ADT7476A
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5
Table 4. PIN ASSIGNMENT
Pin No.
Mnemonic
Description
1
SDA
Digital I/O (Open Drain). SMBus bidirectional serial data. Requires SMBus pullup.
2
SCL
Digital Input (Open Drain). SMBus serial clock input. Requires SMBus pullup.
3
GND
Ground Pin.
4
V
CC
Power Supply. Powered by 3.3 V standby, if monitoring in low power states is required. V
CC
is also
monitored through this pin.
5
VID0/
GPIO0
Digital Input. Voltage supply readouts from CPU. This value is read into the VID/GPIO register (0x43).
General-Purpose Open Drain Digital I/O.
6
VID1/
GPIO1
Digital Input. Voltage supply readouts from CPU. This value is read into the VID/GPIO register (0x43).
General-Purpose Open Drain Digital I/O.
7
VID2/
GPIO2
Digital Input. Voltage supply readouts from CPU. This value is read into the VID/GPIO register (0x43).
General-Purpose Open Drain Digital I/O.
8
VID3/
GPIO3
Digital Input. Voltage supply readouts from CPU. This value is read into the VID/GPIO register (0x43).
General-Purpose Open Drain Digital I/O.
9
TACH3
Digital Input (Open Drain). Fan tachometer input to measure speed of Fan 3.
10
PWM2/
SMBALERT
Digital Output (Open Drain). Requires 10 k
W
typical pullup. Pulse width modulated output to control Fan
2 speed. Can be configured as a high or low frequency drive.
Digital Output (Open Drain). This pin can be reconfigured as an SMBALERT interrupt output to signal
out-of-limit conditions.
11
TACH1
Digital Input (Open Drain). Fan tachometer input to measure speed of Fan 1.
12
TACH2
Digital Input (Open Drain). Fan tachometer input to measure speed of Fan 2.
13
PWM3
ADDREN
Digital I/O (Open Drain). Pulse width modulated output to control the speed of Fan 3 and Fan 4.
Requires 10 k
W
typical pullup. Can be configured as a high or low frequency drive.
If pulled low on powerup, the ADT7476A enters address select mode, and the state of Pin 14 (ADDR
SELECT) determines the ADT7476A’s slave address.
14
TACH4/
Digital Input (Open Drain). Fan tachometer input to measure speed of Fan 4.
THERM/
SMBALERT/
GPIO6/
ADDR SELECT
Alternatively, the pin can be reconfigured as a bidirectional THERM pin. Times and monitors assertions
on the THERM input. For example, it can be connected to the PROCHOT output of Intel’s Pentium
®
4
processor or to the output of a trip point temperature sensor. Can be used as an output to signal
overtemperature conditions.
Digital Output (Open Drain). This pin can be reconfigured as an SMBALERT interrupt output to signal
out-of-limit conditions.
General-Purpose Open Drain Digital I/O.
If in address select mode, the logic state of this pin defines the SMBus device address.
15
D2–
Cathode Connection to Second Thermal Diode.
16
D2+
Anode Connection to Second Thermal Diode.
17
D1–
Cathode Connection to First Thermal Diode.
18
D1+
Anode Connection to First Thermal Diode.
19
VID4/
Digital Input. Voltage supply readouts from CPU. This value is read into the VID/GPIO register (0x43).
GPIO4
General-Purpose Open Drain Digital I/O.
20
+5.0 V
IN
Analog Input. Monitors 5.0 V power supply.
21
+12 V
IN
/
VID5
Analog Input. Monitors 12 V power supply.
Digital Input. Voltage supply readouts from CPU. This value is read into the VID/GPIO register (0x43).
22
+2.5 V
IN
/
THERM
Analog Input. Monitors 2.5 V supply, typically a chipset voltage.
Alternatively, this pin can be reconfigured as a bidirectional/omnidirectional THERM pin. Can be used to
time and monitor assertions on the THERM input. For example, can be connected to the PROCHOT
output of Intel’s Pentium
®
4 processor or to the output of a trip point temperature sensor. Can be used as
an output to signal overtemperature conditions.
23
V
CCP
Analog Input. Monitors processor core voltage (0 V to 3 V).
24
PWM1/
XTO
Digital Output (Open Drain). Pulse width modulated output to control the speed of Fan 1. Requires 10 k
W
typical pullup.
Also functions as the output from the XOR tree in XOR test mode.
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