DRV8842: Max current output

Hi Daniel,

It appears you're using this device as a DC power switch in your application. The two outputs are not designed for parallel operation for driving BDC motors because of potential shoot through possibility. However, in your circuit the inputs are tied to 3.3 V and will neve turn on the LS-FET so you not face this potential issue. The control looks to be via the ^SLEEP pin. 

Daniel Silva33 said:

Therefore, what current capacity can we obtain considering an input voltage of 12.5 volts?

This depends on the application ambient temperature TA and thermal capabilities of the system. Power dissipation due to FET conduction loss for DC would be I^2 x (HS-FET Rdson/2), divide by 2 for parallel FETs. With this power loss you can estimate the die temperature using RθJA specification in the datasheet. This temperature + TA temperature must be less than tTSD specification in the datasheet with some head room. This would define the expected current capacity.

For example if TA = 25 °C, I = 3.5 A, then conduction loss would be 3.5x3.5x0.1 (assuming 0.2 Ω for each FET which includes some derating) = 1.225 W. RθJA  = 31.6 °C/W, so estimated die temperature increase would be 31.6 x 1.225 = 38.7 °C + 25 °C for TA = 63.7 °C which is < tTSD MIN 150 °C. Note, in reality there are other losses in the IC that should be accounted for including Rdson derating for 3.5 A which may be higher than 0.2 Ω. Nonetheless DC conduction losses would be the dominant power loss for our application. I hope this helps. Thank you.   

Regards, Murugavel