2002 Microchip Technology Inc.

DS21450B-page 1

TC650/TC651

Features

· Integrated Temperature Sensing and Multi-speed

Fan Control

· Built-in Over Temperature Alert (T

OVER

)

· Temperature Proportional Fan Speed Control for

Acoustic Noise Reduction and Longer Fan Life

· Pulse Width Modulation Output Drive for Cost and

Power Savings

· Solid-State Temperature Sensing

· ±1

C (Typical) Accuracy from 25

C to +70

· 2.8V 5.5V Operating Range

· TC651 includes Auto Fan Shutdown

· Low Operating Current: 50

A (Typical)

Applications

· Thermal Protection For Personal Computers

· Digital Set-Top Boxes

· Notebook Computers

· Data Communications

· Power Supplies

· Projectors

Related Literature

· Application Note: AN771

Device Selection Table

The "X" denotes a suffix for temperature threshold settings.

Contact factory for other temperature ranges.

Package Type

General Description

The TC650/TC651 are integrated temperature sensors
and brushless DC fan speed controllers. The TC650/
TC651 measure their junction temperature and control
the speed of the fan based on that temperature, making
them especially suited for applications in modern
electronic equipment.

Temperature data is converted from the on-chip
thermal sensing element

and

translated

into

fractional fan speed from 40% to 100%. A temperature
selection guide in the data sheet is used to choose the
low and high temperature limits to control the fan. The
TC650/TC651 also include a single trip point over
temperature alert (T

OVER

) that eliminates the need for

additional temperature sensors. In addition, the TC651
features an auto fan shutdown function for additional
power savings.

The TC650/TC651 are easy to use, require no software
overhead and are therefore the ideal choice for
implementing thermal management in a variety of
systems.

Part Number

Package

Temperature

Range

TC650XXVUA

8-Pin SOIC

-40

C to +125

TC651XXVUA

8-Pin MSOP

-40

C to +125

Temperature

PWM

GND

OVER

GND

8-Pin MSOP

TC650

TC651

SHDN

8-Pin SOIC

Tiny Integrated Temperature Sensor & Brushless DC Fan

Controller with Over-Temperature Alert

2002 Microchip Technology Inc.

DS21450B-page 3

TC650/TC651

1.0

ELECTRICAL
CHARACTERISTICS

Absolute Maximum Ratings*

Input Voltage (V

to GND) ................................... +6V

Output Voltage (OUT to GND) ................................. 6V

Voltage On Any Pin ....... (GND 0.3V) to (V

+ 0.3V)

Package Thermal Resistance (

)

.............. 250

C/W

Operating Temperature Range .......... -40

C to +125

Storage Temperature ......................... -65

C to +150

*Stresses above those listed under "Absolute Maximum Rat-
ings" may cause permanent damage to the device. These are
stress ratings only and functional operation of the device at
these or any other conditions above those indicated in the
operation sections of the specifications is not implied. Expo-
sure to Absolute Maximum Rating conditions for extended
periods may affect device reliability.

TC650/TC651 ELECTRICAL SPECIFICATIONS

Note 1: Transition from 90% to 100% Duty Cycle.

Electrical Characteristics: V

= 2.8V to 5.5V, SHDN = V

, T

= -40

C to 125

C unless otherwise specified.

Symbol

Parameter

Min

Typ.

Max

Units

Test Conditions

Supply Voltage

2.8

5.5

Supply Current

PWM, T

OVER

are open

SHDN Input

SHDN Input High Threshold

SHDN Input Low Threshold

PWM Output

PWM Output Low Voltage

0.3

SINK

= 1mA

PWM Output High Voltage

- 0.5

SOURCE

= 5mA

PWM Rise Time

sec

= 5mA, 1nF from

PWM to GND

PWM Fall Time

sec

= 1mA, 1nF from

PWM to GND

OUT

PWM Frequency

STARTUP

Start-up Time

32/f

OUT

sec

Rises from GND,

or SHDN Released

Temperature Accuracy

H ACC

High Temperature Accuracy

+ 3

Note 1

)

ACC

Temp. Range Accuracy

-1.0

+1.0

- T

)

-2.5

+2.5

- T

)

HYST

Auto-shutdown Hysteresis

-T

)/5

TC651 Only

OVER

Output

HIGH

OVER

Output High Voltage

- 0.5

SOURCE

= 1.2mA

LOW

OVER

Output Low Voltage

0.4

SINK

= 2.5mA

OVER ACC

Absolute Accuracy

+ 10

At Trip Point

OVER HYST

Trip Point Hysteresis

2002 Microchip Technology Inc.

DS21450B-page 5

TC650/TC651

3.0

DETAILED DESCRIPTION

The TC650/TC651 acquire and convert their junction
temperature (T

) 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 (T

OVER

) that gives a low signal

when the temperature of the chip exceeds T

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)

TABLE 3-2:

TEMPERATURE RANGE
DEFINITION FOR TC651
(AUTO-SHUTDOWN MODE)

FIGURE 3-1:

FUNCTIONAL BLOCK
DIAGRAM

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

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

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 (T

OVER

)

This pin goes low when the T

set point is exceeded by

C (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 T

OVER

is asserted. Built-in hysteresis prevents

OVER

from "chattering" when measured temperature

is at or near the T

+ 10°C trip point. As temperature

falls through the T

+ 10°C trip point, hysteresis

maintains the T

OVER

output low until measured

temperature is 5°C above the trip point setting.

Temperature (T = T

)

PWM Duty Cycle

T < T

40%

< = T < T

50%

< = T < T

60%

< = T <T

70%

< = T < T

80%

< = T < T

90%

< = T < T

100%

< = T

100% with Over Temp Alert

OVER

= L)

Temperature (T = T

)

PWM Duty Cycle

T < T

"OFF"

< = T < T

50%

< = T < T

60%

< =T < T

70%

< =T < T

80%

< = T < T

90%

< = T < T

100%

< = T

100% with Over-Temp Alert

OVER

= 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 T

and T

are programmed, the T

thresholds are automatically

equally spaced between T

and T

Temperature Sensor

Duty Cycle

Logic

Control

A/D Converter

Oscillator

Temperature
Set Point and

Trim Range

SHDN

OVER

PWM

V+

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