that an alarm
has occurred and requests action. It is an open drain
active low output.
• Frequency Output Mode. The pin outputs a clock signal
which is related to the crystal frequency. The frequency
output is user selectable and enabled via the I
2
C bus. It is
an open drain output.
X1, X2
The X1 and X2 pins are the input and output, respectively, of
an inverting amplifier. An external 32.768kHz quartz crystal
is used with the ISL12026 to supply a timebase for the real
time clock. Internal compensation circuitry provides high
accuracy over the operating temperature range from
-40°C to +85°C. This oscillator compensation network can
be used to calibrate the crystal timing accuracy over
temperature either during manufacturing or with an external
temperature sensor and microcontroller for active
compensation. X2 is intended to drive a crystal only, and
should not drive any external circuit.
X1
X2
FIGURE 7. RECOMMENDED CRYSTAL CONNECTION
Real Time Clock Operation
The Real Time Clock (RTC) uses an external 32.768kHz
quartz crystal to maintain an accurate internal representation
of the second, minute, hour, day, date, month, and year. The
RTC has leap-year correction. The clock also corrects for
months having fewer than 31 days and has a bit that controls
24 hour or AM/PM format. When the ISL12026 powers up
after the loss of both V
operate until at least one byte is written to the clock register.
Reading the Real Time Clock
The RTC is read by initiating a Read command and
specifying the address corresponding to the register of the
Real Time Clock. The RTC Registers can then be read in a
Sequential Read Mode. Since the clock runs continuously
and a read takes a finite amount of time, there is the
DD
and V
, the clock will not
BAT
7
FN8231.5
October 23, 2006
ISL12026
possibility that the clock could change during the course of a
read operation. In this device, the time is latched by the read
command (falling edge of the clock on the ACK bit prior to
RTC data output) into a separate latch to avoid time changes
during the read operation. The clock continues to run.
Alarms occurring during a read are unaffected by the read
operation.
Writing to the Real Time Clock
The time and date may be set by writing to the RTC
registers. RTC Register should be written ONLY with Page
Write. To avoid changing the current time by an uncompleted
write operation, write to the all 8 bytes in one write operation.
When writing the RTC registers, the new time value is
loaded into a separate buffer at the falling edge of the clock
during the Acknowledge. This new RTC value is loaded into
the RTC Register by a stop bit at the end of a valid write
sequence. An invalid write operation aborts the time update
procedure and the contents of the buffer are discarded. After
a valid write operation the RTC will reflect the newly loaded
data beginning with the next “one second” clock cycle after
the stop bit is written. The RTC continues to update the time
while an RTC register write is in progress and the RTC
continues to run during any non-volatile write sequences.
Accuracy of the Real Time Clock
The accuracy of the Real Time Clock depends on the
accuracy of the quartz crystal that is used as the time base
for the RTC. Since the resonant frequency of a crystal is
temperature dependent, the RTC performance will also be
dependent upon temperature. The frequency deviation of
the crystal is a function of the turnover temperature of the
crystal from the crystal’s nominal frequency. For example, a
>20ppm frequency deviation translates into an accuracy of
>1 minute per month. These parameters are available from
the crystal manufacturer. Intersil’s RTC family provides onchip crystal compensation networks to adjust loadcapacitance to tune oscillator frequency from -34ppm to
+80ppm when using a 12.5pF load crystal. For more detailed
information see the Application section.
Clock/Control Registers (CCR)
The Control/Clock Registers are located in an area separate
from the EEPROM array and are only accessible following a
slave byte of “1101111x” and reads or writes to addresses
[0000h:003Fh]. The clock/control memory map has memory
addresses from 0000h to 003Fh. The defined addresses are
described in the Table 1. Writing to and reading from the
undefined addresses are not recommended.
CCR Access
The contents of the CCR can be modified by performing a
byte or a page write operation directly to any address in the
CCR. Prior to writing to the CCR (except the status register),
however, the WEL and RWEL bits must be set using a three
step process (See section “Writing to the Clock/Control
Registers.”)
The CCR is divided into 5 sections. These are:
1. Alarm 0 (8 bytes; non-volatile)
2. Alarm 1 (8 bytes; non-volatile)
3. Control (5 bytes; non-volatile)
4. Real Time Clock (8 bytes; volatile)
5. Status (1 byte; volatile)
Each register is read and written through buffers. The non-
volatile portion (or the counter portion of the RTC) is updated
only if RWEL is set and only after a valid write operation and
stop bit. A sequential read or page write operation provides
access to the contents of only one section of the CCR per
operation. Access to another section requires a new
operation. A read or write can begin at any address in the
CCR.
It is not necessary to set the RWEL bit prior to writing the
status register. Section 5 (status register) supports a singl e
byte read or write only. Continued reads or writes from this
section terminates the operation.
The state of the CCR can be read by performing a random
read at any address in the CCR at any time. This returns the
contents of that register location. Additional registers are
read by performing a sequential read. The read instruction
latches all Clock registers into a buffer, so an update of the
clock does not change the time being read. A sequential
read of the CCR will not result in the output of data from the
memory array. At the end of a read , the master supplies a
stop condition to end the operation and free the bus. After a
read of the CCR, the address remains at the previous
address +1 so the user can execute a current address read
of the CCR and continue reading the next Register.
These registers depict BCD representations of the time. As
such, SC (Seconds) and MN (Minutes) range from 00 to 59,
HR (Hour) is 1 to 12 with an AM or PM indicator (H21 bit) or
0 to 23 (with MIL = 1), DT (Date) is 1 to 31, MO (Month) is 1
to 12, YR (Year) is 0 to 99.
DW: Day of the Week Register
This register provides a Day of the Week status and uses
three bits DY2 to DY0 to represent the seven days of the
week. The counter advances in the cycle 0-1-2-3-4-5-6-0-12-… The assignment of a numerical value to a specific day
of the week is arbitrary and may be decided by the system
software designer. The default value is defined as ‘0’.
8
FN8231.5
October 23, 2006
ISL12026
24 Hour Time
If the MIL bit of the HR register is 1, the RTC uses a 24-hour
format. If the MIL bit is 0, the RTC uses a 12-hour format and
H21 bit functions as an AM/PM indicator with a ‘1’
representing PM. The clock defaults to standard time with
H21 = 0.
Leap Years
Leap years add the day February 29 and are defined as
those years that are divisible by 4.
Status Register (SR)
The Status Register is located in the CCR memory map at
address 003Fh. This is a volatile register only and is used to
control the WEL and RWEL write enable latches, read power
status and two alarm bits. This register is separate from both
the array and the Clock/Control Registers (CCR).
TABLE 1. STATUS REGISTER (SR)
ADDR76543210
003FhBATAL1 AL0 OSCF0RWEL WEL RTCF
Default00000001
BAT: Battery Supply - Volatile
This bit set to “1” indicates that the device is operating from
V
, not VDD. It is a read-only bit and is set/reset by
BAT
hardware (ISL12026 internally). Once the device begins
operating from V
AL1, AL0: Alarm Bits - Volatile
These bits announce if either alarm 0 or alarm 1 match the
real time clock. If there is a match, the respective bit is set to
‘1’. The falling edge of the last data bit in a SR Read
operation resets the flags. Note: Only the AL bits that are set
when an SR read starts will be reset. An alarm bit that is set
by an alarm occurring during an SR read operation will
remain set after the read operation is complete.
OSCF: Oscillator Fail Indicator
This bit is set to “1” if the oscillator is not operating. The bit is
set to “0” only if the oscillator is functioning. This bit is read
only, and is set/reset by hardware.
, the device sets this bit to “0”.
DD
RWEL: Register Write Enable Latch - Volatile
This bit is a volatile latch that powers up in the LOW
(disabled) state. The RWEL bit must be set to “1” prior to any
writes to the Clock/Control Registers. Writes to RWEL bit do
not cause a non-volatile write cycle, so the device is ready
for the next operation immediately after the stop condition. A
write to the CCR requires both the RWEL and WEL bits to be
set in a specific sequence.
WEL: Write Enable Latch - Volatile
The WEL bit controls the access to the CCR during a write
operation. This bit is a volatile latch that powers up in the
LOW (disabled) state. While the WEL bit is LOW, writes to
the CCR address will be ignored, although acknowledgment
is still issued. The WEL bit is set by writing a “1” to the WEL
bit and zeroes to the other bits of the Status Register. Once
set, WEL remains set until either reset to 0 (by writing a “0”
to the WEL bit and zeroes to the other bits of the Status
Register) or until the part powers up again. Writes to WEL bit
do not cause a non-volatile write cycle, so the device is
ready for the next operation immediately after the stop
condition.
RTCF: Real Time Clock Fail Bit - Volatile
This bit is set to a “1” after a total power failure. This is a read
only bit that is set by hardware (ISL12026 internally) when
the device powers up after having lost all power to the device
(both V
whether V
DD
and V
or V
DD
go to 0V). The bit is set regardless of
BAT
is applied first. The loss of only one of
BAT
the supplies does not set the RTCF bit to “1”. On power up
after a total power failure, all registers are set to their default
states and the clock will not increment until at least one byte
is written to the clock register. The first valid write to the RTC
section after a complete power failure resets the RTCF bit to
“0” (writing one byte is sufficient).
Unused Bits
Bit 3 in the SR is not used, but must be zero. The Data Byte
output during a SR read will contain a zero in this bit
location.
000FAlarm1
000EDWA1EDW10000DY2DY1DY00-600h
000DYRA1Unused - Default = RTC Year value (No EEPROM) - Future expansion
000CMOA1EMO100A1G20A1G13A1G12A1G11A1G101-1200h
000BDTA1EDT10A1D21A1D20A1D13A1D12A1D11A1D101-3100h
000AHRA1EHR10A1H21A1H20A1H13A1H12A1H11A1H100-2300h
0009MNA1EMN1A1M22A1M21A1M20A1M13A1M12A1M11A1M100-5900h
0008SCA1ESC1A1S22A1S21A1S20A1S13A1S12A1S11A1S100-5900h
0007Alarm0
0006DWA0EDW00000DY2DY1DY00-600h
0005YRA0Unused - Default = RTC Year value (No EEPROM) - Future expansion
0004MOA0EMO000A0G20A0G13A0G12A0G11A0G101-1200h
0003DTA0EDT00A0D21A0D20A0D13A0D12A0D11A0D101-3100h
0002HRA0EHR00A0H21A0H20A0H13A0H12A0H11A0H100-2300h
0001MNA0EMN0A0M22A0M21A0M20A0M13A0M12A0M11A0M100-5900h
0000SCA0ESC0A0S22A0S21A0S20A0S13A0S12A0S11A0S100-5900h
(SRAM)
(EEPROM)
(EEPROM)
(EEPROM)
NAME
Y2K00Y2K21Y2K20Y2K1300Y2K1019/2020h
PWRSBIBBSW00000040h
Y2K100A1Y2K21A1Y2K20 A1Y2K1300A1Y2K1019/2020h
Y2K000A0Y2K21A0Y2K20 A0Y2K1300A0Y2K1019/2020h
76543210
RANGE
DEFAULT
Alarm Registers (Non-Volatile)
Alarm0 and Alarm1
The alarm register bytes are set up identical to the RTC
register bytes, except that the MSB of each byte functions as
an enable bit (enable = “1”). These enable bits specify which
alarm registers (seconds, minutes, etc.) are used to make
the comparison. Note that there is no alarm byte for year.
The alarm function works as a comparison between the
alarm registers and the RTC registers. As the RTC
advances, the alarm will be triggered once a match occurs
between the alarm registers and the RTC registers. Any one
alarm register, multiple registers, or all registers can be
10
enabled for a match. See the Device Operation and
Application section for more information.
Control Registers (Non-Volatile)
The Control Bits and Registers described under this section
are non-volatile.
BL Register
BP2, BP1, BP0 - Block Protect Bits
The Block Protect Bits, BP2, BP1 and BP0, determine which
blocks of the array are write protected. A write to a protected
block of memory is ignored. The block protect bits will
prevent write operations to one of eight segments of the
array. The partitions are described in Table 3.
INT Register: Interrupt Control and
Frequency Output Register
IM, AL1E, AL0E - Interrupt Control and Status Bits
There are two Interrupt Control bits, Alarm 1 Interrupt Enable
(AL1E) and Alarm 0 Interrupt Enable (AL0E) to specifically
enable or disable the alarm interrupt signal output (IRQ
F
). The interrupts are enabled when either the AL1E or
OUT
AL0E or both bits are set to ‘1’ and both the FO1 and FO0
bits are set to 0 (F
disabled).
OUT
The IM bit enables the pulsed interrupt mode. To enter this
mode, the AL0E or AL1E bits are set to “1”, and the IM bit to
“1”. The IRQ/
F
output will now be pulsed each time an
OUT
alarm occurs. This means that once the interrupt mode
alarm is set, it will continue to alarm for each occurring
match of the alarm and present time. This mode is
convenient for hourly or daily hardware interrupts in
microcontroller applications such as security cameras or
utility meter reading.
In the case that both Alarm 0 and Alarm 1 are enabled, the
IRQ
/F
pin will be pulsed each time either alarm matches
OUT
the RTC (both alarms can provide hardware interrupt). If the
IM bit is also set to "1", the IRQ
/F
will be pulsed for each
OUT
of the alarms as well.
/
Oscillator Compensation Registers
There are two trimming options.
- ATR. Analog Trimming Register
- DTR. Digital Trimming Register
These registers are non-volatile. The combination of analog
and digital trimming can give up to -64 to +110 ppm of total
adjustment.
Six analog trimming bits, ATR0 to ATR5, are provided in
order to adjust the on-chip load capacitance value for
frequency compensation of the RTC. Each bit has a different
weight for capacitance adjustment. For example, using a
Citizen CFS-206 crystal with different ATR bit combinations
provides an estimated ppm adjustment range from -34 to
+80ppm to the nominal frequency compensation.
X1
C
X1
X2
C
X2
FIGURE 8. DIAGRAM OF ATR
The effective on-chip series load capacitance, C
ranges from 4.5pF to 20.25pF with a mid-scale value of
12.5pF (default). C
controlled capacitors, C
is changed via two digitally
LOAD
and CX2, connected from the X1
X1
and X2 pins to ground (see Figure 8). The value of C
C
is given by the following formula:
X2
CX16 b5⋅8b44b3 2b2 1b10.5b0 9+⋅+⋅+⋅+⋅+⋅+()pF=
CRYSTAL
OSCILLATOR
LOAD
,
X1
and
FO1, FO0 - Programmable Frequency Output Bits
These are two output control bits. They select one of three
divisions of the internal oscillator, that is applied to the IRQ
F
output pin. Table 4 shows the selection bits for this
OUT
output. When using this function, the Alarm output function is
disabled.
TABLE 4. PROGRAMMABLE FREQUENCY OUTPUT BITS
FO1FO0OUTPUT FREQUENCY
00Alarm output (F
01 32.768kHz
104096Hz
111Hz
11
OUT
disabled)
The effective series load capacitance is the combination of
CX1 and CX2:
PWR Register: SBIB, BSW
SBIB: - Serial Bus Interface (Enable)
The serial bus can be disabled in battery backup mode by
setting this bit to “1”. This will minimize power drain on the
battery. The Serial Interface can be enabled in battery
backup mode by setting this bit to “0”. (default is “0”). See
Reset and Power Control section.
BSW: Power Control Bit
The Power Control bit, BSW, determines the conditions for
switching between V
and Back Up Battery. There are two
DD
options.
Option 1. Standard/Default Mode: Set “BSW = 0”
Option 2. Legacy Mode: Set “BSW = 1”
See Power Control Operation later in this document for more
details. Also see “I
2
C Communications During Battery
backup and LVR Operation” in the Applications section for
important details.
Device Operation
Writing to the Clock/Control Registers
Changing any of the bits of the clock/control registers
requires the following steps:
1. Write a 02h to the Status Register to set the Write Enable
Latch (WEL). This is a volatile operation, so there is no
delay after the write. (Operation preceded by a start and
ended with a stop).
2. Write a 06h to the Status Register to set both the Register
Write Enable Latch (RWEL) and the WEL bit. This is also
a volatile cycle. The zeros in the data byte are required.
(Operation proceeded by a start and ended with a stop).
Write all eight bytes to the RTC registers, or one byte to the
SR, or one to five bytes to the control registers. This
sequence starts with a start bit, requires a slave byte of
“11011110” and an address within the CCR and is terminated
by a stop bit. A write to the EEPROM registers in the CCR
will initiate a non-volatile write cycle and will take up to 20ms
to complete. A write to the RTC registers (SRAM) will require
much shorter cycle time (t = t
). Writes to undefined areas
BUF
have no effect. The RWEL bit is reset by the completion of a
write to the CCR, so the sequence must be repeated to
again initiate another change to the CCR contents. If the
sequence is not completed for any reason (by sending an
incorrect number of bits or sending a start instead of a stop,
for example) the RWEL bit is not reset and the device
remains in an active mode. Writing all zeros to the status
register resets both the WEL and RWEL bits. A read
operation occurring between any of the previous operations
will not interrupt the register write operation.
Alarm Operation
Since the alarm works as a comparison between the alarm
registers and the RTC registers, it is ideal for notifying a host
processor of a particular time event and trigger some action
as a result. The host can be notified by either a hardware
interrupt (the IRQ
(SR) Alarm bits. These two volatile bits (AL1for Alarm 1 and
AL0 for Alarm 0), indicate if an alarm has happened. The bits
are set on an alarm condition regardless of whether the IRQ
F
interrupt is enabled. The AL1 and AL0 bits in the status
OUT
register are reset by the falling edge of the eighth clock of
status register read.
There are two alarm operation modes: Single Event and
periodic Interrupt Mode:
1. Single Event Mode is enabled by setting the AL0E or
AL1E bit to “1”, the IM bit to “0”, and disabling the
frequency output. This mode permits a one-time match
between the alarm registers and the RTC registers. Once
this match occurs, the AL0 or AL1 bit is set to “1” and the
IRQ/
F
OUT
until the AL0 or AL1 bit is read, which will automatically
resets it. Both Alarm registers can be set at the same time
to trigger alarms. The IRQ/
either alarm, and will need to be cleared to enable
triggering by a subsequent alarm. Polling the SR will
reveal which alarm has been set.
2. Interrupt Mode (or “Pulsed Interrupt Mode” or PIM) is
enabled by setting the AL0E or AL1E bit to “1” the IM bit
to “1”, and disabling the frequency output. If both AL0E
/F
pin) or by polling the Status Register
OUT
output will be pulled low and will remain low
F
output will be set by
OUT
/
12
FN8231.5
October 23, 2006
ISL12026
and AL1E bits are set to "1", then both AL0E and AL1E
PIM alarms will function. The IRQ/F
output will now
OUT
be pulsed each time each of the alarms occurs. This
means that once the interrupt mode alarm is set, it will
continue to alarm for each occurring match of the alarm
and present time. This mode is convenient for hourly or
daily hardware interrupts in microcontroller applications
such as security cameras or utility meter reading.
Interrupt Mode CANNOT be used for general periodic
alarms, however, since a specific time period cannot be
programmed for interrupt, only matches to a specific time
of day. The interrupt mode is only stopped by disabling
the IM bit or the Alarm Enable bits.
Writing to the Alarm Registers
The Alarm Registers are non-volatile but require special
attention to insure a proper non-volatile write takes place.
Specifically , byte writes to individual registers are good for all
but registers 0006h and 0000Eh, which are the DWA0 and
DWA1 registers, respectively. Those registers will require a
special page write for nonvolatile storage. The
recommended page write sequences are as follows:
1. 16-byte page writes: The best way to write or update the
Alarm Registers is to perform a 16-byte write beginning at
address 0001h (MNA0) and wrapping around and ending
at address 0000h (SCA0). This will insure that nonvolatile storage takes place. This means that the code
must be designed so that the Alarm0 data is written
starting with Minutes register, and then all the Alarm1
data, with the last byte being the Alarm0 Seconds (the
page ends at the Alarm1 Y2k register and then wraps
around to address 0000h).
Alternatively, the 16-byte page write could start with
address 0009h, wrap around and finish with address
0008h. Note that any page write ending at address
0007h or 000Fh (the highest byte in each Alarm) will not
trigger a nonvolatile write, so wrapping around or
overlapping to the following Alarm's Seconds register is
advised.
2. Other nonvolatile writes: It is possible to do writes of
less than an entire page, but the final byte must always
be addresses 0000h through 0004h or 0008h though
000Ch to trigger a nonvolatile write. Writing to those
blocks of 5 bytes sequentially, or individually , will trigger a
nonvolatile write. If the DWA0 or DWA1 registers need to
be set, then enough bytes will need to be written to
overlap with the other Alarm register and trigger the
nonvolatile write. For Example, if the DWA0 register is
being set, then the code can start with a multiple byte
write beginning at address 0006h, and then write 3 bytes
ending with the SCA1 register as follows:
Addr Name
0006h DWA0
0007h Y2K0
0008h SCA1
If the Alarm1 is used, SCA1 would need to have the correct
data written.
Power Control Operation
The power control circuit accepts a VDD and a V
Many types of batteries can be used with Intersil RTC
products. For example, 3.0V or 3.6V Lithium batteries are
appropriate, and battery sizes are available that can power
an Intersil RTC device for up to 10 years. Another option is
to use a SuperCap for applications where V
DD
for up to a month. See the Applications Section for more
information.
There are two options for setting the change-over conditions
from V
to Battery back-up mode. The BSW bit in the PWR
DD
register controls this operation.
- Option 1 - Standard Mode
- Option 2 - Legacy Mode (Default)
2
Note that the I
C bus may or may not be operational during
battery backup, that function is controlled by the SBIB bit.
That operation is covered after the power control section.
OPTION 1- STANDARD POWER CONTROL MODE
In the Standard mode , the supply will switch over to the
battery when V
drops below V
DD
TRIP
or V
BAT
lower. In th is mode , accident al ope ration from the ba tte ry is
prevented since the battery backup input will only be used
when the V
supply is shut off.
DD
To select Option 1, BSW bit in the Power Register must be
set to “BSW = 0”. A description of power switchover follows
Standard Mode Power Switchover
• Normal Operating Mode (VDD) to Battery Backup Mode
)
(V
BAT
To transition from the V
DD
to V
mode, both of the
BAT
following conditions must be met:
- Condition 1:
V
< V
DD
where V
- V
BAT
BATHYS
BATHYS
≈ 50mV
- Condition 2:
< V
V
DD
where V
• Battery Backup Mode (V
TRIP
TRIP
≈ 2.2V
) to Normal Mode (VDD)
BAT
The ISL12026ISL12026 device will switch from the V
V
mode when one of the following conditions occurs:
DD
- Condition 1:
V
> V
DD
where V
+ V
BAT
BATHYS
BATHYS
≈ 50mV
- Condition 2:
> V
V
DD
where V
+ V
TRIP
TRIPHYS
TRIPHYS
≈ 30mV
There are two discrete situations that are possible when
using Standard Mode: V
BAT
< V
TRIP
and V
BAT
input.
BAT
is interrupted
, whichever is
to
BAT
>V
TRIP
.
13
FN8231.5
October 23, 2006
These two power control situations are illustrated in Figures
9 and 10.
BATTERY BACKUP
V
DD
V
TRIP
V
BAT
V
- V
BAT
BATHYS
FIGURE 9. BATTERY SWITCHOVER WHEN V
V
DD
V
BAT
V
TRIP
V
TRIP
MODE
BATTERY BACKUP
MODE
V
V
TRIP
BAT
BAT
+ V
+ V
BATHYS
< V
TRIPHYS
2.2V
1.8V
TRIP
3.0V
2.2V
ISL12026
V
DD
V
BAT
Off
FIGURE 11. BATTERY SWITCHOVER IN LEGACY MODE
VOLTAGE
On
In
Serial Communication
The device supports the I2C protocol.
Clock and Data
Data states on the SDA line can change only during SCL
LOW. SDA state changes during SCL HIGH are reserved for
indicating start and stop conditions (See Figure 12).
Start Condition
All commands are preceded by the start condition, which is a
HIGH to LOW transition of SDA when SCL is HIGH. The
device continuously monitors the SDA and SCL lines for the
start condition and will not respond to any command until
this condition has been met (See Figure 13).
FIGURE 10. BATTERY SWITCHOVER WHEN V
BAT
> V
TRIP
OPTION 2 -LEGACY POWER CONTROL MODE
(DEFAULT)
The Legacy Mode follows conditions set in X1226 products.
In this mode, switching from V
DD
to V
is simply done by
BAT
comparing the voltages and the device operates from
whichever is the higher voltage. Care should be taken when
changing from Normal to Legacy Mode. If the V
higher than V
, then the device will enter battery back up
DD
voltage is
BAT
and unless the battery is disconnected or the voltage
decreases, the device will no longer operate from V
DD
.
To select the Option 2, BSW bit in the Power Register must
be set to “BSW = 1”
• Normal Mode (V
To transition from the V
) to Battery Backup Mode (V
DD
DD
to V
mode, the following
BAT
BAT
)
conditions must be met:
V
< V
DD
• Battery Backup Mode (V
The device will switch from the V
BAT
- V
BATHYS
) to Normal Mode (VDD)
BAT
to VDD mode when the
BAT
following condition occurs:
V
> V
DD
BAT +VBATHYS
The Legacy Mode power control conditions are illustrated in
Figure11.
Stop Condition
All communications must be terminated by a stop condition,
which is a LOW to HIGH transition of SDA when SCL is
HIGH. The stop condition is also used to place the device
into the Standby power mode after a read sequence. A stop
condition can only be issued after the transmitting device
has released the bus (See Figure 13).
Acknowledge
Acknowledge is a software convention used to indicate
successful data transfer. The transmitting device, either
master or slave, will release the bus after transmitting eight
bits. During the ninth clock cycle, the receiver will pull the
SDA line LOW to acknowledge that it received the eight bits of
data (Refer to Figure 14).
The device will respond with an acknowledge after
recognition of a start condition and if the correct Device
Identifier and Select bits are contained in the Slave Address
Byte. If a write operation is selected, the device will respond
with an acknowledge after the receipt of each subsequent
eight bit word. The device will not acknowledge if the slave
address byte is incorrect.
In the read mode, the device will transmit eight bits of data,
release the SDA line, then monitor the line for an
acknowledge. If an acknowledge is detected and no stop
condition is generated by the master, the device will continue
to transmit data. The device will terminate further data
transmissions if an acknowledge is not detected. The master
must then issue a stop condition to return the device to
Standby mode and place the device into a known state.
14
FN8231.5
October 23, 2006
SCL
SDA
SCL
SDA
ISL12026
DATA STABLEDATA CHANGEDATA STABLE
FIGURE 12. VALID DATA CHANGES ON THE SDA BUS
STARTSTOP
FIGURE 13. VALID START AND STOP CONDITIONS
SCL FROM
MASTER
DATA OUTPUT
FROM TRANSMITTER
DATA OUTPUT
FROM RECEIVER
STARTACKNOWLEDGE
FIGURE 14. ACKNOWLEDGE RESPONSE FROM RECEIVER
Device Addressing
Following a start condition, the master must output a Slave
Address Byte. The first four bits of the Slave Address Byte
specify access to either the EEPROM array or to the CCR.
Slave bits ‘1010’ access the EEPROM array. Slave bits
‘1101’ access the CCR.
When shipped from the factory, EEPROM array is
UNDEFINED, and should be programmed by the customer
to a known state.
Bit 3 through Bit 1 of the slave byte specify the device select
bits. These are set to ‘111’.
The last bit of the Slave Address Byte defines the operation
to be performed. When this R/W
operation is selected. A zero selects a write operation (Refer
to Figure 15).
After loading the entire Slave Address Byte from the SDA
bus, the ISL12026 compares the device identifier and device
bit is a one, then a read
819
select bits with ‘1010111’ or ‘1101111’. Upon a correct
compare, the device outputs an acknowledge on the SDA
line.
Following the Slave Byte is a two byte word address. The
word address is either supplied by the master device or
obtained from an internal counter. On power up the internal
address counter is set to address 0h, so a current address
read of the EEPROM array starts at address 0. When
required, as part of a random read, the master must supply
the 2 Word Address Bytes as shown in Figure 15.
In a random read operation, the slave byte in the “dummy
write” portion must match the slave byte in the “read”
section. That is if the random read is from the array the slave
byte must be 1010111x in both instances. Similarly, for a
random read of the Clock/Control Registers, the slave byte
must be 1101111x in both places.
15
FN8231.5
October 23, 2006
DEVICE IDENTIFIER
ISL12026
ARRAY
CCR
1
1
D7D6D5D2D4D3D1D0
0
1
0000 0A80
A6A5
1
0
0
0
1
1
FIGURE 15. SLAVE ADDRESS, WORD ADDRESS, AND DATA BYTES (16 BYTE PAGES)
Write Operations
Byte Write
For a write operation, the device requires the Slave Address
Byte and the Word Address Bytes. This gives the master
access to any one of the words in the array or CCR. (Note:
Prior to writing to the CCR, the master must write a 02h, then
06h to the status register in two preceding operations to
enable the write operation. See “Writing to the Clock/Control
Registers.”) Upon receipt of each address byte, the
ISL12026 responds with an acknowledge. After receiving
both address bytes the ISL12026 awaits the eight bits of
data. After receiving the 8 data bits, the ISL12026 again
responds with an acknowledge. The master then terminates
the transfer by generating a stop condition. The ISL12026
then begins an internal write cycle of the data to the nonvolatile memory. During the internal write cycle, the device
inputs are disabled, so the device will not respond to any
requests from the master . The SDA outpu t is at high
impedance (See Figure 16).
1
1
R/W
A0A7A2A4A3A1
SLAVE ADDRESS BYTE
BYTE 0
WORD ADDRESS 1
BYTE 1
WORD ADDRESS 0
BYTE 2
DATA BYTE
BYTE 3
A write to a protected block of memory is ignored, but will still
receive an acknowledge. At the end of the write command,
the ISL12026 will not initiate an internal write cycle, and will
continue to ACK commands.
Byte writes to all of the nonvolatile registers are allowed,
except the DWAn registers which require multiple byte writes
or page writes to trigger nonvolatile writes. See the Device
Operation section for more information.
Page Write
The ISL12026 has a page write operation. It is initiated in the
same manner as the byte write operation; but instead of
terminating the write cycle after the first data byte is
transferred, the master can transmit up to 15 more bytes to
the memory array and up to 7 more bytes to the clock/control
registers. The RTC registers require a page write (8 bytes),
individual register writes are not allowed. (Note: Prior to
writing to the CCR, the master must write a 02h, then 06h to
the status register in two preceding operations to enable the
write operation. See “Writing to the Clock/Control
Registers.”)
SIGNALS FROM
THE MASTER
SDA BUS
SIGNALS FROM
THE SLAVE
16
S
T
A
R
T
ADDRESS
SLAVE
1111
WORD
ADDRESS 1
0
0000000
A
C
K
A
C
K
FIGURE 16. BYTE WRITE SEQUENCE
WORD
ADDRESS 0
S
DATA
A
C
K
T
O
P
A
C
K
FN8231.5
October 23, 2006
ISL12026
S
SIGNALS FROM
THE MASTER
SDA BUS
SIGNALS FROM
THE SLAVE
T
A
R
T
SLAVE
ADDRESS
WORD
ADDRESS 1
0
1111
0000000
A
C
K
FIGURE 17. PAGE WRITE SEQUENCE
After the receipt of each byte, the ISL12026 responds with
an acknowledge, and the address is internally incremented
by one. The address pointer remains at the last address byte
written. When the counter reaches the end of the page, it
“rolls over” and goes back to the first address on the same
page. This means that the master can write 16 bytes to a
memory array page or 8 bytes to a CCR section starting at
any location on that page. For example, if the master begins
writing at location 10 of the memory and loads 15 bytes, then
the first 6 bytes are written to addresses 10 through 15, and
the last 6 bytes are written to columns 0 through 5.
Afterwards, the address counter would point to location 6 on
the page that was just written. If the master supplies more
than the maximum bytes in a page, then the previously
loaded data is over-written by the new data, one byte at a
time. Refer to Figure 18. The master terminates the Data
Byte loading by issuing a stop condition, which causes the
ISL12026 to begin the non-volatile write cycle. As with the
byte write operation, all inputs are disabled until completion
of the internal write cycle. Refer to Figure 17 for the address,
acknowledge, and data transfer sequence.
Stops and Write Modes
Stop conditions that terminate write operations must be sent
by the master after sending at least 1 full data byte and it’s
associated ACK signal. If a stop is issued in the middle of a
data byte, or before 1 full data byte + ACK is sent, then the
ISL12026 resets itself without performing the write. The
contents of the array are not affected.
.
1 ≤ n ≤ 16 for EEPROM array
1 ≤ n ≤ 8 for CCR
A
C
K
WORD
ADDRESS 0
DATA
(1)
A
C
K
DATA
(n)
Acknowledge Polling
Disabling of the inputs during non-volatile write cycles can
be used to take advantage of the 12ms (typ) write cycle time.
Once the stop condition is issued to indicate the end of the
master’s byte load operation, the ISL12026 initiates the
internal non-volatile write cycle. Acknowledge polling can
begin immediately. To do this, the ma ster issues a start
condition followed by the Memory Array Slave Address Byte
for a write or read operation (AEh or AFh). If the ISL12026 is
still busy with the non-volatile write cycle then no ACK will be
returned. When the ISL12026 has completed the write
operation, an ACK is returned and the host can proceed with
the read or write operation. Refer to the flow chart in
Figure 20. Note: Do not use the CCR Slave byte (DEh or
DFh) for Acknowledge Polling.
Read Operations
There are three basic read operations: Current Address
Read, Random Read, and Sequential Read.
Current Address Read
Internally the ISL12026 contains an address counter that
maintains the address of the last word read incremented by
one. Therefore, if the last read was to address n, the next
read operation would access data from address n+1. On
power up, the sixteen bit address is initialized to 00h. In this
way, a current address read immediately after the power on
reset can download the entire contents of memory starting at
the first location.Upon receipt of the Slave Address Byte with
the R/W
acknowledge, then transmits eight data bits. The master
terminates the read operation by not responding with an
bit set to one, the ISL12026 issues an
S
T
O
P
A
C
K
6 BYTES
ADDRESS = 5
ADDRESS POINTER ENDS
AT ADDR = 5
FIGURE 18. WRITING 12 BYTES TO A 16-BYTE MEMORY PAGE STARTING AT ADDRESS 10
ADDRESS
10
6 BYTES
17
ADDRESS
15
FN8231.5
October 23, 2006
ISL12026
acknowledge during the ninth clock and issuing a stop
condition. Refer to Figure 19 for the address, acknowledge,
and data transfer sequence.
S
SIGNALS FROM
THE MASTER
SDA BUS
SIGNALS FROM
THE SLAVE
FIGURE 19. CURRENT ADDRESS READ SEQUENCE
Byte load completed
Issue Memory Array Slave
AFh (Read) or AEh (Write)
Cycle complete. Continue
command sequence?
T
A
R
ADDRESS
T
by issuing STOP.
Enter ACK Polling
Issue START
Address Byte
ACK
returned?
YES
non-volatile write
YES
Continue normal
Read or Write
command
sequence
PROCEED
SLAVE
NO
NO
11111
A
C
K
Issue STOP
Issue STOP
DATA
S
T
O
P
Random Read
Random read operations allow the master to access any
location in the ISL12026. Prior to issuing the Slave Address
Byte with the R/W
bit set to zero, the master must first
perform a “dummy” write operation.
The master issues the start condition and the slave address
byte, receives an acknowledge, then issues the word
address bytes. After acknowledging receipt of each word
address byte, the master immediately issues another start
condition and the slave address byte with the R/W
bit set to
one. This is followed by an acknowledge from the device and
then by the eight bit data word. The master terminates the
read operation by not responding with an acknowledge and
then issuing a stop condition. Refer to Figure 21 for the
address, acknowledge, and data transfer sequence.
In a similar operation called “Set Current Address,” the
device sets the address if a stop is issued instead of the
second start shown in Figure 21. The ISL12026 then goes
into standby mode after the stop and all bus activity will be
ignored until a start is detected. This operation loads the new
address into the address counter. The next Current Address
Read operation will read from the newly loaded address.
This operation could be useful if the master knows the next
address it needs to read, but is not ready for the data.
Sequential Read
Sequential reads can be initiated as either a current address
read or random address read. The first data byte is
transmitted as with the other modes; however, the master
now responds with an acknowledge, indicating it requires
additional data. The device continues to output data for each
acknowledge received. The master terminates the read
operation by not responding with an acknowledge and then
issuing a stop condition.
The data output is sequential, with the data from address n
followed by the data from address n + 1. The address
counter for read operations increments through all page and
column addresses, allowing the entire memory contents to
be serially read during one operation. At the end of the
address space the counter “rolls over” to the start of the
address space and the ISL12026 continues to output data
for each acknowledge received. Refer to Figure 22 for the
acknowledge and data transfer sequence.
FIGURE 20. ACKNOWLEDGE POLLING SEQUENCE
It should be noted that the ninth clock cycle of the read
operation is not a “don’t care.” To terminate a read operation,
the master must either issue a stop condition during the
ninth cycle or hold SDA HIGH during the ninth clock cycle
and then issue a stop condition.
18
FN8231.5
October 23, 2006
ISL12026
SIGNALS FROM
THE MASTER
SDA BUS
SIGNALS FROM
THE SLAVE
SIGNALS FROM
THE MASTER
SDA BUS
SIGNALS FROM
THE SLAVE
S
T
SLAVE
A
R
T
ADDRESS
0
1111
A
C
K
WORD
ADDRESS 1
0000000
ADDRESS 0
A
C
K
WORD
FIGURE 21. RANDOM ADDRESS READ SEQUENCE
SLAVE
ADDRESS
1
A
C
DATA
K
(1)
A
C
K
DATA
(2)
FIGURE 22. SEQUENTIAL READ SEQUENCE
S
T
A
SLAVE
R
ADDRESS
T
1
1111
A
C
K
A
C
K
DATA
(n-1)
A
C
K
A
C
K
(n is any integer greater than 1)
DATA
DATA
(n)
S
T
O
P
S
T
O
P
Application Section
Crystal Oscillator and Temperature Compensation
Intersil has now integrated the oscillator compensation
circuity on-chip, to eliminate the need for external
components and adjust for crystal drift over temperature and
enable very high accuracy time keeping (<5ppm drift).
The Intersil RTC family uses an oscillator circuit with on-chip
crystal compensation network, including adjustable loadcapacitance. The only external component required is the
crystal. The compensation network is optimized for operation
with certain crystal parameters which are common in many
of the surface mount or tuning-fork crystals available today.
Table 6 summarizes these parameters.
Table 7 contains some crystal manufacturers and part
numbers that meet the requirements for the Intersil RTC
products.
The turnover temperature in Table 6 describes the
temperature where the apex of the of the drift vs.
temperature curve occurs. This curve is parabolic with the
drift increasing as (T-T0)
example, the turnover temperature is typically +25°C, and a
peak drift of >110ppm occurs at the temperature extremes of
-40 and +85°C. It is possible to address this variable drift by
adjusting the load capacitance of the crystal, which will result
in predictable change to the crystal frequency. The Intersil
RTC family allows this adjustment over temperature since
the devices include on-chip load capacitor trimming. This
control is handled by the Analog Trimming Register, or ATR,
2
. For an Epson MC-405 device, for
which has 6 bits of control. The load capacitance range
covered by the ATR circuit is approximately 3.25pF to
18.75pF , in 0.25pF increments. Note that actual capacitance
would also include about 2pF of package related
capacitance. In-circuit tests with commercially available
crystals demonstrate that this range of capacitance allows
frequency control from +80ppm to -34ppm, using a 12.5pF
load crystal.
In addition to the analog compensation afforded by the
adjustable load capacitance, a digital compensation feature
is available for the Intersil RTC family. There are three bits
known as the Digital Trimming Register or DTR, and they
operate by adding or skipping pulses in the clock signal. The
range provided is ±30ppm in increments of 10ppm. The
default setting is 0ppm. The DTR control can be used for
coarse adjustments of frequency drift over temperature or for
crystal initial accuracy correction.
19
FN8231.5
October 23, 2006
ISL12026
TABLE 6. CRYSTAL PARAMETERS REQUIRED FOR INTERSIL RTCs
PARAMETERMINTYPMAXUNITSNOTES
Frequency32.768kHz
Frequency Tolerance±100ppmDown to 20ppm if desired
Turnover Temperature2025 30°CTypically the value used for most crystals
Operating Temperature Range-4085°C
Parallel Load Capacitance12.5pF
Equivalent Series Resistance50k
TABLE 7. CRYSTAL MANUFACTURERS
MANUFACTURERPART NUMBERTEMP RANGE+25°C FREQUENCY TOLERANCE
Citizen CM201, CM202, CM200S-40 to +85°C±20ppm
Epson MC-405, MC-406-40 to +85°C±20ppm
RaltronRSM-200S-A or B-40 to +85°C±20ppm
SaRonix 32S12A or B-40 to +85°C±20ppm
Ecliptek ECPSM29T-32.768K-10 to +60°C±20ppm
ECS ECX-306/ECX-306I-10 to +60°C±20ppm
Fox FSM-327-40 to +85°C±20ppm
ΩFor best oscillator performance
A final application for the ATR control is in-circuit calibration
for high accuracy applications, along with a temperature
sensor chip. Once the RTC circuit is powered up with battery
backup, the IRQ
/F
output is set at 32.768kHz and
OUT
frequency drift is measured. The ATR control is then
adjusted to a setting which minimizes drift. Once adjusted at
a particular temperature, it is possible to adjust at other
discrete temperatures for minimal overall drift, and store the
resulting settings in the EEPROM. Extremely low overall
temperature drift is possible with this method. The Intersil
evaluation board contains the circuitry necessary to
implement this control.
For more detailed operation see Intersil’s application note
AN154 on Intersil’s website at www.intersil.com.
Layout Considerations
The crystal input at X1 has a very high impedance and will
pick up high frequency signals from other circuits on the
board. Since the X2 pin is tied to the other side of the crystal,
it is also a sensitive node. These signals can couple into the
oscillator circuit and produce double clocking or misclocking, seriously affecting the accuracy of the RTC. Care
needs to be taken in layout of the RTC circuit to avoid noise
pickup. In Figure 23 is a suggested layout for the ISL12026
or ISL12027 devices in 8 pin SO package.
FIGURE 23. SUGGESTED LAYOUT FOR INTERSIL RTC IN SO-8
The X1 and X2 connections to the crystal are to be kept as
short as possible. A thick ground trace around the crystal is
advised to minimize noise intrusion, but ground near the X1
and X2 pins should be avoided as it will add to the load
capacitance at those pins. Keep in mind these guidelines for
other PCB layers in the vicinity of the RTC device. A small
decoupling capacitor at the V
pin of the chip is mandatory,
DD
with a solid connection to ground.
20
The ISL12026 product has a special consideration. The IRQ
F
- pin on the 8-lead SOIC package is located next to the
OUT
X2 pin. When this pin is used as a frequency output (IRQ
F
) and is set to 32.768kHz noise can couple to the X1 or
OUT
/
X2 pins and cause double-clocking. The layout in Figure 23
FN8231.5
October 23, 2006
/
ISL12026
minimizes this by running the IRQ/F
output away from
OUT
the X1 and X2 pins. Also, reducing the switching current at
this pin by careful selection of the pull-up resistor value will
reduce noise. Intersil suggests a minimum value of 5.1kΩ for
32.768kHz, and higher values (up to 20kΩ) for lower
frequency IRQ
/F
OUT
outputs.
For other RTC products, the same rules stated above should
be observed, but adjusted slightly since the
packages and pinouts are different.
Oscillator Measurements
When a proper crystal is selected and the layout guidelines
above are observed, the oscillator should start up in most
circuits in less than one second. Some circuits may take
slightly longer, but startup should definitely occur in less than
5 seconds. When testing RTC circuits, the most common
impulse is to apply a scope probe to the circuit at the X2 pin
(oscillator output) and observe the waveform. DO NOT DO
THIS! Although in some cases you may see a useable
waveform, due to the parasitics (usually 10pF to ground)
applied with the scope probe, there will be no useful
information in that waveform other than the fact that the
circuit is oscillating. The X2 output is sensitive to capacitive
impedance so the voltage levels and the frequency will be
affected by the parasitic elements in the scope probe.
Applying a scope probe can possibly cause a faulty oscillator
to start up, hiding other issues (although in the Intersil RTCs,
the internal circuitry assures startup when using the proper
crystal and layout).
The best way to analyze the RTC circuit is to power it up and
read the real time clock as time advances, or if the chip has
the IRQ
/F
output, look at the output of that pin on an
OUT
oscilloscope (after enabling it with the control register, and
using a pull-up resistor for an open-drain output).
Alternatively, the ISL12026 device has an IRQ
/F
OUT
output
which can be checked by setting an alarm for each minute.
Using the pulse interrupt mode setting, the once-per-minute
interrupt functions as an indication of proper oscillation.
Backup Battery Operation
Many types of batteries can be used with the Intersil RTC
products. 3.0V or 3.6V Lithium batteries are appropriate, and
sizes are available that can power a Intersil RTC device for
up to 10 years. Another option is to use a supercapacitor for
applications where V
short periods of time. Depending on the value of
supercapacitor used, backup time can last from a few days
to two weeks (with >1F). A simple silicon or Schottky barrier
diode can be used in series with V
supercapacitor, which is connected to the V
use Schottky diodes with very low leakages, <1
Do not use the diode to charge a battery (especially lithium
batteries!).
may disappear intermittently for
DD
to charge the
DD
pin. Try to
BAT
µA desirable.
operational concerns when switching over to battery backup
since all other devices functions are disabled. Battery drain
is minimal in Standard mode, and return to Normal V
powered operations is predictable. In Legacy mode the V
pin can power the chip if the voltage is above V
than V
In this mode, it is possible to generate alarm and
TRIP.,
and less
DD
DD
BAT
communicate with the device, unless SBI = 1, but the supply
current drain is much higher than the Standard mode and
backup time is reduced. In this case if alarms are used in
backup mode, the IRQ
connected to V
BAT
/F
pull up resistor must be
OUT
voltage source. During initial power up
the default mode is the Standard mode.
2.7-5.5V
FIGURE 24. SUPERCAPACITOR CHARGING CIRCUIT
V
CC
V
back
Supercapacitor
V
SS
Alarm Operation Examples
Below are examples of both Single Event and periodic
Interrupt Mode alarms.
Example 1 – Alarm 0 set with single interrupt (IM = ”0”)
A single alarm will occur on January 1 at 11:30am.
A. Set Alarm 0 registers as follows:
ALARM0
REGISTER
SCA0 00000000 00hSeconds disabled
MNA0 10110000 B0hMinutes set to 30,
HRA0 10010001 91hHours set to 11,
DTA0 10000001 81hDate set to 1,
MOA0 10000001 81hMonth set to 1,
DWA0 0000000000hDay of week
B. Also the AL0E bit must be set as follows:
CONTROL
REGISTER
INT00100000 x0hEnable Alarm
BIT
DESCRIPTION76543210HEX
enabled
enabled
enabled
enabled
disabled
BIT
DESCRIPTION76543210HEX
There are two possible modes for battery backup operation,
Standard and Legacy mode. In S tandard mode, there are no
21
After these registers are set, an alarm will be generated when
the RTC advances to exactly 11:30am on January 1 (after
FN8231.5
October 23, 2006
ISL12026
seconds changes from 59 to 00) by setting the AL0 bit in the
status register to “1” and also bringing the IRQ/
F
OUT
output
low.
Example 2 – Pulsed interrupt once per minute (IM = ”1”)
Interrupts at one minute intervals when the seconds register
is at 30 seconds.
A. Set Alarm 0 registers as follows:
Once the registers are set, the following waveform will be
seen at IRQ/
F
-:
OUT
RTC and alarm registers are both “30” sec
60 sec
Note that the status register AL0 bit will be set each time the
alarm is triggered, but does not need to be read or cleared.
I2C Communications During Battery backup
Operation in Battery Backup mode is affected by the BSW
and SBIB bits as described earlier. These bits allow flexible
operation of the serial bus and EEPROM in battery backup
mode, but certain operational details need to be clear before
utilizing the different modes. Table 8 describes 4 different
modes possible with using the BSW and SBIB bits, and how
they are affect the serial interface and battery backup
operation.
• Mode A - In this mode selection bits indicate a Standard
Mode switchover combined with I
backup mode. When the V
lower of V
TRIP
or V
, then the device will enter battery
BAT
backup mode. If the microcontroller and bus pullups are
also powered by the battery, then the ISL12026 can
communicate in battery backup mode.
• Mode B - In this mode selection bits indicate Legacy mode
switchover combined with I
mode. When the VDD voltage drops below V
device will enter battery backup mode. If the
microcontroller and bus pullups are also powered by the
battery, then the ISL12026 can communicate in battery
backup mode. This mode places the ISL12026 device in
the same operating mode as the X1226 legacy device.
• Mode C - This mode combines Standard mode battery
switchover with no I
When the V
V
BAT
DD
, then the device will enter battery backup mode and
2
C operation in battery backup mode.
voltage drops below the lower of V
the I2C interface will be disabled, minimizing V
drain.
• Mode D - This mode combines Legacy mode battery
switchover with no I
When the V
DD
2
C operation in battery backup mode.
voltage drops below V
enter battery backup mode and the I2C interface will be
disabled, minimizing V
Note that the IRQ
BAT
/F
open drain output pin is active in
OUT
battery backup for all modes, allowing clocking of devices
while in battery backup mode. The pullup on the pin will
need to go to V
, and thus battery mode current draw will
BAT
increase accordingly.
2
C operation in battery
voltage drops below the
DD
2
C operation in battery backup
, the
BAT
TRIP
current
BAT
, the device will
BAT
current drain.
or
V
BAT
SWITCHOVER
MODESBIB BIT BSW BIT
A00Standard Mode,
B (X1226
Mode)
C 10Standard Mode,
D11Legacy Mode,
01Legacy Mode,
VOLTAGE
V
TRIP
V
DD
V
TRIP
V
DD
= 2.2V typ
< V
BAT
= 2.2V typ
< V
BAT
22
2
I
C ACTIVE IN
BATTERY
BACKUP?
YesNOYES, needs
YesNOYES, needs
NONOYES, needs
NONOYES, needs
EE PROM WRITE/
READ IN BATTER Y
BACKUP?
pullup to V
pullup to V
pullup to V
pullup to V
FREQ/IRQ
ACTIVE?NOTES
V
switchover at lower of V
BAT
V
BAT
BAT
BAT
BAT
.Pullups needed on I2C to V
TRIP
to operate in Battery Backup.
V
switchover at <VDD. Pullups
BAT
needed on I2C to V
Battery Backup.
V
switchover at lower of V
BAT
V
.
TRIP
V
switchover at <VDD.
BAT
to operate in
BAT
October 23, 2006
or
BAT
BAT
or
BAT
FN8231.5
Small Outline Plastic Packages (SOIC)
ISL12026
N
INDEX
AREA
123
-A-
E
-B-
SEATING PLANE
D
A
-C-
0.25(0.010)BMM
H
L
h x 45°
α
e
B
0.25(0.010)C AMBS
M
NOTES:
1. Symbols are defined in the “MO Series Symbol List” in Section 2.2 of
Publication Number 95.
2. Dimensioning and tolerancing per ANSI Y14.5M-1982.
3. Dimension “D” does not include mold flash, protrusions or gate burrs.
Mold flash, protrusion and gate burrs shall not exceed 0.15mm (0.006
inch) per side.
4. Dimension “E” does not include interlead flash or protrusions. Interlead flash and protrusions shall not exceed 0.25mm (0.010 inch) per
side.
5. The chamfer on the body is optional. If it is not present, a visual index
feature must be located within the crosshatched area.
6. “L ” is the length of terminal for soldering to a substrate.
7. “N” is the number of terminal positions.
8. Terminal numbers are shown for reference only.
9. The lead width “B”, as measured 0.36mm (0.014 inch) or greater
above the seating plane, shall not exceed a maximum value of
0.61mm (0.024 inch).
10. Controlling dimension: MILLIMETER. Converted inch dimensions
are not necessarily exact.
A1
C
0.10(0.004)
M8.15 (JEDEC MS-012-AA ISSUE C)
8 LEAD NARROW BODY SMALL OUTLINE PLASTIC PACKAGE
INCHESMILLIMETERS
SYMBOL
A0.05320.06881.351.75-
A10.00400.00980.100.25-
B0.0130.0200.330.519
C0.00750.00980.190.25-
D0.18900.19684.805.003
E0.14970.15743.804.004
e0.050 BSC1.27 BSC-
H0.22840.24405.806.20-
h0.00990.01960.250.505
L0.0160.0500.401.276
N887
α
0°8°0°8°-
NOTESMINMAXMINMAX
Rev. 1 6/05
23
FN8231.5
October 23, 2006
ISL12026
Thin Shrink Small Outline Plastic Packages (TSSOP)
N
INDEX
AREA
123
-A-
0.05(0.002)
D
SEATING PLANE
e
b
0.10(0.004)C AMBS
M
E1
-B-
A
-C-
0.25(0.010)BMM
E
α
A1
0.10(0.004)
GAUGE
PLANE
0.25
0.010
A2
L
c
NOTES:
1. These package dimensions are within allowable dimensions of
JEDEC MO-153-AC, Issue E.
2. Dimensioning and tolerancing per ANSI Y14.5M-1982.
3. Dimension “D” does not include mold flash, protrusions or gate burrs.
Mold flash, protrusion and gate burrs shall not exceed 0.15mm
(0.006 inch) per side.
4. Dimension “E1” does not include interlead flash or protrusions. Inter-
lead flash and protrusions shall not exceed 0.15mm (0.006 inch) per
side.
5. The chamfer on the body is optional. If it is not present, a visual index
feature must be located within the crosshatched area.
6. “L” is the length of terminal for soldering to a substrate.
7. “N” is the number of terminal positions.
8. Terminal numbers are shown for reference only.
9. Dimension “b” does not include dambar protrusion. Allowable dambar
protrusion shall be 0.08mm (0.003 inch) total in excess of “b” dimension at maximum material condition. Minimum space between protrusion and adjacent lead is 0.07mm (0.0027 inch).
10. Controlling dimension: MILLIMETER. Converted inch dimensions
are not necessarily exact. (Angles in degrees)
M8.173
8 LEAD THIN SHRINK NARROW BODY SMALL OUTLINE
PLASTIC PACKAGE
INCHESMILLIMETERS
SYMBOL
A-0.047-1.20-
A10.0020.0060.050.15-
A20.0310.0510.801.05-
b0.00750.01180.190.309
c0.00350.00790.090.20-
D0.1160.1202.953.053
E10.1690.1774.304.504
e0.026 BSC0.65 BSC-
E0.2460.2566.256.50-
L0.01770.02950.450.756
N887
o
α
0
o
8
o
0
o
8
Rev. 1 12/00
NOTESMINMAXMINMAX
-
All Intersil U.S. products are manufactured, assembled and tested utilizing ISO9000 quality systems.
Intersil Corporation’s quality certifications can be viewed at www.intersil.com/design/quality
Intersil products are sold by description only. Intersil Corporation reserves the right to make changes in circuit design, software and/or specifications at any time without
notice. Accordingly, the reader is cautioned to verify that data sheets are current before placing orders. Information furnished by Intersil is believed to be accurate and
reliable. However, no responsibility is assumed by Intersil or its subsidiaries for its use; nor for any infringements of patents or other rights of third parties which may result
from its use. No license is granted by implicat ion or oth erwise u nde r any p a tent or p at ent r ights of Intersil or its subsidiaries.
For information regarding Intersil Corporation and its products, see www.intersil.com
24
FN8231.5
October 23, 2006
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