Feature Integration Technology Inc.
Fintek
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:
R2
VIN = V+3.3V
×
R1 + R2
where V+3.3V is the analog input voltage, for example.
If we choose R1=2K, R2=1K, the exact input voltage for V+3.3V will be 1.1V, which is within the tolerance.
As for application circuit, it can be refer to the figure shown as follows.
4
V0.25P
FINTEK [ FEATURE INTEGRATION TECHNOLOGY INC. ]
