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LM2903: In+/In- range

Joyce Li
Intellectual 2170 points
Part Number: LM2903
Other Parts Discussed in Thread: LM393, TLV7022

Hi dear expert,

My customer uses LM2903 as below application:

Vs=4V; In-=Vref1=2.5V; In+=4.5V;

In+ exceeds Vs 0.5V, and In- >Vs-2V as datasheet requires. Will this cause device damage and function not correctly?

datasheet also says: "The comparator consists of a PNP darlington pair input, allowing the device to operate with very high gain and fast response with minimal input bias current. The input Darlington pair creates a limit on the input common mode voltage capability, allowing the comparator to accurately function from ground to VCC– 1.5 V input. Allow for VCC– 2 V at cold temperature."

Customer mainly uses LM2903 in higher temp, so it meets Vicp< Vcc-1.5V. If customer uses in high temp scenario, will this application work correctly?

Thanks a lot for your reply in advance.

Joyce Li

  • 0
    TI__Guru 53536 points

    Hello Joyce,

    At temperatures above room temp, it should still function, but there may be shifts in offset voltage and speed. There can also be variations in the input level where the threshold starts. I would expect wide variation in the trip points and response times across the devices since they are operating both inputs in the "grey" zone.

    Going cold, I would expect failures.

    This is explained in the LM393 family application note, section 2.3:

     https://www.ti.com/lit/an/snoaa35a/snoaa35a.pdf

    They need to either change the trip point value to under 2V, or increase the supply voltage to >4.5V, or replace the LM2903 with a R-R input device such as the TLV7022 for reliable operation.