Fintek

Feature Integration Technology Inc.

V0.25P

4

F75373

5 Functional Description

F75373S is a system hardware monitoring and automatic fan speed controlling IC specific designed for

graphic cards. The chip can monitor up to 4 analog voltage inputs, 2 fan tachometer inputs and 2 remote

temperature sensors. The remote temperature sensor is suggested to be performed by thermistor. The

F75373S can provide automatic fan speed control so that the system can operate at the minimum acoustic

noise. Also the users can set up the upper and lower limits (alarm thresholds) of all monitored parameters and

this chip can also issue warning messages for system protection when there is something wrong with

monitored items.

5.1

Analog Input

For the 8-bit ADC has the 7.8125mv LSB, the maximum input voltage of the analog pin is 2V. Therefore the voltage under 2V

(ex:1.5V) can directly connected to these analog inputs. The voltage higher than 2V should be reduced by a factor with external

resistors so as to obtain the input range. Only 3VCC is an exception for it is main power of the F75373S. Therefore 3VCC can

directly connect to this chip and need no external resistors. There are two functions in this pin with 3.3V. The first function is to

supply internal analog power of the F75373S and the second function is that this voltage with 3.3V is connected to internal serial

resistors to monitor the +3.3V voltage. The internal serial resistors are two 50K ohm, so that the internal reduced voltage is half

+3.3V.

There are four voltage inputs in the F75373S and the voltage divided formula is shown as follows:

2

1

2

3

.

3

R

R

R

V

VIN

V

+

×

=

+

where

If we choose R1=2K, R2=1K, the exact input voltage for

As for application circuit, it can be refer to the figure shown as follows.