drv8220drlr exploding, when powering a DC motor - Page 1
Forum section: electronics / projects

author: lavaman
author_rank: Contributor
timestamp: June 25, 2023, 05:14:52 pm
content: Hi, I am working on a DCC decoder, all things seem to be working fine, except the motor driver. When i wanted to test it on a 100% duty cycle, in the moment i connected it to the motor, it blew up leaving a hole in its case. The board itself continued to function normally no damage was done to other components, only the DRV8220. When i measured the output voltage of the burnt driver it was 0v. Can someone please help me resolve this problem? The driver is the only thing stopping me from completing this project. The motor I used is a regular dc motor for model railway trains. Power supply used was 16v dc. In normal operation, the power supply would be a 16v data line which will get rectified, the signal isolated and processed by the attiny.Thanks in advance.

author: DavidAlfa
author_rank: Super Contributor
timestamp: June 25, 2023, 05:24:55 pm
content: Maybe a short between VM and one of the outputs?Did it work before?

author: lavaman
author_rank: Contributor
timestamp: June 25, 2023, 05:29:03 pm
content: I don't think that is what happened. The only thing I did was connect the outputs of the driver to the motor. This circuit is working except for the H bridge IC. Before I fully tested only a proof of concept built with other components on a bread board. This is an PCB designed to fit in model trains.

author: NiHaoMike
author_rank: Super Contributor
timestamp: June 25, 2023, 08:16:21 pm
content: Add additional capacitance from VM to ground to suppress inductive spikes.

author: Benta
author_rank: Super Contributor
timestamp: June 25, 2023, 08:28:05 pm
content: The DRV8220 is almost impossible to kill.Silly question, but... are you certain you mounted it in the correct direction?

author: lavaman
author_rank: Contributor
timestamp: June 25, 2023, 08:44:26 pm
content: The additional capacitance on the Vm pin is a good idea, but I don't think that is the cause of the problem. Yes, I mounted it correctly, before i connected the motor i tested the outputs and tested the PWM with LED. All seemed to be fine, so I proceeded with connecting the motor, which killed the DRV.

author: SiliconWizard
author_rank: Super Contributor
timestamp: June 25, 2023, 10:40:57 pm
content: Quote from: lavaman on June 25, 2023, 08:44:26 pmI can't say for sure that it is, of course, but it's not something I would rule out.Quoting the datasheet:QuoteWe're talking about the internal charge pump, and if it's not stable enough, I wouldn't be surprised if that could kill internal transistors due to having transients during which both transistors of the same half-bridge would short the power supply and blow up. The chip is well protected, but probably not against a dodgy behavior from the charge pump.

author: lavaman
author_rank: Contributor
timestamp: June 26, 2023, 04:42:53 am
content: What if I put a PPTC in front of the motor. wouldn’t that work in combination with installing capacitors between gnd and Vm and output pins of the driver.

author: Tnixsw
author_rank: Contributor
timestamp: June 26, 2023, 11:36:30 am
content: For the chip to "blow up" would mean some large inductive spike or high current flow. The DRV IC is supposed to have over current and over temp protection, so I would imagine you could connect up a car starter motor and it may just shut down because of the load. For the spikes, that may be a different matter.What sort of current does the motor use?Is there any heat sinking for the device?How long are the leads to the motor.Are you sure your software is driving it properly, maybe causing many start and brake cycles leading to spikes. The LEDs will not give much of a problem here, but a high current motor might.Capacitor selection for the device is outlined in section 11 of the data sheet.

author: CaptDon
author_rank: Super Contributor
timestamp: June 26, 2023, 12:21:06 pm
content: Are you sure this whole thing can run from steady D.C.? DCC on the model rails is never D.C., it is A.C. with varying duty cycle. Also, depending on the charge pump design you can only expect safe operation between 5% to 95% 'on' time. When you exceed those numbers the high side H-bridge FET begins to lose gate drive, goes linear and burns up. At 100% on-time I would expect possible failures at motor current levels, you may have gotten away with it just driving your LED. The DCC design has a 50/50 duty cycle on the rails at rest with about 16 to 19 A.C. volts very nearly a square wave. An old D.C. motor train will sit idle with its lights lit. When controlling the old D.C. train the motor is integrating the A.C. duty cycle and when it shifts one way or the other from 50/50 the motor begins to see it as a shift toward D.C. I am not sure you DCC motor controller will work on a D.C. only input voltage? It may need the A.C. waveform of the DCC control standard to operate or clock internal charge pumps for the H-bridge hi-side FET's??

author: DavidAlfa
author_rank: Super Contributor
timestamp: June 26, 2023, 01:12:26 pm
content: From the datasheet:Quote

author: thm_w
author_rank: Super Contributor
timestamp: June 27, 2023, 12:22:06 am
content: Quote from: lavaman on June 26, 2023, 04:42:53 amThat is only going to help if the motor shorts out somehow.Start with the recommendation SiliconWizard has given you, the eval board uses 44uF:https://www.ti.com/lit/ug/slou540a/slou540a.pdf?ts=1687825095632Then maybe consider a ~10nF capacitor across the motor if you are worried about EMI issues (I think thats what you meant by output pins).QuoteIf you are rectifying an AC source, you might need even more input capacitance for smoothing.

author: ArdWar
author_rank: Frequent Contributor
timestamp: June 27, 2023, 01:20:17 am
content: Start with supplying +12V with a stable power supply, not DCC, and see if it's working properly.