LM63 datasheet(2/28 Pages) NSC

2 / 28 page

Pin Descriptions

Name

Input/Output

Function and Connection

Power Supply Input

Connect to a low-noise +3.3 ± 0.3 VDC power supply, and bypass to GND

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 LM63’s V

pin.

D+

Analog Input

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

capacitor must be connected between pins 2 and 3.

D−

Analog Input

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

ceramic capacitor must be connected between pins 2 and 3.

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).

GND

Ground

This is the analog and digital ground return.

ALERT/TACH

Digital I/O

Depending on how the LM63 is programmed, this pin is either an

open-drain ALERT output or a tachometer input for measuring fan speed.

The power-on default for this pin is the ALERT function.

SMBDAT

Digital Input/

Open-Drain Output

This is the bi-directional SMBus data line.

SMBCLK

Digital Input

Digital Input. This is the SMBus clock input.

Simplified Block Diagram

20057002

LM63 Datasheet(PDF) 2 Page - National Semiconductor (TI)