Compiler: DRV8841 OUTPUT out of sync

user4099176

Other Parts Discussed in Thread: DRV8841, DRV8847

Tool/software: TI C/C++ Compiler

Hello,I input 3 channel PWM. I found input is sync,but out of sync aftern DRV8841.There is one output deviation of about 2 microseconds.

What can I do make output sync,because I want to output 3 channel with center PWM.

Thanks very much!

over 5 years ago

0 user4099176 over 5 years ago

Intellectual 265 points

I found the A and B output is not sync.

And the Bout is delay about 4us from IN.the Aout is delay about 1.5us from IN.Why the delay is different?

0 Wang5577 over 5 years ago in reply to user4099176

TI__Guru 56650 points

Hello,

DRV8841 doesn't support paralleling operation between different half bridges. Also, the load in general has a large inductance.

What application do you have? Why does it require the synchronization?

Some of devices can support half bridge's paralleling operation, such as DRV8847. It can support half bridge's FETs switching at same time.

0 user4099176 over 5 years ago in reply to Wang5577

Intellectual 265 points

because I want to output wave look like the picture. I think it need sync for A、B、 C with PWM。

Best Regards,

0 Wang5577 over 5 years ago in reply to user4099176

TI__Guru 56650 points

Hello,

There is no timing spec in DRV8841 datasheet. Basically, you have to give long PWM cycle time to ignore the propagation delay if you use DRV8841.

DRV8847 and some new release devices provide the propagation delay in the spec.

0 user4099176 over 5 years ago in reply to Wang5577

Intellectual 265 points

hello,I don't mind the tpd,but I don't understand why tThe relative delay of A and B so much(about 2.5us).

The hardware dictates that B is much longer delayed than A?

and I test L6205,it can sync for 4 channel output.

Best Regards,

0 Wang5577 over 5 years ago in reply to user4099176

TI__Guru 56650 points

Hello,

What application needs A bridge delay matches B bridge delay?

0 user4099176 over 5 years ago in reply to Wang5577

Intellectual 265 points

hello,

Iwant to output svpwm.if one channel out delay likes the red wave.it make the Actual value range <Tpwm(look like green).and the effect affter(t0-t7) will not be match
the theory .

Best Regards,

0 Wang5577 over 5 years ago in reply to user4099176

TI__Guru 56650 points

Hello,

DRV8841 is designed for brushed DC motor and stepper motor, not servo motor. That may be why the A-bridge and B-bridge delay is different.

back to the original recommendation, if tpd is short (such as DRV8847), the delay mismatch number should be smaller tpd_maximum-tpd_minimum which is 500ns.

Comparing L6205, it only has 1.6us typical delay time. It is hard to guarantee the delay mismatch between different half bridges.

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Compiler: DRV8841 OUTPUT out of sync