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Using LME49811TB as a high voltage comparator

Aman Muthreja1
Prodigy 40 points


Hi,


I am trying to find a high voltage comparator (+/- 100V rails)  and was unable to do so, instead opting to use the LME49811TB as a comparator.

It seems ok for my application, but my question is do I still need the push-pull driver output stage externally, or can I utilize the SOURCE and SINK output pins directly?

Alternatively, is there a comparator that fits the requirement? Switching speed would be low <5kHz.

Thanks,

Aman

  • 0
    TI__Intellectual 1240 points

    Hello Arman-san,

    Yes, you can use LME49811 as comparator you are thinking of.  You can connect Sink and Source pin together if your load current is smaller than specified output current ex 9mA typ, 7mA min at +/-100V supply. If your load needs larger current than specified current you need to add external pushpull driver.

    Hope this help for your requirement.

    T NAOKAWA

  • 0 in reply to Toyojiro Naokawa
    Prodigy 40 points

    Hi Naokawa-san,

    Thank you for your quick reply. Another question I have is that my +100V and -100V is referenced to a different GND than my 5V supply and my inputs to the op-amp. Does this matter, and if so, what would be necessary to make this work?

    Thanks,

    Aman

  • 0 in reply to Aman Muthreja1
    TI__Intellectual 1240 points

    Hello Arman-san,

    To enable the device, you need to feed min 1mA, typ 1.5mA and max 2mA current into SD pin. To do this, you can take you +100V via about 68k or 62k ohms resistor to SD pin. Then the device can enable. In this case the GND potential will be refference for +/-100V side. The you don't need 5V supply for enabling the device.  For your refference, please take look at the datasheet pg 10 "Shutdown Function" portion. there is some idea for device shutdown and enable approach.

    Best regards

    T NAOKAWA