Page 1
General Description
The DS1087L is a clock generator that produces a
spread-spectrum (dithered) square-wave output of frequencies from 130kHz to 66.6MHz. The DS1087L is
shipped from the factory programmed at a specific frequency and spread-spectrum percentage. The user still
has access to an internal frequency divider, selectable
2% or 4% dithered output, and programmable output
power-down/disable mode through a 2-wire programming interface. All the device settings are stored in nonvolatile (NV) EEPROM allowing it to operate in
stand-alone applications. The DS1087L has powerdown and output-enable control pins for power-sensitive applications.
Applications
Printers
Copiers
PCs
Computer Peripherals
Cell Phones
Cable Modems
Features
♦ Factory Programmed Square-Wave Generator
from 130kHz to 66.6MHz
♦ No External Timing Components Required
♦ EMI Reduction
♦ 2.7V to 3.6V Supply
♦ User Programmable Down to 130kHz with Divider
(Dependent on Master Oscillator Frequency)
♦ 2% or 4% Selectable Dithered Output
♦ Glitchless Output-Enable Control
♦ 2-Wire Serial Interface
♦ Nonvolatile Settings
♦ Power-Down Mode
♦ Programmable Output Power-Down/Disable Mode
DS1087L
3.3V Spread-Spectrum EconOscillator
______________________________________________ Maxim Integrated Products 1
Pin Configuration
Ordering Information
Rev 1; 11/03
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.
EconOscillator is a trademark of Dallas Semiconductor.
Typical Operating Circuits appear at end of data sheet.
Standard Frequency Options
Custom frequencies and over 20 standard frequencies available, contact factory.
PART TEMP RANGE PIN-PACKAGE
DS1087LU-yxx -40°C to +85°C 8 µSOP (118 mils)
PART FREQUENCY (MHz) SPREAD (%)
DS1087LU-202 2.0480 2
DS1087LU-402 2.0480 4
DS1087LU-210 10.0 2
DS1087LU-216 16.6 2
DS1087LU-266 66.6 2
DS1087LU-466 66.6 4
DS1087LU-yxx Fixed up to 66.6 2 or 4
TOP VIEW
OUT
V
CC
1
2
DS1087L
3
4
µSOP (118 mils)
87SCL
SDASPRD
PDN
6
OEGND
5
Page 2
DS1087L
3.3V Spread-Spectrum EconOscillator
2 _____________________________________________________________________
ABSOLUTE MAXIMUM RATINGS
RECOMMENDED DC OPERATING CONDITIONS
(VCC= 2.7V to 3.6V, TA= -40°C to +85°C.)
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.
DC ELECTRICAL CHARACTERISTICS
(VCC= 2.7V to 3.6V, TA= -40°C to +85°C.)
Voltage Range on VCCRelative to Ground ..........-0.5V to +6.0V
Voltage Range on SPRD, PDN, OE, SDA, SCL
Relative to Ground* ................................-0.5V to (V
CC
+ 0.5V)
Operating Temperature Range ...........................-40°C to +85°C
Programming Temperature Range .........................0°C to +70°C
Storage Temperature Range .............................-55°C to +125°C
Soldering Temperature ..................See IPC/JEDEC J-STD-020A
*This voltage must not exceed 6.0V.
PARAMETER SYMBOL CONDITION MIN TYP MAX UNITS
Supply Voltage V
High-Level Input Voltage
(SDA, SCL, SPRD, PDN, OE)
Low-Level Input Voltage
(SDA, SCL, SPRD, PDN, OE)
CC
V
V
(Note 1) 2.7 3.6 V
IH
IL
0.7 x
V
CC
-0.3
V
CC
0.3
0.3 x
V
+
CC
V
V
PARAMETER SYMBOL CONDITION MIN TYP MAX UNITS
High-Level Output Voltage (OUT) V
Low-Level Output Voltage (OUT) V
Low-Level Output Voltage (SDA)
High-Level Input Current I
Low-Level Input Current I
Supply Current (Active) I
Standby Current (Power-Down) I
V
OL1
V
OL2
CC
CCQ
OH
OL
IH
IL
IOH = -4mA, VCC = min 2.4 V
IOL = 4mA 0.4 V
3mA sink current 0 0.4
6mA sink current 0 0.6
VCC = 3.6V 1 µA
VIL = 0 -1 µA
CL = 15pF (output at f0)15mA
Power-down mode 5 µA
V
Page 3
DS1087L
3.3V Spread-Spectrum EconOscillator
_____________________________________________________________________ 3
MASTER OSCILLATOR CHARACTERISTICS
(VCC= 2.7V to 3.6V, TA= -40°C to +85°C.)
AC ELECTRICAL CHARACTERISTICS
(VCC= 2.7V to 3.6V, TA= -40°C to +85°C.)
PARAMETER SYMBOL CONDITION MIN TYP MAX UNITS
Master Oscillator Range
Available
Master Oscillator Frequency
Tolerance
Voltage Frequency
Variation
Temperature Frequency Variation
Temperature Frequency Variation
Dither Frequency Range
Dither Rate f0 / 4096 Hz
f
0
∆ f
0
f
∆ f
f
∆
f
∆
f
VCC = 3.3V, TA = +25°C (Notes 2, 13) -0.5 +0.5 %
0
V
Over voltage range, TA = +25°C (Note 3) -0.75 +0.75 %
0
f
T
0°C to +70°C, VCC = 3.3V (Note 4) -0.5 +0.5 %
0
f
T
-40°C to +85°C, VCC = 3.3V (Note 4) -1.5 +0.5 %
0
Prescaler bit J0 = 1 (Note 5) 2
Prescaler bit J0 = 0 (Note 5) 4
33.3 66.6 MHz
%
PARAMETER SYMBOL CONDITION MIN TYP MAX UNITS
Frequency Stable After
PRESCALER Change
+
t
Power-Up Time
Enable of OUT After Exiting
Power-Down Mode
OUT Disabled After Entering
Power-Down Mode
Load Capacitance C
Output Duty Cycle (OUT) TA = +25°C 45 55 %
POR
t
STAB
t
STAB
t
PDN
(Note 6) 0.1 0.5 ms
(Note 7) 15 50 pF
L
1 period
500 µs
1ms
Page 4
DS1087L
3.3V Spread-Spectrum EconOscillator
4 _____________________________________________________________________
AC ELECTRICAL CHARACTERISTICS—2-WIRE INTERFACE
(VCC= 2.7V to 3.6V, TA= 0°C to +70°C.)
NONVOLATILE MEMORY CHARACTERISTICS
(VCC= 2.7V to 3.6V)
PARAMETER SYMBOL CONDITION MIN TYP MAX UNITS
SCL Clock Frequency f
Bus Free Time Between a STOP
and START Condition
Hold Time (repeated) START
Condition
LOW Period of SCL t
HIGH Period of SCL t
Setup Time for a Repeated
START
Data Hold Time t
Data Setup Time t
Rise Time of Both SDA and SCL
Signals
Fall Time of Both SDA and SCL
Signals
Setup Time for STOP t
Capacitive Load for Each Bus
NV Write Cycle Time t
Input Capacitance C
SCL
t
BUF
t
HD:STA
LOW
HIGH
t
SU:STA
HD:DAT
SU:DAT
t
t
SU:STO
C
WR
Fast mode (Note 8) 400
Standard mode (Note 8) 100
Fast mode (Note 8) 1.3
Standard mode (Note 8) 4.7
Fast mode (Notes 8 and 9) 0.6
Standard mode (Notes 8 and 9) 4.0
Fast mode (Note 8) 1.3
Standard mode (Note 8) 4.7
Fast mode (Note 8) 0.6
Standard mode (Note 8) 4.0
Fast mode 0.6
Standard mode 4.7
Fast mode (Notes 8, 10, and 11) 0 0.9
Standard mode (Notes 8, 10, and 11) 0 0.9
Fast mode (Note 8) 100
Standard mode (Note 8) 250
Fast mode (Note 12) 20 + 0.1C
R
Standard mode (Note 12) 20 + 0.1C
Fast mode (Note 12) 20 + 0.1C
F
Standard mode (Note 12) 20 + 0.1C
Fast mode 0.6
Standard mode 4.0
(Note 12) 400 pF
B
I
kHz
µs
µs
µs
µs
µs
µs
ns
B
B
B
B
5pF
300
1000
300
1000
10 ms
ns
ns
µs
PARAMETER SYMBOL CONDITION MIN TYP MAX UNITS
Writes +70°C 10,000
Page 5
DS1087L
3.3V Spread-Spectrum EconOscillator
_____________________________________________________________________ 5
Note 1: All voltages are referenced to ground.
Note 2: This is the absolute accuracy of the master oscillator frequency at the default settings.
Note 3: This is the change that is observed in master oscillator frequency with changes in voltage from nominal voltage at
T
A
= +25°C.
Note 4: This is the percentage frequency change from the +25°C frequency due to temperature at V
CC
= 3.3V.
Note 5: The dither deviation of the master oscillator frequency is unidirectional and lower than the undithered frequency.
Note 6: This indicates the time elapsed between power-up and the output becoming active. An on-chip delay is intentionally
introduced to allow the oscillator to stabilize. t
stab
is equivalent to approximately 512 master clock cycles and depends
on the programmed master oscillator frequency.
Note 7: Output voltage swings may be impaired at high frequencies combined with high output loading.
Note 8: A fast-mode device can be used in a standard-mode system, but the requirement t
SU:DAT
> 250ns must then be met. This
is automatically the case if the device does not stretch the LOW period of the SCL signal. If such a device does stretch
the LOW period of the SCL signal, it must output the next data bit to the SDA line at least t
R MAX
+ t
SU:DAT
= 1000ns +
250ns = 1250ns before the SCL line is released.
Note 9: After this period, the first clock pulse is generated.
Note 10: A device must internally provide a hold time of at least 300ns for the SDA signal (referred to as the V
IH MIN
of the SCL sig-
nal) to bridge the undefined region of the falling edge of SCL.
Note 11: The maximum t
HD:DAT
need only be met if the device does not stretch the LOW period (t
LOW
) of the SCL signal.
Note 12: C
B
—total capacitance of one bus line, timing referenced to 0.9 x VCCand 0.1 x VCC.
Note 13: Typical frequency shift due to aging is ±0.5%. Aging stressing includes Level 1 moisture reflow preconditioning (24hr
+125°C bake, 168hr 85°C/85%RH moisture soak, and 3 solder reflow passes +240 +0/-5°C peak) followed by 1000hr
max V
CC
biased 125°C HTOL, 1000 temperature cycles at -55°C to +125°C, and 168hr 121°C/2 ATM Steam/Unbiased
Autoclave.
Typical Operating Characteristics
(VCC= 3.3V, TA= +25°C, unless otherwise noted.)
ACTIVE SUPPLY CURRENT
vs. TEMPERATURE
DS1087L toc01
TEMPERATURE (°C)
CURRENT (mA)
80706050403020100-10-20-30
5.5
6.0
6.5
7.0
7.5
5.0
-40 90
VCC = 3.3V
FREQUENCY = 66.6MHz
OE = PDN = V
CC
15pF LOAD
8.2pF LOAD
4.7pF LOAD
UNLOADED
VOLTAGE (V)
3.5
3.42.8 2.9 3.0 3.23.1 3.3
1.0
2.0
3.0
4.0
5.0
6.0
7.0
8.0
0
2.7 3.6
ACTIVE SUPPLY CURRENT
vs. VOLTAGE
DS1087L toc02
CURRENT (mA)
FREQUENCY = 66.6MHz
OUTPUT UNLOADED
OE = PDN = V
CC
SUPPLY CURRENT vs. PRESCALER
DS1087L toc03
PRESCALER (DECIMAL)
10010
11000
1
2
3
4
5
6
7
0
CURRENT (mA)
OUTPUT UNLOADED
3.6V
3.3V
2.7V
Page 6
DS1087L
3.3V Spread-Spectrum EconOscillator
6 _____________________________________________________________________
Typical Operating Characteristics
(VCC= 3.3V, TA= +25°C, unless otherwise noted.)
1
2
3
4
5
6
0
SUPPLY CURRENT vs. PRESCALER
DS1087L toc04
PRESCALER (DECIMAL)
100101 1000
CURRENT (mA)
VCC = 3.3V
OUPUT UNLOADED
-40°C, +25°C, +85°C
0.5
1.0
1.5
2.0
2.5
3.0
3.5
4.0
0
SUPPLY CURRENT
vs. TEMPERATURE WITH OE = 0
DS1087L toc05
TEMPERATURE (°C)
CURRENT (mA)
80706050403020100-10-20-30-40 90
FREQUENCY = 66.6MHz
VCC = 2.7V
OUTPUT UNLOADED
FREQUENCY = 206.4kHz
SHUTDOWN SUPPLY CURRENT
vs. TEMPERATURE
DS1087L toc06
TEMPERATURE (°C)
CURRENT (µA)
807050 60-10 0 10 20 30 40-30 -20
0.2
0.4
0.6
0.8
1.0
1.2
1.4
1.6
1.8
2.0
0
-40 90
VCC = 3.3V
OUTPUT UNLOADED
FREQUENCY % CHANGE vs.
1.00
OUTPUT LOADED WITH
0.80
12pF OSCILLOSCOPE PROBE
0.60
FREQUENCY = 66.6MHz
0.40
0.20
0
-0.20
-0.40
-0.60
FREQUENCY % CHANGE (FROM 3.3V)
-0.80
-1.00
2.7 3.6
SUPPLY VOLTAGE
VOLTAGE (V)
60
59
58
57
56
55
54
DUTY CYCLE (%)
53
52
51
50
2.7 3.6
DS1087L toc07
FREQUENCY % CHANGE (FROM 25°C)
3.53.43.2 3.32.9 3.0 3.12.8
DUTY CYCLE vs. VOLTAGE
FREQUENCY = 66.6MHz
= +25°C
T
A
OUTPUT LOADED WITH
12pF OSCILLOSCOPE PROBE
VOLTAGE (V)
FREQUENCY % CHANGE vs.
TEMPERATURE
1.50
VCC = 3.3V
FREQUENCY = 66.6MHz
1.00
OUTPUT LOADED WITH
12pF OSCILLOSCOPE PROBE
0.50
0
-0.50
-1.00
-1.50
-40 90
TEMPERATURE (°C)
60
VCC = 3.3V
59
DS1087L toc10
3.53.43.2 3.32.9 3.0 3.12.8
FREQUENCY = 66.6MHz
OUTPUT LOADED WITH
58
12pF OSCILLOSCOPE PROBE
57
56
55
54
DUTY CYCLE (%)
53
52
51
50
7
VCC = SDA = 3.3V
6
DS1087L toc08
SUPPLY CURRENT (mA)
80706050403020100-10-20-30
FREQUENCY = 66.6MHz
OUTPUT UNLOADED
5
4
3
2
1
0
0 400
DUTY CYCLE vs. TEMPERATURE
5030 402010070
60
TEMPERATURE (°C)
ACTIVE SUPPLY CURRENT
vs. SCL FREQUENCY
DS1087L toc09
300200100
SCL FREQUENCY (kHz)
DS1087L toc11
Page 7
DS1087L
3.3V Spread-Spectrum EconOscillator
_____________________________________________________________________ 7
Pin Description
Figure 1. Functional Diagram
PIN NAME FUNCTION
1 OUT Oscillator Output
2 SPRD Dither Enable. When the pin is high, the dither is enabled. When the pin is low, the dither is disabled.
3VCCPower Supply
4 GND Ground
5OE
6 PDN
7 SDA 2-Wire Serial Data. This pin is for serial data transfer to and from the device.
8 SCL 2-Wire Serial Clock. This pin is used to clock data into and out of the device.
Output Enable. When the pin is high, the output buffer is enabled. When the pin is low, the output is
disabled but the internal master oscillator is still on.
Power-Down. When the pin is high, the master oscillator is enabled. When the pin is low, the master
oscillator is disabled (power-down mode).
V
SDA
SCL
PDN
SPRD
GND
CC
2-WIRE
INTERFACE
OE
TRIANGLE WAVE
PRESCALER
DITHER
CONTROL
GENERATOR
EEPROM CONTROL
REGISTERS
ADDR
DITHER SIGNAL
DS1087L
FACTORY-PROGRAMMED
OSCILLATOR
MASTER
OSCILLATOR
PRESCALER
BY 1, 2, 4...256
OUTPUT
OUT
Page 8
DS1087L
3.3V Spread-Spectrum EconOscillator
8 _____________________________________________________________________
Detailed Description
A block diagram of the DS1087L is shown in Figure 1.
Output Frequency
The internal master oscillator can generate a square
wave with a frequency range of 33.3MHz to 66.6MHz.
The master oscillator frequency and output frequency
are factory programmed, although the user can use the
programmable divider to divide the master oscillator
frequency by 2
x
(where x equals 0 to 8).
Output Control and Power-Down
Two user control signals control the output. The outputenable pin, OE, gates the clock output buffer and the
PDN pin disables the master oscillator and turns off the
output for power-sensitive applications (note: the
power-down command must persist for at least two output frequency cycles plus 10µs for deglitching purposes). On power-up, the output is disabled until power is
stable and the master oscillator has generated 512
clock cycles.
Both controls feature a synchronous enable, which
ensures there are no output glitches when the output is
enabled. The synchronous enable also ensures a constant time interval (for a given frequency setting) from
an enable signal to the first output transition.
Spread Spectrum
The DS1087L can reduce radiated emission peaks. The
output frequency can be dithered 2% or 4% below the
programmed frequency. Although the output frequency
changes when the dither is enabled, the duty cycle
does not change.
The dither is controlled by the J0 bit in the PRESCALER
register and enabled with the SPRD pin. The maximum
spectral attenuation occurs when the prescaler is set to
1. The spectral attenuation is reduced by 2.7dB for
every factor of 2 that is used in the prescaler. This happens because the prescaler’s divider function tends to
average the dither in creating the lower frequency.
However, the most stringent spectral emission limits are
imposed on the higher frequencies where the prescaler
is set to a low divider ratio.
A triangle-wave generator injects an offset element into
the master oscillator to dither its output. The dither rate
(see Equation 1) is based on the master oscillator frequency. Figure 2 shows a plot of the output frequency
versus dither rate.
where f
0
= master oscillator frequency
Register Summary
The DS1087L registers are used to change the dither
amount, output frequency, and slave address. A summary of the registers is shown in Table 1. Once programmed into EEPROM, the settings only need to be
reprogrammed if it is desired to reconfigure the device.
PRESCALER Register
Bit 5: Output Low or High-Z. The LO/HIZ bit
controls the output. During power-down,
while the output is deactivated, if the
LO/HIZ bit is set to 0, the output is high-Z.
If the LO/HIZ bit is set to 1, the output is
driven low.
Bit 4: Dither Control. The J0 bit controls the
dither applied to the output. When J0 is
high, 2% peak dither is selected. When
J0 is low, 4% peak dither is selected.
Table 1. Register Summary
Figure 2. Output Frequency vs. Dither Rate
(1)
X1= Don’t care; read as one.
REGISTER ADDR BINARY FACTORY DEFAULT ACCESS
LO/
PRESCALER 02h X
ADDR 0Dh X
WRITE EE 3Fh No Data — —
X
1
1
X
1
1
J0 P3 P2 P1 P0 110- - - - - b R/W
HIZ
X
X1WC A2 A1 A0 11110000b R/W
1
OUTPUT FREQUENCY
(f
f
/N
O
/N) - 4%
O
0
WHERE N = (2X)
= FACTORY PROGRAMMED MASTER OSCILLATOR FREQUENCY
f
0
2f
/4096fO/4096
O
DITHER RATE
0
4096
Dither Ratef =
Page 9
DS1087L
3.3V Spread-Spectrum EconOscillator
_____________________________________________________________________ 9
Bits 3 to 0: Prescaler Divider. The prescaler bits
(bits P3 to P0) divide the master oscillator
frequency by 2
x
where x can be from 0 to
8. Any prescaler bit value entered that is
greater than 8 decodes as 8.
ADDR Register
Bit 3: Write Control. The WC bit determines if
the EEPROM is to be written to after register contents have been changed. If WC
= 0 (default), EEPROM is written automatically after a write. If WC = 1, the EEPROM is only written when the WRITE EE
command is issued. See the WRITE EE
Command section for more information.
Bits 2 to 0: Address. The A0, A1, A2 bits determine
the lower nibble of the 2-wire slave
address.
WRITE EE Command
The WRITE EE command is useful in closed-loop applications where the registers are frequently written. In
applications where the register contents are frequently
written, the WC bit should be set to 1 to prevent wearing out the EEPROM. Regardless of the value of the WC
bit, the value of the ADDR register is always written
immediately to EEPROM. When the WRITE EE command has been received, the contents of the registers
are copied into the EEPROM, thus locking in the register settings.
_______2-Wire Serial Port Operation
2-Wire Serial Data Bus
The DS1087L communicates through a 2-wire serial
interface. A device that sends data onto the bus is
defined as a transmitter, and a device receiving data
as a receiver. The device that controls the message is
called a "master." The devices that are controlled by the
master are "slaves." A master device that generates the
serial clock (SCL), controls the bus access, and generates the START and STOP conditions must control the
bus. The DS1087L operates as a slave on the 2-wire
bus. Connections to the bus are made through the
open-drain I/O lines SDA and SCL.
The following bus protocol has been defined (see
Figures 3 and 5):
• Data transfer can be initiated only when the bus is
not busy.
• During data transfer, the data line must remain
stable whenever the clock line is HIGH. Changes
in the data line while the clock line is HIGH are
interpreted as control signals.
Accordingly, the following bus conditions have been
defined:
Bus not busy: Both data and clock lines remain
HIGH.
Start data transfer: A change in the state of the
data line, from HIGH to LOW, while the clock is
HIGH, defines a START condition.
Stop data transfer: A change in the state of the
data line, from LOW to HIGH, while the clock line
is HIGH, defines the STOP condition.
Figure 3. 2-Wire Data Transfer Protocol
SDA
MSB
SLAVE ADDRESS
SCL
START
CONDITION
12 678 9 12 893–7
R/W
DIRECTION
BIT
ACKNOWLEDGEMENT
SIGNAL FROM RECEIVER
ACK
REPEATED IF MORE BYTES
ACKNOWLEDGEMENT
SIGNAL FROM RECEIVER
ARE TRANSFERRED
ACK
STOP
CONDITION
OR REPEATED
START
CONDITION
Page 10
DS1087L
3.3V Spread-Spectrum EconOscillator
10 ____________________________________________________________________
Data valid: The state of the data line represents
valid data when, after a START condition, the data
line is stable for the duration of the HIGH period of
the clock signal. The data on the line must be
changed during the LOW period of the clock signal. There is one clock pulse per bit of data.
Each data transfer is initiated with a START condition and terminated with a STOP condition. The
number of data bytes transferred between START
and STOP conditions is not limited, and is determined by the master device. The information is
transferred byte-wise and each receiver acknowledges with a ninth bit.
Within the bus specifications a standard mode
(100kHz clock rate) and a fast mode (400kHz
clock rate) are defined. The DS1087L works in
both modes.
Acknowledge: Each receiving device, when
addressed, is obliged to generate an acknowledge after the byte has been received. The master
device must generate an extra clock pulse that is
associated with this acknowledge bit.
A device that acknowledges must pull down the
SDA line during the acknowledge clock pulse in
such a way that the SDA line is stable LOW during
the HIGH period of the acknowledge-related clock
pulse. Of course, setup and hold times must be
taken into account. When the DS1087L EEPROM
is being written to, it is not able to perform additional responses. In this case, the slave DS1087L
sends a not acknowledge to any data transfer
request made by the master. It resumes normal
operation when the EEPROM operation is complete.
A master must signal an end of data to the slave
by not generating an acknowledge bit on the last
byte that has been clocked out of the slave. In this
case, the slave must leave the data line HIGH to
enable the master to generate the STOP condition.
Figures 3, 4, 5, and 6 detail how data transfer is
accomplished on the 2-wire bus. Depending upon
the state of the R/W bit, two types of data transfer
are possible:
1) Data transfer from a master transmitter to a slave
receiver. The first byte transmitted by the master is
the slave address. Next follows a number of data
bytes. The slave returns an acknowledge bit after
each received byte.
2) Data transfer from a slave transmitter to a master
receiver. The first byte (the slave address) is transmitted by the master. The slave then returns an
acknowledge bit. Next follows a number of data
bytes transmitted by the slave to the master. The
master returns an acknowledge bit after all
received bytes other than the last byte. At the end
of the last received byte, a not acknowledge is
returned.
The master device generates all the serial clock
pulses and the START and STOP conditions. A
transfer is ended with a STOP condition or with a
repeated START condition. Since a repeated
START condition is also the beginning of the next
serial transfer, the bus is not released.
The DS1087L can operate in the following two modes:
Slave receiver mode: Serial data and clock are
received through SDA and SCL. After each byte is
received, an acknowledge bit is transmitted.
START and STOP conditions are recognized as
the beginning and end of a serial transfer.
Address recognition is performed by hardware
after reception of the slave address and direction
bit.
Slave transmitter mode: The first byte is received
and handled as in the slave receiver mode.
However, in this mode, the direction bit indicates
that the transfer direction is reversed. Serial data
is transmitted on SDA by the DS1087L while the
serial clock is input on SCL. START and STOP
conditions are recognized as the beginning and
end of a serial transfer.
Slave Address
Figure 4 shows the first byte sent to the device. It
includes the device identifier, device address, and the
R/W bit. The device address must match the address
set in the ADDR register (bits A0, A1, and A2).
Registers/Commands
See Table 1 for the complete list of registers/commands and Figure 6 for an example of using them.
Figure 4. Slave Address
MSB
1 0 1 1 A2 A1 A0 R/W
DEVICE
IDENTIFIER
DEVICE
ADDRESS
LSB
READ/WRITE BIT
Page 11
DS1087L
3.3V Spread-Spectrum EconOscillator
____________________________________________________________________ 11
Application Information
Power-Supply Decoupling
To achieve the best results when using the DS1087L,
decouple the power supply with 0.01µF and 0.1µF
high-quality, ceramic, surface-mount capacitors.
Surface-mount components minimize lead inductance,
which improves performance, and ceramic capacitors
tend to have adequate high-frequency response for
decoupling applications. These capacitors should be
placed as close to the V
CC
and GND pins as possible.
Stand-alone Mode
SCL and SDA cannot be left floating even in standalone mode. If the DS1087L never needs to be programmed in-circuit, including during production
testing, SDA and SCL can be wired high.
Figure 5. 2-Wire AC Characteristics
Figure 6. 2-Wire Transactions
SDA
t
BUF
t
LOW
SCL
t
HD:STA
STOP START
TYPICAL 2-WIRE WRITE TRANSACTION
MSB
1
START
10 1
DEVICE IDENTIFIER
A2*
DEVICE
ADDRESS
LSB
R/WA0*A1*
READ/
WRITE
t
R
t
HD:DAT
SLAVE
ACK
t
F
t
HIGH
t
SU:DAT
MSB LSB
b7 b6 b5 b4 b3 b2 b1 b0
COMMAND/REGISTER ADDRESS
REPEATED
START
t
HD:STA
t
SU:STA
MSB LSB
SLAVE
SLAVE
b7 b6 b5 b4 b3 b2 b1 b0
ACK
ACK
DATA
t
SP
t
SU:STO
SLAVE
STOP
ACK
EXAMPLE 2-WIRE TRANSACTIONS (WHEN A0, A1, AND A2 ARE ZERO)
A) SINGLE BYTE WRITE
-WRITE PRESCALER
REGISTER TO 128
B) SINGLE BYTE READ
-READ PRESCALER
REGISTER
*THE ADDRESS DETERMINED BY A0, A1, AND A2 MUST
MATCH THE ADDRESS SET IN THE ADDR REGISTER.
START
START
B0h
10110000
B0h
10110000
02h
SLAVE
00000010 10000000
ACK
02h
SLAVE
00000010
ACK
DATA
SLAVE
ACK
SLAVE
ACK
REPEATED
START
SLAVE
ACK
B1h
10110001
STOP
SLAVE
ACK
DATA
10000000
MASTER
NACK
STOP
Page 12
DS1087L
3.3V Spread-Spectrum EconOscillator
Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are
implied. Maxim reserves the right to change the circuitry and specifications without notice at any time.
12 ____________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600
© 2003 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products.
Chip Topology
TRANSISTOR COUNT: 10000
SUBSTRATE CONNECTED TO GROUND
Typical Operating Circuits
Package Information
For the latest package outline information, go to
www.maxim-ic.com/DallasPackInfo
Processor-Controlled Mode
Stand-Alone Mode
DITHERED 130kHz TO
66.6MHz OUTPUT
V
CC
DECOUPLING CAPACITORS
(0.1µF and 0.01µF)
OUT
SPRD
V
CC
GND
DS1087L
V
CC
4.7kΩ 4.7kΩ
SCL
SDA
PDN
V
CC
OE
2-WIRE
INTERFACE
MICRO-
PROCESSOR
XTL1/OSC1
XTL2/OSC2
*SDA AND SCL CAN BE CONNECTED DIRECTLY HIGH IF THE DS1087L NEVER NEEDS
TO BE PROGRAMMED IN-CIRCUIT, INCLUDING DURING PRODUCTION TESTING.
DITHERED 130kHz TO
66.6MHz OUTPUT
V
CC
N.C.
DECOUPLING CAPACITORS
(0.1µF and 0.01µF)
OUT
SPRD
V
CC
GND
DS1087L
SCL*
SDA*
PDN
OE
V
CC
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