Current Sensing Nanoampere

Jose Manuel Vidal Rico15

Other Parts Discussed in Thread: INA110, OPA192

Hello,

I want to measure the current that consume my circuit. This circuit normally consume a few mA (10mA-80mA) during a small interval time and then go to deep sleep and consume around uA (0.8uA-5uA). The voltage would be between 5V and 1.8V.

I want to design a circuit that allow me to measure that current with a bandwidth of 350 KHz. I do not going to use an ADC I want to use the oscilloscope with a resolution of 1mV/division, so I do not need a great gain.

I was taking a look to your products but there are not any application note about that.

Do you recommend me some IC for that propose?. Do you know if exist some application note about that?.

Thank in advance.

Jose.

over 7 years ago

0 Carlos Silva85 over 7 years ago

TI__Expert 4915 points

Hi Jose,

I will discuss with the team on Monday. For the uA currents you will require a high speed opamp, our current sense amplifiers can't go that low.

0 Jason Bridgmon over 7 years ago in reply to Carlos Silva85

TI__Genius 14825 points

Jose,
The input bias currents of our current shunt monitors (say, 20uA per input) dwarf your sleep current, so when you part is sleeping at .8uA, the current shunt monitor would be pulling around 40.8uA from the supply. Also, it would be measuring at least 20.8uA through the shunt resistor, giving you 2600% error. It would be best to look into a device with low input bias currents, so I have informed a colleague of mine who supports instrumentation amps to look into this question for you.

0 Jose Manuel Vidal Rico15 over 7 years ago in reply to Jason Bridgmon

Intellectual 526 points

Thanks to both of you. I will waiting a good news asap.

BR.

Jose.

0 Jose Manuel Vidal Rico15 over 7 years ago in reply to Jason Bridgmon

Intellectual 526 points

Hello guys,

Do you have some news about this question?.

BR.

Jose.

0 Carlos Silva85 over 7 years ago in reply to Jose Manuel Vidal Rico15

TI__Expert 4915 points

Hi Jose,

I'm working on a solution and should get back to you early next week. Thank you for your patience on this matter.

0 Errol Leon6 over 7 years ago

TI__Expert 5830 points

Hello Jose,

Given the specifications, INA110 has a flat bandwidth (2.5MHz) of at a gain of 10 as well as low Ib(20pA typical) and broadband noise(10nV/rtHz). For applications notes, I am not aware of any applications notes that address measuring nanoamperes.

Best,

Errol Leon
Texas Instruments
Precision Op Amps Applications

0 Jose Manuel Vidal Rico15 over 7 years ago in reply to Errol Leon6

Intellectual 526 points

Hello Errol,

Thanks for your swift reply.

This is one of the most expensive O.A. that TI have xD

Do you have evaluation board of INA110?. Do you recommned me some application note in order to develop current shunt resistor as grounding, shielding, cables, return path, etc...with this IC or similar?.

Thanks in advance.

Jose.

0 Errol Leon6 over 7 years ago in reply to Jose Manuel Vidal Rico15

TI__Expert 5830 points

Hello Jose,

We do not have an evaluation board for the INA110. Here are 2 TI designs that might be useful for current shunt monitoring.

http://www.ti.com/tool/tipd104
http://www.ti.com/tool/TIPD135

One other possible solution would also be to build a discrete INA with JFET input Op Amps such as OPA192.

Best,

Errol

Amplifiers

Amplifiers forum

Current Sensing Nanoampere