TDA7575B PCB Design

IHus.1 · ‎2021-12-07

Hello there, I am newbie to PCB design and I am going to use TDA7575B. Here I have an input from a mobile which have two wires. I have few question regarding its design:

Can I joint In1+ to In2+, In1- to In2- ? then those joints will be connected to signal from phone
Secondly, CD_OUT, V, MUTE, ST-BY/HE pins connected where as its just a simple design.
On Pin 17, 17ohm setting is written, what's its purpose?

Peter BENSCH · ‎2021-12-08

As mentioned before it is explained in section 5.5 of the datasheet: it is recommended to leave 1 ohm pin floating or shorted to GND to set the two channels mode configuration, or to short 1 ohm pin to VCC to set the one channel configuration. So if you only use IN2 and want to have the two channels connected in parallel = single channel, you have to switch the pin to VCC, but this also requires paralleling OUT1 and OUT2.
CD_OUT is an open drain output and would need a pull up if used. Since you don't want to use it, you don't need a pull-up and therefore also no voltage V. Otherwise, V would be the voltage, which is typically 3.3V or 5V depending on the connected logic.
See datasheet, table 4: Vm: Mute pin voltage for play mode = 3.5-18V
Standard Bridge mode: classical class AB amp, High Efficiency mode = The dissipated output power under average listening condition is in fact reduced up to 50% when compared to the level provided by conventional class AB solutions. (description of the datasheet)
The type of the input caps depends on your requirements: ceramic caps are typically MLCCs and, due to the piezo effect, could be sensitive to external sound or hard impacts. Polyester ones would be an alternative, but ecaps should also be sufficient.
A tone control must be implemented in front of the input of the amplifier and depends very much on the application: for a subwoofer, for example, you normally do not need to control frequencies above 100Hz. Otherwise you can use everything here: from a passive shelving filter with two potentiometers and a few resistore/capacitors to a graphics equalizer.

Good luck!

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/Peter

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Peter BENSCH · ‎2021-12-07

Welcome, @IHus.1, to the community!

You can connect the inputs in this way if you want to control both inputs with the same signal. However, the question arises, why do you want to do this? If it is to be used to switch both channels in parallel in order to increase the output power, there is the 1-Ohm pin. Section 5.5 of the datasheet describes how it works and also mentions that IN1 should left floating in this case and IN2 is the input.
CD:OUT can be ignored; V is not a pin, but supplies the pull-up at CD_OUT; MUTE is low active and should be connected using the RC networks shown in the application circuits (mutes the amp during powered on); ST-BY/HE should either be connected to 3.5-5V (standard bridge) or to 7-18 (high efficiency), as shown in table 4 (standby pin).
see 1 above

Good luck!

If the problem is resolved, please mark this topic as answered by selecting Select as best. This will help other users find that answer faster.

/Peter

In order to give better visibility on the answered topics, please click on Accept as Solution on the reply which solved your issue or answered your question.

IHus.1 · ‎2021-12-07

@Peter BENSCH thanks you very much for the kind and detailed answer, I am very thankful of you. I got many things cleared but here I have a couple more questions, I appreciate your time:

I will connect input at IN2 and left IN1 floating. So the output can be increased by using 1ohm pin. I will left 1ohm pin open for the mentioned purpose configuration. please correct me if I am wrong.
CD:OUT will be ignored. Can I still apply pull-up voltage at point V? if yes then how much voltage?
As you said MUTE is low active, I dont want to use this feature so should I connect the mute RC circuit to GND or 5V? amp will on when it will be power up.
ST-BY/HE will be connected to 5V or 14V. Can you please differentiate between standard bridge & high efficiency so that I can apply relevant voltage there.
At input there are caps in series whose values are 0.22uF. Can you please clear that is it ceramic caps or polyester?
Lastly, is there any way to implement tone control circuit with it? do we have circuit for it?

I am very thankful of you. I hope my PCB will work great.

Peter BENSCH · ‎2021-12-08

As mentioned before it is explained in section 5.5 of the datasheet: it is recommended to leave 1 ohm pin floating or shorted to GND to set the two channels mode configuration, or to short 1 ohm pin to VCC to set the one channel configuration. So if you only use IN2 and want to have the two channels connected in parallel = single channel, you have to switch the pin to VCC, but this also requires paralleling OUT1 and OUT2.
CD_OUT is an open drain output and would need a pull up if used. Since you don't want to use it, you don't need a pull-up and therefore also no voltage V. Otherwise, V would be the voltage, which is typically 3.3V or 5V depending on the connected logic.
See datasheet, table 4: Vm: Mute pin voltage for play mode = 3.5-18V
Standard Bridge mode: classical class AB amp, High Efficiency mode = The dissipated output power under average listening condition is in fact reduced up to 50% when compared to the level provided by conventional class AB solutions. (description of the datasheet)
The type of the input caps depends on your requirements: ceramic caps are typically MLCCs and, due to the piezo effect, could be sensitive to external sound or hard impacts. Polyester ones would be an alternative, but ecaps should also be sufficient.
A tone control must be implemented in front of the input of the amplifier and depends very much on the application: for a subwoofer, for example, you normally do not need to control frequencies above 100Hz. Otherwise you can use everything here: from a passive shelving filter with two potentiometers and a few resistore/capacitors to a graphics equalizer.

Good luck!

If the problem is resolved, please mark this topic as answered by selecting Select as best. This will help other users find that answer faster.

/Peter

In order to give better visibility on the answered topics, please click on Accept as Solution on the reply which solved your issue or answered your question.

IHus.1 · ‎2021-12-08

Thank you very much for your kind response and detailed answers. Now I have cleared above most of the things.

Kind Regards!