TPA3220: Simplest Way to Use the Internal LDO and Resolve the RESET Issue - Resistive Divider or External Regulator

Bradley W Wiitala

Part Number: TPA3220
Other Parts Discussed in Thread: LM317,

Okay, I had the same issue with the RESET line and verified that applying an external 5V on RESET started the part. This is mentioned in the forum here. (Nick and Luis contributing.)

However, I do not have a 5V supply in the design I was doing. Can I use a simple resistor divider with my 30 volt supply to generate 5 volts for the RESET pullup? Or do I need a more elaborate scheme. i.e. add some sort or regulator powered off the 30 volts?

Thanks in advance.

over 4 years ago

0 Robert Clifton56 over 4 years ago

TI__Mastermind 24080 points

Hi Bradley,

You can use a resistor divider for the 30V to 5V as long as you make sure that if there's any voltage sag in the PVDD line it doesn't drop the 5V to be below the operating voltage of the device (4.5V minimum).

We actually have a resistor divider network as an option on the TPA3220EVM.

Best Regards,

Robert Clifton

0 Bradley W Wiitala over 4 years ago in reply to Robert Clifton56

Prodigy 110 points

Hi Robert,

Thanks very much for the prompt response.

Brad Wiitala

0 Robert Clifton56 over 4 years ago in reply to Bradley W Wiitala

TI__Mastermind 24080 points

Hi Brad,

That's what we are here for :)

Best Regards,

Robert Clifton

0 Bradley W Wiitala over 4 years ago in reply to Bradley W Wiitala

Prodigy 110 points

Hi Robert,

I am looking at the eval board PDF you described and I see a divider of R7/R13 with values of 4.99K and 1.00K. I take it that this is the divider you mentioned?

If I do that, then I must run this voltage to every pullup resistor...RESET, FAULT and CLIP LEDs, etc?

Is it maybe better to use a small external linear regulator? i.e. LM317 style? I don't care about the extra cost or power dissipation?

Thanks,

Brad

0 Robert Clifton56 over 4 years ago in reply to Bradley W Wiitala

TI__Mastermind 24080 points

Hi Brad,

As I'm sure you are aware, there are many different ways to implement this!

Consideration for how the other components running off the 5V resistor divider would have to be taken into consideration. If their resistances are large enough it wouldn't have much effect on the divider though.

The LM317 would also work as an option.

And not to add yet another option but this device does have a built in 5V LDO that you could also use. The efficiency would go down to now also having the power loss from the LDO so there will be more heat in the system but it's an option.

Best Regards,

Robert Clifton

0 Bradley W Wiitala over 4 years ago in reply to Robert Clifton56

Prodigy 110 points

Hi Robert,

Hmmm...I thought my design was using the internal LDO. I must have copied something wrong from the evaluation board. Could you check over my schematic? I've attached it here.

Thanks,

BradPedalboard Power Amp TPA3220 Power Amp.pdf

0 Robert Clifton56 over 4 years ago in reply to Bradley W Wiitala

TI__Mastermind 24080 points

Hi Brad,

I had forgotten about Reset needing the external 5V line. Sorry for creating confusion.

You can just use the voltage divider for the Reset and everything else can be powered by the internal 5V LDO. Or you could have an external LDO supply the 5V rail.

I'm noticing the LM317 does state that the system needs a minimum load current that might cause issues when in the TPA3220 is in Reset. You might want to take a look into this before choosing to use the LM317.

Regards,

Robert Clifton

0 Bradley W Wiitala over 4 years ago in reply to Robert Clifton56

Prodigy 110 points

Hi Robert,

Okay, it sounds like the voltage divider for just the Reset is the way to go. If all the other stuff like the Clip and Fault, LEDs had to go on that line, then I would probably go with the LM317.

Thanks again,

Brad

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TPA3220: Simplest Way to Use the Internal LDO and Resolve the RESET Issue - Resistive Divider or External Regulator