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DRV595: Selected doesn't match with expected gain.

Part Number: DRV595

Hello,

i was alpha testing our new hardware and realized that the selected gain wasn't matching with our expected gain at all. However, the datasheet doesn't really tell how to calculate the output values in reference to the input values at all, so I was expecting that it should be simply "G = 10 * log(Pout/Pin)" where G is 20db (Pout is the output and Pin is the input power). The datasheet tells if you select 20db gain in Master-Mode, you'll have an differential input resistance of 60kOhm (Page 10: Table 1. GAIN and MASTER/SLAVE, I assumed the differential part). Therefore the new equation is "G = 10 * log(Pout * Rin / dUin²)" (Rin --> differential input resistance, dUin --> differential input voltage).

Now I fixed the IN- Pin to 2.5V and set the IN+ Input to 2.6V. After that I could measure an output current of 0.583A and an differential output voltage of 1.049V. When I put those values in the equation above, I get around 65.65db as gain. 

Have I maybe made the wrong assumptions?

Regards,

Andreas