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TLV3603: Need help to calculate resistor value for Hysteresis

GAURAV UPADHYAY
Prodigy 100 points
Part Number: TLV3603
Other Parts Discussed in Thread: INA333,

Tool/software:

Hi,

Below thread will give you details about input of comparator:

https://e2e.ti.com/support/amplifiers-group/amplifiers/f/amplifiers-forum/1445400/ina333-need-help-in-hardware-design-guidelines-for-microvolt-v-signals

Please help me to determine the hysteresis resistor value.

Thanks,

Gaurav

  • 0
    TI__Genius 12225 points

    Hi Gaurav,

    I'm unsure about what your application is and how much hysteresis you're looking for.

    What does the signal look like? Is it truly going to be in the uV range?

    In the post you've linked, you're using an INA333 to linearly scale the voltage signal up. A comparator will output a digital high or low depending on if the input signal crosses the reference at the inverting/non-inverting input. Is this the output behavior that you want?

    The TLV3603 has the following hysteresis voltage vs hysteresis resistor plot:

  • 0 in reply to HO SIU
    Prodigy 100 points

    Hi SIU,

    Thanks a lot for your response.

    HO SIU said:
    I'm unsure about what your application is

    I want to minor variation of mechanical rotation.

    HO SIU said:
    how much hysteresis you're looking for.

    Can you please suggest as per my application?

    HO SIU said:
    What does the signal look like? Is it truly going to be in the uV range?

    Yes 

    HO SIU said:
    In the post you've linked, you're using an INA333 to linearly scale the voltage signal up. A comparator will output a digital high or low depending on if the input signal crosses the reference at the inverting/non-inverting input. Is this the output behavior that you want?

    Yes,Amplify output of INA333 will be the input of TLV3603.

    Thanks,

    Gaurav

  • +1 in reply to GAURAV UPADHYAY
    TI__Genius 12225 points

    Hi Gaurav,

    The purpose of hysteresis is to mitigate unwanted switching of the output due to noise and/or interference. It's hard to tell at a glance exactly how much you need; it depends on factors like the speed of your input signal, the amplitude of your input signal, and the amplitude of the noise/interference you're expecting in your system. You can create your PCB with the pads for a hysteresis resistor, and subsequently swap the resistor should you end up needing more or less hysteresis. You can start off with ~5mV to 10mV of hysteresis (400kΩ to 500kΩ) and then change the value as needed if you observe any unwanted switching (chattering) of the output.

  • 0 in reply to HO SIU
    Prodigy 100 points

    Hi SIU,

    Thanks for suggestions and comments.

    Thanks,

    Gaurav