TC651CEVUATR データシートの表示（PDF） - Microchip Technology

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TC651CEVUATR

Tiny Integrated Temperature Sensor & Brushless DC Fan Controller with Over-Temperature Alert

Microchip Technology 

3.0 DETAILED DESCRIPTION

The TC650/TC651 acquire and convert their junction

temperature (TJ) information from an on-chip solid-state

sensor with a typical accuracy of ±1°C. The temperature

data is digitally stored in an internal register. The

register is compared with pre-defined threshold values.

The six threshold values are equally distributed over a

pre-defined range of temperatures (see Table 3-1 and

Table 3-2). The TC650/TC651 control the speed of a

DC brushless fan using a fractional speed control

scheme. The output stage requires only a 2N2222-type

small-signal BJT for fans up to 300mA. For larger

current fans (up to 1 Amp) a logic-level N-channel

MOSFET may be used. In addition to controlling the

speed of the fan, the TC650/TC651 include an on-chip

over-temperature alarm (TOVER) that gives a low signal

when the temperature of the chip exceeds TH by 10°C,

(typical). This feature eliminates the need for a separate

temperature sensor for over-temperature monitoring.

TABLE 3-1:

TEMPERATURE RANGE

DEFINITION FOR TC650

(MINIMUM-SPEED MODE)

Temperature (T = TJ)

PWM Duty Cycle

T < TL

TL< = T < T1

T1 < = T < T2

T2 < = T <T3

T3 < = T < T4

T4 < = T < TH

TH < = T < TOV

TOV < = T

40%

50%

60%

70%

80%

90%

100%

100% with Over Temp Alert

(TOVER = L)

TABLE 3-2:

TEMPERATURE RANGE

DEFINITION FOR TC651

(AUTO-SHUTDOWN MODE)

Temperature (T = TJ)

PWM Duty Cycle

T < TL

“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 Over-Temp Alert

(TOVER = L)

Note:The temperature regions defined by the six temperature thresh-

olds are pre-defined in the TC650/TC651 by means of trimming. Once

a TL and TH are programmed, the T1 – T4 thresholds are automatically

equally spaced between TL and TH.

TC650/TC651

FIGURE 3-1:

FUNCTIONAL BLOCK

DIAGRAM

VDD

TOVER SHDN

V+

Temperature

Set Point and

Trim Range

Duty Cycle

Logic

Control

PWM

A/D Converter

Temperature Sensor

Oscillator

3.1 PWM Output

The PWM pin is designed to drive a low cost transistor

or MOSFET as the low side power switching element in

the system. This output has an asymmetric

complementary drive and is optimized for driving NPN

transistors or N-channel MOSFETs. Since the system

relies on PWM rather than linear power control, the

dissipation in the power switch is kept to a minimum.

Generally, very small devices (TO-92 or SOT

packages) will suffice. The frequency of the PWM is

about 15Hz. The PWM is also the time base for the

Start-up Timer (see paragraphs below). The PWM duty

cycle has a range of 40% to 100% for the TC650 and

50% to 100% for the TC651.

3.2 Start-Up Timer

To ensure reliable fan start-up, the Start-up Timer turns

PWM high for about 2 seconds whenever the fan is

started from the off state. This occurs at power-up and

when coming out of Shutdown mode.

3.3 Over-Temperature Alert (TOVER)

This pin goes low when the TH set point is exceeded by

10oC (typical). This indicates that the fan is at

maximum drive and the potential exists for system

overheating; either heat dissipation in the system has

gone beyond the cooling system's design limits, or

some FAULT exists such as fan bearing failure or an

airflow obstruction. This output may be treated as a

“System Overheat” warning and used to trigger system

shutdown, or bring other fans to full speed in the

system. The fan will continue to run at 100% speed

while TOVER is asserted. Built-in hysteresis prevents

TOVER from “chattering” when measured temperature

is at or near the TH + 10°C trip point. As temperature

falls through the TH + 10°C trip point, hysteresis

maintains the TOVER output low until measured

temperature is 5°C above the trip point setting.

© 2002 Microchip Technology Inc.

DS21450B-page 5

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