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MAX6640 Datasheet(PDF) 6 Page - Maxim Integrated Products |
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MAX6640 Datasheet(HTML) 6 Page - Maxim Integrated Products |
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6 / 21 page 
Detailed Description The MAX6640 monitors its own temperature and a remote diode-connected transistor or the temperatures of two external diode-connected transistors, which typi- cally reside on the die of a CPU or other integrated cir- cuit. The 2-wire serial interface accepts standard SMBus write byte, read byte, send byte, and receive byte commands to read the temperature data and pro- gram the alarm thresholds. Temperature data can be read at any time over the SMBus, and a programmable alarm output can be used to generate interrupts, throt- tle signals, or overtemperature shutdown signals. The temperature data is also used by the internal dual PWM fan-speed controller to adjust the speed of up to two cooling fans, thereby minimizing noise when the system is running cool, but providing maximum cooling when power dissipation increases. RPM feedback allows the MAX6640 to control the fan’s actual speed. 2-Channel Temperature Monitor with Dual Automatic PWM Fan-Speed Controller 6 _______________________________________________________________________________________ GND SMBus INTERFACE AND REGISTERS LOGIC PWM GENERATOR BLOCK VCC TEMPERATURE PROCESSING BLOCK SDA SCL DXP1 DXN PWM1 PWM2 TACH1 TACH2 DXP2 OT THERM FANFAIL ALERT MAX6640 Block Diagram Write Byte Format Read Byte Format Send Byte Format Receive Byte Format Slave Address: equiva- lent to chip-select line of a 3-wire interface 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) Slave Address: equiva- lent to chip-select line Command Byte: selects which register you are reading from Slave Address: repeated due to change in data- flow direction Data Byte: reads from the register set by the command byte Command Byte: sends com- mand with no data, usually used for one-shot command Data Byte: reads data from the register commanded by the last Read Byte or Write Byte transmission; also used for SMBus Alert Response return address S = Start condition Shaded = Slave transmission P = Stop condition /// = Not acknowledged Figure 1. SMBus Protocols S ADDRESS RD ACK DATA /// P 7 bits 8 bits WR S ACK COMMAND ACK P 8 bits ADDRESS 7 bits P 1 ACK DATA 8 bits ACK COMMAND 8 bits ACK WR ADDRESS 7 bits S S ADDRESS WR ACK COMMAND ACK S ADDRESS 7 bits 8 bits 7 bits RD ACK DATA 8 bits /// P |
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