PCM1792A: PCAM17292 implementation question and design review
Part Number: PCM1792
I'm designing an audio hifi power amplifier with integrated DAC, a PCM1792.
I build first prototype and I can't made the PCM1792DB (I purchase PCM1792DB) working.
The I2S come from an XMOS MCU, data format is I2S 24bit.
Then, I look on SCK pin, 24.576Mhz is present, on BCK I have the right frequency (around 2.8Mhz for a 48khz datarate), on LRCK I found the 48Khz frequency and I see bitstream on DATA pin.
nRST is high level, but maybe the init sequence is wrong.
1- 3.3VDAC is up, SCK is feed with a clock (24.576Mhz) analog power is OFF (5VA feeding analog pins of PCM1792), nRST is low
2-5VA analog is ON when I press a button (before I press buton 5VA is OFF)
3-XMOS MCU start init sequence with nRST only (I2C pins stays high level, no communication)
I expected PCM1792 start with right config (default I2S 24b format) and then seeing some sound from PCM1792 but nothing, 0VDC even the I bias which should give me about 2.5VDC on the 390R resistor is not working.
I see a voltage around 2.45V on IREF pin connected to a 10KR resistor.
Attached my schematics and a screen shoot showing nRST pin (nRST pin stay low when device power up, then XMOS MCU apply reset and put nRST in high level)
Tripple check solders, change PCM1792 with a new one; nothing change.
Any ideas ?
There could be many things effecting this. First, you should ensure that the XMOS is actually providing a data signal, and that signal is known, like a sine wave.
You also have a error in your schematic. You have shorted the VCOM pins together and shorted them to VCC. That is not correct.
Please try correcting that first.
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In reply to Paul_Frost:
You point the right issue!
After a iron solder and strap session my amp is playing music!
First time I build a DAC, on scope FFT I see 80dB THD full power @ 10khz looks good ! At 1Khz only the noise floor.
A big thank to you, you save me time!
Here fews picture of the first prototype of my amp and the straps over dac :)
Lot's of TI inside :) (all dc dc regulators, low noise ldo and charge pump, pga4311, opamps...)
In reply to Briquel Florian:
Very cool project! It must put off some heat!
Too bad I didn't catch the VCOM issue on the first review :)
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