Rainbow Electronics MAX6901 User Manual
General Description
The MAX6901 3-wire serial interface real-time clock in a
TDFN package contains a real-time clock/calendar and
31 x 8 bits of static RAM (SRAM). The real-time
clock/calendar provides seconds, minutes, hours, day,
date, month, year, and century information. A
time/date-programmable polled ALARM is included in
the MAX6901. The end of the month date is automatically adjusted for months with fewer than 31 days,
including corrections for leap year up to the year 2100.
The clock operates in either the 24hr or 12hr format
with an AM/PM indicator. A push-pull 32kHz output is
also included. The MAX6901 operates with a supply
voltage of +2V to +5.5V, is available in the ultra-small 8pin TDFN package, and works over the industrial temperature range, -40°C to +85°C.
Applications
Point-of-Sale Equipment
Intelligent Instruments
Fax Machines
Battery-Powered Products
Portable Instruments
Features
♦ Real-Time Clock Counts Seconds, Minutes,
Hours, Day of Week, Date of Month, Month, Year,
and Century
♦ Leap-Year Compensation Valid up to Year 2100
♦ Wide +2V to +5.5V Operating Voltage Range
♦ 3-Wire Serial Interface, 2MHz at 5V, 500kHz at 2V
♦ 31 x 8-Bit SRAM for Scratchpad Data Storage
♦ Uses Standard 32.768kHz, 12.5pF Watch Crystal
♦ Low Timekeeping Current (400nA at 2V)
♦ Single-Byte or Multiple-Byte (Burst Mode)
Data Transfer for Read or Write of Clock
Registers or SRAM
♦ 8-Pin 3mm x 3mm x 0.8mm TDFN
Surface-Mount Package
♦ Push-Pull 32.768kHz Clock Output
♦ Programmable Time/Date Polled ALARM Function
♦ No External Crystal Bias Resistors or Capacitors
Required
MAX6901
3-Wire Serial RTC in a TDFN
________________________________________________________________ Maxim Integrated Products 1
19-2085; Rev 1; 2/03
Ordering Information
Related Real-Time Clock Products
Pin Configuration appears at end of data sheet.
Functional Diagram appears at end of data sheet.
µC
0.1µF
32.768kHz
CRYSTAL
1
4
3
6
2
5
3.3V
3.3V
MAX6901
7
8
P1.0
CLKIN
P1.1
P1.2
SCLK
CS
I/O
32KHZ
GND
V
CC
X1
X2
Typical Operating Circuit
For pricing, delivery, and ordering information, please contact Maxim/Dallas Direct! at
1-888-629-4642, or visit Maxim’s website at www.maxim-ic.com.
I2C is a trademark of Philips Corp. Purchase of I2C components of Maxim Integrated Products, Inc., or one of its sublicensed Associated
Companies, conveys a license under the Philips I
2
C Patent rights to use these components in an I2C system provided that the system
conforms to the I
2
C Standard Specification as defined by Philips.
SPI is a trademark of Motorola, Inc.
PART
MAX6901ETA-T -40°C to +85°C 8 TDFN AGV
ALARM
FUNCTION
PART
MAX6900 I2C™ compatible 31 x 8 ——6 TDFN
MAX6901 3 wire 31 x 8 Polled 32kHz 8 TDFN
MAX6902 SPI™ compatible 31 x 8 Polled — 8 TDFN
INTERFACE
SERIAL
ALARM
(bits)
TEMP
RANGE
OUTPUT
FREQUENCY
PINPACKAGE
PIN-PACKAGE
TOP
MARK
MAX6901
3-Wire Serial RTC in a TDFN
2 _______________________________________________________________________________________
ABSOLUTE MAXIMUM RATINGS
Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress ratings only, and functional
operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to
absolute maximum rating conditions for extended periods may affect device reliability.
VCCto GND.......................................................……-0.3V to +6V
All Other Pins to GND ................................-0.3V to (Vcc + 0.3V)
Current into Any Pin..........................................................±20mA
Rate-of-Rise, V
CC
............................................................100V/µs
Continuous Power Dissipation (T
A
= +70°C)
8-Pin TDFN (derate 24.4mW/°C above +70°C).........1951.0mW
Junction Temperature .....................................................+150°C
Storage Temperature Range .............................-65°C to +150°C
ESD Protection (all pins, Human Body Model) ..................2000V
Lead Temperature (soldering, 10s) .................................+300°C
DC ELECTRICAL CHARACTERISTICS
(VCC= +2.0V to +5.5V, TA= -40°C to +85°C, unless otherwise noted. Typical values are at VCC= +3.3V, TA= +25°C.) (Note 1)
PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS
Operating Voltage Range V
Active Supply Current (Note 2) I
Timekeeping Supply Current
(Note 3)
32kHz OUTPUT
Output High Voltage (Note 5) V
Output Low Voltage (Note 5) V
Duty Cycle 40 %
Output Leakage Current VIN = 0 to VCC, 32kHz output disabled -10 10 nA
3-WIRE DIGITAL INPUTS AND OUTPUTS (SCLK, I/O, CS)
Input High Voltage V
Input Low Voltage V
Input Leakage Current VIN = 0 to V
SCLK, RST Capacitance 5pF
I/O Capacitance 10 pF
I/O Output Low Voltage V
I/O Output High Voltage V
I
CC
CC
TK
OH
OL
OL
OH
VCC = +2.0V 0°C < TA < +70°C 110
VCC = +5V 0°C < TA < +70°C 800
VCC = +2.0V 0.4 0.7
VCC = +5V 1.3 1.7
VCC = +2.0V, I
VCC = +5.0V, I
VCC = +2.0V, I
VCC = +5.0V, I
VCC = +2.0V 1.4
IH
VCC = +5.0V 2.2
VCC = +2.0V 0.6
IL
VCC = +5.0V 0.8
CC
VCC = +2.0V, I
VCC = +5.0V, I
VCC = +2.0V, I
VCC = +5.0V, I
2 5.5 V
= -0.4mA 1.8
SOURCE
= -1mA 4.5
SOURCE
= 1.5mA 0.4
SINK
= 4mA 0.4
SINK
-10 10 nA
= 1.5mA 0.4
SINK
= 4mA 0.4
SINK
= -0.4mA 1.8
SOURCE
= -1mA 4.5
SOURCE
µA
µA
V
V
V
V
V
V
MAX6901
3-Wire Serial RTC in a TDFN
_______________________________________________________________________________________ 3
Note 1: All parameters are 100% tested at TA= +25°C. Limits over temperature are guaranteed by design and not production tested.
Note 2: I
CC
is specified with the I/O grounded, CS high, SCLK = 2MHz at VCC= +5V; SCLK = 500kHz at VCC= +2.0V, 32kHz output
enabled, and no load on 32kHz output.
Note 3: Timekeeping current is specified with CS = GND, SCLK = GND, I/O = GND, 32kHz = GND, and 32kHz disabled.
Note 4: All values referred to V
IH
min and VILmax levels.
Note 5: Guaranteed by design. Not production tested.
AC ELECTRICAL CHARACTERISTICS
(VCC= +2.0V to +5.5V, TA= -40°C to +85°C, unless otherwise noted. Typical values are at VCC= +3.3V, TA= +25°C.) (Figures 4, 5
and Notes 1, 4)
OSCILLATOR
X1 to Ground Capacitance (Note 5) 25 pF
X2 to Ground Capacitance (Note 5) 25 pF
3-WIRE SERIAL TIMING
Data to CLK Setup t
CLK to Data Hold t
CLK to Data Delay t
CLK Low Time t
CLK High Time t
CLK Frequency f
CLK Rise and Fall Time tR, t
CS to CLK Setup t
CLK to CS Hold t
CS Inactive Time t
CS to I/O High Z t
SCLK to I/O High Z t
PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS
DC
CDH
CDD
CL
CH
CLK
CC
CCH
CWH
CDZ
CCZ
VCC = +2V 200
VCC = +5V 50
VCC = +2V 280
VCC = +5V 70
CL = 50pF
VCC = +2V 1000
VCC = +5V 250
VCC = +2V 1000
VCC = +5V 250
VCC = +2V DC 0.5
VCC = +5V DC 2.0
VCC = +2V 2000
F
VCC = +5V 500
VCC = +2V 4
VCC = +5V 1
VCC = +2V 240
VCC = +5V 60
VCC = +2V 4
VCC = +5V 1
RL = 1kΩ, CL = 60pF
RL = 1kΩ, CL = 60pF
VCC = +2V 800
V
= +5V 200
CC
VCC = +2V 0 280
= +5V 0 70
V
CC
VCC = +2V 0 280
V
= +5V 0 70
CC
ns
ns
ns
ns
ns
MHz
ns
µs
ns
µs
ns
ns
MAX6901
Detailed Description
The MAX6901 is a real-time clock/calendar with a 3-wire
serial interface and 31 ✕8 bits of SRAM. It provides seconds, minutes, hours, day of the week, date of the
month, month, and year information, held in seven 8-bit
timekeeping registers (Functional Diagram). An on-chip
32.768kHz oscillator circuit does not require any external resistors or capacitors to operate. Table 1 specifies
the parameters for the external crystal, and Figure 1
shows a functional schematic of the oscillator circuit.
The MAX6901’s register addresses and definitions are
described in Tables 2 and 3. Time and calendar data
are stored in the registers in binary coded decimal
(BCD) format. A polled alarm function is included for
scheduled timing of user-defined times or intervals.
Command and Control
Address/Command Byte
Each data transfer into or out of the MAX6901 is initiated by an Address/Command byte. The Address/
Command byte specifies which registers are to be
accessed, and if the access is a read or a write. Table
2 shows the Address/Command bytes and their associated registers, and Table 3 lists the hex codes for all
read and write operations. The Address/Command
bytes are input LSB (bit 0) first. Bit 0 specifies a write
(logic 0) or read (logic 1). Bits 1 to 5 specify the designated register to be written or read. Bit 6 specifies register data (logic 0), or RAM data (logic 1). The MSB (bit
7) must be logic 1. If the MSB is a zero, writes to the
MAX6901 are disabled.
3-Wire Serial RTC in a TDFN
4 _______________________________________________________________________________________
Typical Operating Characteristics
(TA = +25°C, unless otherwise noted.)
0.1
2.0 2.5 3.5 4.0 5.54.5 5.03.0
TIMEKEEPING CURRENT
vs. SUPPLY VOLTAGE
1.0
10.0
MAX6901 toc01
SUPPLY VOLTAGE (V)
SUPPLY CURRENT (µA)
Pin Description
PIN NAME FUNCTION
1 SCLK Serial Clock Input. 3-wire serial clock for I/O data transfers.
2VCCPower-Supply Pin. Bypass VCC to GND with a 0.1µF capacitor.
3 X2 External 32.768kHz Crystal Connection
4 X1 External 32.768kHz Crystal Connection
5 32KHZ
6 GND Ground Connection
7 CS Chip-Select Input. Active-high for valid data transfers.
8 I/O Data Input/Output. 3-wire serial data input/output connection.
— PAD Ground
Buffered Push-Pull 32.768kHz Output. When enabled, 32KHZ puts a buffered version of the timekeeping clock.
When disabled, 32KHZ is high impedance. The power-on reset (POR) default state of 32KHZ is enabled.
Clock Burst Mode
Accessing the Clock Burst register specifies burstmode operation. In this mode, multiple bytes are read
or written with a single Address/Command write. If the
Clock Burst register is accessed (BEh for Write and
BFh for Read), the first seven clock/calendar registers
(Seconds, Minutes, Hours, Date, Month, Day, and Year)
and the Control register, are consecutively read or written, starting with the LSB of the Seconds register. When
writing to the clock registers in burst mode, all seven
registers must be written in order for the data to be
transferred (see Example: Setting the Clock with a
Burst Write).
RAM Burst Mode
Sending the RAM Burst Address/Command specifies
Burst-Mode operation. In this mode, the 31 RAM registers can be consecutively read or written, starting with
bit 0 of address C0h for Writes, and C1h for Reads.
Burst Read outputs all 31 registers of RAM. When writing to RAM in burst mode, it is not necessary to write all
31 bytes for the data to transfer; each complete byte
written is transferred to RAM. When reading from RAM,
data bits are output until all 31 bytes have been read,
or until CS is driven low.
Setting the Clock
Writing to the Timekeeping Registers
The Time and Date are set by writing to the timekeeping registers (Seconds, Minutes, Hours, Date, Month,
Day, Year, and Century). During a write operation, an
input buffer accepts the new time data while the timekeeping registers continue to increment normally,
based on the crystal counter. The buffer also keeps the
timekeeping registers from changing as the result of an
incomplete Write operation, and collision detection circuitry ensures that a time write does not occur coincident with a Seconds register increment. The updated
time data are loaded into the timekeeping registers on
the falling edge of CS, at the end of the 3-wire serial
Write operation. An incomplete Write operation aborts
the update procedure, and the contents of the input
buffer are discarded. The timekeeping registers reflect
the new time, beginning with the first Seconds register
increment after the falling edge of CS.
Although both Single Writes and Burst Writes are possible, the best way to write to the timekeeping registers is
with a Burst Write. With a Burst Write, main timekeeping
registers (Seconds, Minutes, Hours, Date, Month, Day,
Year), and the Control register are written sequentially
following the Address/Command byte. They must be
written as a group of eight registers, with 8 bits each,
for proper execution of the Burst Write function. All
seven timekeeping registers are simultaneously loaded
into the clock counters by the falling edge of CS, at the
end of the 3-wire serial Write operation. For a normal
burst data transfer, the worst-case error that can occur
between the actual time and the written time update is
1 second.
If Single Write operations are used to enter data into the
timekeeping registers, error checking is required. If the
Seconds register is not to be written, then begin by
reading the Seconds register and save it as initial-seconds. Write to the required timekeeping registers and
MAX6901
3-Wire Serial RTC in a TDFN
_______________________________________________________________________________________ 5
Figure 1. Oscillator Circuit Schematic
Table 1. Acceptable Quartz Crystal Parameters
Frequency f
Equivalent Series Resistance (ESR) R
Parallel Load Capacitance C
Q Factor Q
PARAMETER SYMBOL MIN TYP MAX UNITS
Rf
MAX6901
Rd
25pF
Cg
X1 X2
EXTERNAL
CRYSTAL
Cd
25pF
32.76
s
L
40 60 kΩ
11.2 12.5 13.7 pF
40,000 60,000
kHz
MAX6901
then read the Seconds register again (final-seconds).
Check to see that final-seconds is equal to initial-seconds. If not, repeat the write process. If the Seconds
register is to be written, update the Seconds register
first, and then read it back and store its value (initialseconds). Update the remaining timekeeping registers
and then read the Seconds register again (final-sec-
3-Wire Serial RTC in a TDFN
6 _______________________________________________________________________________________
Table 2. Register Address/Definition
FUNCTION A7 A6 A5 A4 A3 A2 A1 A0 VALUE D7 D6 D5 D4 D3 D2 D1 D0
TIMEKEEPING
SECOND
REGISTER ADDRESS REGISTER DEFINITION
1000 000
MINUTE
HOUR
DATE
MONTH
1000 001
1000 010
1000 011
1000 100
RD
/W
RD
/W
RD
/W
RD
/W
RD
/W
00-59
*POR STATE 0 0 0 0 0000
00-59
*POR STATE
00-23 12/24
01-12 1/0
*POR STATE 0 0 0 00000
01-28/29
01-30
01-31
*POR STATE
01-12 0 0 0 10M 1 MONTH
*POR STATE
32kHz
EN
ALM
OUT
10 SEC 1 SEC
10 MIN 1 MIN
0 0000000
10
HR
A/P
0/1
10
HR
1 HR
0
0 0 10 DATE 1 DATE
0 0 000001
0 0 0 00001
DAY
1000 101
YEAR
CONTROL
CENTURY
Note: *POR STATE
1000 110
1000 111
1001 001
defines power-on reset state of register content.
RD
/W
RD
/W
RD
/W
RD
/W
*POR STATE 0
*POR STATE 0 0 0 1 1 0 0 1
01-07 0 0 0 0 0 WEEKDAY
*POR STATE
00-99 10 YEAR 1 YEAR
*POR STATE 0 1 1 1 0 0 0 0
00-99 1000 YEAR 100 YEAR
0 0 0 0 0 00 1
WP 0 0 0 0 0 0 0
0 0 0 0 0 0 0
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