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INA745: Using EZ-shunt device with parallel external shunt

Renan Santos Adriano
Mastermind 23420 points
Part Number: INA745
Other Parts Discussed in Thread: INA780B, INA238, INA228

Hello Experts,

Posting on behalf of my customer:

Is it safe to add one or more parallel external shunt resistors with one of the EZ-shunt devices such as INA745?  The device has an internal 0.8mOhm shunt and is rated for ~40A max full-scale. Hypothetically, could I add a parallel 0.8mOhm resistor and effectively get 80A full-scale, or add a second resistor and get 120A, and so on?  The only downside I can think of is that the accuracy would be lower. 

Regards,

Renan

  • 0
    TI__Expert 5995 points

    Hi Renan,

    You can not add parallel resistors to our EZ-shunt devices. The internal resistance in those devices varies a lot over temperature and we therefore have temperature compensation circuitry to account for this. You will not be able to match our internal resistance with an external parallel shunt.

    If you are needing more current range you have some options. The INA780B is an EZ-shunt that can do ±75A.

    The INA228 (or INA238 but this has no accumulation registers) have similar specs as the INA745 and can be used and you can choose the shunt value you want based on the max current range you expect.

    Another option is to link two INA745s together.

    Best,

    Holly