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LM49450: Help review schematic

Haiwen Huang
Intellectual 1740 points
Part Number: LM49450

Dears:

Below questions need you help :

1: Power supply voltage  VDD, LSVDD_1, LSVDD_2 use 5.0V;  DVDD, IOVDD use 3.3V; is it okay? Output power is less than 0.5W.

2: Power supply voltage CPVDD, HPVDDSCHEMATIC _ P04_LT7911D.pdf; can it be floated?  As we don’t need headphone function.

3: What is the proper capacitance value around the circuit? As it doesn’t have EVM schematic for reference. Please help give some advises.

  • 0
    TI__Guru** 102045 points

    Hi Haiwen,

    After review of the schematic, it looks OK. Some comments on your specific questions below:

    1. This is OK
    2. You may be able to do this, unfortunately I cannot test it as there is no EVM available, but I think it should be OK to leave these pins floating if HP driver is not used.
    3. Decoupling capacitance on supplies are usually recommended to follow some general guidelines:
      1. Use at least 1 small capacitor to filter high frequency noise, like 0.1uF
      2. Use at least 1 bigger capacitor that will work as charge reservoir for any current variations from the supply. Since you're using low power outputs this may not be too much of a problem but it would be still recommended.
      3. Voltage rating is usually 3 times the supply voltage, in order to keep good capacitance value after DC derating

    Best regards,
    -Ivan Salazar
    Applications Engineer - Low Power Audio & Actuators