TPA3116D2: Slave amplifier PWM frequency

Hi Tommaso

    It shouldn't a normal phenomenon. Can you let us check the schematic?

Hi,

Here an image of the configuration. Note that for the LC filter, the actual inductance is 10uH and the capacitor is 1uF, as suggested in the datasheet.

Thank you

Hi,

Did you check the PVDD idle current? Is it correlated to datasheet spec(see 6.5 part in datasheet) ?

And did you short audio input to GND through 1uF caps?

Did you check PWM switching duty cycle? Is it 50%?

Regards,

Derek

Hi,

Idle current is too much: more than 300mA compare to the 50mA max written on the datasheet.

The Audio input at GND are not connected to capacitors, I've followed the datasheet, where they don't appear.

PWM is 50%. Attached the output pwm signal from master and slave amplifiers.

Hello,

For the slave configuration only or for both of them?

Thank you, regards.

Hi,

The device which has high idle current issue.

Regards,

Derek

Are you sure? On the datasheet is written "directly to GND (without capacitors)" for the PBTL mode.

I'll remove snubber and zoble in any case.

Regards

Hello, 

Sorry for the late reply. I've tried to short the channel with 1uF to GND and to remove the zobel, but the idle current isstill too high.

I confirm that in Master-Slave mode, the PWM frequency for the master is 400kHz, but the SYNC and PWM frequency for the slave is 100kHz (both measured at the output before the inductance). 

Is that normal? I saw a lot of issues related to it.

Then, while the LC filter (10uH, 1uF for PBTL Mode) is well dimensioned for the first frequency, it works bad for the second one, so it drains a lot of current and gets hot. It probably should have a higher value, is it?

Is it an IC problem or an inductance problem?

If it is an inductance problem, can you suggest a code?

Thanks again

Hi,

The 100KHz frequency SYNC is normal, but the 100KHz PWM output is abnormal.

The Master device PWM and SYNC are fine, right? 

What's the capacitor value on Slave device SYNC pin? You can refer Figure 37 in datasheet.

And the sequence should be: firstly power up master device; when master sync output is normal, then enable slave device. 

Please check the sequence is correct or not.

Regards,

Derek

Hi,

Master device and  SYNC are ok.

The capacitor is 1nF, as suggested by datasheet. I followed the datasheet alseo for the master-slave configuration and there are not any explanation of the power on sequence.

I tried to delay manually the the enable of the slave but nothing changes. The output is first quiet and then it oscillate with slower frequency.

Is there a proper sequence to follow to dalay the enable of the slave device? (I attached the PWM images several messages ago, that condition is a constant, for all the devices)

Thank you

Hi,

You should power up the master device, and check the SYNC output of master is fine(100KHz). Then power up slave device.

One question: if you set slave device to master, does it work well?

Hi,

I tried to do it and nothing changes.

If I set the slave to master it correctly oscillates and the amplifiers work well in idle too.

Hi,

It seems the device can not work well on slave mode?

Can you capture the waveform of SYNC pin, SD pin of Slave, PWM switching of slave together? I want to check the sequence.

Regards,

Derek

Hi,

I tried to modify the SYINC capacitor value to 100pF, now the PWM switching is 400kHz for the slave too.

Probably the RC filter for the SYNC do not have proper values to allow the slave to work correctly

So the idle current and heat issue are both fixed, right?

Yes, they are. Thank you