TAS5624A Gain of BTL Mode

Kato-san,

I asked my colleague to look into this post. Unfortunately, he won't be back in office until next week. 

Hi Damian-san,

Thank you for your reply.
Could you please obtain that information from your colleague since I need to inform our customer of our opinion in this week?

Best Regards,
Kato

Kato-san,

I'm working on getting you an answer this week.

Hi Damian-san,

Thank you for your cooperation.
I am looking forward to hearing from you.

Best Regards,
Kato

Hi Damian-san,

Thank you very much for your advice.
I understood the calculation of the output voltage amplitude as below.
Could you please give me your advice if I have any misunderstanding?

<Condition>
Input Signal     : -20dBFS
Gain             : 0.4264(SE Mode) / 0.8528(BTL Mode)
Volume Level     : 0dB
Modulation Level : 97.7%

for SE Mode :
Output Voltage = 0.1(-20dBFS) * 1(0dB) * 0.4264(Gain) * 97.7(Modulation Level) = 4.166Vrms

for BTL Mode :
Output Voltage = 0.1(-20dBFS) * 1(0dB) * 0.8528(Gain) * 97.7(Modulation Level) = 8.332Vrms

Best Regards,
Kato

Hi Damian-san,

Thank you for confirming.
I will contact you if I have any questions.

Best Regards,
Kato

Hi Damian-san,

Could you please confirm the unit of the SE gain just in case?
I doubt whether Vrms/% of the unit which you mentioned is correct since that gain is too high, so I am considering as below.
Is my understanding correct?

The gain in Vrms/% is 0.151 if the unit of 0.426 is Vpp/%.

Best Regards,
Kato

Hi Damian-san,

I obtained 0.289Vrms/% as the gain of the BTL mode by evaluating TAS5624A evm.
So, I believe that 0.151Vrms/% is maybe correct as the gain of the SE mode.

Best Regards,
Kato

Hi Kato-san,

Measuring is always best. Can you share your measurement details? Input PWM voltage rail and duty cycle used?

Hi Damian-san,

I have evaluated the evm which TAS5538 and TAS5624A are mounted, those results are shown as below.
Could you please give me your advice if I have any misunderstanding?

(a) case1
PVDD                   : 28[V]
PWM Input Voltage Rail : 3.3[V]
Input Signal           : 0[dBFS]
Volume Level           : -12[dB]
Modulation Index Limit : 93.7[%]
Vrms for BTL           : 6.779[Vrms]

---> Calculated Gain   : 0.2880[Vrms/%]

(b) case2
PVDD                   : 28[V]
PWM Input Voltage Rail : 3.3[V]
Input Signal           : 0[dBFS]
Volume Level           : -6[dB]
Modulation Index Limit : 93.7[%]
Vrms for BTL           : 13.560[Vrms]

---> Calculated Gain   : 0.2887[Vrms/%]

(c) case3
PVDD                   : 28[V]
PWM Input Voltage Rail : 3.3[V]
Input Signal           : 0[dBFS]
Volume Level           : -3[dB]
Modulation Index Limit : 93.7[%]
Vrms for BTL           : 19.150[Vrms]

---> Calculated Gain   : 0.2886[Vrms/%]

Best Regards,
Kato

Kato-san,

Thanks for sharing. Yes you are correct based on the assumption that 0dB (fullscale) is 2Vrms.

Hi Damian-san,

Thank you for confirming.
I will contact you if I have additional questions.

Best Regards,
Kato