NCT80

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2

A−TO−D

CONVERTER

ON−CHIP

TEMPERATURE

SENSOR

ANALOG

MUX

I2C INTERFACE

3

2

4

5

7

GND

SDA

SCL

A1

10

AIN0

AIN1

A0

6

9

AIN2

AIN3

8

11

12

1

14

A2

CI

17

19

22

15

20

13

16

21

18

23

24

AIN6

AIN5

AIN4

Fan

Counter

Limit and

Config

Data

Status Register

Interrupt

Control

CI

AGND

NCT80

TACH1

TACH2

Figure 1. Functional Block Diagram of NCT80

BTI INT_IN

INT

RST_OUT/

THERM

NTEST_IN/

RST_IN

GPO

Registers

Registers

Speed

Table 1. PIN FUNCTION DESCRIPTION

Pin No.

Pin Name

Description

1

INT_IN

Active low digital input. This signal is propagated to the INT output pin of the NCT80.

2

SDA

3

SCL

Serial Clock Input. Open−drain pin; needs a pull−up resistor.

4

TACH1

Digital Input. Fan tachometer input to measure speed of Fan.

5

TACH2

Digital Input. Fan tachometer input to measure speed of Fan.

6

BTI

Digital Input. Board Temperature Interrupt driven by O.S. outputs of additional temperature sensors

such as the NCT75.

7

CI

(Chassis Intrusion)

Digital I/O. An active high input from an external latch which captures a Chassis Intrusion event.

This line can go high without any clamping action, regardless of the powered state of the NCT80

8

GND

Power Supply Ground.

9

Positive Supply Voltage. Bypass to ground with a 0.1 mF bypass capacitor.

10

INT

Digital Output. Open drain Interrupt Request pin.

11

GPO

Digital Output. An active low open drain output intended to drive an external

P−channel power MOSFET in order to offer software power control.

12

NTEST_IN/RST_IN

Dual function pin. Active low input that enables NAND Tree Test functionality. Once enabled the part

is reset to its power on default.

13

RST_OUT/THERM

Dual function pin. RST_OUT: Active low reset output pin. THERM:

Overtemperature shutdown output pin.

14

AGND

Analog Ground.

15

AIN6

Analog Input. 0 V to 2.56 V.

16

AIN5

Analog Input. 0 V to 2.56 V.

17

AIN4

Analog Input. 0 V to 2.56 V.

18

AIN3

Analog Input. 0 V to 2.56 V.

19

AIN2

Analog Input. 0 V to 2.56 V.

20

AIN1

Analog Input. 0 V to 2.56 V.

21

AIN0

Analog Input. 0 V to 2.56 V.

22

A0/NTEST_OUT

functions as an output when performing a NAND test.

23

A1

24

A2