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LM2903B: LTspice simulation shows different output compared to LM293

Alice Dong
Prodigy 80 points
Part Number: LM2903B
Other Parts Discussed in Thread: LM2903, LM339

Hello,

I am doing the simulation in LTspice. With the same circuit, I see something wrong with the output of LM2903B. May I ask for some help? Either my circuit is wrong or the model itself is not correct. 

Vcc=5V Vin: 5V PWM 

Thank you,

Alice 

  • 0
    TI__Guru 53966 points

    Hello Alice,

    Actually, it is working as expected.

    For the newer models (LM2903B), when a specification is exceeded, such as supply voltage or input voltage, the output is forced to 1/2 the supply voltage to indicate an error.

    The maximum input voltage for the LM2903 family is Vcc-2V, or 3V on a 5V supply.

    You must be applying more than 3V to one of the inputs (assuming a 5V Vcc).

    Please see the LM339 family appnote, section 2:

    Application Design Guidelines for LM339, LM393, TL331 Family Comparators

    Reduce the input below 3V and the output should function as expected. The actual device will NOT go to 1/2 supply.