TC652DEVUA Ver la hoja de datos (PDF) - Microchip Technology

Número de pieza

componentes Descripción

Fabricante

TC652DEVUA

Integrated Temperature Sensor & Brushless DC Fan Controller with FanSense™ Detect & Over-Temperature

Microchip Technology 

3.0 DETAILED DESCRIPTION

The TC652/TC653 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 TC652/TC653

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 TC652/

TC653 include an on-chip over-temperature alarm

(TOVER) that gives a low-true signal when the

temperature of the chip exceeds TH by 10°C. This

feature eliminates the need for a separate temperature

sensor for over-temperature monitoring.

In normal fan operation, a pulse-train is present at

SENSE, Pin 5. A Missing Pulse Detector monitors this

pin during fan operation (FanSense™ technology). A

stalled, open, or unconnected fan causes the TC652/

TC653 to trigger its Start-up Timer once. If the FAULT

persists, the FAULT output goes low, and the device is

latched in its Shutdown mode. To release the fan from

shutdown, toggle the SHDN or VDD pin.

TABLE 3-1:

TEMPERATURE RANGE

DEFINITION FOR TC652

(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)

© 2002 Microchip Technology Inc.

TC652/TC653

TABLE 3-2:

TEMPERATURE RANGE

DEFINITION FOR TC653

(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 tempera-

ture thresholds are pre-defined in the TC650/651 by means

of trimming. Once a TL and TH are programmed, the T1 - T4

thresholds are automatically equally spaced between TL and

TH.

FIGURE 3-1:

FUNCTIONAL BLOCK

DIAGRAM

VDD

TOVER

SHDN

V+

Temperature

Set Point and

Trim Range

Duty Cycle

Logic

Control

-

PWM

AD Converter

Temp Sensor

Fan Detect

Logic

Oscillator

CMPTR

20k

90mV

-

FAULT

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 TC652 and

50% to 100% for the TC653.

DS21453B-page 5

Share Link: