help me in designing a bldc driver..!!

The problem with disabling internal PWM is that overcurrent detection is disabled.

See what happens in your application when PWM input is tied high, using PWM on the coast input to control speed. I'd start with a PWM freq just above audible.

Thread Starter


Joined Jan 13, 2015
1. Internal current control is not at all working. Even I tried with zero,1,2 amp current ref.
2. If I apply load to the motor it stops without drawing much current (much lesser than one set by the current ref). and then to start it again everytime I have to reset the system by switching OFF main supply.
3. motor doesn't start directly even with duty cycle of 50%(Vbb=12V). but if I start from zero and go on increasing it runs upto 90%(Vbb=12V) ,75%(Vbb=18V), 65%(Vbb=20V). motor is rated for 24V and 300W

Thread Starter


Joined Jan 13, 2015
Hello everyone

now I designed a new pcb and followed the layout of allegro's a3930/31 (both are same as per datasheet) demo board. But still I am having some problems-
1. Motor doesn't start on its own
2. Now motor can run with full pwm of 100% with 10khz freq but torque is very less.
3. I am hard wiring the digital inputs like brake=1, coast=1, ESF=1, and mode=1. With this configuration motor takes current of more than 4amp (motor rating is 24V and 300watts). But fault led F1 is continuously ON.

can somebody suggest me the exact modification . ??

Attached is the schematic of demo board from allegro. The only difference between this schematic and my schematic is



Joined Apr 29, 2015
i think he is shorting Rsense in this video for more current means more power i'm not an expert but this is what i found >>>>>>>>>>>>>>>>>I REALLY WANNA SAY THANKS TO FOR THIS DEMO BOARD DIAGRAM i have also two of this chip and now i found diagram thanks i helped me a lot by the way is it original diagram from allegro or it is made by u ?and where can i find allegro systems another chips demo board pcb and diagram thanks alot !