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LM4890 Support Need

Patrick Zeng
Intellectual 1090 points
Other Parts Discussed in Thread: LM4890, TPA4861, TPA2001D1, TPA2005D1

Hi Team,

 My customer met an issue with LM4890 when using a GPIO to control its shutdown pin. As it shows below, when a high output generates from GPIO, LM4890 is supposed to turn on. But there're some occasions that the register is set to high in MCU while no high signal is measured on the GPIO. Customer suspects if the shutdown pin of LM4890 causes the issue. It'll be appreciated if you can share the internal structure of shutdonw pin to me so that I can better convince customer. Thanks.

Regards,

Patrick

  • 0
    TI__Mastermind 20085 points
    Hi Patrick

    Unfortunately, the people who worked in these parts aren't longer on TI and it is quite difficult to find this kind of information.
    On the other hand, you could try to use a pull up resistor, that could work better than pull down resistor.

    Best Regards
    Jose Luis Figueroa
    Audio Applications Engineer | LPAA
  • 0 in reply to José Luis
    TI__Intellectual 1090 points

    Hi Jose,

      Thanks for the quick response. 

      I'm aware that this is a very old part and it's hard to find such information. I'll suggest customer to have 100K pulled-up.

      Just judging from your experience, what might have been the equilevant circuitary inside the shutdown pin? Is it something like this shown below(without pull down res)?

      Besides, what do you suggest if we want to promote a new part to replace LM4890? Thanks.

    Regards,

    Patrick

  • 0 in reply to Patrick Zeng
    TI__Mastermind 20085 points
    Hello Patrick

    I'm not sure about internal structure of shutdown, but your circuit could be similar to the real circuit.
    You could have a look to the TPA4861 is a Class AB amplifier. Other options are TPA2001D1 or TPA2005D1 are Class D amplifiers, they have much better efficiency, therefore lower power dissipation.

    Best Regards
    Jose Luis Figueroa
    Audio Applications Engineer | LPAA