TAS5782M: Undershoot Voltage Level for SPK_OUTxx Pins

Sadanori Kato

Part Number: TAS5782M

Hi,

Could you please tell me the actual value for the undershoot voltage level which TAS5782M can allow at SPK_OUTxx pins ?
There is mentioned on page 9 of TAS5782M data sheet as below however the undershoot voltage was less than -0.3V when our customer observed their pins using TAS5782MEVM.
So, please double-check it and tell me an allowable excess period for the absolute maximum ratings.

Best regards,
Kato

over 6 years ago

0 Jeff Kohnle over 6 years ago

TI__Expert 6985 points

Hello Kato-san! Andy can help with follow-on questions... but this can depend on configuration details as our testing is based on the noted fixed configuration. What is your PVDD and what type of load are you trying to drive? Thanks, Jeff

0 Sadanori Kato over 6 years ago in reply to Jeff Kohnle

Guru 36490 points

Hi Jeff-san,

Thank you for your reply.

Our customer assumes PVDD = 12V and speaker impedance = 4ohm however there is a possibility that those may be modified.
I am looking forward to getting the information from Andy-san.

Best regards,
Kato

0 Andy Liu (BMS) over 6 years ago in reply to Sadanori Kato

TI__Guru 52115 points

Hi Kato,

The undershoot voltage varies with different PCB designs, so we don't provide the spec in our datasheet.

Take a closer look at the following highlighted symbols. All of them mean the input voltage for certain pins. Likewise, the “Voltage at speaker output pins" means the input (NOT output) voltage for SPK_OUT pins. It doesn’t specify the min or max voltage that the SPK_OUT pins can output.

Andy

0 Sadanori Kato over 6 years ago in reply to Andy Liu (BMS)

Guru 36490 points

Hi Andy-san,

Thank you for your reply.

Does it mean that the VI(SPK_OUTxx) parameter doesn't care as long as using the SPK_OUTxx pins as the output ports ?
In addition, could you please verify the undershoot voltage using your TAS5782MEVM ?

Best regards,
Kato

0 Sadanori Kato over 6 years ago in reply to Sadanori Kato

Guru 36490 points

Hi Andy-san,

I will meet and discuss this issue with our customer today, so please let me know as soon as possible if you have any updates on it.

Best regards,
Kato

0 Andy Liu (BMS) over 6 years ago in reply to Sadanori Kato

TI__Guru 52115 points

Hi Kato,

The undershoot voltage is around 900mV with the following test conditions.

a) TAS5872MEVM

b) PVDD = 12V

c) Load = 4 Ohm

Andy

0 Sadanori Kato over 6 years ago in reply to Andy Liu (BMS)

Guru 36490 points

Hi Andy-san,

Thank you for your continuous support.

The undershoot peak voltage changes and increases depended on the inductor current if inputting the 1kHz sine to TAS5782MEVM.
At that time, the undershoot voltage is clamped by the body diode of the low side MOSFET so I believe that the clamped period depends on the dead time which is approximately ~8ns.
Is my understanding correct above it ?
In addition, could you please tell me the design expected value for that dead time ?

Best regards,
Kato

0 Andy Liu (BMS) over 6 years ago in reply to Sadanori Kato

TI__Guru 52115 points

Hi Kato,

Your understanding is correct. The dead time we expect is close to 8ns.

Andy

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TAS5782M: Undershoot Voltage Level for SPK_OUTxx Pins