TC651 datasheet(6/14 Pages) MICROCHIP

6 / 14 page

TC650/TC651

DS21450B-page 6

3.4

Shutdown (SHDN)

The fan can be unconditionally shutdown by pulling low

the SHDN pin. During shutdown, the PWM output is

low. This is ideal for notebook computers and other

portable applications when you need to change

batteries and must not have the fan running at that

time. Thermal monitoring and TOVER are still in

operation during shutdown. IDD shutdown current is

around 50

µA.

3.5

Auto-Shutdown Mode

The

TC651

features

auto-shutdown;

when

the

temperature is below the factory set point at minimum

speed (TL), PWM is low and the fan is automatically

shut off (Auto-shutdown mode). This feature is ideal for

notebook computers and other portable equipment that

need to conserve as much battery power as possible

and thus run a fan when it is only absolutely needed.

The TC651 will continue to be active so as to monitor

temperature for Tover. The TC651 exits Auto-shutdown

mode when the temperature rises above the factory set

point (T1).

3.6

Temperature Selection Guide

(Minimum Fan Speed/Full Speed)

The five temperature regions defined by the six

thresholds are defined in the TC650/TC651 by means

of factory trimming. Once a TL and TH are set, the T1 –

T4 thresholds are automatically equally spaced

between TL and TH.

Note: The Bold Type temperature settings are available for

ordering. Contact factory for other temperature selec-

tions.

TL and TH canbeselectedin5°C increments. TH must

be chosen at least 10oC higher than TL.TL can range

anywhere from 25°C to 35°C.

As an example, suppose you wanted the fan to run at

40% speed at 25°C or less and go to full speed at

45°C. You would order the part number TC650AEVUA.

As another example, suppose you wanted the fan to

turn on at 30°C and go to full speed at 45°C. You

would order the part number TC651BEVUA.

Temp.

Range

Part #

10°C

15°C

20°C

30°C

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