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Q: TAS5704 DC/DC converter for AVDD and DVDD
Hi team,
Our customer wants to use 3.3V DC/DC converter for AVDD and DVDD of TAS5704. Is it OK? If it is OK, could you tell us the maximum ripple voltage of DC/DC converter?
A: Re: TAS5704 DC/DC converter for AVDD and DVDD
A DC/DC converter is fine. Our EVM's use a DC/DC to create the 3.3V for AVDD/DVDD.
The ripple on the AVDD should be below 80mV for best performance. I calculated this number with the PSRR of AVDD ( about 65dB) and the noise floor of the device. In other words I calculated the ripple on AVDD which would cause a signal at the output larger than the output noise (56uV from D/S).
The ripple can be larger, but audio performance will degrade. Of course, AVDD MUST remain over 3V in order for the amplifier to remain operational.
DVDD is more lenient and can handle more ripple, although it also should not fall below 3V.
Do you know which DC/DC the customer is using? (hopefully a TI device!). If you have a part number, I can help them select a cap size that will be appropriate for this device.