THMC45 Datasheet, PDF (1/16 Pages) Texas Instruments – 5-V AND 3.3-V DC BRUSHLESS FAN MOTOR DRIVER WITH SINGLE WIRE CONTOL

THMC45
5ĆV AND 3.3ĆV DC BRUSHLESS FAN MOTOR DRIVER
WITH SINGLE WIRE CONTROL
SLIS101A − MAY 2001
D 5-V DC Fan Motor PWM Drive for Speed
Control With No External Power Drive
Stage Required
D High Efficiency H-Bridge Topology With
Integrated Low R_DSON MOS Output Drivers
to Drive Single Winding, Bipolar Wound,
Two-Phase BLMs
D Digital PWM Input to Control Output PWM
Frequency and Duty Cycle—Suited for
Cooling Fan Applications Requiring
Variable RPM Control to Reduce
Noise/Increase MTBF
D Single Wire RPM Control, Tachometer
Feedback Signal, and Locked Rotor Detect
Feedback Signal
D Low Current Sleep State
D Tachometer Signal Valid Over Entire RPM
Range
D Noise Immune Signal Conditioning to Allow
Use of Low Cost Hall Effect Position
Sensor
D Locked Rotor Protection With Auto Retry
D Thermal Shutdown Protection
D 8-Pin MSOP PowerPad Package Suited
for Small Fan Circuit Board and Rotor
Housing
V_PWR
OUTA
OUTB
GND
DGN Package
(TOP VIEW)
1
8
2
7
3
6
4
5
PWM
H−
H+
TACH
description
The THMC45 is a dc brushless motor (BLM) driver and control device designed for use with low-voltage (5 V
or 3.3 V) dc cooling fans having two-phase motors with a single-winding stator. The device includes a
high-efficiency H-bridge pulse width modulation (PWM) drive topology with integrated MOS high-side and
low-side drivers, plus a PWM control input stage to provide the industry’s first efficient speed control solution
inside low-voltage dc cooling fans. This solution eliminates the need for any power drive components on the
main system board, reducing printed-circuit board (PCB) component count, PCB space, and assembly time.
The device also offers two advantages over the other commonly used fan speed control methods, adjustable
external dc supply voltage and adjustable external PWM drive duty cycle.
Unlike the external linear voltage regulation method, the THMC45 high-efficiency PWM drive method adjusts
the level of motor winding power while all other circuitry inside the fan obtains a fixed dc voltage from the fan
supply. This eliminates problems with loss of headroom to internal control circuitry at low fan supply voltage and
the resulting limitation of low-speed operation of 40% that is typically associated with external dc voltage
regulation. The high-efficiency PWM drive method employed by the THMC45 reduces fan supply power
consumption and maximizes full-scale RPM speed over the external linear voltage regulation method, which
has V × I power loss due to the voltage drop across the regulator.
The THMC45 includes a Hall sensor amplifier and signal conditioning, global thermal shutdown, and locked
rotor protection with automatic restart after a locked rotor condition. The device provides a sleep state to
eliminate the need for an external power component to disconnect the fan from the supply during a system sleep
state. The device also has internal reverse blocking capability to prevent excessive reverse leakage current due
to reversal of power line. The THMC45 is primarily designed for 5-V dc notebook PC cooling fan applications
that require single-wire RPM speed control and tachometer feedback. However, with an open-drain tachometer
output, the device is also suitable for applications that require two wires for RPM speed control and tachometer
signal.
Please be aware that an important notice concerning availability, standard warranty, and use in critical applications of
Texas Instruments semiconductor products and disclaimers thereto appears at the end of this data sheet.
PowerPAD is a trademark of Texas Instruments.
PRODUCTION DATA information is current as of publication date.
Products conform to specifications per the terms of Texas Instruments
standard warranty. Production processing does not necessarily include
testing of all parameters.
Copyright  2001, Texas Instruments Incorporated
• POST OFFICE BOX 655303 DALLAS, TEXAS 75265
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