
REV. B
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.
4GND
Ground. Power and signal ground.
5VCC3AUX
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.
9D–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
Digital Output (Open Drain with Integrated VCC3AUX Pull-Up). An active low thermal
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
Digital Output or Open Drain with Integrated VCC3AUX Pull-Up. Remote off (power-
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
VCC3AUX
RST
R_RST
FAN_SPD/NTEST_IN
SDA
SCL
INT
R_OFF
THERMB
THERMA/NTEST_OUT
D+
D–
ADM1028