ROHM BD6721FS Technical Note
Summary
The BD6721FS is an advanced, multifunctional motor driver optimized for controlling brushless DC fan motors in consumer electronics. This comprehensive manual details its H-bridge architecture, including features like PWM speed control, current limiting, soft switching, and lock alarm protection. It provides all necessary technical specifications (including pinouts and operating ranges) for engineers integrating reliable cooling solutions into devices such as desktop PCs and projectors.
Page 1 Text Content
Datasheet
DC Brushless Fan Motor Drivers Multifunction Single-phase Full-wave Fan Motor Driver BD6721FS
●General description ●Package W (Typ.) x D (Typ.) x H (Max.) BD6721FS is a 1chip driver that composes H-bridge of SSOP-A16 6.60mm x 6.20mm x 1.71mm power DMOS FET. Moreover, because the level amplifier is installed, the temperature control by the thermistor is also easy.
●Features Driver including power DMOS FET Speed controllable by DC / direct PWM input PWM soft switching Quick start Current limit Lock protection and automatic restart Rotation speed pulse signal (FG) output
Lock alarm signal (AL) output SSOP-A16
●Application Fan motors for general consumer equipment of desktop PC, and Projector, etc.
●Absolute maximum ratings
Parameter Symbol Limit Unit
Supply voltage Vcc 20 V Power dissipation Pd 812.5 *1 m W Operating temperature range Topr –40 to +100 °C Storage temperature range Tstg –55 to +150 °C Output voltage Vo 20 V Output current Io 1.0 *2 A Rotation speed pulse signal (FG) output voltage Vfg 20 V Rotation speed pulse signal (FG) output current Ifg 10 m A Lock alarm signal (AL) output voltage Val 20 V Lock alarm signal (AL) output current Ial 10 m A Reference voltage (REF) output current Iref 8 m A Junction temperature Tj 150 °C *1 Reduce by 6.5m W/°C over Ta=25°C. (On 70.0mm×70.0mm×1.6mm glass epoxy board) *2 This value is not to exceed Pd.
●Recommended operating conditions
Parameter Symbol Limit Unit
Operating supply voltage range Vcc 4.5 to 17.0 V Operating input voltage range
0 to 7 V
(H+, H–, TH, MIN, LAIN) (more than Vcc=9V)
Operating input voltage range
0 to Vcc–2 V
(H+, H–, TH, MIN, LAIN) (less than Vcc=9V)
○Product structure：Silicon monolithic integrated circuit ○This product is not designed protection against radioactive rays www.rohm.com
TSZ02201-0H1H0B100170-1-2© 2012 ROHM Co., Ltd. All rights reserved.
TSZ22111・14・001 28.JUL.2012 Rev.002
Page Summary Contents For ROHM BD6721FS Technical Note
Manual Details
| Brand | ROHM |
|---|---|
| Pages | 16 |
| File Size | 563.04 KB |
| Published | July 12, 2026 |
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Frequently Asked Questions
How can I control the rotation speed of a fan motor using this driver?
The motor speed can be controlled by applying a direct PWM (Pulse Width Modulation) DC input.
What voltage range should I use for reliable operation?
The recommended operating supply voltage range (Vcc) is 4.5 V to 17.0 V.
How does the unit handle situations where the motor stops or locks?
It includes lock protection and outputs an AL signal; this output indicates if the motor is locking up.
Are there different wiring protocols depending on the supply voltage (Vcc)?
Yes, if Vcc is less than 9V, the input uses H+, H–, TH, MIN, and LAIN; if Vcc is greater than 9V, it must be within 0 to Vcc–2 V.