TC648 Ver la hoja de datos (PDF) - Microchip Technology

Número de pieza

componentes Descripción

Fabricante

TC648

Fan Speed Controller with Auto-Shutdown and Over-Temperature Alert

Microchip Technology 

TC648

TC646

Status

2.6V

Normal

Operation

Auto-Shutdown

Mode

Normal

Operation

Shut-

Down

Normal

Operation

HI

VAS + VHAS

VAS

1.2V

VIN

VREL

VSHDN

GND

FIGURE 3-1:

Time

TC648 Nominal Operation.

tRESET

TEMP.

LO

4.0 SYSTEM BEHAVIOR

The flowcharts describing the TC648’s behavioral

algorithms are shown in Figure 4-1. They can be

summarized as follows:

4.1 Power-Up

(1) Assuming the device is not being held in shut-

down or auto-shutdown mode (VIN > VAS)..........

(2) Turn VOUT output on for 32 cycles of the PWM

clock. This ensures that the fan will start from a

dead stop.

(3) Branch to Normal Operation.

(4) End.

4.2 Normal Operation

Normal Operation is an endless loop which may only

be exited by entering shutdown or auto-shutdown

mode. The loop can be thought of as executing at the

frequency of the oscillator and PWM.

(1) Drive VOUT to a duty cycle proportional to VIN on a

cycle by cycle basis.

(2) If an over-temperature fault occurs, (VIN > VOTF),

activate OTF; release OTF when VIN < VOTF.

(3) Is the TC648 in shutdown or auto-shutdown

mode?

If so.....

a. VOUT duty cycle goes to zero.

b. OTF is disabled.

c. Exit the loop and wait for VIN > (VAS + VHAS),

then execute Power-up sequence.

(4) End.

 2002 Microchip Technology Inc.

DS21448C-page 7

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