f75387 Feature Integration Technology Inc., f75387 Datasheet - Page 9

• Manufacturer Part Number: f75387
• Description: ?1o C Accuracy H/w Monitor Ic With Automatic Fan Speed Control
• Manufacturer: Feature Integration Technology Inc.

6. Function Description
voltage under 2.048V (ex:1.5V) can be directly connected to these analog inputs. The voltage higher than 2.048V
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 F75387. Therefore 3Vcc can directly connect to this chip’s power pin 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 F75387 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 150K ohm, so that the internal reduced voltage is half of +3.3V.
6.1.
6.2.
6
13
8
7
F75387 is a system hardware monitoring and automatic fan speed controlling IC specific designed for graphic
cards and PC etc. An 11-bit analog-to-digital converter (ADC) was built inside F75387. The chip can monitor
up to 4 analog voltage inputs, 2 fan tachometer inputs and 3 temperature inputs (2 remote and 1 local sensor).
The remote temperature sensor can be performed by thermistor, transistor 2N3906 and CPU/GPU thermal
diode. The F75387 can provide automatic fan speed control so that the system can operate at the minimum
acoustic noise. This chip supports not only PWM duty mode (PWMOUT) but also linear mode (DACOUT) for
fan speed control. Also the users can set up the upper and lower limits (alarm thresholds) of all monitored
parameters and the F75387 can also issue warning messages for system protection when there is something
wrong with monitored items.
For the 11-bit ADC has the 8mv LSB, the maximum input voltage of the analog pin is 2.048V. Therefore the
General Description
Analog Inputs
OVT#(Default)
GPIO3
FAN_FAULT#
CLKIN
VREF
SDATA
SCLK
IN
OD
IN
AOUT
IN
IN
OD
ts5V
ts5V
ts5V
ts5V
12
12
/OD
/OD
12
12
Default open drain active-low output. This pin will be a logic LOW when the
General purpose I/O function.
This pin will be a logic LOW when the fan speed is abnormal.
24MHz/48MHz external clock input for chip operation source. When input
external clock, the fan speed count will be more accurate.
Reference voltage 2.304V.
Serial bus data
Serial bus clock
temperature exceeds its limit. Default output enable when the temperature
exceeds 100
7
o
C on initial.
July, 2007
F75387
0.27P