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19-1574; Rev 0; 1/00
Fan Controller and Remote Temperature Sensor with SMBus Serial Interface
General Description
The MAX1669 fan controller includes a precise digital thermometer that reports the temperature of a remote sensor. The remote sensor is a diode-connected transistor--typically a low-cost, easily mounted 2N3906 PNP type--replacing conventional thermistors or thermocouples. Remote accuracy is 3C for transistors from multiple manufacturers, with no calibration needed. The MAX1669 has an independent fan controller with a lowcurrent logic output requiring external power components to interface to a DC brushless fan. The fan controller has two modes of operation: a low-frequency (20Hz to 160Hz) PWM mode intended for driving the fan motor, or a high-impedance DAC output that generates a variable DC control voltage. In PWM mode, the FAN frequency can be synchronized to an external clock. Other key features include general-purpose inputs/outputs (GPIOs) for fan presence detection and a thermostat output intended as a fan override signal in case the host system loses the ability to communicate. The internal ADC has a wide input voltage range and gives overrange readings when too large an input voltage is applied. Other error-checking includes temperature out-of-range indication and diode open/short faults. The MAX1669 is available in a space-saving 16-pin QSOP package that allows it to fit adjacent to the SLOT1 connector.
PART
Features
o Measures Remote CPU Temperature o No Calibration Required o 20Hz to 160Hz PWM Output for Fan o PWM Frequency Sync Input (260kHz) o Flexible Fan Interface: Linear or PWM o SMBus 2-Wire Serial Interface o Programmable Under/Overtemperature Alarms o ALERT Latched Interrupt Output o OVERT Thermostat Output o Two GPIO Pins o Write-Once Configuration Protection o Supports SMBus Alert Response o 3C Temperature Accuracy (-40C to +125C, remote) o 3A Standby Supply Current o +3V to +5.5V Supply Range o Small 16-Pin QSOP Package
MAX1669
Ordering Information
TEMP. RANGE -40C to +85C PIN-PACKAGE 16 QSOP MAX1669EEE
Applications
Pentium(R) CPU Cooling Desktop Computers Notebook Computers Servers Workstations
Pin Configuration
TOP VIEW
I/O1 1 I/O2 2 16 OVERT 15 ALERT 14 SMBDATA
Typical Operating Circuit appears at end of data sheet.
ADD0 3 ADD1 4 ADD2 5 AGND 6 DXN 7 DXP 8
MAX1669
13 SMBCLK 12 PGND 11 FAN 10 SYNC 9 VCC
QSOP
Pentium is a registered trademark of Intel Corp. ________________________________________________________________ Maxim Integrated Products 1
For free samples & the latest literature: http://www.maxim-ic.com, or phone 1-800-998-8800. For small orders, phone 1-800-835-8769.
Fan Controller and Remote Temperature Sensor with SMBus Serial Interface MAX1669
ABSOLUTE MAXIMUM RATINGS
VCC to AGND...........................................................-0.3V to +6V DXP, ADD_ to AGND.................................-0.3V to (VCC + 0.3V) DXN to AGND.......................................................-0.3V to +0.8V SMBCLK, SMBDATA, ALERT, SYNC, I/O1, I/O2, OVERT, FAN to AGND ......................-0.3V to +6V FAN to PGND ............................................-0.3V to (VCC + 0.3V) PGND to AGND ....................................................-0.3V to +0.3V PWM Current....................................................-50mA to +50mA SMBDATA Current .............................................-1mA to +50mA I/O1, I/O2 Current...............................................-1mA to +25mA DXN Current ......................................................................1mA ESD Protection (all pins, Human Body Model) .................2000V Continuous Power Dissipation (TA = +70C) 16-Pin QSOP (derate 8.30mW/C above +70C).......667mW Operating Temperature Range (extended) ......-55C to +125C Junction Temperature .....................................................+150C Storage Temperature Range ............................-65C to +150C Lead Temperature (soldering, 10s) ................................+300C
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.
ELECTRICAL CHARACTERISTICS
(VCC = +3.3V, TA = 0C to +85C, unless otherwise noted. Typical values are at TA = +25C.) PARAMETER ADC AND POWER SUPPLY Resolution (Note 1) Temperature Error, Remote Diode (Note 2) Supply Voltage Range Undervoltage Lockout Threshold Undervoltage Lockout Hysteresis Power-On Reset Threshold POR Threshold Hysteresis Standby Supply Current SMBus static SMBCLK at 10kHz FAN output set to 150Hz mode Autoconvert mode, average measured over 1s FAN output set to DAC mode From stop bit to conversion complete Autoconvert mode VDXP forced to VDXN + 0.65V High level Low level 47 1.6 80 8 VCC, falling edge 1 VCC input, disables A/D conversion, rising edge Monotonicity guaranteed TR = 0C to +100C, diode ideality factor = 1.013 8 -3 3 2.6 2.8 50 1.9 50 3 3 75 360 62 2 100 10 0.7 PWM mode, VFAN forced to 2.9V PWM mode, VFAN forced to 0.4V 10 -10 78 2.4 120 12 150 10 2.5 3 5.5 2.95 Bits C V V mV V mV A A A ms Hz A V mA mA CONDITIONS MIN TYP MAX UNITS
Average Operating Supply Current
Conversion Time Conversion Rate Remote-Diode Source Current DXN Source Voltage FAN OUTPUT FAN Output Source Current FAN Output Sink Current
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Fan Controller and Remote Temperature Sensor with SMBus Serial Interface
ELECTRICAL CHARACTERISTICS (continued)
(VCC = +3.3V, TA = 0C to +85C, unless otherwise noted. Typical values are at TA = +25C.) PARAMETER FAN PWM Frequency Error FAN Total Unadjusted Error FAN Output Voltage High FAN Output Voltage Low SYNC Capture Range SYNC Input High Period SYNC Input Low Period SMBus INTERFACE (Figures 7, 8) Logic Input High Voltage Logic Input Low Voltage SMBDATA, ALERT, OVERT, I/O1, I/O2 Output Low Sink Current ALERT, OVERT, I/O1, I/O2 Output High Leakage Current Logic Input Current SMBus Input Capacitance SMBus Clock Frequency SMBCLK Clock Low Time (tLOW) SMBCLK Clock High Time (tHIGH) SMBus Rise Time SMBus Fall Time SMBus Start Condition Setup Time SMBus Repeated Start Condition Setup Time (tSU:STA) SMBus Start Condition Hold Time (tHD:STA) SMBus Data Valid to SMBCLK Rising-Edge Time (tSU:DAT) SMBus Data-Hold Time (tHD:DAT) SMBus Bus-Free Time (tBUF) SMBCLK Falling Edge to SMBus Data-Valid Time 90% to 90% points 10% of SMBDATA to 90% of SMBCLK ADD_, I/O1, I/O2, SYNC, SMBCLK, SMBDATA; VCC = 3V to 5.5V ADD_, I/O1, I/O2, SYNC, SMBCLK, SMBDATA; VCC = 3V to 5.5V Pin forced to 0.4V Pin forced to 5.5V Logic inputs forced to VCC or GND SMBCLK, SMBDATA (Note 3) 10% to 10% points 90% to 90% points SMBCLK, SMBDATA, 10% to 90% points SMBCLK, SMBDATA, 90% to 10% points 4.7 500 4 4 250 0 4.7 1 DC 4.7 4 1 300 -1 5 100 6 1 1 2.1 0.8 V V mA A A pF kHz s s s ns s ns s s ns s s s CONDITIONS PWM mode, any setting DAC mode, any setting, RL = 10k to GND DAC mode, FAN duty factor = 1111b, IOUT = 5mA DAC mode, FAN duty factor = 0000b, IOUT = -5mA 140 500 500 MIN -20 -4 2.96 3.06 0.05 260 0.2 400 TYP MAX +20 4 UNITS % %FS V V kHz ns ns
MAX1669
SMBus Stop Condition Setup Time (tSU:STO) 90% of SMBCLK to 10% of SMBDATA 10% or 90% of SMBDATA to 10% of SMBCLK (Note 4) Between start/stop conditions Master clocking-in data
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Fan Controller and Remote Temperature Sensor with SMBus Serial Interface MAX1669
ELECTRICAL CHARACTERISTICS
(VCC = +3.3V, TA = -40C to +85C, unless otherwise noted.) (Note 5) PARAMETER ADC AND POWER SUPPLY Temperature Resolution (Note 1) Temperature Error, Remote Diode (Note 2) Supply Voltage Range Average Operating Supply Current Conversion Time Conversion Rate FAN OUTPUT FAN Output Source Current FAN Output Sink Current FAN PWM Frequency Error FAN Total Unadjusted Error FAN Output Voltage High FAN Output Voltage Low SMBus INTERFACE Logic Input High Voltage Logic Input Low Voltage SMBDATA, ALERT, OVERT, I/O1, I/O2 Output Low Sink Current ALERT, OVERT, I/O1, I/O2 Output High Leakage Current Logic Input Current ADD_, I/O1, I/O2, SYNC, SMBCLK, SMBDATA; VCC = 3V to 5.5V ADD_, I/O1, I/O2, SYNC, SMBCLK, SMBDATA; VCC = 3V to 5.5V Pin forced to 0.4V Pin forced to 5.5V Logic inputs forced to VCC or GND -1 6 1 1 2.1 0.8 V V mA A A PWM mode, VFAN forced to 2.9V PWM mode, VFAN forced to 0.4V PWM mode, any setting DAC mode, any setting, RL = 10k to GND DAC mode, FAN duty factor = 1111b, IOUT = 5mA DAC mode, FAN duty factor = 0000b, IOUT = -5mA -25 -5 2.94 0.2 10 -10 +25 5 mA mA % %FS V V Autoconvert mode, average measured over 1sec, FAN output set to 150Hz mode From stop bit to conversion complete Autoconvert mode 47 1.6 2.4 Monotonicity guaranteed TR = -55C to +125C, diode ideality factor = 1.013 8 -5 3 5 5.5 100 Bits C V A ms Hz CONDITIONS MIN MAX UNITS
Note 1: Guaranteed but not 100% tested. Note 2: TR is the junction temperature of the remote diode. The temperature error specification is optimized to and guaranteed for a diode-connected 2N3906 transistor with ideality factor = 1.013. Variations in the ideality factor "m" of the actual transistor used will increase the temperature error by *. See the Temperature Error vs. Remote Diode Temperature graph in the Typical Operating Characteristics for typical temperature errors using several random 2N3906s. See Remote Diode Selection for remote diode forward-voltage requirements. Note 3: The SMBus logic block is a static design that works with clock frequencies down to DC. While slow operation is possible, it violates the 10kHz minimum clock frequency and SMBus specifications, and may monopolize the bus. Note 4: Note that a transition must internally provide at least a hold time in order to bridge the undefined region (300ns max) of SMBCLK's falling edge. Note 5: Specifications to -40C are guaranteed by design and not production tested.
1.013 * T = - 1 273.15k + TR m
(
) (C)
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Fan Controller and Remote Temperature Sensor with SMBus Serial Interface
Typical Operating Characteristics
(Temperature error = measured - actual, TA = +25C, unless otherwise noted.)
MAX1669
TEMPERATURE ERROR vs. LEAKAGE RESISTANCE
MAX1669-01
TEMPERATURE ERROR vs. REMOTE DIODE TEMPERATURE
MAX1669-02
TEMPERATURE ERROR vs. POWER-SUPPLY NOISE FREQUENCY
16 TEMPERATURE ERROR (C) 14 12 10 8 6 4 2 0 -2 VIN = 100mVp-p VIN = 250mVp-p VIN = SQUARE WAVE APPLIED TO VCC WITH NO 0.1F VCC CAPACITOR
MAX1669-03
40 30 TEMPERATURE ERROR (C) 20 PATH = DXP TO GND; CONFIG = 02h 10 0 -10 -20 PATH = DXP TO VCC (5V); CONFIG = 02h -30 -40 1 10 LEAKAGE RESISTANCE (M)
2.0 1.5 TEMPERATURE ERROR (C) 1.0 0.5 0 -0.5 -1.0 -1.5 -2.0 RANDOM 2N3906s FROM DIFFERENT MANUFACTURERS
18
100
-60 -40 -20 0
20 40 60 80 100 120 140
1K
10K
100K
1M
10M
100M
TEMPERATURE (C)
PSNF (Hz)
TEMPERATURE ERROR vs. COMMON-MODE NOISE FREQUENCY
MAX1669-04
TEMPERATURE ERROR vs. DXP - DXN CAPACITANCE
0 TEMPERATURE ERROR (C) -2 -4 -6 -8 -10 -12 -14 -16 VCC = 5V
MAX1669-05
STANDBY SUPPLY CURRENT vs. SUPPLY VOLTAGE
MAX1669-06
8 7 TEMPERATURE ERROR (C) 6 5 4 3 2 1 0 -1 -2 1M 10M 100M C = 27nF C = 2200pF VIN = 50mVp-p AC-COUPLED TO DXN C = DXN - DXP CAPACITANCE
2
7 STANDBY SUPPLY CURRENT (A) 6 5 4 3 2 1 0
1G
0
10
20
30
40
50
3.0
3.5
4.0
4.5
5.0
5.5
FREQUENCY (Hz)
DXP-DXN CAPACITANCE (nF)
SUPPLY VOLTAGE (V)
RESPONSE TO THERMAL SHOCK
MAX1669-07
PWM FREQUENCY vs. CODE (F3F2F1F0)
160 140 PWM FREQUENCY (Hz) 120 100 80 60 40 VCC = +3.3V VCC = +5V
MAX1669-08
120 100 TEMPERATURE (C) 80 60 40 20 0 -2 0 2 4 TIME (sec) 6 8
180
CMPT3906 IMMERSED IN +115C FLUORINERT BATH 10
20 0 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 CODE (F3F2F1F0)
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Fan Controller and Remote Temperature Sensor with SMBus Serial Interface MAX1669
Typical Operating Characteristics (continued)
(Temperature error = measured - actual, TA = +25C, unless otherwise noted.)
PWM DUTY FACTOR vs. CODE (D3D2D1D0)
MAX1669-09
DAC OUTPUT vs. CODE (D3D2D1D0)
4.5 4.0 DAC OUTPUT (V) 3.5 3.0 2.5 2.0 1.5 ILOAD = +10mA TO -10mA VCC = +5V
MAX1669-10
100 VCC = +3.3V OR +5V 80 DUTY FACTOR (%)
5.0
60
40
20
1.0 0.5
0 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 CODE (D3D2D1D0)
0 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 CODE (D3D2D1D0)
Pin Description
PIN NAME I/O1 I/O2 ADD0 ADD1 ADD2 AGND DXN DXP VCC SYNC FAN PGND SMBCLK SMBDATA ALERT OVERT FUNCTION General-Purpose Open-Drain Logic Input/Output 1. I/O1 is intended for driving LEDs, driving power-plane switching MOSFETs, or detecting fan presence or chassis intrusion. General-Purpose Open-Drain Logic Input/Output 2. I/O2 is intended for driving LEDs, driving power-plane switching MOSFETs, or detecting fan presence or chassis intrusion. SMBus Address Select Pin 0. See Table 11. SMBus Address Select Pin 1. See Table 11. SMBus Address Select Pin 2. See Table 11. Analog Ground Combined Current Sink and ADC Negative Input from Remote Diode. DXN is normally biased to a diode voltage above ground. Combined Current Source and ADC Positive Input from Remote Diode. Place a 2200pF capacitor between DXP and DXN for noise filtering. Supply Voltage Input, +3V to +5.5V. Bypass to AGND with a 0.1F capacitor. Oscillator Synchronization Input. Connect to AGND to use internal clock. Capture range is 140kHz to 400kHz. The synchronization signal is internally applied to the FAN PWM clock. See Table 5 for synchronized frequencies. Fan-Control Logic Output. Swings from PGND to VCC in PWM mode, or PGND to 0.94 * VCC in DAC mode. Power Ground SMBus Serial-Clock Input Open-Drain SMBus Serial-Data Input/Output Active-Low, Open-Drain SMBus Alert (interrupt) Output Active-Low, Open-Drain Thermostat Output. Activated by TCRIT threshold
1
2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 6
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Fan Controller and Remote Temperature Sensor with SMBus Serial Interface MAX1669
VCC ADD0 ADD1 ADD2
ADDRESS DECODER
DXP DXN
MUX
ADC
SMBDATA
CONTROL LOGIC
SMB
SMBCLK READ 8 WRITE 8
GND COMMAND-BYTE (INDEX) REGISTER 8 REMOTE-TEMPERATURE DATA REGISTER CONFIGURATION BYTE REGISTER
8
HIGH-TEMPERATURE THRESHOLD LOW-TEMPERATURE THRESHOLD 8
MAX1669
STATUS BYTE REGISTER
ALERT RESPONSE ADDRESS REGISTER ALERT R
DIGITAL COMPARATOR
S
Q
CONTROL LOGIC
TEMPERATURE SENSOR I/O1 GENERAL-PURPOSE I/O CONTROLLER I/O2 -5C R Q TEMPERATURE TCRIT S OVERT
CONTROL LOGIC
Figure 1. MAX1669 Temperature Sensor Functional Diagram
_______________Detailed Description
The MAX1669 temperature sensor is designed to work with an external microcontroller (C) or other intelligent devices in computer fan-control applications. The C is typically a power-management or keyboard controller, generating SMBus serial commands by "bit-banging'' general-purpose input/output (GPIO) pins or through a dedicated SMBus interface block.
Essentially an 8-bit serial analog-to-digital converter (ADC) with a sophisticated front end, the temperature measurement channel contains a switched-current source, a multiplexer, and an integrating ADC. Temperature data from the ADC is loaded into a data register, where it is automatically compared with data previously stored in over/undertemperature alarm registers and the critical register (Figure 1).
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Fan Controller and Remote Temperature Sensor with SMBus Serial Interface MAX1669
The PWM or DAC fan control circuitry is completely independent from the temperature measurement, and software closes the temperature-control feedback loop (Figure 2). supply current is 18A. In standby mode, supply current drops to 3A and the fan output is disabled.
SMBus Digital Interface
From a software perspective, the MAX1669 appears as a set of byte-wide registers that contain temperature data, alarm threshold values, or control bits. A standard SMBus 2-wire serial interface is used to read temperature data and write control bits and alarm threshold data. The MAX1669 employs four standard SMBus protocols: write byte, read byte, send byte, and receive byte (Figure 3). The two shorter protocols (receive and send) allow quicker transfers, provided that the correct data register was previously selected by a write or read byte instruction. Use caution with the shorter protocols in multimaster systems since a second master could overwrite the command byte without informing the first master. The temperature data format is 7 bits plus sign in two's complement form for each channel, with the LSB representing +1C (Table 1), MSB transmitted first. Measurements are offset by +1/2C to minimize internal rounding errors; for example, +99.5C to +100.4C is reported as +100C.
ADC and Multiplexer
The ADC is an averaging type that integrates over a 62ms period (typ), with excellent noise rejection. The multiplexer automatically steers bias currents through the remote diode, measures the forward voltage, and calculates the temperature.
FREQ REGISTER DUTY REGISTER
PWM CONTROLLER MUX DAC
MAX1669
DRIVER FAN
(0XF0) UPPER NIBBLE 4 AND FANON OVERT CONTROL LOGIC
Alarm Threshold Registers
Three registers store alarm threshold data, with hightemperature (THIGH) and low-temperature (TLOW) registers that activate the ALERT output, and a critical overtemperature register (T CRIT ) that activates the OVERT output. If a measured temperature equals or exceeds the THIGH or TLOW threshold value, an ALERT interrupt is asserted. Do not set the TCRIT register to values outside of the temperatures in Table 1. The power-on-reset (POR) state of the THIGH register is full scale (0111 1111b or +127C). The POR state of the TLOW register is 1100 1001b or -55C. The POR state of the TCRIT register is 0110 0100b or +100C.
Figure 2. MAX1669 Fan-Control Functional Diagram
The DXN input is biased at 0.7V above ground by an internal diode to set up the analog-to-digital (A/D) inputs for a differential measurement. The worst-case DXP-DXN differential input voltage range is 0.21V to 0.95V. Diode voltages that are outside the ADC input range cause overrange indications rather than nonmonotonic readings. Overrange readings will return +127C. Excess resistance in series with the remote diode causes approximately +1/2C error/. Likewise, 200V of offset voltage forced on DXP-DXN causes approximately +1C error.
OVERT Thermostat Output
The OVERT output is a self-clearing interrupt output that is activated when the temperature equals or exceeds TCRIT. OVERT normally goes low when active, but this polarity can be changed through the configuration register. The latch is cleared when the temperature reading is equal to or less than TCRIT minus 5C, which provides for 5C of hysteresis. The ALERT and OVERT comparisons are made after each conversion, and at the end of a write command to their respective temperature limit registers. For example, if the limit is changed while the device is in standby
A/D Conversion Sequence
When the device is taken out of standby mode, the result of the measurement is available one conversion time later (78ms max). If the ADC is busy, the results of the previous conversion are always available. Toggling the standby mode on and off is a good way to initiate a new conversion since this action resets the rate timer.
Low-Power Standby Mode
Supply-current drain during the 62ms conversion period is 500A. Between conversions, the instantaneous
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Fan Controller and Remote Temperature Sensor with SMBus Serial Interface MAX1669
Write Byte Format S 1 ADDRESS 7 bits WR 1 ACK 1 COMMAND 8 bits ACK 1 DATA 8 bits ACK 1 P 1
7-bit slave address: equivalent to chip-select line
Command byte: selects which register you are writing to
Data byte: data goes into the register set by the command byte (to set thresholds, configuration masks, and sampling rate)
Read Byte Format S 1 ADDRESS 7 bits WR 1 ACK 1 COMMAND 8 bits ACK 1 S 1 ADDRESS 7 bits RD 1 ACK 1 DATA 8 bits A 1 P 1
Slave address: equivalent to chip-select line S = Start condition P = Stop condition
Command byte: selects which register you are reading from
Slave address: repeated due to change in dataflow direction
Data byte: reads from the register set by the command byte
Shaded = Slave transmission A = Not acknowledged
Figure 3. SMBus Protocols
Table 1. Data Format (Two's Complement)
TEMP (C) +130.00 +127.00 +126.50 +126.00 +25.25 +0.50 +0.25 +0.00 -0.25 -0.50 -0.75 -1.00 -25.00 -25.50 -54.75 -55.00 -65.00 -70.00 ROUNDED TEMP (C) +127 +127 +127 +126 +25 +1 +0 +0 +0 +0 -1 -1 -25 -26 -55 -55 -65 -65 DIGITAL OUTPUT DATA BITS SIGN MSBs LSBs 0 0 0 0 0 0 0 0 0 0 1 1 1 1 1 1 1 1 111 111 111 111 001 000 000 000 000 000 111 111 110 110 100 100 011 011 1111 1111 1111 1110 1001 0001 0000 0000 0000 0000 1111 1111 0111 0110 1001 1001 1111 1111
mode, the ALERT and OVERT outputs respond correctly according to the last valid A/D result. Note that the ALERT output does not respond to TCRIT (OVERT) comparisons. The OVERT latch can implement an override control to the FAN output, which forces the fan to VCC whenever the TCRIT threshold is crossed. This override switch is the backup fan control loop, and is enabled through the FAN ON bit in the configuration register (bit 2). Note that changing the duty to 100% in this way doesn't affect the contents of the DUTY register, and the FAN output reverts to the preprogrammed duty factor (or DAC voltage) when the OVERT latch is reset.
Diode Fault Alarm
A continuity fault detector at DXP detects whether the remote diode has an open-circuit condition, short-circuit to GND, or short-circuit DXP-to-DXN condition. At the beginning of each conversion, the diode fault is checked and the status byte updated. This fault detector is a simple voltage detector; DXP rising above VCC 1V or falling below DXN + 40mV constitutes a fault condition. Also, if the ADC has an extremely low differential input voltage, the diode is assumed to be shorted and a fault occurs. Note that the diode fault isn't checked until a conversion is initiated, so immediately after power-on reset the status byte indicates no fault is present even if the diode path is broken. Any diode fault will return a +127C fault reading and cause ALERT to go low.
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Fan Controller and Remote Temperature Sensor with SMBus Serial Interface MAX1669
ALERT Interrupts
The ALERT interrupt output signal is latched and can only be cleared by reading the Alert Response address. Interrupts are generated in response to THIGH and TLOW comparisons, when there is a fault with the remote diode, or when a high-to-low or low-to-high transition at I/O1 or I/O2 is detected. The interrupt does not halt automatic conversions; new temperature data continues to be available over the SMBus interface after ALERT is asserted. The interrupt output is open-drain so that devices can share a common interrupt line. The interface responds to the SMBus Alert Response address, an interrupt pointer returnaddress feature (see the Alert Response Address section). The ALERT interrupt latch is set when the temperature exceeds an ALARM threshold. ALERT will not be set again until the threshold is reprogrammed. This prevents the ALERT latch from being set again during the interval between reading the Alert Response address and updating the offending alarm threshold. Note that this behavior is identical to the MAX1618 but is slightly different from the MAX1617, which continues to interrupt until the temperature no longer exceeds the alarm threshold. Note also that if some new alarm condition occurs, such as crossing the other alarm threshold or having a GPIO transition, a new interrupt is generated.
Table 2. Read Format for the Alert Response Address (0001100b)
BIT 7 (MSB) 6 5 4 3 2 1 0 (LSB) NAME ADD7 ADD6 ADD5 ADD4 ADD3 ADD2 ADD1 1 Logic 1 Provide the MAX1669 slave address FUNCTION
that occurs immediately after POR returns the current remote temperature data.
One-Shot Conversion
The one-shot command immediately forces a new conversion cycle to begin. In software standby mode (STBY bit = 1), a new conversion starts, after which the device returns to standby mode. If a conversion is in progress when a one-shot command is received, the command is ignored. If a one-shot command is received in autoconvert mode (STBY bit = 0) between conversions, a new conversion begins, the conversion rate timer is reset, and the next automatic conversion takes place after a full period.
ALERT Response Address
The SMBus Alert Response interrupt pointer provides quick fault identification for simple slave devices that lack the complex, expensive logic needed to be a bus master. Upon receiving an ALERT interrupt signal, the host master can broadcast a receive byte transmission to the Alert Response slave address (0001100b). Then any slave device that generated an interrupt attempts to identify itself by putting its own address on the bus (Table 2). The Alert Response can activate several different slave devices simultaneously, similar to the I 2 C General Call. If more than one slave attempts to respond, bus arbitration rules apply, and the device with the lower address code wins. The losing device does not generate an acknowledge and continues to hold the ALERT line low until serviced. Successful reading of the alert response address clears the interrupt latch.
Configuration Byte Functions
The configuration byte register (Table 4) is used to mask (disable) interrupts, set the OVERT output polarity, and put the device in software standby mode. Bit 1 of the configuration byte in Table 4 is for factory use only and must be set to 1 (value at POR). This register's contents can be read back over the serial interface.
FAN PWM Frequency and Duty Factor Control
The fan speed is controlled by the average voltage applied to the fan. The average voltage is equal to the product of the motor power-supply voltage and the duty factor. The duty factor is equal to zero upon startup and it is software controlled. The FAN output frequency is controlled by the PWM frequency register unless this register's code is set to 1111b (Table 5). A PWM frequency code of 1111b puts the FAN output in DAC mode. For all other codes, the FAN frequency is in the 20Hz to 160Hz range as shown in Table 5. For the possible synchronized frequencies, also see Table 5. The FAN output duty factor is controlled by the FAN duty factor register unless the PWM frequency code is
Command Byte Functions
The 8-bit command byte register (Table 3) is the master index that points to the MAX1669's other registers. The register's POR state is 00000001b, so a receive byte transmission (a protocol that lacks the command byte)
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Fan Controller and Remote Temperature Sensor with SMBus Serial Interface MAX1669
Table 3. Command Byte Bit Assignments
REGISTER RTEMP RSTAT RCFG COMMAND 00h 01h 02h 03h 04h 05h 06h RHI RLOW WCFG 07h 08h 09h 0Ah 0Bh 0Ch WHI WLOW OSHT RCRIT RPROT RFREQ RDUTY RGPIO 0Dh 0Eh 0Fh 10h 11h 12h 13h 14h 15h 16h 17h WCRIT WPROT WFREQ WDUTY WGPIO RFU ID Codes MFG ID DEV ID FEh FFh Least Sig Byte 0100 1101b Least Sig Byte 0000 0101b Manufacturing ID code = 4Dh, ASCII code for "M" (for Maxim) Device ID code, specific to MAX1669 18h 19h 1Ah 1Bh 1Ch 1Dh-FDh POR STATE N/A N/A N/A 0000 0010b N/A N/A N/A 0111 1111b 1100 1001b N/A N/A N/A N/A N/A N/A N/A 0110 0100b 0000 0000b 0000 0000b 0000 0000b 1100 0000b N/A N/A N/A N/A N/A N/A N/A N/A N/A Reserved for future use Read latest temperature Read status byte (temp flags, I/O_ states) Read configuration byte Reserved for future use Reserved for future use Reserved for future use Read THIGH limit Read TLOW limit Write configuration byte Reserved for future use Reserved for future use Reserved for future use Write THIGH limit Write TLOW limit One-shot command. Will execute a single conversion even if the device is in software standby. Read TCRIT limit Read write-once protection byte Read PWM frequency Read FAN duty factor Read GPIO data Reserved for future use Reserved for future use Reserved for future use Write TCRIT limit Write write-once protection byte Write PWM frequency Write FAN duty factor Write GPIO data Reserved for future use FUNCTION
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Fan Controller and Remote Temperature Sensor with SMBus Serial Interface MAX1669
Table 4. Configuration Byte Bit Assignments
BIT 7 (MSB) 6 NAME MASK0 STBY POR STATE 0 0 FUNCTION Masks THIGH, TLOW, and diode fault ALERT interrupts when high. If all three MASK_ bits are set high, ALERT interrupts are totally masked. Standby mode control bit. If high, the device immediately stops converting, forces FAN low, and enters standby mode. If low, the device continuously autoconverts at a 2Hz rate. OVERT pin polarity control: 0 = active low (low when TCRIT is crossed) 1 = active high Masks I/O1 ALERT interrupts when high. Set MASK1 = 1 and connect a 10k to 100k pull-up resistor on I/O1 to configure I/O1 as an output. Masks I/O2 ALERT interrupts when high. Set MASK2 = 1 and connect a 10k to 100k pull-up resistor on I/O2 to configure I/O2 as an output. Enables FAN duty factor override when high. Must be "1" Reserved for future use
5
POL
0
4 3 2 1 0
MASK1 MASK2 FAN ON RFU
0 0 0 1 0
Table 5. PWM Frequency Data Byte Bit Assignments (Write Command = 1Ah)
BIT NAME POR STATE FUNCTION Frequency control bit. F3-F0 are decoded as follows: F3-F0 Frequency (SYNC = GND) Synchronized Frequency (SYNC Clocked) 0000b 20Hz fSYNC/13100 0001b 30Hz fSYNC/8730 0010b 40Hz fSYNC/6550 0011b 50Hz fSYNC/5240 0100b 60Hz fSYNC/4370 0101b 70Hz fSYNC/3740 0110b 80Hz fSYNC/3270 0111b 90Hz fSYNC/2910 1000b 100Hz fSYNC/2620 1001b 110Hz fSYNC/2380 1010b 120Hz fSYNC/2180 1011b 130Hz fSYNC/2020 1100b 140Hz fSYNC/1870 1101b 150Hz fSYNC/1750 1110b 160Hz fSYNC/1640 1111b DAC Mode Frequency control bit Frequency control bit Frequency control bit Reserved for future use
7 (MSB)
F3
0
6 5 4 3-0
F2 F1 F0 RFU
0 0 0 0
set to 1111b. The FAN duty factor can be selected from 0% to 100% in increments of 6.67%.
FAN Output in DAC Mode
If the PWM frequency register is set to code 1111b, the DAC is multiplexed to the FAN output and the FAN duty factor register (Table 6) now controls the DAC output
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voltage rather than the duty factor. In DAC mode, the output swing is 0 to 0.94 * VCC (out of 4 bits of resolution). To ensure a smooth transition, make sure that the FAN duty factor code is 0000b prior to setting the PWM frequency code for DAC mode (1111b). External circuitry must accept an initial FAN DAC voltage of 0.
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Fan Controller and Remote Temperature Sensor with SMBus Serial Interface MAX1669
Table 6. Fan Duty-Factor Data Byte Bit Assignments (Write Command = 1Bh)
BIT NAME NAME FUNCTION FAN duty-factor control bit. D3-D0 are decoded as follows: D3-D0 Duty VOUT (nominal) 0000b 0% 0V 0001b 6.67% 0.0625 * VCC 0010b 13.33% 0.125 * VCC 0011b 20% 0.1875 * VCC 0100b 26.67% 0.25 * VCC 0101b 33.33% 0.3125 * VCC 0110b 40% 0.375 * VCC 0111b 46.67% 0.4375 * VCC 1000b 53.33% 0.5 * VCC 1001b 60% 0.5625 * VCC 1010b 66.67% 0.625 * VCC 1011b 73.33% 0.6875 * VCC 1100b 80% 0.75 * VCC 1101b 86.67% 0.8125 * VCC 1110b 93.33% 0.875 * VCC 1111b 100% 0.9375 * VCC FAN duty-factor control bit FAN duty-factor control bit FAN duty-factor control bit Reserved for future use
7 (MSB)
D3
0
6 5 4 3-0
D2 D1 D0 RFU
0 0 0 0
MASK_ BITS S R DELAY ALERT
I/O_ PIN
GPIO DATA_ BITS
ALERT RESPONSE
Figure 4. GPIO Logic Diagram
GPIO Data Register
I/O1 and I/O2 are configured through the GPIO data register and CONFIG byte register (Table 7 and Table 3). Upon power-up, the GPIOs are set as inputs. To ensure the I/Os are configured as inputs, set the state of the DATA1 and DATA2 bits high within the GPIO data register for I/O1 and I/O2, respectively. Figure 4 shows that by setting the GPIO DATA_ bits high, the open-drain FET connected to the I/O_ pins goes high impedance. Next, clear the MASK1 and MASK2 bits low within the
CONFIG byte register to remove the masks on the ALERT interrupts for I/O1 and I/O2, respectively. To use I/O1 or I/O2 as an output, first set the MASK1 and MASK2 bits high, respectively. Setting the MASK_ bits high within the CONFIG byte register masks out the corresponding I/O ALERT interrupts. Since the internal FETs are open-drain, a pull-up resistor is required from I/O_ to VCC. The DATA1 and DATA2 bits within the GPIO data register directly control the state of the outputs of I/O1 and I/O2, respectively (Figure 4).
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Fan Controller and Remote Temperature Sensor with SMBus Serial Interface MAX1669
Table 7. GPIO Input/Output Data Byte Bit Assignments
BIT 7 (MSB) NAME POR STATE FUNCTION For I/O1 configured as an output (MASK1 bit set high and a pull-up resistor on I/O1), this bit corresponds to the GPIO DATA1 block in Figure 4 and controls the output state of I/O1. To configure I/O1 as an input, set this bit high and clear the MASK1 bit low (Figure 4). For I/O2 configured as an output (MASK2 bit set high and a pull-up resistor on I/O2 ), this bit corresponds to the GPIO DATA2 block in Figure 4 and controls the output state of I/O2. To configure I/O2 as an input, set this bit high and clear the MASK2 bit low (Figure 4). Reserved for future use
DATA1
1
6 5-0
DATA2 RFU
1 0
Table 8. Write-Once Protection Byte Bit Assignments
BIT 7 (MSB) NAME PROT1 POR STATE 0 FUNCTION Write-protects the TCRIT limit threshold register when high. Write-protects certain bits in the configuration register when high: - STBY standby-mode control (bit 6) - POL polarity control (bit 5) - FAN ON control (bit 2) Write-protects bit 7 in the GPIO register when high (DATA1). Write-protects bit 6 in the GPIO register when high (DATA2). Reserved for future use
6
PROT2
0
5 4 3-0
PROT3 PROT4 RFU
0 0 0
Write-Once Protection
Write-once protection allows the host BIOS code to configure the MAX1669 and protect against data corruption in the host that might cause spurious writes to the MAX1669. In particular, write protection allows a foolproof overtemperature override that forces the fan on, independent of the host system whether in DAC mode or PWM mode. The bits in the write-protection register (Table 8), once set high, cannot be reset low except by power-on reset. Having a separate write-protect master register rather than making the actual registers themselves write once allows the host to read back and verify each register's contents before applying final write protection. Having individual write-protect control over different registers allows flexibility in application; for example, the TCRIT and configuration register could be protected while leaving one or both GPIO outputs free to be used as actuators.
status byte also indicates changes in GPIO states and transitions and whether there is a fault in the remote diode DXP-DXN path. After POR, the normal state of all the flag bits is 0, assuming none of the alarm conditions are present. Bits 2 to 5 of the status byte are cleared by any successful read of the status byte. Note that the ALERT interrupt latch is not automatically cleared when the status flag bit is cleared.
Manufacturer and Device ID Codes
This code identifies the functional capabilities of a particular device. New devices having enhanced or reduced software or hardware capabilities must be assigned a new code. The device ID allows the host system to interrogate the device to determine its capabilities, and use extra features if they're available. The device ID code is 2 bytes, for a total of 256X256 possible combinations. The device ID codes are located at command code 1111 1111b (FFh). If a read-byte operation (as opposed to a read-word) is applied to the device, it returns the least-significant byte correctly without the most-significant byte. Table 10 shows the device ID code for the MAX1669.
Status Byte Functions
The status byte register (Table 9) indicates which (if any) temperature thresholds have been exceeded. The
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Fan Controller and Remote Temperature Sensor with SMBus Serial Interface MAX1669
Table 9. Status Byte Bit Assignments
BIT 7 (MSB) 6 5 NAME I/O1 I/O2 TRAN1* FUNCTION This bit indicates the current state of I/O1 (unlatched). This bit indicates the current state of I/O2 (unlatched). This bit is set if a low-to-high or high-to-low transition has occurred at I/O1 (regardless of the state of the mask bits). This bit is set if a low-to-high or high-to-low transition has occurred at I/O2 (regardless of the state of the mask bits). A high indicates that the high-temperature alarm has activated A high indicates that the low-temperature alarm has activated. A high indicates a remote-diode fault (open-circuit, shorted diode, or DXP short to GND). When the TCRIT threshold is crossed, this bit goes high. The polarity of this bit does not depend on the POL bit (bit 5 in configuration byte).
4 3 2 1 0 (LSB)
TRAN2* RHIGH* RLOW* DIODE OVERT
*TRAN1 and TRAN2 alarm flags stay high until cleared by POR or until the status byte register is read. RHIGH and RLOW alarm flags stay high until cleared by POR or the temperature fault is removed and the status byte is read.
Table 10. Device ID Code
MAX1669 ID CODE LS BYTE LSBs MSBs 0000 0101 MS BYTE LSBs MSBs 0000 0000
Slave Addresses
The MAX1669 appears to the SMBus as one device having a common address for the temperature sensor section, GPIO section, and fan-control section. The device address can be set to one of eight different values by pin-strapping ADD_ pins so that more than one MAX1669 can reside on the same bus without address conflicts (Table 11). The MAX1669 also responds to the SMBus Alert Response slave address (see the Alert Response Address section).
Table 11. Slave Address Decoding (ADD_ Pins)
ADD0 GND GND GND GND VCC VCC VCC VCC ADD1 GND GND VCC VCC GND GND VCC VCC ADD2 GND VCC GND VCC GND VCC GND VCC ADDRESS 0011 000b 0011 001b 0011 010b 0101 001b 0101 010b 0101 011b 1001 100b 1001 101b
POR and UVLO
The MAX1669's memory is volatile. To prevent ambiguous power-supply conditions from corrupting the data in memory and causing erratic behavior, a POR voltage detector monitors VCC and clears the memory if VCC falls below 1.85V (typical, see the Electrical Characteristics table). When power is first applied and VCC rises above 1.9V (typ), the logic blocks begin operating; although reads and writes at VCC levels below 3V are not recommended. A second V CC comparator, the ADC UVLO comparator, prevents the ADC from converting until there is sufficient headroom (VCC = 2.8V typ).
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Fan Controller and Remote Temperature Sensor with SMBus Serial Interface MAX1669
Power-Up Defaults
* Interrupt latch is cleared. * ADC begins autoconverting at a 2Hz rate. * Command byte is set to 01h to facilitate quick remote receive-byte queries. * THIGH and TLOW registers are set to +127C and -55C limits, respectively. * TCRIT register is set to +100C. * ALERT and OVERT are reset to high-Z state. * Device is in low-frequency PWM mode, 20Hz setting. * PWM output is off (duty factor set to 0%). * I/O1, I/O2 are high-Z (configured as inputs).
Table 12. Component Manufacturers
MANUFACTURER SOT23 BJT Central Semiconductor (USA) Fairchild Semiconductor (USA) Motorola (USA) Rohm Semiconductor (Japan) Samsung (Korea) MOSFET N-CHANNEL International Rectifier (USA) IRF7201 FDN359AN CMPT3906 MMBT3906 MMBT3906 SST3906 KST3906 MODEL NUMBER
__________Applications Information
Remote Diode Selection
Temperature accuracy depends on having a goodquality, diode-connected, small-signal transistor. Accuracy has been experimentally verified for all of the devices listed in Table 12. The MAX1669 can also directly measure the die temperature of CPUs and other ICs having on-board temperature-sensing diodes, such as the Intel Pentium II. The transistor must be a small-signal type having a relatively high forward voltage; otherwise, the A/D input voltage range can be violated. The forward voltage must be greater than 0.25V at 10A; check to ensure this is true at the highest expected temperature. The forward voltage must be <0.95V at 100A; check to ensure this is true at the lowest expected temperature. Do not use large power transistors. Also, ensure that the base resistance is <100. Tight specifications for forward-current gain (+50 to +150, for example) indicate that the manufacturer has good process controls and the devices have consistent VBE characteristics. Series resistance causes +1/2C error per ohm. When monitoring the temperature of a remote unit's internal diode, ensure that trace series resistance does not introduce significant error.
Fairchild Semiconductor (USA) MOSFET P-CHANNEL International Rectifier (USA)
IRF7205
Note: Transistors must be diode-connected (base shorted to collector).
remote measurements in electrically noisy environments. High-frequency EMI is best filtered at DXP and DXN with an external 2200pF capacitor. This value can be increased to about 3300pF (max), including cable capacitance. Capacitance higher than 3300pF introduces errors due to the rise time of the switched-current source. Nearly all noise sources tested cause the ADC measurements to be higher than the actual temperature, typically by +1C to +10C, depending on frequency and amplitude (see Typical Operating Characteristics).
FAN Application Circuits
In PWM mode, the output impedance at FAN is <50, enabling it to drive an N-channel MOSFET as shown in the Typical Operating Circuit. Return the source of the N-channel MOSFET to the system power ground, away from the ground of the MAX1669. For 3.3V applications, use low-threshold N-channel MOSFETs (Table 1). In DAC mode, the FAN output can be linearly controlled (Figure 5). Upon power-up, the fan is off. The N-channel MOSFET is biased at the threshold of turning on. As VFAN rises, the fan turns on linearly. To have the fan turned on at power-up, use the circuit shown in Figure 6.
ADC Noise Filtering
The ADC is an integrating type with inherently good noise rejection, especially of low-frequency signals such as 60Hz/120Hz power-supply hum. Micropower operation places constraints on high-frequency noise rejection; therefore, careful PC board layout and proper external noise filtering is required for high-accuracy
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Fan Controller and Remote Temperature Sensor with SMBus Serial Interface MAX1669
+5V
10k
10k
10k
10k SMBCLK SMBDATA ALERT OVERT VCC
0.1F +12V
2N3906 2200pF
DXP 100k
MAX1669
DXN SYNC ADD0 ADD1 ADD2 AGND PGND I/O1 I/O2 FAN
38k
N-CH IRF7201 38k
SYSTEM POWER GROUND
Figure 5. Linear Fan Control (DAC Mode) with Fan "Off" at Power-Up
+5V
10k
10k
10k
10k SMBCLK SMBDATA ALERT OVERT VCC
0.1F +12V
22k 33k FAN 5.1V ZENER P-CH IRF7205 100k
2N3906 2200pF
DXP
MAX1669
DXN SYNC ADD0 ADD1 ADD2 AGND PGND I/O1 I/O2
SYSTEM POWER GROUND
Figure 6. Linear Fan Control (DAC Mode) with Fan "On" at Power-Up ______________________________________________________________________________________ 17
Fan Controller and Remote Temperature Sensor with SMBus Serial Interface MAX1669
Typical Operating Circuit
A tLOW
B tHIGH
C
D
E
F
G
H
I
J
K
SMBCLK
SMBDATA
tSU:STA tHD:STA A = START CONDITION B = MSB OF ADDRESS CLOCKED INTO SLAVE C = LSB OF ADDRESS CLOCKED INTO SLAVE D = R/W BIT CLOCKED INTO SLAVE
tSU:DAT E = SLAVE PULLS SMBDATA LINE LOW F = ACKNOWLEDGE BIT CLOCKED INTO MASTER G = MSB OF DATA CLOCKED INTO MASTER H = LSB OF DATA CLOCKED INTO MASTER
tSU:STO I = ACKNOWLEDGE CLOCK PULSE J = STOP CONDITION K = NEW START CONDITION
tBUF
Figure 7. SMBus Write Timing Diagram
A
tLOW
B
tHIGH
C
D
E
F
G
H
I
J
K
L
M
SMBCLK
SMBDATA
tSU:STA
tHD:STA
tSU:DAT
tHD:DAT
tSU:STO tBUF
A = START CONDITION B = MSB OF ADDRESS CLOCKED INTO SLAVE C = LSB OF ADDRESS CLOCKED INTO SLAVE D = R/W BIT CLOCKED INTO SLAVE E = SLAVE PULLS SMBDATA LINE LOW
F = ACKNOWLEDGE BIT CLOCKED INTO MASTER G = MSB OF DATA CLOCKED INTO SLAVE H = LSB OF DATA CLOCKED INTO SLAVE I = SLAVE PULLS SMBDATA LINE LOW
J = ACKNOWLEDGE CLOCKED INTO MASTER K = ACKNOWLEDGE CLOCK PULSE L = STOP CONDITION, DATA EXECUTED BY SLAVE M = NEW START CONDITION
Figure 8. SMBus Read Timing Diagram
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Fan Controller and Remote Temperature Sensor with SMBus Serial Interface
Typical Operating Circuit
+3V TO +5.5V
MAX1669
10k
10k
10k
10k SMBCLK SMBDATA ALERT OVERT VCC
0.1F
+12V
2N3906 2200pF
DXP
MAX1669
DXN SYNC ADD0 ADD1 ADD2 AGND PGND I/O1 I/O2 FAN
N-CH FDN 359AN
SYSTEM POWER GROUND
Chip Information
TRANSISTOR COUNT: 12,924
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Fan Controller and Remote Temperature Sensor with SMBus Serial Interface MAX1669
Package Information
QSOP.EPS
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.
20 ____________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600 (c) 2000 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products.

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