Audio

Audio forum

General requests about TPA3XXX family

Lulu Lulu

Prodigy 220 points

Other Parts Discussed in Thread: TPA3255, TPA3116D2, TAS6424

Hello, i would like to know some tips to design properly some boards implementing tpa3255 and tpa3116 chips.

First, on the tpa3255 datasheet, for the stereo btl application, is the circuit operational? By operationnal, i mean, could a board exactly designed like the one shown can work, without the "fancy" or extra fonctionalities used (like those allowed with the pins: OSC_IOM, OSC_IOP, RESET, FAULT and CLIP OTW) i know that i can leave the osc pins unconnected, but for the reset, fault and clip otw pins, could i just ground them or leave them unconnected, if yes, which ones ?

For the tpa 3255, can i use a separated power supply for the 12v entry (dedicated to the low power circuitry) that is independant of the high voltage one, so that is not coming from the high power supply by being regulated but with a distinct transformer (can this transformer be unregulated, but just rectified with big reservoir capacitors to have the most linear voltage as possible)?

Also, is it possible to synchronize multiple tpa3255 board to each others? If yes, how far can this go?

For the tpa3116 boards, also can it is possible to combine more than 2 board all togethers, if yes how?

For the tpa3116 design one the datashep version, there is only one 100k resistor going from sdz and faultz pins to pvcc, while the modsel is going directly to ground, on the evaluation board there is a distinc 100k resistor for each of those pins, it's (i assume) for testing purposes, but did i have to apply the datasheet or evaluation configurations for best results?

For the tpa3116 design, if i use only one board and i don't want to connect it to another device, could i juste have to simply connect this pin to ground or make a rc filter (with a 4,7k resistor and a 47pf capacitor) on this pin, like it is done in the evaluation module ?

I really would like to know if the fact of using trough hole rather than smd components affect the sound quality of the system ? I know that trough hole metal film resistor generate less noise than smd resistor, but, for the capacitors used, i know that plastic film capacitors are usually better in all aspects of performance, with no taking care of the cost and the size, but, comparatively, they prone to pickup more rf noise than the smd ceramic capacitors (who are smaller). So what is the best, what is the advantage of those smd components over those old through hole components (other than cost and size)?

Finally, according to users who tried tpa3116 and 3255 board, all of them said that the tpa3255 chip is really better; despite the higher power output and the better snr ratio of the tpa3255 (that is a sound quality factor, among others), for low volume listening (using no more than 20w of power by example, so the tpa3116 does not generate audible distortion) is the tpa3255 really better?

Thanks for your futures reply to my (relatively) dumb questions, i tried my best to formulate them and i hope that you can respond to them!

over 5 years ago

0 Shawn Zheng over 5 years ago

TI__Mastermind 24835 points

Hello,
We are looking into this and will get back you later.
Best regards,
Shawn Zheng

0 Justin Bohr over 5 years ago in reply to Shawn Zheng

TI__Mastermind 27850 points

Hi Lulu,

There are quite a few questions in your post, so I will copy them to my post and answer them.

"Could a board exactly designed like the one shown can work, without the "fancy" or extra fonctionalities used (like those allowed with the pins: OSC_IOM, OSC_IOP, RESET, FAULT and CLIP OTW) i know that i can leave the osc pins unconnected, but for the reset, fault and clip otw pins, could i just ground them or leave them unconnected, if yes, which ones ?"

JB: OSC_IOM, OSC_IOP, FAULT, and CLIP_OTW can be left open/floating. Reset must be driven high for the device to operate. If a fault condition like OTE occurs, reset will need to be toggled for the device to clear the fault.

"For the tpa 3255, can i use a separated power supply for the 12v entry (dedicated to the low power circuitry) that is independant of the high voltage one, so that is not coming from the high power supply by being regulated but with a distinct transformer (can this transformer be unregulated, but just rectified with big reservoir capacitors to have the most linear voltage as possible)?"

JB: I would not recommend using an unregulated supply for the 12V rail, this will have a big impact on performance, and may cause an unplanned shutdown of the outputs.

"Also, is it possible to synchronize multiple tpa3255 board to each others? If yes, how far can this go?"

JB: It is possible to make a single board design with multiple devices, please take a look at this Multi-Device Configuration for TPA32xx Amplifiers app note.

For the TPA3116 questions, Shawn will need to respond as he is the expert for this device.

"I really would like to know if the fact of using trough hole rather than smd components affect the sound quality of the system ?"

JB: It is not so much the packaging, but the component quality and type itself that impacts the performance. In generally larger through hole components are able to focus less on space savings and more on performance.

For a comparison between TPA3116 and TPA3255, the TPA3255 has much better THD at 1W and the noise floor is only about 20uV higher than the TPA3116, resulting in a much higher SNR due to the full output power of the TPA3255.

Justin

0 Lulu Lulu over 5 years ago in reply to Justin Bohr

Prodigy 220 points

Ok, thanks for your usefull reply. By "reset must be driven high" and "OTE", what to you mean exactly, do i need a transistor for this purpose?
Also, for the tpa3116 design one the datasheet version, there is only one 100k resistor going from sdz and faultz pins to pvcc, while the modsel is going directly to ground, on the evaluation board there is a distinc 100k resistor for each of those pins, it's (i assume) for testing purposes, but did i have to apply the datasheet or evaluation configurations and; if i use only one board and i don't want to connect it to another device, could i juste have to simply connect this pin to ground or make a rc filter (with a 4,7k resistor and a 47pf capacitor) on this pin, like it is done in the evaluation module ?
At last, if i configure the tpa3116 to operate at a different switching frequency than it's nominal that is 400khz, by making it working at 600khz, can it allow me to use smaller and less powerfull emi ouput filters, like ferrite beads, even at the full output power? If i increase the switching frequency at the maximum, does the sound quality of the amplifier remain the same? Also, in a perspective of sound quality, is it better to use ferrite beads or traditonnal inductors filters? I think the difference of sound quality between the using of ferrite beads and chokes (mostly on thd) is proportionnal to output power, in favor of the use of inductors.
Cordially

0 Justin Bohr over 5 years ago in reply to Lulu Lulu

TI__Mastermind 27850 points

Hi lulu,

In order for the TPA3255 to operate, RESET has to be at 3.3V, or DVDD.

Shawn will have to respond on the TPA3116 questions.

Justin

0 Shawn Zheng over 5 years ago in reply to Justin Bohr

TI__Mastermind 24835 points

Hi Lulu,
TPA3116D2 supports 600kHz PWM frequency, but it's still hard to pass EMI test with ferrite bead filter and full output power. And THD performance is better with inductor filter than ferrite bead filter. We recommend customers to use inductor filter in TPA3116D2 application.
Best regards,
Shawn Zheng

0 Lulu Lulu over 5 years ago in reply to Shawn Zheng

Prodigy 220 points

Thanks a lot for all of your responses. For final, i just want to know the tpa3255's input impedance, if it is possible without any inconveniance to combine tpa3116 and tpa3255 in the same system by synchronizing them (even if it's explained in the " Multi-Device Configuration for TPA32xx Amplifiers"), just to be sure. Also, (if you can request to those auxiliary asking because i recycled them a lot and that could annoy you) for the tpa3116 design on the datasheet version, there is only one 100k resistor going from sdz and faultz pins to pvcc, while the modsel is going directly to ground, on the evaluation board there is a distinc 100k resistor for each of those pins, it's (i assume) for testing purposes, but did i have to apply the datasheet or evaluation configurations and; if i use only one board but i don't want to connect it to an another device, could i juste have to simply connect this pin to ground or make a rc filter on it (with a 4,7k resistor and a 47pf capacitor), like it is done in the evaluation module ? Thanks

0 Lulu Lulu over 5 years ago in reply to Lulu Lulu

Prodigy 220 points

Oh, and to get the tpa3116 on the 1200 khz switching frequency, i just have to the connect AM1 and AM0 pins to ground and AM2 left unconnected, right? Thanks

0 Justin Bohr over 5 years ago in reply to Lulu Lulu

TI__Mastermind 27850 points

Hi Lulu,

I don't believe you can synchronize the TPA3116 with the TPA3255 since they have different Oscillation/switching frequency rates/dividers.

Justin

0 Lulu Lulu over 5 years ago in reply to Justin Bohr

Prodigy 220 points

Ok, and what is the input impedance of the tpa3255 chip? Thanks

0 Justin Bohr over 5 years ago in reply to Lulu Lulu

TI__Mastermind 27850 points

Hi Lulu,

The TPA3255 input impedance is noted in the datasheet in the electrical char table, under Analog Inputs, and it is 20 kOhm.

Justin

0 Lulu Lulu over 5 years ago in reply to Shawn Zheng

Prodigy 220 points

For the tpa3116 design on the datasheet version, there is only one 100k resistor going from sdz and faultz pins to pvcc, while the modsel is going directly to ground, on the evaluation board there is a distinc 100k resistor for each of those pins, it's (i assume) for testing purposes, but did i have to apply the datasheet or evaluation configurations and; if i use only one board but i don't want to connect it to an another device, could i juste have to simply connect this pin to ground or make a rc filter on it (with a 4,7k resistor and a 47pf capacitor), like it is done in the evaluation module, and how to proceed to change the am switching frequency ? Thanks

0 Shawn Zheng over 5 years ago in reply to Lulu Lulu

TI__Mastermind 24835 points

Hello,
The EVM provides the mode selection for for the convenience of customers' evaluation. You can also reserve the selection on your board. The PWM frequency can be selected on AM0~AM2 pins, please find detailed explanation in section 7.3.16 in the datasheet.
Best regards,
Shawn Zheng

0 Lulu Lulu over 5 years ago in reply to Justin Bohr

Prodigy 220 points

Hello, i saw the great and detailled application report document about the selection of output lc filter's components and their value. After interpretation of the various results obtained by the tested inductors, the engineer has founded the "7443630700" of the brand "wurth" to be worthing the use (pun intended) if the sound quality is the primary goal. Because the pricing of this product is quite high and none air core inductor were tested, i am asking myself if it's not better or similar to use instead a 7uh air core inductor wich, certainly suffer from higher impedance, residual capacitance and higher rfi radiation but lower core losses and maybe better sound quality?

I think that, while the impedance is higher with an air core inductor so that it is more resistive than his counterpart, the magnetic core inductor, the impedance of a 7uh air core inductor is such low, that it's not really a issue and, according to you, does the sound quality will be worse than the preconised parts?

Speaking of inductor's material, what type is the best for this application, ferrite or iron based core?

Thanks

0 Shawn Zheng over 5 years ago in reply to Lulu Lulu

TI__Mastermind 24835 points

Hi Lulu,
Here is a document that introduces the inductor selection for class-d amp: www.ti.com/.../sloa242.pdf
Basically we use THD measurement to evaluate the sound quality. And please be noted that this document is for TAS6424 which has much higher PWM frequency and then 3.3uH inductors can be used there, while for TPA3116D2 the inductors need to be higher than 10uH for lower ripple current.
Best regards,
Shawn Zheng