I have designed a full digital amp using the TAS5518C.
When i power up the amplifier the output "Valid" of TAS5518C gives a spike which activates the output devices making "cracking" noise i the speakers.This spike also appears when the reset pin is pulled low.I there a simple fix of do i need to add more circuitry to filter the spike?
In some devices, there may be a glitch in the logic where VALID signal is not being held low during power on. To keep everything quiet, you may want to add a pre-bias circuit on VR_PLL (internal 1.8V regulator) - 3.3V to 60.4 kOHm resistor to pin 11 (VR_PLL), pin 11 to 49.9 kOhm resistor to ground and 0.01uF cap from pin 11 to ground. This will help your power up noise.
Texas Instruments, Inc.
I have tried your suggestion but it did not solve the problem.Instead i have added a pre-bias circuit on the vr_pwm pin using : 3,3v > 47k > vrpwm > 56k + 100n > ground.This solved the problem, can this circuit inject any noise?
I also figured out I need a brown-out detection, and pull the reset line low as soon as it is detected.This eliminated the noise generated when the amp is turned off.
Thank you for your help.
Thanks for closing the loop with us on your solution!
Audio Applications Engineering Manager
Dallas, TX USA
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