Gain of TAS5352A

Hello Hasebe-san,

Since the TAS5352A is an open loop device, the gain is dependent on the power supply voltage.

For example if the output PWM duty cycle is 50% and the supply voltage is 12V, the output voltage level will be 6V. If the supply voltage is 24V, the output voltage will be 12V.

If you are looking for a gain vs. power supply voltage curve, this will need to be tested.

Best Regards,
Matt

Hello Matt-san,

Thank you for your quick reply.

I understand your comments.

I forgot to confirm that TAS5352A is OpenLoop.

Also my customer used 30V power supply.

However, can you test the gain vs. power supply voltage curve?
If you can be it, please let me know the above characteristics result.

Best Regards,

Y.Hasebe

Hello Hasebe-san,

I apologize but since this is an older device, we do not have EVMs available to test the gain. As long as the modulator used can hit a high modulation index ex.97%, then full output power can be achieved regardless of the supply rail used.

Has your customer considered TAS56xx series devices?

What is the target application?

Best Regards,

Matt

Hello Matt-san,

Thank you for your reply, and sorry for my late reply.
I have another question.

My customer is using two types of circuit configuration.
One is TAS5558 + TAS5352A.
Another is the TAS5558 + TAS5624A.

In this two configurations, to set the output (that is, the input to each of the amplifier) conditions of the TAS5558 to 0dBFS.

When you confirm the output of each amplifier in the above conditions, we differ about 3dB as follows.
TAS5352A: 27.50dB
TAS5624A: 30.48dB
(Output of TAS5624A becomes 3dB higher than TAS5352A)

Is this correct?
Please tell us about this difference.

Hello Matt-san,

I got additional information from the customer.
Output MODE: BTL
PVDD of P.Stage: 30V
Setting of Modulator is the same also as both P.Stage.

Best Regards,
Y.Hasebe

Hello Hasebe-san,

Yes, 3dB difference in gain is an expected result.

Since the TAS5624A is a higher output power amplifier, it is designed with more gain compared to the lower power TAS5352A. The higher gain of the TAS5624A is required to hit higher output power (larger voltage swing) for the maximum modulation index (0dBFS) when compared to the TAS5352A.

If the gains of the TAS5624A and TAS5352A were the same, with an input 0dBFS the output power would be the same.

Best Regards,
Matt

Hello Matt-san,

Thank you for your reply.
I understand your comment.

I will send to my customer this comment.

Best Regards,
Y.Hasebe

Hello Matt-san,

My Customer asked me about below question.

How to calculate the Gain of 3dB different basis and TAS5624A and TAS5352A?
The reason is because there is a need to Gain calculation in the process and the product design.

Please tell me about above question.

Best Regards,
Y. Hasebe

Hello Hasebe-san,

Sorry for the delay as I was traveling. I am catching up now.

As mentioned, I don't have any more information on the TAS5352A since it is such an old device. I recommend that your customer tests the gain under the desired used case (PVDD voltage and speaker load) and use those gain values for their design. This will be even more accurate than calculations since it is a measured value.

3dB gain difference between TAS5624A and TAS5352A for the same PVDD voltage is expected due to the power level difference between these amplifiers.

Best Regards,

Matt

Hello Matt-san,

Thank you for your reply.

I understand the there is no information about the calculation formula of TAS5352A.

So, please tell me the formula of TAS5624A.

Best Regards,

Y.Hasebe

Hello Hasebe-san,

PWM input class-D amplifier don't have gain in an analog sense since they scale PWM signals. Instead they have a modulation index.

The TAS5624A has a closed loop PWM duty cycle gain of 0.125dB at the normal supply voltage of 36V. Since this is a closed loop amplifier, the PWM gain increases with reduced PVDD such that the output voltage remains constant. Therefore, at 18V PVDD the PWM duty cycle gain is now 0.125dB + 6dB = 6.125dB. The +6dB comes from 36V/18V = 2 = +6dB.

Therefore the PWM duty cycle gain can be expressed:
PWM Gain = [0.125dB + (20 x LOG(36V/PVDD))]

Best Regards,
Matt

Hello Matt-san,

Thank you for your reply.

I understand it.

I will tell my customer your answer.



Best Regards,

Y.Hasebe