TPA3255 / TPA3251 / TPA3245 Rev.1B Final

In continuation / expansion of implementations based on the TPA3255 / TPA3251 / TPA3245 now the final approach of amplifier design for the Akita family. Differently to the past designs , the analog front end is now implemented on a dedicated circuit board powered by a balanced supply. This results in the ability to provide different approaches of signal input/suppl<. For example, it now is possible to directly feed the amplifier with I2S by i.e. a PCM5242 .

This post is in continuation to the following articles:

http://www.360customs.de/2015/07/tpa3251d2-2-x-175w-stereo-350w-mono/

http://www.360customs.de/2017/06/universal-afe-analog-front-end-tpa32xx-tpa3245-tpa3251-tpa3255-mit-pffb/

http://www.360customs.de/2016/10/tpa3255-tpa3251-tpa3245-universal-one-for-all/

Visualization Rev1.B

TPA3255 Rev.1A vs Rev.1B with AFE

TPA3255 Rev1.A vs Rev1.B with AFE

TPA3255 Rev.1B with AFE

TPA3255 Rev1.B with AFE

Build

A first trial assembly before the boards were fitted.

TPA3255 Rev1.B Testbuild

TPA3255 Rev1.B Testbuild

2 boards with an AFE module each were built up. One was locally measured and valued, the other went to "Voltwide", member of the forum "stromrichter.org".

TPA3255 Rev1.B Testsystem #1

TPA3255 Rev1.B Testsystem #1

TPA3255 Rev1.B Testsystem #2

TPA3255 Rev1.B Testsystem #2

TPA3255 Rev1.B Heatsink

TPA3255 Rev1.B Heatsink

The supply of the AFE module (analog front end) and AVCC of TPA32XX is done by a LM5017 in flybuck configuration for +/-12V. The converter runs at approx. 850kHz, far outside of the audio spectrum.

TPA3255 Rev1.B Flybuck

TPA3255 Rev1.B Flybuck

Measured values / performance

Supply analog +/-AVCC

For the LM5017 in flybuck configuration there are these +/-AVCC ripple plots:

LM5017 AVCC+ output

LM5017 AVCC+ output

LM5017 AVCC- output

LM5017 AVCC- output

The RMS ripple is less than 10mV, without any ripple no COT would work. Related to +/-12V, the ripple is less than 0.1%. With additional 100n, the ripple at the AFE pinheader shows up as follows:

LM5017 AVCC- 100n Pinheader AFE

LM5017 AVCC- 100n Pinheader AFE

LM5017 AVCC- 100n Pinheader AFE

LM5017 AVCC- 100n Pinheader AFE

There's an additional RC filtering followed by a fedd-trough capacitor on the AFE module.

AVCC+  AFE filtered

AVCC+ AFE filtered

2mV ripple equals ro 0.017%, relative to AVCC = 12V. In the AFE related OPA1654 offer 30dB PSRR at 850kHz, with better than 65dB in the 20 kHz audio band.

Audio THD/THD+N

The design delivers the following performance on 3.8Ohm load resistance:

1W

THD: 0.0016%
THD+N: 0.02%
K1: 11.9dBV
K2: -94.22dBV
K3: -89.8dBV
K1/K2: 106.12dBV
K1/K3: 101.7dBV

10W

THD: 0.0016%
THD+N: 0.013%
K1: 16dBV
K2: -90.4dBV
K3: -82.5dBV
K1/K2: 106.4dBV
K1/K3: 98.5dBV

100W

THD: 0.0039%
THD+N: 0.046%
K1: 25.9dBV
K2: -68.4dBV
K3: -65.4dBV
K1/K2: 94.3dBV
K1/K3: 91.3dBV

Plots for 3.8Ohm load in BTL at PVCC = 51V, 600kHz AFE module with minimal PFFB at 1 kHz and for different frequencies:

THD vs POUT into 3R8 at 51V 600kHz BTL

THD vs POUT into 3R8 at 51V 600kHz BTL

THD f(freq) vs POUT into 3R8 at 51V 600kHz BTL

THD f(freq) vs POUT into 3R8 at 51V 600kHz BTL

Utilizing prefilter PBTL, connecting the TPA32XX outputs together right before the output filter, result in even lower values. The test setup:

TPA3255 Rev1.V PBTL Testsetup

TPA3255 Rev1.V PBTL Testsetup

Measurements taken with a load of 5.0Ohm connected at PVCC = 30V without PFFB and AFE module:

THD vs POUT into 5R0 at 30V 600kHz PBTL no AFE PFFB

THD vs POUT into 5R0 at 30V 600kHz PBTLTHD vs POUT into 5R0 at 30V 600kHz PBTL no AFE PFFB

The following can be achieved with a load of 10.0Ohm:

THD vs POUT into 10R0 at 30V 600kHz PBTL no AFE PFFB

THD vs POUT into 10R0 at 30V 600kHz PBTL no AFE PFFB

Supply

In the same form factor (10x10cm), an LLC power supply module was developed by "Voltwide" which provides 50V for the powerstage and 12V AUX. A unit in 10x10x10cm results with the appropriate bolts.

TPA3255 Rev1.B   50V Voltwide LLC #1

TPA3255 Rev1.B 50V Voltwide LLC #1

TPA3255 Rev1.B   50V Voltwide LLC #1

TPA3255 Rev1.B 50V Voltwide LLC #2

You may so like...

1 response

  1. irs20957 says:

    Very nice job!

Leave a reply

Your email address will not be published. Required fields are marked *

* Checkbox GDPR is required,,en,This form collects your name, email and content so that we can keep track of the comments placed on the website. For more info check our privacy policy where you'll get more info on where, how and why we store your data.,,en,I agree,,en

*

I agree

This website stores some user agent data. These data are used to provide a more personalized experience and to track your whereabouts around our website in compliance with the European General Data Protection Regulation. If you decide to opt-out of any future tracking, a cookie will be set up in your browser to remember this choice for one year. I Agree, Deny
602