REV. A

ADM1028

–4–

PIN FUNCTION DESCRIPTIONS

Pin No.

Mnemonic

Description

1

FAN_OFF

Digital Output (Open Drain) Fan Off Request. When asserted low, this indicates a

request to shut off the fan independent of the FAN_SPD output. When negated (output

FET off) it indicates that the fan may be turned on.

2

GPI

Digital Input (12 V tolerant). This pin is a general-purpose logic input with 12 V toler-

ance. It can be programmed as an active high or active low input that sets Bit 4 of the

Interrupt Status Register. A voltage >2.2 V on this pin, represents a Logic “1,” while a

floating condition is interpreted as Logic “0.”

3

AUXRST

Digital Input. This pin can be driven low as an input to reset the ADM1028.

4

GND

Ground. Power and signal ground.

Power 3.3 V Aux. Power source and voltage monitor input for power-on reset.

6

RST

Digital Input. This pin can be pulled low externally to indicate to the ADM1028 that the

main system power has been removed. The ADM1028 will shut off the FAN_SPD out-

put and reset its

R_OFF output.

7

R_RST

Digital Output (Open Drain). This pin is a remote reset output that pulses low on

receipt of a specific SMBus message.

8

FAN_SPD/NTEST_IN

Analog Output/Test Input. An active-high input that enables NAND board-level

connectivity testing. Refer to section on NAND testing.

Used as an analog output for fan speed control when NAND test is not selected.

9

D–

Remote Thermal Diode Negative Input. This is the negative input (current sink) from

the remote thermal diode. This also serves as the negative input into the A/D.

10

D+

Remote Thermal Diode Positive Input. This is the positive input (current source) from

the remote thermal diode. This serves as the positive input into the A/D.

11

THERMA/NTEST_OUT

overload output that indicates a violation of a temperature setpoint (over temperature).

The fan is on full-speed whenever this pin is asserted low. Acts as the output of the NAND

Tree when the ADM1028 is in NAND Tree Test Mode.

12

THERMB

Digital Output (Open Drain). This pin is a second

THERM signal. It can be used to

drive external circuitry with a different external pull-up supply rail.

13

R_OFF

down) output. This pin is driven high on receipt of a specific SMBus message. The pin

(and its associated register bit) remain high until the

RST input is asserted low.

14

INT

Digital Output (Open Drain), System Interrupt Output. This signal indicates a violation

of a set trip point. The output is enabled when Bit 1 of the Configuration Register is set

to 1. The default state is disabled.

15

SCL

Digital Input. SMBus Clock.

16

SDA

Digital I/O (Open Drain). SMBus Bidirectional Data.

PIN CONFIGURATION

TOP VIEW

(Not to Scale)

16

15

14

13

12

11

10

9

1

2

3

4

5

6

7

8

FAN_OFF

GPI

AUXRST

GND

RST

R_RST

FAN_SPD/NTEST_IN

SDA

SCL

INT

R_OFF

THERMB

THERMA/NTEST_OUT

D+

D–

ADM1028