f75377 Feature Integration Technology Inc., f75377 Datasheet - Page 15

• Manufacturer Part Number: f75377
• Description: Monitor With Automatic Speed Control
• Manufacturer: Feature Integration Technology Inc.

6.4 PECI/SST Master
6.5 Fan Control Machine
Fan speed count
measurement. For example, 15% variation in beta for two forced IE currents and the beta is 0.5 would
contribute about 11.12℃ error per 100℃.
In Order to solve the second issue, the F75377 provides a beta compensation solution for accurate
temperature sensing. The F75377 can support the beta range over 0.2 for beta compensation. In this
new method, the F75377 will provide two IE currents, and feedback two IB currents. The F75377 will
auto-adjust IE (IE1 and IE2) current and feedback IB (IB1 and IB2) promptly for getting proper IC
proportion (IC1/ IC2), then calculates the accurate temperature. This algorithm of beta compensation is
suitable for substrate transistor or new generational CPU (i.e. 45nm CPU) because small beta and high
proportional beta variation.
F75377 Support 6 external device inputs for temperature reading by SST and pass to host by I2C. It’s
really a SST to I2C bridge IC for some specific SST temperature sensors’ application. User can ready
SST temperature sensor by F75377 bridge function. For instance, user would like to read an external
SST temperature sensor by F75377. She could follow below list to read the SST Device Temperature.
Totally the F75377 can support 6 external device inputs by SST master. About the detail setting of register,
please refer the register description.
Others, the F75377 also support PECI Master for CPU temperature reading.
machine can implement the Fan to cool down CPU temperature Please refer the register
description for detail.
Inputs are provided by the signals from fans equipped with tachometer outputs. The level of these signals
should be set to TTL level, and maximum input voltage cannot be over 5V. If the input signals from the
tachometer outputs are over the 5V, the external trimming circuit should be added to reduce the voltage
If the address/index of SST device is 49h/00h.Before you read the temperature from SST
device. You should do below list:
1.
2.
3.
4. read register 78h to get the temperature value of SST device
write 00h to register 48h (Define external device0 index)
write “1” to register 50h bit 0 (Enable external device0)
write register 49h to register 40h (Define external device0 address)
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Than the fan control
F75377
March.
V0.12P
, 2008