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I'm going to use speaker connected to internal Class D amplifier in WM8998 in my PCB. Power source of my PCB is Li-Pol battery with 3.2-4.1V range or external 4V adapter. Audio codec speaker power pins(SPKVDD) should be connected to battery according WM8998 datasheet.

Do I understand correctly that WM8998 doesn't consider battery voltage to stabilize PWM amplitude and output volume will be depends not only on value in register OUT4R_VOL/OUT4L_VOL but also on current battery voltage? Is it possible to avoid this dependence on battery voltage without using an additional DC/DC converter for SPKVDD? WM8998datasheet

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  • \$\begingroup\$ It would be a good idea to add a datasheet link for the amplifier. (Add it into the question. Don't bury it in the comments.) \$\endgroup\$ – Transistor Feb 28 at 18:08
  • \$\begingroup\$ It is possible but damping factor may suffer and LPF protection of speaker may be necessary. The chip is designed for max power at a Vdd=5V with 5.5 max. How many Wh does the LiPo have? \$\endgroup\$ – Tony Stewart EE75 Feb 28 at 18:22
  • \$\begingroup\$ The first question is why do you care? Unless you're running it flat out, just turn the volume up a click or two as the battery discharges. If your system is software controlled, periodically measure Vbatt and have the MCU do that for you. There's only about 2dB between fully charged and flat anyway, which is barely perceptible. Why does that matter? \$\endgroup\$ – user_1818839 Feb 28 at 18:32
  • \$\begingroup\$ The power source of PCB also can be constant from battery charger (4.2V). LiPo has 14.5Wh. As I understand it, the gain should increase / decrease in proportion to the change in SPKVDD? \$\endgroup\$ – Nice Work Feb 28 at 22:36

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