DRV8811 heating problem

Hi Pankaj,

Based on your description, the likely cause is overtemperature. If the device overheats, the outputs will disable until the junction cools down. Overheating can be cause be a poor connection to the thermal pad, or loss of current regulation.

Do you have a solid connection to the thermal pad? If you do, there are a few things to try.

If you have a current probe, please look at the current waveforms to confirm proper current regulation. If you do not, you can monitor the current across the sense resistor with a scope to determine proper current regulation.

If current regulation is incorrect,
Please try VDECAY at <0.5V. This will reduce the average current.
Next try SRn = 1. This will further reduce the average current, but may add heat since the current decays through the body diodes.

Hello,

thanks for the reply.
>Do you have a solid connection to the thermal pad? If you do, there are a few things to try.

I am sure that DRV is properly connected to the thermal pad.

I don't have a oscilloscope. I have properly mounted a 100mE resistors at ISENA and ISENB. 

>If current regulation is incorrect,
>Please try VDECAY at <0.5V. This will reduce the average current.
>Next try SRn = 1. This will further reduce the average current, but may add heat since the current decays through the body diodes.

As you have suggested, I kept VDECAY at 0.3V and with both SRN conditions( SRN=1 and SRN=0), I checked the performance of DRV. But It is getting too hot with only 5 to 6 rotations of motor. With VDECAY=1.6V the DRV shows little bit good performance. It takes more than 10 rotations of motor without any thermal shutdown.

Hi Pankaj,

Without an oscilloscope, it will be difficult to determine if the current is being regulated properly.

You can try lowering VREF, which should reduce the current.