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TPA3221: Startup instability

6363474
Prodigy 20 points
Part Number: TPA3221

Hi,

I'm having an "starup" issue with my TPA3221 design. I run the amp as a 2ch stereo amp.

1. I have a bluethooth module that controls the RESET-pin. It has 3.3V level but that should be OK according to the datasheet as VIH = min 1.9V on the RESET-pin.

2. I control the CMUTE pin also from the same bluetootrh module. Also here with 3.3V-level which should be OK as VIH is also 1.9V for CMUTE-pin! Or am I wrong? The CMUTE-pin is kind of special as it charges an external cap to achieve a softer ramp up/down! So maybe I am doing something wrong here?

3. Note that VDD (5V) and PVDD (24V) are stable before I drive RESET high!

NOTE: NM = Not Mounted

The problem I have is the following:

Most of the times when I drive RESET high (3.3V) the amp does not start! I drive CMUTE high 400 ms after I have driven RESET high. Once I have even got one of the two channels (sma chip) to start but not the other one. When I say "does not start" I mean that the outputs from the amp is Hi Z!

Please help me understand what I am doing wrong here!Best regards

Markus

 

  • 0
    Prodigy 20 points

    Just realized that the schematic screenshot did not show up!

    I use 10uF ac-coupling caps in the inputs! According to the datasheet it should be OK but read in another similar thread that 1uF is the recommended!

    BR

    Markus 

  • 0 in reply to 6363474
    TI__Mastermind 27550 points

    Hi Markus,

    As a first step, I would recommend switching to a 1uF ac-coupling capacitor on the inputs. I've seen in the past where a larger capacitor prevents startup. I'll check to see if 10uF also caused that issue.

    Let me know if that solves the problem!

    Best Regards,

    Robert Clifton