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TL391B: Positive and negative inputs in a single power supply

Yuta Nishie
Genius 5005 points
Part Number: TL391B
Other Parts Discussed in Thread: TL331B, , LM339, TL331

Tool/software:

Hi,

I found the following thread about TL331B which has similar electrical characteristics to TL391B. This article says that IC will not be damaged even if ±12 V signal is input with VS=3.3V and GND=0V.

https://e2e.ti.com/support/amplifiers-group/amplifiers/f/amplifiers-forum/1210694/tl331b-power-supply-of-tl331b

If ±15V signal is input with VS=3.3V using TL391B, I think IC will not be damaged, but can output High and Low normally? I would like to output High and Low depending on positive and negative input with reference voltage of 0V.

Best Regards,

Nishie

  • +1
    TI__Guru 60536 points

    Hello Yuta,

    NO. The inputs will NOT accept a -12V input. The inputs cannot accept voltage lower than the GND pin.

    On a VS=3.3V and GND=0V supply, the inputs can accept a -0.3V to +36V input signal WITHOUT DAMAGE. But normal output behavior is not expected (depending on what is being violated).

    The valid input voltage range is VCC-2V, or +1.3V max on a +3.3V supply.

    Please see sections 6.4, 6.7, 6.8, 6.9 and 6.93 of the LM339 family Appnote. This is all explained there...

    Application Design Guidelines for LM339, LM393, TL331 Family Comparators

    For a bipolar ±15V input, clamping will be required. I would recommend the "split" clamped divider in section 6.9.3.2.1.

    The TL391 is just a different pin-out of the TL331 - same die.