Question on TPA2012D2

Cheok Loon Lee

Other Parts Discussed in Thread: TPA2012D2EVM, TPA2012D2

Is there a way to calculate the input voltage (non clipping) and the max input voltage value?

My test result shows a sudden increase in power when input signal at the Class D Amp IC increase from 600mVp-p to 1.2Vp-p.

The power is measured (codec+Class D Amp+ Speaker circuit) at Class-D Amp

Input signal Power measured

150mVp-p 1.2W

210mVp-p 1.44W

330mVp-p 2.28W

600mVp-p 3.48W

1.2Vp-p 6.36W

2.25Vp-p 8.52W

If I disconnect Class D Amp and Speaker from Codec IC.

Codec maintain at 1.2W power when increase from 150mVp-p to 2.25Vp-p.

Therefore,the increase of power is confirmed coming from Class-D Amp and Speaker side.

Is this behaviour correct?

This test is done with Gain of 24dB, Vdd @ 5V, impedance 4ohm.

over 16 years ago

0 holl123 over 16 years ago

TI__Prodigy 120 points

Hello Cheok Loon Lee,

Please refer to the application report link below for calculation of gain for different amplifier types:

http://focus.ti.com/general/docs/techdocsabstract.tsp?abstractName=sloa105a

Please let me know if this answers your question.

0 Cheok Loon Lee over 16 years ago in reply to holl123

Intellectual 610 points

Hi holl123,

Thank you for the information.

Assuming the gain of 24dB (16V/V) is gonna be used, the output from my codec is only in the range of 170mA since amp's output power is calculated at 2.8Vrms

This may degrade my Dynamic range and jeapordize the sound quality.

0 Don Dapkus over 16 years ago in reply to Cheok Loon Lee

TI__Guru**** 189401 points

Mr Lee,

Nick is on holiday, so let me jump in here.

You are correct, using too high of a gain will kill your system performance.

You should use the lowest gain you can in the amplifier, and move your gain to the previous stage. This will greatly help sound quality, and SNR.

Best regards,

Don

0 Cheok Loon Lee over 16 years ago in reply to Don Dapkus

Intellectual 610 points

Hi Don,

Thank you for the advice.

Just managed to got hold of TPA2012D2EVM. Seems like the IC used in the evm is WSCP instead of QFN which I've decided to use. Is there any QFN evm around since my spec is 2.1W/ch

Thanks,

Lee

0 Don Dapkus over 16 years ago in reply to Cheok Loon Lee

TI__Guru**** 189401 points

Lee,

Sorry, the only released EVM we have for the TPA2012D2 uses the WCSP package. It is indeed thermally limited when you run it at 5V. If you play audio thru it, the crest factor will most likely save you. So, unless you need to do testing with sine waves at full power, the WCSP EVM should work just fine for you.

Best regards,

Don

0 Cheok Loon Lee over 16 years ago in reply to Don Dapkus

Intellectual 610 points

Hi Don,

Thanks. I'll try to test it with the WCSP evm :)

0 Cheok Loon Lee over 16 years ago in reply to Cheok Loon Lee

Intellectual 610 points

Hi,

Using the gain setting table on datasheet, e.g. 6dB Gain. How do I find the output power of the TPA2012evm.

Input signal until it clips at 1%, measure the output power?

Settings are:
1) 4ohm load
2) 5V supply

If this is correct, can I say that the gain setting table is based on 1% distortion?

0 Don Dapkus over 16 years ago in reply to Cheok Loon Lee

TI__Guru**** 189401 points

Lee,

The gain is defined as the voltage gain of the amplifier. It does not have anything to do with THD.

The output power is nearly independent of gain setting. You do have to adjust your input amplitude to achieve the same output power as you change the gain.

there is a plot in the d/s that shows the output power for the conditions you've mentioned above.

Please review it, as well as Nick's excellent app note. I think all your answers are discussed in those two documents.

-d2

Audio

Audio forum

Question on TPA2012D2