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# INA210-Q1: Regarding Capacitive load, Quiescent current

Part Number: INA210-Q1
Other Parts Discussed in Thread: INA213-Q1, , INA210, INA190, INA191, INA186
I would like to know about your part INA213A-Q. Our requirement is to sense 0-50mA. we are using your part INA210-Q1 /INA213-Q1 for our application. Power Supply is 16V battery Voltage. Aim is to detect 7mA, 14mA, 21mA, 30mA, 0mA.
1) Could  you show you cover this specification?  Please kindly review our schematics. Also I would like to know about the stability of the INA210 with  Capacitive load ?
2) What is the Quiescent current for sensing of 0-50mA ?
Regards,
Grace
• Hello Grace,

Thanks for posting to the forum. Hope we can quickly help you.

It's hard to read what the shunt resistance is (R803) in your schematic, but the INA21x should be able to distinguish the current levels you want given the proper shunt resistance value. If your shunt is 820 mOhm, then at 7mA, VOUT = 0.82*0.007*50 = 0.287V and this is well within VOUT linear range.

1. The INA210-INA215 has operation common-mode voltage (VCM) range 0V to 36V. It can survive a VCM range of GND-0.3V to 26V (Version A) or GND-0.1V to 26V (Version B and C). So we do cover this specification. You can determine operational range from the specification table and the survival range from the Absolute Maximum Ratings table.

As for the capacitive load, we specify a maximum 1nF capacitive load with no sustained VOUT oscillation. Your schematic shows a 100nF with not isolation resistance to isolate VOUT and 100nF load (C807). So as it stands now, your system will not be stable and VOUT will show oscillation. Unfortunately, we do not have a data plot to show closed-loop output impedance (ZOUT), but experimenting with Riso values of 100-Ohm, 500-Ohm, and 1-kOhm should be enough to determine what level of isolation is needed.

2. The quiescent current (IQ) for sensing 0-50mA depends on what the output current (IOUT) from the VOUT pin is. If you are driving a low-resistance load (small resistor off UC_SENS2_LVL to ground), then this current will be directly sourced from your VCC_5V0 node. So total current consumed by INA21x from VCC_5V = IQ + IOUT. So current sunk into INA21x V+ pin is not dependent upon the input sensing (or input differential shunt voltage).

You can read more about currents consumed and see data for various devices (including INA21) here in this application note:

For your system, since you have no resistive load (even with Riso), you will have no DC IOUT. now if there is some input step response and VOUT changes quickly, there will be some momentary IOUT current to charge the 100nF cap, but that will be it.

Hope this helps.

Best,
Peter Iliya

• Hello Peter,

Thank you very much for the reply. I would also Iike to know how could we protect the amplifier against +/-8kV ESD ( 330pf and R 2kOhm?). Do you have any suggestions?

Regards,

Grace

• Hey Grace,

We have an reference design/analysis on protecting the INA210 from high-voltage ESD surges here:

http://www.ti.com/lit/ug/tidu473/tidu473.pdf

While 2kOhm can certainly limit the current that would go into the IN+/IN- pins, this will add significant gain error. Ultimately you will still want to use TVS diodes at the inputs as this will provide the most protection to these ESD events.

The INA190, INA186, and INA191 are other current sensing solutions that have slightly better performance than INA210 and low IQ. They also have high input impedance so you could use 2kOhm input resistors in a protection scheme and sacrifice much less gain error (3 orders of magnitude) compared to using 2kOhm input resistors with INA210.

Sincerely,

Peter Iliya

• Hey Grace,

In addition to the input protection needed for +/-8kV ESD strikes, please consider using the B and C versions of INA210. These versions have ESD structures that are different from the INA210Ax version. The B and C version devices have ESD cells which are less susceptible to latching up to very fast common-mode voltage transients. They still need input protection however. You can read about these different versions in 7.4.5 of INA210 datasheet.

Sincerely,
Peter Iliya