I have some Diodes Inc.
ZXBM5210 motor driver ICs that I am experimenting with on breadboard, but I'm having some weird problems that I can't figure out. I have one hooked up in a circuit to a single small DC motor as per the diagram below.
The problem I'm having is two-fold:
1. When I drive the motor in reverse (switching pin 5 high), it will either immediately trip the over-current protection on my PSU (set to 700mA, which is normally plenty of headroom to run these particular motors on 12V), or will run the motor but with a frequent stutter.
2. When I drive the motor forward (pin 4 switched high), it will run the motor perfectly up until I stop, but then the IC starts drawing ~50mA of current from +5V (VDD pin), and any subsequent switching forward/reverse will immediately trip the over-current. Also, very occasionally, after a few 10's of seconds of the motor running fwd, OCP will suddenly trip, even though up until that point only around 150mA was being drawn.
The second issue in particular is puzzling me greatly.
The normal operating VDD current draw should be < 2mA when operating, and microamps when in 'standby' (i.e. not operating, both FWD & REV low). Could it be some form of latch-up?
Things I've tried:
- Another chip. No difference, both of them behave in the same way.
- Another identical motor. Also no difference, although the second one seemed to make it want to trip the OCP more than run but with stuttering.
- Adding pull-down resistors (10K) to the FWD/REV pins, in case maybe they were floating and intermittently causing both to be high, putting the driver briefly into 'brake' mode. I thought this might have explained the momentary stuttering, but didn't make any difference.
- Substituted the ZXBM5210 for an old L293E. Everything works perfectly with that and operates within the set 700mA current limit.
Things I'm worried may be impacting the situation:
- These ICs are SMD SO8 package, and for breadboarding I have them soldered to an adapter PCB with pin headers. The traces on these adapter boards are fairly thin - I estimate about 10 mil - but given there's only a few hundred mA at play, I thought it'd probably be okay, at least for testing. But maybe not?
- The diodes I'm using for flyback protection are only 'slow' 1N4007s. Normally I'd use a 1N5819 (or similar) schottky, but I don't have any right now. Have ordered some, though, to see if it makes any difference. But, they work fine for the L293E.
- Perhaps the chip may be getting too hot? But surely not with it only handling a couple-hundred mA at most steady-state?
Are any of those concerns?
So, I'm at a loss as to how to figure out what the problem is and need some help.
Anyone with any ideas?