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LM2904 questions

Longchang Chen
Intellectual 1350 points
Other Parts Discussed in Thread: LM2904, TLV2372, LMC6482

pls see following schematic:

    customer use LM2904 in negative power supply, and V+ is GND, and V- is -10V, and they found when ref voltage on Pin3(in+) great than -1.1V, then output PIn1

haven't output, so they provide -1.2V on Pin3, the output is ok at room temperature,  but when test it in lower temperature(-20degree), the output is incorrect, pls help to fix it.

  • 0
    TI__Guru 53306 points

    Hello Lonchang,


    They are violating the upper Common mode limit. It cannot sense to V+. They are using the device "upside down" from how it is designed. It cannot sense 1.5V below V+.

    With V+ at "Ground", and V- at -10, the valid common mode range is -1.5V to -10V. 

    They need a R-R input device, or a device that senses to V+.

    See the LMC6482, but it is only to 85°C. If you need up to 125°C, see the TLV2372.

    Regards,