INA240-Q1: Gain <20

Hi Shinji,

no, this is not possible.

Have you thought about decreasing the shunt by a factor of two?

Kai

Hi Kai-san, Guang-san,

Thank you for your reply.

Could you advise what is the drawback of reducing gain externally?

If I can accept the drawback, is it technically feasible to reduce gain externally?

Since the resistance I measure is MOS FET on resistance, I cannot change the shunt resistance.

regards,

Hi Tsuji-san,

The system gain is reduced by external resistors Rs. The calculation is described in this paragraph:

There are a few drawbacks, the main one is that calculated gain is nominal value; the actual gain may be off by a significant percentage. This is because the internal resistors (3000Ohm) have a tolerance of 15%. The external resistor tolerance also contributes to the uncertainty. You may estimate the worst cases to see if the uncertainty is acceptable.

Regards, Guang

Hi Guang,

If I chose Rs=3000ohm, then the Gain error = 50%.

Does it mean I can reduce the gain by 50% from original gain?

If I consider 15% internal resistor tolerance and 1% external resistor tolerance,

it should be 46% to 53%?

I plan to use 20V/V device and reduce down to 10V/V.

In this case, if I select Rs=3000ohm, then I can get 9.2V/V to 10.6V/V?

Is my understanding correct?

regards,

Hi Shinji,

but you could put a low ohmic shunt in parallel to the MOSFET's Ron :-)

Kai

Hi Tsuji-san,

Your calculations are correct considering the extremes, the expected gain would span 9.14 to 10.75.

Regards, Guang