G768B

The G768B contains a precise digital thermometer, 2 fan controllers, and a system-reset circuit.The G768B is backward compatible with G768, Except that there is an additional watchdog function. This function prevents fan from being out of control when system fails.

The thermometer reports the temperature of 2 remote sensors and its own package. The remote sensors are diode-connected transistors typically a low-cost, easily mounted 2N3904 NPN type that replace conventional thermistors or thermocouples. Remote accuracy is ±5°C for multiple transistor manufacturers, with no calibration needed. The remote channel of G768B can also measure the die temperature of other ICs, such as microprocessors, that contain an on-chip, diode-connected transistor.
 
The 2-wire serial interface accepts standard System Management Bus (SMBus_TM ) Write Byte, Read Byte, Send Byte, and Receive Byte commands to program the alarm thresholds and to read temperature data. The data format of G768B is 7 bits plus sign, with each bit cor-responding to 1°C, in two's-complement format. Measurements can be done automatically and autonomously, with the conversion rate programmed by the user or programmed to operate in a single-shot mode. The adjustable rate of G768B allows the user to control the supply-current drain.

G768B also contains a 2-channel fan speed controller. It connects directly to the fans and performs closed-loop control of the fan speedindependently. The only external component required is a 10F ca-pacitor per channel. It determines the current fan speed based on the fan rotation pulses and an exter-nally supplied clock. (To be continued)