TC651 datasheet(8/18 Pages) MICROCHIP

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TC650/TC651

DS21450D-page 8

 2001-2012 Microchip Technology Inc.

4.6

Temperature Selection Guide

(Minimum Fan Speed/Full Speed)

There are two temperature thresholds that determine

the characteristics of the device. The minimum fan

speed temperature (TL) and the full fan speed temper-

ature (TH). Depending on the TC65X device selected,

when the temperature is below the TL trip point, the

PWM output will perform a different operation. For the

TC650, the PWM will be driven at the minimum PWM

frequency, while the TC651 will shut down the PWM

(PWM = L).

TL and TH can be selected in 5°C increments. TL can

range from 25°C to 35°C. TH can range from 35°C to

55°C and must be 10°C (or more) than the specified TL.

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. Table 4-1 shows these 5 regions and what the

corresponding PWM duty cycle is.

TABLE 4-1:

TEMPERATURE RANGE

DEFINITION

Table 4-2 shows the device codes that specify the TH

and TL temperature thresholds. The following exam-

ples are given to assist in understanding the device-

ordering nomenclature.

Example 1: 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.

Example 2: 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.

TABLE 4-2:

DEVICE CODES FOR

TEMPERATURE

THRESHOLDS

Temperature

(T = TJ)

(Note 1)

PWM Duty Cycle

TC650

(Minimum

Speed mode)

TC651

(Auto-shutdown

mode)

T < TL

40%

Off

TL< = T < T1

50%

T1 < = T < T2

60%

T2 < = T <T3

70%

T3 < = T < T4

80%

T4 < = T < TH

90%

TH < = T < TOV

100%

TOV < = T

100% with Overtemperature Alert

(TOVER = L)

Note 1:

The temperature regions defined by the

six temperature thresholds are pre-

defined in the TC650/TC651 by means of

factory trimming. Once a TL and TH are

programmed, the T1 – T4 thresholds are

automatically equally spaced between TL

and TH.

Temp.

Threshold

Difference

Threshold

Limits Code

10°C

AC (1)

BD (2)

CE (2)

15°C

AD (2)

BE (1)

CF (2)

20°C

AE (1)

BF (2)

CG (1)

30°C

AG (1)

Note 1:

This temperature threshold option is

available for ordering.

This is a custom temperature threshold

option. Please contact the factory for

more information.

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