Solution suggest for very low current sensing...

Peter Tseng

Mastermind 6450 points

Other Parts Discussed in Thread: INA190, INA228, INA238, INA293, LOG114

Hi Team,

May I have your suggestion for customer reuest.

They want to sense Min. current is 1uA and the Max. current is ~700mA.

Is there any solution suggest for customer?

Thanks.

over 2 years ago

0 Peter Iliya over 2 years ago

TI__Mastermind 32395 points

Hello Appreciate Engineer,

This is a difficult task because it covers a dynamic range of 700,000:1. You will either have to split up the current range into separate ranges with different amplifier responsible for different sections and/or switch out different resistors for different ranges.

One limiting factor is how much power you are will to dissipate at the 700mA level.

The INA190 is the best analog option to measure 1uA because it is high input impedance. See this circuit note.

The INA228, INA238 are good digital power monitors that can also measure small current and have good dynamic ranges.

The INA293 can use a 20V supply so it could be a good option for dynamic range at the hundreds of milli-Amps range; however, you would need to disable the device when load is low <1mA because of the 20uA input bias currents.

Other options are a logarithmic amplifier LOG114, programmable gain amplifiers, precise instrumentation amplifiers with adjustable gain is also another option where you can adjust gain setting resistors.

Here are some previous informative posts for similar question.

https://e2e.ti.com/support/amplifiers-group/amplifiers/f/amplifiers-forum/1020081/log114-dynamic-range-and-resolution

https://e2e.ti.com/support/amplifiers-group/amplifiers/f/amplifiers-forum/988330/ina226-wide-current-range-application-with-ua-precision-needs

https://e2e.ti.com/support/amplifiers-group/amplifiers/f/amplifiers-forum/796282/current-sensing-amplifier-solution

https://e2e.ti.com/support/amplifiers-group/amplifiers/f/amplifiers-forum/463720/high-side-6-decade-current-measure

Sincerely,

Peter