The description web page for the md01b states that at 6A the chip will not be noticeably warm but my chip gets VERY hot with less than 1A. I’ve scoped my pwm signal and it is exactly 10KHz. My MOTA-MOTB signals are always 90 degrees out of phase. Voltage is 17.5. Not sure what else I could be doing that would cause the module to run so hot. Any suggestions?
-rob
Hello,
The 6 A observation was at 12 V with 100% duty cycle (i.e. no switching losses). Unfortunately, the VN3SP30 has some shoot-through problems (both MOSFETs on the same side of the H-bridge briefly being on simultaneously) that start showing up at higher voltages, and especially with the 10 kHz switching rate, that extra current adds up, and 100% of it gets dissipated by the chip. The only workarounds are to lower the PWM frequency or the voltage. If you can get by with 16 V and want high-frequency PWM, the VN2SP30 is much better, so I’d recommend that. If you need higher voltage but don’t need that much current, the Freescale MC33887 might work better for you, too.
- Jan
Rats! I should have asked more hard questions before buying and interfacing to this board. I was hoping to drive a 100 watt DC brushed servo at 24V.
-rob
Lowering the pwm does solve the heating issue but, in my case, results in unacceptable levels of high pitched noise.
We don’t know of any good high-voltage, high-power integrated solutions (lots of the good stuff is automotive and targeted at 12 V), so we are working on a discrete h-bridge solution that will offer the kind of performance you’re looking for. Unfortunately, that probably won’t be out for a few months.
- Jan
