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Class D Switching Power Amplifiers and Power D/A conversion

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Old 22nd February 2018, 10:15 PM   #81
ccss is offline ccss  United States
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Join Date: Sep 2017
Another reason the TPS3802K33DCKR voltage supervisor responds too slowly is becausethe LM5010A 15V converter operates down to 6V, so it will continue outputting 15V until PVDD has drained to 6V.
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Old 22nd February 2018, 10:49 PM   #82
voltwide is offline voltwide  Ireland
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Although the reset circuits worked fine in suppressing pop-noise on power-up and power down, I was looking for some way to automatically reset global error flag of TPA3255 as well and so I choosed a 8-pin AVR Attiny25/45/85. The micro-program now incorporates a 1sec turn-on delay and VPP is monitored by one AVR-input connected through a voltage divider to VPP. When VPP drops to a critical value (set to 18V here) the AVR pulls TPA-reset low thus muting the whole amp.
With this configuration VPP supply voltage can be hotswapped without plopps on power-up or power down.
Even mains disruptions are inaudible.
It should be noted that excessive big TPA input coupling capacitors will spoil turn-on plop suppression.
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Old 23rd February 2018, 12:31 AM   #83
DrewT is offline DrewT  United States
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ccss, this sounds like a great, easy solution. Would a more common value resistor like 220k or 330k work, or is it a matter of experimenting? Where on the board do the RESET+ and RESET-GND wires attach?
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Old 23rd February 2018, 04:22 AM   #84
ccss is offline ccss  United States
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220k might work, 330k probably wouldn't, as it would drop the current below the 0.18mA activation threshold for the CPC1333. But it depends on your input voltage, or the range of input voltages you expect to use. Some folks use 36V, I use 51V.

The resistance calculation is the same calculation you would do for an LED. You should be able to find an LED resistance calculator online.

The CPC1333 datasheet indicates voltage drop of 1.26V, and activation current of 0.18-2mA. For efficiency, and to make it more sensitive to power drop, aim for low current, around 0.2mA.

Also, RESET+ goes to pin 10 and GND goes to pin 4 of the onboard interface block.

Last edited by ccss; 23rd February 2018 at 04:24 AM.
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Old 28th February 2018, 11:34 PM   #85
ccss is offline ccss  United States
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In addition to power-off pop, you can use a second XYSX CPC1333 to control power-on pop too. All it takes is the addition of a capacitor to add a small delay.

I decided to run the 2nd CPC1333 from the onboard 3.3V rail, because it starts after the 15V supply. Runnnig from 3.3V, I used a series 10k resistor and a 220uF polarized cap parallel to the CPC133. This adds enough delay to eliminate the (very small) power-on noise.

The outputs from both CPC1333 are paralleled to control RESET, so if either relay is unpowered, RESET stays engaged.

Altogether, power consumption is just a few mW.

See attached image
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