DRV632: DRV632

Hi Ian,

I'll check this, but I have some questions:
- From the diagram I see the capacitor in series, so it is actually a HPF with Fc = ~25Hz, right?
- Have you tried to rearrange the input filter placement? Like placing the Audio Switch before 1uF? or after 6.34kohm?
- The DRV632 designed as above is a mutiple-feedback filter topology, which is a LPF, and also by adding the input coupling capacitors you create a HPF determined by C3 and R1 (as explained in section 9.3.5 Input-Blocking Capacitors): why not adjusting C3 and R1 to get the desired HPF Fc instead of adding an additional filter at the input?

Best regards,
-Ivan Salazar
Applications Engineer - Low Power Audio & Actuators

Ivan,

1. Yes, 25Hz

2. Not yet.

3. This is based on customer existed product’s design. (In picture, the left part is the existed design and the right part is the newly added design.)

There is an audio switch IC put on the signal path and the extra C-R is used for it -- The 1uF capacitor is to be a DC block between previous IC output port and the audio switch IC input port. Also, the 6.34kohm is used to overcome the possible overshoot issue caused by the audio switch IC.

I think if the audio switch IC can be removed from design, then the extra C-R could be removed as well. However, this is still under checking since customer don’t want to carelessly change the existed design to cause any possible issue which was already met by the previous designer.

Thanks, Ian.

Ian,

Have you measured the THD+N performance of the audio source? Perhaps the increased THD+N at low frequencies is coming from the previous stage.
Also please let me know if removing switch and HPF is an option and the results by testing that. It would clarify if the filter or the switch are contributing to the increased THD+N.

Best regards,
-Ivan Salazar
Applications Engineer - Low Power Audio & Actuators

Ivan,

Comdirm audio source is good, remove switch and LRC is also good. That's why I asked THD performance will worse with extra RC.

Thanks, Ian.

Hi Ian,

the DRV632 in your schematic is wired for providing differential inputs. But you drive it with a non differential source. Figure 8 of datasheet shows a circuit providing an inverting input. This might be better suited.

Kai

Guys,

We modify customer's PCB only with DRV632 and relative components in board to measure again, it looks a little bit worse than DRV632 EVM.

Do you have idea what possible cause worse performance in customer board?

Thanks, Ian.

Hi Ian,

the audio switch itself can produce distortion. This is not unusual. Have you checked this? Can you disconnect the whole DRV632 circuit and measure the THD directly at the 6k34 resistor?

Kai

Kai,

The tested result already disconnect switch, only measure in DRV632 pin.

Thanks, Ian.

Hi Ian,

We haven't heard back from you, so we are assuming that you were able to solve your problem. If not, you can just reply this post or create a new one if this was locked for the time-out.

Best Regards
José Luis Figueroa
Audio Applications Engineer