REV. 0

ADM1031

–4–

PIN FUNCTION DESCRIPTIONS

Pin No.

Mnemonic

Description

1

PWM_OUT1

Digital Output (Open-Drain). Pulsewidth modulated output to control fan speed. Requires pull-

up resistor (10 k

Ω typical).

2

TACH1/AIN1

Digital/Analog Input. Fan tachometer input to measure FAN1 fan speed. May be reprogrammed as

an analog input to measure speed of a 2-wire fan via a sense resistor (2

Ω typical).

3

PWM_OUT2

Digital Output (Open-Drain). Pulsewidth Modulated output to control FAN2 fan speed.

Requires pull-up resistor (10 k

Ω typical).

4

TACH2/AIN2

Digital/Analog Input. Fan tachometer input to measure FAN2 fan speed. May be repro-

grammed as an analog input to measure speed of a 2-wire fan via a sense resistor (2

Ω typical).

5

GND

System Ground.

Power. Can be powered by 3.3 V Standby power if monitoring in low power states is required.

7

THERM

Digital I/O (Open-Drain). An active low thermal overload output that indicates a violation of a

temperature set point (overtemperature). Also acts as an input to provide external fan control.

When this pin is pulled low by an external signal, a status bit is set, and the fan speed is set to

full-on. Requires pull-up resistor (10 k

Ω).

8

FAN_FAULT

Digital Output (Open-Drain). Can be used to signal a fan fault. Drives second fan to full speed

if one fan fails. Requires pull-up resistor (typically 10 k

Ω).

9

D1–

Analog Input. Connected to cathode of first remote temperature-sensing diode. The temperature-

sensing element is either a Pentium III substrate transistor or a general-purpose 2N3904.

10

D1+

Analog Input. Connected to anode of first remote temperature-sensing diode.

11

D2–

Analog Input. Connected to cathode of second remote temperature-sensing diode.

12

D2+

Analog Input. Connected to anode of second remote temperature-sensing diode.

13

ADD

Three-State Logic Input. Sets two lower bits of device SMBus address.

14

INT (SMBALERT)

Digital Output (Open-Drain). Can be programmed as an interrupt (SMBus ALERT) output for

temperature/fan speed interrupts. Requires pull-up resistor (10 k

Ω typical).

15

SDA

Digital I/O. Serial Bus Bidirectional Data. Open-drain output. Requires pull-up resistor

(2.2 k

Ω typical).

16

SCL

Digital Input. Serial Bus Clock. Requires pull-up resistor (2.2 k

Ω typical).

PIN CONFIGURATION

TACH2/AIN2

TOP VIEW

(Not to Scale)

16

15

14

13

12

11

10

9

1

2

3

4

5

6

7

8

PWM_OUT1

SCL

ADM1031

SDA

PWM_OUT2

INT (SMBALERT)

ADD

GND

D2+

D2–

THERM

D1+

FAN_FAULT

D1–

TACH1/AIN1