TC654 datasheet(8/38 Pages) MICROCHIP

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TC654/TC655

DS20001734C-page 8

 2002-2014 Microchip Technology Inc.

3.0

PIN FUNCTIONS

The descriptions of the pins are listed in Table 3-1.

TABLE 3-1:

PIN FUNCTION TABLE

3.1

Analog Input (VIN)

A voltage range of 1.62V to 2.6V (typical) on this pin

drives an active duty-cycle of 30% to 100% on the

VOUT pin.

3.2

Analog Output (CF)

Positive terminal for the PWM ramp generator timing

capacitor. The recommended CF is 1 µF for 30 Hz

PWM operation.

3.3

SMBus Serial Clock Input (SCLK)

Clocks data into and out of the TC654/TC655. See

Section 5.0 “Serial Communication” for more infor-

mation on the serial interface.

3.4

Serial Data (Bi-directional) (SDA)

Serial data is transferred on the SMBus in both direc-

tions using this pin. See Section 5.0 “Serial Commu-

nication” for more information on the serial interface.

3.5

Digital (Open Drain) Output

(FAULT)

When the fan’s RPM falls below the user-set RPM

threshold (or OTF occurs with TC655), a logic low sig-

nal is asserted.

3.6

Analog Input (SENSE2)

Fan current pulses are detected at this pin. These

pulses are counted and used in the calculation of the

Fan 2 RPM.

3.7

Analog Input (SENSE1)

Fan current pulses are detected at this pin. These

pulses are counted and used in the calculation of the

Fan 1 RPM.

3.8

Digital Output (VOUT)

This active high complimentary output drives the base

of an external transistor or the gate of a MOSFET.

3.9

Power Supply Input (VDD)

The VDD pin with respect to GND provides power to the

device. This bias supply voltage may be independent of

the fan power supply.

Name

Function

VIN

Analog Input

Analog Output

SCLK

Serial Clock Input

SDA

Serial Data In/Out (Open Drain)

GND

Ground

FAULT

Digital (Open Drain) Output

SENSE2

Analog Input

SENSE1

Analog Input

VOUT

Digital Output

VDD

Power Supply Input

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