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INA168: Useing large capacitor for filtering at OUT PIN

Moon Byoungsarm
Prodigy 10 points
Part Number: INA168

Hello, sir

Circuit : 

Input - 20-50V LED converter (especiallay, with 120Hz Current noise)

load - LED 70mA - 3A

Sensing R - 60m ohm

RL = 60.4k // 1uF

VCC - 5V

Result : 

ILOAD0 - UNIT FUNCTION 50V after 10msec

Output at OUT PIN : It's stable is OK(simulation and real testing)


Question:

I'd like know using large capacitor, 1uF to RL to make to unstable circuit.

Is there a way to check the impact on the satibiliztion of the chip by using a large capacitor at the output?

Thank you, sir,

Have a good time,

I'd like to know that INA168 

  • 0
    TI__Mastermind 21730 points

    Hello Moon,

    Thanks for considering to use Texas Instruments. I am looking into your question now and will try to have a response for you later today on this particular issue.

  • 0 in reply to Patrick Simmons
    TI__Mastermind 21730 points

    Hello Moon,

    I spoke with our design team about your issue.  It is one of our older parts and as such its list of specifications is not quite as comprehensive as our newer parts. We do not have any unpublished curves relating to a max output capacitor.  However, the design team did say this is an inherently stable topology.  They do not expect this device to have any stability issues for a capacitor on the output.  Additionally under the bandwidth  section of the datasheet including the from the original 1999 datasheet draft, they say that a output capacitor should not cause instability.

    If you have doubts, I might recommend placing a capacitor an order of magnitude larger than what you intend to design with and see if that causes any issues.  If it does not cause issues, our manufacturing tolerances should be tight enough to indicate this is not going to be an issue.  Alternatively, we do have an appnote that discusses how you can measure the device zout to extrapolate what value of impedance might lead to instability.  If you are interested in this approach, it can be found here.