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Rev 1; 5/04
Multiphase Spread-Spectrum EconOscillator
General Description
The DS1094L is a silicon oscillator that generates four multiphase, spread-spectrum, square-wave outputs. Frequencies between 2MHz and 31.25kHz can be output in either two, three, or four-phase mode. The internal master oscillator can be dithered by either 0, 2, 4, or 8% to reduce the amount of peak spectral energy at the fundamental and harmonic clock frequencies. This significantly reduces the amount of electromagnetic interference (EMI) radiation that is generated at the system level. The DS1094L is ideally suited as a clock generator for switched-mode power supplies. The outputs generated by the DS1094L are used by DC-DC circuitry to efficiently shift voltages either up or down. The DS1094L can be programmed using the I2CTM-compatible, 2-wire serial interface to select the output frequency, number of clock phases, and dither rate, or optionally it can be shipped from the factory custom programmed.
Features
EconOscillatorTM with Two, Three, or Four Phase Outputs Ideally Suited as the Clock Generator for SwitchMode Power Supplies Output Frequencies Programmable from 2MHz to 31.25kHz Dithered Output Significantly Reduces EMI Emissions No External Timing Components Required Nonvolatile (NV) Configuration Settings User-Programmable--Factory Programmed Options Available Operating Temperature Range: -40C to +85C
DS1094L
Applications
Switch-Mode Power Supplies Servers Printers Automotive Telematics and Infotainment
PART DS1094LU
Ordering Information
TEMP RANGE -40C to +85C PIN-PACKAGE 8 SOP
Pin Configuration Typical Operating Circuit
TOP VIEW
VIN VCC DC-DC STEP-DOWN CONVERTER VOUT
OUT1 1 OUT2 VCC 2 3
8
SCL SDA OUT4 OUT3
RPULLUP
VCC SCL SDA GND DS1094L
OUT1 OUT2 OUT3 OUT4
PHASE 1
DS1094L
7 6 5
PHASE 2
THREE-PHASE EXAMPLE WITH DITHERED CLOCKS TO REDUCE EMI PHASE 3
DC-DC STEP-DOWN CONVERTER
GND 4
SOP
DC-DC STEP-DOWN CONVERTER
EconOscillator is a trademark of Dallas Semiconductor.
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 I2C Patent Rights to use these components in an I2C system, provided that the system conforms to the I2C Standard Specification as defined by Philips. 1
______________________________________________ Maxim Integrated Products
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.
Multiphase Spread-Spectrum EconOscillator DS1094L
ABSOLUTE MAXIMUM RATINGS
Voltage Range on VCC, SDA, and SCL Relative to Ground.............................................-0.5V to +6.0V Operating Temperature Range ...........................-40C to +85C EEPROM Programming Temperature Range .........0C to +70C Storage Temperature Range .............................-55C to +125C Soldering Temperature .......................................See IPC/JEDEC J-STD-020A Specification
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.
RECOMMENDED DC OPERATING CONDITIONS
(TA = -40C to +85C)
PARAMETER Supply Voltage Input Logic 1 (SDA, SCL) Input Logic 0 (SDA, SCL) SYMBOL VCC VIH VIL (Note 1) CONDITIONS MIN 3.0 0.7 x VCC -0.3 TYP MAX 3.6 VCC + 0.3 +0.3 x VCC UNITS V V V
DC ELECTRICAL CHARACTERISTICS
(VCC = +3.0 to 3.6V, TA = -40C to +85C, unless otherwise noted.)
PARAMETER Active Supply Current High-Level Output Voltage (OUT1-4) Low-Level Output Voltage (OUT1-4) Low-Level Output Voltage (SDA) High-Level Input Current (SDA, SCL) Low-Level Input Current (SDA, SCL) SYMBOL ICC VOH VOL VOL IIH IIL CONDITIONS CL = 15pF per output, SDA = SCL = VCC IOH = -4mA; VCC = min IOL = 3.5mA 3mA sink current 6mA sink current VIH = VCC VIL = 0.0V -1.0 MIN TYP 1.4 MAX 3 UNITS mA V 0.4 0.4 0.6 +1.0 V V A A
2.4
2
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Multiphase Spread-Spectrum EconOscillator
AC ELECTRICAL CHARACTERISTICS
(VCC = +3.0V to 3.6V, TA = -40C to +85C, unless otherwise noted.)
PARAMETER Master Oscillator Frequency Output Frequency Tolerance Voltage Frequency Variation Temperature Frequency Variation DAC Step Size Peak-to-Peak Jitter (3) Load Capacitance Output Duty Cycle (Note 4) tPOR + tSTAB CL 2 Phase 3 Phase 4 Phase Power-Up Time (Note 5) P1:P0 = 11 (Note 3) SYMBOL fMOSC fOUT fOUT fOUT VCC = 3.3V, TA = +25C (Note 8) TA = +25C (Note 2) VCC = 3.3V (Note 2) 0 to +70C -40C to +85C CONDITIONS MIN 1 -2.5 -0.5 -1.1 -2.5 -0.75 8 15 50 33.3 50 0.1 0.5 ms % 50 TYP MAX 2 +2.5 +0.5 +1.1 +1.1 +0.75 UNITS MHz % % % % % pF
DS1094L
AC ELECTRICAL CHARACTERISTICS (See Figure 3)
(VCC = +3.0V to 3.6V, TA = -40C to +85C, unless otherwise noted. Timing referenced to VIL(MAX) and VIH(MIN).)
PARAMETER SCL Clock Frequency Bus Free Time Between Stop and Start Conditions Hold Time (Repeated) Start Condition Low Period of SCL High Period of SCL Data Hold Time Data Setup Time Start Setup time SDA and SCL Rise Time SDA and SCL Fall Time Stop Setup Time SDA and SCL Capacitive Loading EEPROM Write Time Input Capacitance SYMBOL fSCL tBUF tHD:STA tLOW tHIGH tHD:DAT tSU:DAT tSU:STA tR tF tSU:STO CB tWR CI (Note 7) 5 5 (Note 7) (Note 7) (Note 6) CONDITIONS MIN 0 1.3 0.6 1.3 0.6 0 100 0.6 20 + 0.1CB 20 + 0.1CB 0.6 400 10 300 300 0.9 TYP MAX 400 UNITS kHz s s s s s ns s ns ns s pF ms pF
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3
Multiphase Spread-Spectrum EconOscillator DS1094L
NONVOLATILE MEMORY CHARACTERISTICS
(VCC = +3.0V to 3.6V, unless otherwise noted.)
PARAMETER EEPROM Writes SYMBOL +70C (Note 4) CONDITIONS MIN 10,000 TYP MAX UNITS
Note 1: All voltages referenced to ground. Note 2: This is the change observed in output frequency due to changes in temperature or voltage. Note 3: This is a percentage of the output period. Parameter is characterized but not production tested. This can be varied from 2%, 4%, or 8%. Note 4: This parameter is guaranteed by design. Note 5: This indicates the time between power-up and the outputs becoming active. An on-chip delay is intentionally introduced to allow the oscillator to stabilize. tSTAB is equivalent to approximately 64 fMOSC cycles and, hence, will depend on the programmed clock frequency. Note 6: Timing shown is for fast-mode (400kHz) operation. This device is also backward compatible with I2C standard-mode timing. Note 7: CB--total capacitance of one bus line in picofarads. Note 8: Typical frequency shift due to aging is 0.5%. Aging stressing includes Level 1 moisture reflow preconditioning (24hr +125C bake, 168hr 85C/85%RH moisture soak, and 3 solder reflow passes +240 +0/-5C peak) followed by 1000hr max VCC biased 125C HTOL, 1000 temperature cycles at -55C to +125C, and 168hr 121C/2 ATM Steam/Unbiased Autoclave.
Typical Operating Characteristics
(VCC = +3.3V, TA = +25C, unless otherwise noted.)
SUPPLY CURRENT vs. SUPPLY VOLTAGE fOUT = 1MHz, 2 MODE
DS1094L toc01
SUPPLY CURRENT vs. FREQUENCY VCC = 3.3V, 2 MODE
DS1094L toc02
DUTY CYCLE vs. SUPPLY VOLTAGE fOUT = 2MHz, 2 MODE
DS1094L toc03
1.50
2.5
51.00
SUPPLY CURRENT (mA)
SUPPLY CURRENT (mA)
1.25 TA = +85C TA = +25C 1.00 TA = -40C 0.75
2.0
50.75 DUTY CYCLE (%) TA = +25C 50.50
TA = +85C
1.0
1.5
0.5
50.25
TA = -40C
0.50 3.00 3.15 3.30 3.45 3.60 SUPPLY VOLTAGE (V)
0 0.1 1.00 fOUT (MHz) 10.00
50.00 3.00 3.15 3.30 3.45 3.60 SUPPLY VOLTAGE (V)
4
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Multiphase Spread-Spectrum EconOscillator DS1094L
Typical Operating Characteristics (continued)
(VCC = +3.3V, TA = +25C, unless otherwise noted.)
DUTY CYCLE vs. FREQUENCY VCC = 3.3V, +25C
DS1094L toc04
OUTPUT FREQUENCY TOLERANCE VCC = 3.3V, +25C
DS1094L toc05
VOLTAGE FREQUENCY VARIATION
DS1094L toc06
55
2
0.5
0.50
50 DUTY CYCLE (%) 4
0 ERROR (%) ERROR (%)
0.25
fOUT = 1MHz
45
-0.5
0 fOUT = 2MHz
40 3 35
-1.0
-0.25
fOUT = 125kHz
30 1.00 1.25 1.50 fOUT (MHz) 1.75 2.00
-1.5 1.00 1.25 1.50 fOUT (MHz) 1.75 2.00
-0.50 3.0 3.2 3.0 3.5 3.6 SUPPLY VOLTAGE (V)
TEMPERATURE FREQUENCY VARIATON
DS1094L toc07
PEAK-TO-PEAK JITTER vs. fMOSC
DS1094L toc08
0.4 0 fOUT = 2MHz -.04 ERROR (%) fOUT = 1MHz -0.8 fOUT = 125kHz -1.2
2.5
2.0 JITTER (%) 85
1.5
1.0 -1.6 -2.0 -40 -15 10 35 60 TEMPERATURE (C) 0.8 1.0 1.2 1.4 1.6 1.8 2.0 fMOSC (MHz)
Pin Description
PIN 1 2 3 4 5 6 7 8 NAME OUT1 OUT2 VCC GND OUT3 OUT4 SDA SCL FUNCTION Oscillator Output 1 Oscillator Output 2 Positive Supply Terminal Ground Oscillator Output 3 Oscillator Output 4 2-Wire Serial-Interface Data Input/Output 2-Wire Serial-Interface Clock Input
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5
Multiphase Spread-Spectrum EconOscillator DS1094L
Functional Diagram
SDA SCL
CONTROL REGISTERS 2-WIRE SERIAL INTERFACE 2-WIRE ADDRESS BITS
DS1094L
fOUT
WRITE EE COMMAND
X
X
X
X WC A2 A1 A0 DAC SETTING
MASTER OSCILLATOR
fMOSC
PRESCALER DIVIDE BY 1, 2, 4, OR 8
OUT1 OUT2 OUT3 OUT4
fOSC TWO/THREE/ FOUR-PHASE GENERATOR
ADDR EEPROM WRITE CONTROL
1MHz TO 2MHz EEPROM X DAC VCC VCC DITHER RATE DITHER % D1 D0 PH1 PH0 J1 J0 P1 P0 X X X D3 D2 D1 D0 fMOD TRIANGLE WAVE GENERATOR
fMOSC
GND
PRESCALER SETTING PRESCALER
PHASE SELECT
Detailed Description
The DS1094L consists of a master oscillator, prescaler, phase generator, and triangle-wave generator (used to dither the master oscillator), which are all programmable using the 2-wire interface and stored in NV memory.
LSBs (D3 to D0) are the DAC value. The master oscillator frequency is determined using the following equation: fMOSC = 1MHz + (DAC value x 100kHz) Valid values for DAC are 0 to 10 (dec). DAC values greater than 10 exceed the 2MHz limit and are not permitted. The master oscillator also determines the spread-spectrum dither frequency. This is described in the Triangle Wave Generator section.
Master Oscillator
The master oscillator is responsible for generating the timing (frequency) of the outputs. The master oscillator frequency, f MOSC , can be programmed anywhere between 1MHz to 2MHz in 100kHz steps. The master oscillator is programmed using the DAC register. The four MSBs of the DAC register are don't cares, while the four
Table 1. Master Oscillator Settings
DAC VALUE (dec) 0 1 2 -- 10 11 to 15 DAC REGISTER 00h 01h 02h -- 0Ah 0Bh to 0Fh fMOSC 1.0MHz 1.1MHz 1.2MHz -- 2.0MHz Reserved
Table 2. Prescaler Settings
BITS P1, P0 00 01 10 11 DIVISOR 20 21 2
2
fOSC = fMOSC/1 fMOSC/2 fMOSC/4 fMOSC/8
23
6
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Multiphase Spread-Spectrum EconOscillator
Table 3. Phase Generator Settings
BITS Ph1, Ph0 00 01 10 11 MODE Two-Phase Three-Phase Four-Phase Reserved
DS1094L
fOSC TWO-PHASE OUT1 OUT2 OUT3 OUT4 THREE-PHASE OUT1 OUT2 OUT3 OUT4 FOUR-PHASE OUT1 OUT2 OUT3 OUT4
fOUT = fOSC
50% DUTY CYCLE 180 DEGREES OUT OF PHASE fOUT = fOSC / 3 33% DUTY CYCLE 120 DEGREES OUT OF PHASE fOUT = fOSC / 4 50% DUTY CYCLE 90 DEGREES OUT OF PHASE
Table 4. Dither Amount Settings
BITS J1, J0 00 01 10 11 DITHER AMOUNT* 0% 2% 4% 8%
Figure 1. DS1094L Output Waveforms
*The frequency is dithered down from the programmed value of fMOSC.
IF DITHER AMOUNT = 0% PROGRAMMED fMOSC PROGRAMMED fMOSC (2, 4, OR 8% OF fMOSC) fMOSC DITHER AMOUNT (2, 4, OR 8%)
Table 5. Dither Frequency Settings
BITS D1, D0 00 01 10 11 DITHER FREQUENCY fMOSC/128 fMOSC/256 fMOSC/512 fMOSC/1024
1 DITHER FREQ.
TIME
Prescaler
The prescaler divides the master oscillator frequency, fMOSC, by 1, 2, 4, or 8. The resultant frequency, fOSC, is calculated using the following formula: fOSC = fMOSC / 2PRESCALER where PRESCALER can be 0 to 3. The prescaler is configured using bits P1 and P0 in the PRESCALER register. Valid settings are shown in Table 2. The location of bits P1 and P0 in the PRESCALER register is shown in the Control Registers section. Note that the PRESCALER register also contains bits controlling other features of the device (dither amount, dither rate, and phase).
Figure 2. DS1094L Dither Waveform
and Ph0 in the PRESCALER register is shown in the Control Registers section.
Triangle Wave Generator
The triangle wave generator is used to dither the master oscillator frequency, adding spread-spectrum functionality to the DS1094L by injecting an offset element into the master oscillator. Both the dither amount (%) and dither frequency are programmable. The dither amount is controlled by bits J1 and J0 in the PRESCALER register. The dither frequency is controlled by bits D1 and D0, also in the PRESCALER register. The bit settings are shown in Table 4 and 5. The location of bits J1, J0, D1, and D0 in the PRESCALER register is shown in the Control Registers section. When dither is enabled (by selecting a percentage other than 0%), the master oscillator frequency, fMOSC, is dithered between the programmed fMOSC and the selected percentage down from the programmed fMOSC (see Figure 2). For example, if fMOSC is programmed to 2MHz (DAC register = 0Ah) and the dither amount is programmed to 2%, the frequency of fMOSC
7
Phase Generator
The four oscillator outputs (OUT1 to OUT4) can be configured in either two-phase, three-phase, or four-phase mode. The output waveforms of each mode are illustrated in Figure 1. Likewise, the figure also shows a comparison of f OUT, the duty cycle, and the output phase shifts between the three modes. Bits Ph1 and Ph0 in the PRESCALER register are used to select the desired mode (see Table 3). The location of bits Ph1
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Multiphase Spread-Spectrum EconOscillator DS1094L
will dither between 2MHz and 1.96MHz at a modulation frequency determined by the selected dither frequency. Continuing with the same example, if D1 and D0 both equal zero, selecting fMOSC/128, then the dither frequency would be 15.625kHz. DS1094L's control registers and illustrates bit locations as well as other valuable information. The memory address of each register is shown in the ADDRESS column. The factory default values programmed into EEPROM are shown in the DEFAULT column. Refer to the corresponding sections to determine what values to write to the registers. PRESCALER (02h) D1, D0 Selects the dither frequency. Refer to Table 5. Ph1, Ph0 Determines whether the two-phase, threephase, or four-phase mode is selected. Refer to Table 3. J1, J0 Selects the dither amount. Refer to Table 4. P1, P0 Determines the prescaler value. Refer to Table 2. DAC (08h) D3 to D0 This four-bit value determines the master oscillator frequency, fMOSC. Refer to Table 1 and the Master Oscillator section for a detailed information on calculating the DAC value. ADDR (0Dh) WC The EEPROM write control bit determines if writes to control registers are automatically backed up in NV memory (EEPROM) or whether a write EE command is required to write to NV memory. See the EEPROM Write Control section for more information. A2 to A0 This three-bit value determines the 2-wire slave address. WRITE EE COMMAND (3Fh) This command can be used when the WC bit = 1 (see explanation in the EEPROM Write Control section) to transfer registers internally from SRAM to EEPROM. The time required to store the values is one EEPROM write cycle time. This command is not needed if WC = 0.
2-Wire Slave Address
The 2-wire serial interface is used to read and write the control registers of the DS1094L. The default slave address of the DS1094L is B0h (see Figure 4). Using the 3 address bits (A2, A1, and A0) in the ADDR register, the slave address can be changed to allow as many as eight DS1094Ls reside on the same 2-wire bus or to simply prevent address conflicts with other 2wire devices. The location of the address bits within the ADDR register is shown in the Control Registers section. A detailed description of the 2-wire interface is found in the 2-Wire Serial Interface Description section.
EEPROM Write Control
Since EEPROM does have a limited number of lifetime write cycles (specified in the NONVOLATILE MEMORY CHARACTERISTICS electrical table), it is possible to configure the DS1094L to prevent EEPROM wear out and eliminate the EEPROM write cycle time by using the WC bit in the ADDR register. When the WC bit is 0 (default), register writes are automatically written into EEPROM. The Write EE Command is not needed. However, if WC = 1, then register writes are stored in SRAM and only written to EEPROM when the user sends the Write EE Command. If power to the device is cycled, the last value stored in EEPROM is recalled. The time required to store the values is one EEPROM write cycle time. WC = 1 is ideal for applications that frequently modify the frequency/registers. Regardless of the value of the WC bit, the value of the ADDR register is always written immediately to EEPROM.
Control Registers
The DS1094L control registers are used to program the frequency and features of the device. Table 6 lists the
Table 6. Control Registers
REGISTER PRESCALER DAC ADDR WRITE EE Command ADDRESS 02h 08h 0Dh 3Fh BINARY MSB D1 X1 X1 D0 X1 X1 Ph1 X1 X1 Ph0 X1 J1 D3 J0 D2 A2 P1 D1 A1 LSB P0 D0 A0 DEFAULT 11001101b XXXX0000b XXXX0000b ACCESS R/W R/W R/W W
X1 WC No Data
X = Don't care X1 = Don't care, reads as 1 8 _____________________________________________________________________
Multiphase Spread-Spectrum EconOscillator
2-Wire Serial Interface Description
Definitions
The following terminology is commonly used to describe 2-wire data transfers. Master Device: The master device controls the slave devices on the bus. The master device generates SCL clock pulses, start, and stop conditions. Slave Devices: Slave devices send and receive data at the master's request. Bus Idle or Not Busy: Time between stop and start conditions when both SDA and SCL are inactive and in their logic high states. When the bus is idle it often initiates a low-power mode for slave devices. Start Condition: A start condition is generated by the master to initiate a new data transfer with a slave. Transitioning SDA from high to low while SCL remains high generates a start condition. See the timing diagram for applicable timing. Stop Condition: A stop condition is generated by the master to end a data transfer with a slave. Transitioning SDA from low to high while SCL remains high generates a stop condition. See the timing diagram for applicable timing. Repeated Start Condition: The master can use a repeated start condition at the end of one data transfer to indicate that it will immediately initiate a new data transfer following the current one. Repeated starts are commonly used during read operations to identify a specific memory address to begin a data transfer. A repeated start condition is issued identically to a normal start condition. See the timing diagram for applicable timing. Bit Write: Transitions of SDA must occur during the low state of SCL. The data on SDA must remain valid and unchanged during the entire high pulse of SCL plus the setup and hold time requirements (see Figure 3). Data is shifted into the device during the rising edge of the SCL. Bit Read: At the end of a write operation, the master must release the SDA bus line for the proper amount of setup time (see Figure 3) before the next rising edge of SCL during a bit read. The device shifts out each bit of data on SDA at the falling edge of the previous SCL pulse, and the data bit is valid at the rising edge of the current SCL pulse. Remember that the master generates all SCL clock pulses including when it is reading bits from the slave. Acknowledgement (ACK and NACK): An Acknowledgement (ACK) or Not Acknowledge (NACK) is always the 9th bit transmitted during a byte transfer. The device receiving data (the master during a read or the slave during a write operation) performs an ACK by transmitting a zero during the 9th bit. A device performs a NACK by transmitting a one during the 9th bit. Timing (Figure 3) for the ACK and NACK is identical to all other bit writes. An ACK is the acknowledgement that the device is properly receiving data. A NACK is used to terminate a read sequence or as an indication that the device is not receiving data. Byte Write: A byte write consists of 8 bits of information transferred from the master to the slave (most significant bit first) plus a 1-bit acknowledgement from the slave to the master. The 8 bits transmitted by the master are done according to the bit write definition, and the acknowledgement is read using the bit read definition. Byte Read: A byte read is an 8-bit information transfer from the slave to the master plus a 1-bit ACK or NACK from the master to the slave. The 8 bits of information
DS1094L
SDA
tBUF tLOW tR tF
tHD:STA
tSP
SCL tHD:STA STOP START tHD:DAT NOTE: TIMING IS REFERENCED TO VIL(MAX) AND VIH(MIN). tHIGH tSU:DAT REPEATED START tSU:STA tSU:STO
Figure 3. 2-Wire Timing Diagram _____________________________________________________________________ 9
Multiphase Spread-Spectrum EconOscillator
MSB 1 0 1 1 A2* A1* A0* LSB R/W
7-BIT SLAVE ADDRESS
READ/WRITE BIT
*THESE BITS MUST MATCH THE CORRESPONDING BITS IN THE ADDR REGISTER.
Figure 4. Slave Address Byte
that are transferred (most significant bit first) from the slave to the master are read by the master using the bit read definition above, and the master transmits an ACK using the bit write definition to receive additional data bytes. The master must NACK the last byte read to terminate communication so the slave will return control of SDA to the master. Slave Address Byte: The slave address byte consists of a 7-bit slave address followed by the R/W bit (see Figure 4). The slave address is the most significant 7 bits and the R/W bit is the least significant bit. The 3 address bits in the slave address (A2 to A0) permit a maximum of eight DS1094Ls to share the same 2-wire bus. Each slave on the 2-wire bus has a unique slave address, which is used by the master to select which slave it wishes to communicate with. Following a start condition, all slaves on the 2-wire bus await the slave address byte from the master. Each slave compares its own slave address with the slave address sent from the master. If the slave address matches, the slave acknowledges and continues communication with the master (based on the R/W bit). Otherwise, if the slave address does not match, the slave ignores communication until the next start condition. When the R/W bit is zero, the master writes data to the specified slave. When the R/W is one, the master reads data from the specified slave. Memory Address: During a 2-wire write operation, the master must transmit a memory address to identify the memory location where the slave is to store the data. The memory address is always the second byte transmitted during a write operation following the slave address byte (R/W = 0).
Acknowledge Polling: Any time EEPROM is written, the EEPROM write time (tW) is required following the stop condition to write to EEPROM. During the EEPROM write time, the DS1094L will not acknowledge its slave address because it is busy. It is possible to take advantage of this phenomenon by repeatedly addressing the DS1094L until it finally acknowledges its slave address. The alternative to acknowledge polling is to wait for maximum period of t W to elapse before attempting to write to EEPROM again. Reading a Single Byte from a Slave: A dummy write cycle is used to read a particular register. To do this the master generates a start condition, writes the slave address byte (with R/W = 0), writes the memory address of the desired register to read, generates a repeated start condition, writes the slave address byte (with R/W = 1), reads the register and follows with a NACK (since only one byte is read), and generates a stop condition. See Figure 5 for examples of reading DS1094L registers.
DS1094L
Application Information
SDA and SCL Pullup Resistors
SDA is an open-collector output and requires a pullup resistor to realize high logic levels. Because the DS1094L does not utilize clock cycle stretching, a master using either an open-collector output with a pullup resistor or CMOS output driver (push-pull) can be utilized for SCL. Pullup resistor values should be chosen to ensure that the rise and fall times listed in the AC electrical characteristics are within specification.
Stand-Alone Operation
If the DS1094L is used stand-alone (without a 2-wire master), SDA and SCL should not be left unconnected, or floating. It is recommended that pullup resistors be used on both SDA and SCL to prevent the pins from floating to unknown voltages and transitions. Likewise, pullups are recommended over tying SDA and SCL directly to VCC to allow future programmability.
Power-Supply Decoupling
To achieve best results, it is highly recommended that a decoupling capacitor is used on the IC power supply pins. Typical values of decoupling capacitors are 0.01F and 0.1F. Use high-quality, ceramic, surfacemount capacitors. Mount the capacitors as close as possible to the VCC and GND pins of the IC to minimize lead inductance.
2-Wire Communication
Writing a Single Byte to a Slave: The master must generate a start condition, write the slave address byte (with R/W = 0), write the memory address, write the byte of data, and generate a stop condition. The master must read the slave's acknowledgement following each byte write.
10
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Multiphase Spread-Spectrum EconOscillator DS1094L
TYPICAL 2-WIRE WRITE TRANSACTION MSB START 1 0 1 1
LSB SLAVE ACK
MSB b7 b6 b5 b4 b3 b2 b1
LSB b0 SLAVE ACK
MSB b7 b6 b5 b4 b3 b2 b1
LSB b0 SLAVE ACK STOP
A2* A1* A0* R/W
SLAVE ADDRESS
READ/ WRITE
COMMAND/REGISTER ADDRESS
DATA
* THE ADDRESS DETERMINED BY A0, A1, AND A2 MUST MATCH THE ADDRESS SET IN THE ADDR REGISTER. EXAMPLE 2-WIRE TRANSACTIONS (WHEN A0, A1, AND A2 ARE ZERO) B0h A) SINGLE BYTE WRITE -WRITE DAC REGISTER TO 0Ah START 1 0 1 1 0 0 0 0 B0h B) SINGLE BYTE READ -READ DAC REGISTER START 1 0 1 1 0 0 0 0 B0h C) SINGLE BYTE WRITE -WRITE PRESCALER REGISTER TO CDh D) WRITE EE COMMAND - NEEDED ONLY IF WC = 1 START 1 0 1 1 0 0 0 0 B0h 0Ah 08h SLAVE SLAVE 0 0 0 0 1 0 0 0 ACK 0 0 0 0 1 0 1 0 ACK 08h SLAVE SLAVE ACK 0 0 0 0 1 0 0 0 ACK SLAVE ACK B1h REPEATED 1 0 1 1 0 0 0 1 SLAVE ACK START
STOP DATA DAC VALUE MASTER NACK STOP
CDh 02h SLAVE SLAVE SLAVE ACK 0 0 0 0 0 0 1 0 ACK 1 1 0 0 1 1 0 1 ACK 3Fh
STOP
SLAVE SLAVE START 1 0 1 1 0 0 0 0 ACK 0 0 1 1 1 1 1 1 ACK STOP
Figure 5. 2-Wire Communication Examples
Chip Topology
TRANSISTOR COUNT: 7987 SUBSTRATE CONNECTED TO: GROUND
Package Information
For the latest package outline information, go to www.maxim-ic.com/DallasPackInfo.
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.
Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600 ____________________ 11 (c) 2004 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products.
DALLAS is a registered trademark of Dallas Semiconductor Corporation.

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