Pin Descriptions

Pin

Name

Input/Output

Function and Connection

1

GPIO1

Digital Input/

Open-Drain Output

General Purpose Open-Drain Digital Output or Digital Input. Typical pull-up

resistor is 10 k

Ω to V

2

GPIO2

Digital Input/

Open-Drain Output

General Purpose Open-Drain Digital Output or Digital Input. Typical pull-up

resistor is 10 k

Ω to V

3

GPIO3

Digital Input/

Open-Drain Output

General Purpose Open-Drain Digital Output or Digital Input. Typical pull-up

resistor is 10 k

Ω to V

4

PWM

Open-Drain

Digital Output

Open-Drain Digital Output. Connect to fan drive circuitry. The power-on

default for this pin is low (pin 4 pulled to ground).

5V

DD

Power Supply Input

with a 0.1 µF ceramic capacitor in parallel with a 100 pF ceramic capacitor.

A bulk capacitance of 10 µF needs to be in the vicinity of the LM64’s V

DD

pin.

6

D+

Analog Input

Connect to the anode (positive side) of the remote diode. A 2.2 nF ceramic

capacitor must be connected between pins 6 and 7.

7

D-

Analog Input

Connect to the cathode (negative side) of the remote diode. A 2.2 nF

ceramic capacitor must be connected between pins 6 and 7.

8

T_Crit

Open-Drain

Digital Output

Open-Drain Digital Output. Typical pull-up resistor is 3 k

Ω to V

9

N/C

N/A

No Connection.

10

N/C

N/A

No Connection.

11

N/C

N/A

No Connection.

12

A0

Digital Input

SMBus Address Select pin. If High, the SMBus address is 0x4E or, if Low,

the SMBus address is 0x18. Typical pull-up resistor is 10 k

Ω to V

13

GND

Ground

This is the analog and digital ground return.

14

ALERT

Open-Drain

Digital Output

This pin is an open-drain ALERT Output. Typical pull-up resistor is 3 k

Ω to

V

15

TACH

Digital Input

This pin is a digital tachometer input. Typical pull-up resistor is 3 k

Ω to

V

16

SMBDAT

Digital Input/

Open-Drain Output

This is the bi-directional SMBus data line. Typical pull-up resistor is 1.5 k

Ω

to V

17

SMBCLK

Digital Input

This is the SMBus clock input. Typical pull-up resistor is 1.5 k

Ω to V

18

GPIO5

Digital Input/

Open-Drain Output

General Purpose Open-Drain Digital Output or Digital Input. Typical pull-up

resistor is 10 k

Ω to V

19

GPIO4

Digital Input/

Open-Drain Output

General Purpose Open-Drain Digital Output or Digital Input. Typical pull-up

resistor is 10 k

Ω to V

20

GPD1

Digital Input

General Purpose Default Input Pin. Typical pull-up resistor is 10 k

Ω to V

Always connect to a logical High or Low level.

21

GPD2

Digital Input

General Purpose Default Input Pin. Typical pull-up resistor is 10 k

Ω to V

Always connect to a logical High or Low level.

22

GPD3

Digital Input

General Purpose Default Input Pin. Typical pull-up resistor is 10 k

Ω to V

Always connect to a logical High or Low level.

23

GPD4

Digital Input

General Purpose Default Input Pin. Typical pull-up resistor is 10 k

Ω to V

Always connect to a logical High or Low level.

24

GPD5

Digital Input

General Purpose Default Input Pin. Typical pull-up resistor is 10 k

Ω to V

Always connect to a logical High or Low level.

www.national.com

2