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Attiny1606 burning out when controlling a drv8251

lavaman

Apr 20, 2024
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I meant that the inputs of the drv are connected to pins PA3 and PA4 of the attiny. Unfortunately i can not send the updated schematic, as i dont have acces to it right now, i am at school.
 
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lavaman

Apr 20, 2024
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This is the updated schematic, hope it helps. As soon as i will be able to edit the schematic directly i will post it here.
 

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Bluejets

Oct 5, 2014
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According to the specs you still have insufficient voltage level for the DRV8251.
 

lavaman

Apr 20, 2024
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Do you mean the motor voltage? In testing I also tried plugging in 11V, with the same result.

I feel like i have tried everything. Separately everything seems to work fine, but when connected together it stops working.
I think the only option i havent tryed yet is changing the reference voltage. Not sure if that would make a diffefence.
 
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Harald Kapp

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Do you mean the motor voltage?
I'm pretty sure this is not what @Bluejets meant. Obviously you expect a logic High level at the B-input of the drv chip - whatever this input is.
But you get only 0.2 V (post #17). This has absolutely nothing to do with the motor voltage or the reference voltage.

By the way: you really need to be more concise. In your schematic the inputs of the drv-chip are IN1 and IN2, there is no "B-input". Also be careful which pins are inputs or outputs. Otherwise you leave us perplexed.

Separately everything seems to work fine,
Looks like the output of the attiny is overloaded and therefore can't drive the drv-chip to a logic High level. This can happen when the current from the output of the attiny to the drv-chip is too high. Without the drv-chip there is no current and then the attiny can drive the output to logic-High.

the other (input B) cannot be controlled at all and is constantly pulled down, probably by the integrated pulldown resistors of the drv.
This is unreasonable. The pull-down resistor is 100 kOhm, this will not overload the Attiny's output. If it would, the same thing would happen to the other input, which it doesn't.

On the pcb it is correctly wired.
As much as you may dislike it, a fault in the wiring on the PCB is a real possibility. Have you checked that the outputs of the attiny are not short-circuited to any other signal or supply voltage? Even if the design is correct, a fault in the manufacturing process may leave a very thin trace that creates a short circuit.
What happens, wehn you remove the attiny, then connect a 5 V supply voltage to the signals PA2 or PA3 (not simultaneously, one after the other)? I assume you have a multimeter and can measure the current going into these signals ?
 

lavaman

Apr 20, 2024
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It finally works. Turned out to be a problem with the voltage regulator as it is rated only for 100mA max it couldn't deliver enough power for the drv reference and power the attiny. Not sure why it was causing this kind of problem, but after exchanging the old regulator (MCP1792T-3302H/CB) for a new one (AP2210N-3.3TRE1, rated for 300mA), I just seemed to have to laying around, everything works just fine. No overheating, no other problems. Thanks for your help, I really appreciate it.
 
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