LM87 datasheet(3/32 Pages) NSC

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Pin Description (Continued)

Name(s)

Number

of Pins

Type

Description

GND

GROUND

The system ground pin. Internally connected to all circuitry. The

ground reference for all analog inputs and the DAC output. This pin

needs to be connected to a low noise analog ground plane for

optimum performance of the DAC output.

+ (+2.8 V to

+3.8 V)

POWER

+3.3 V V

+ power. Bypass with the parallel combination of 10 µF

(electrolytic or tantalum) and 0.1 µF (ceramic) bypass capacitors.

INT# /ALERT#

Digital Output

Interrupt active low open-drain output. This output is enabled when

Bit 1 in the Configuration Register is set to 1. The default state is

disabled. It has an on-chip 100 k

Ω pullup resistor. Alternately used

as an active low output to signal SMBus Alert Response Protocol.

DACOut/NTEST_IN

Analog

Output/Digital

Input

0 V to +2.5 V amplitude 8-bit DAC output. When forced high on

power up by an external voltage the NAND Tree Test mode is

enabled which provides board-level connectivity testing.

RESET#

Digital I/O

Master Reset, 5 mA driver (open-drain), active low output with a 20

ms minimum pulse width. Available when enabled via Bit 4 in the

Configuration register. It also acts as an active low power on

RESET input. It has an on-chip 100 k

Ω pullup resistor.

D1−

Analog Input

Analog input for monitoring the cathode of the first external

temperature sensing diode.

D1+

Analog Input

Analog input for monitoring the anode of the first external

temperature sensing diode.

+12Vin

Analog Input

Analog input for monitoring +12 V.

+5Vin

Analog Input

Analog input for monitoring +5 V.

Vccp2/D2−

Analog Input

Digitally programmable analog input for monitoring Vccp2 (0 to 3.6

V input range) or the cathode of the second external temperature

sensing diode.

+2.5Vin/D2+

Analog Input

Digitally programmable analog input for monitoring +2.5 V or the

anode of the second external temperature sensing diode.

Vccp1

Analog Input

Analog input (0 to 3.6 V input range) for monitoring Vccp1, the core

voltage of processore 1.

VID4/IRQ4-

VID0/IRQ0

20-24

Digital Inputs

Digitally programmable dual function digital inputs. Can be

programmed to monitor the VID pins of the Pentium/PRO and

Pentium II processors, that indicate the operating voltage of the

processor, or as interrupt inputs. The values are read in the

VID/Fan Divisor Register and the VID4 Register. These inputs have

on-chip 100 k

Ω pullup resistors.

TOTAL PINS

# Indicates Active Low (“Not”)

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