The production line found that the TPA3138 had no audio output. After investigating the cause, it was discovered that the GVDD was only 4.3V. Under normal circumstances, GVDD should be synchronized with the SD pin. However, on a defective board, when sd is pulled down, GVDD drops to 4.3V. When SD returns to a high level, GVDD remains at 4.3V, resulting in no audio output.
Please confirm the schematic of this part .
and we use TPA3138 to our product from 2021, till now more 4 years, this is the first time to find this problem.
This issue is reflected under the following conditions： when the surface temperature of the IC rises above 30℃, 100% repeatable, and the chip surface temperature drops to 27℃ , the chip will function normally.
the below is the wave form of SD and GVDD.
GVDD cannot sync to SD. No audio output.
GVDD can sync to SD, the IC will function normally.
when No audio output, found PVDD waveform. (is the internal LDO is getting oscillated？）
Please check and replay. thank you .
