TAS2770: SAR ADC measure of VBAT above 14V

Diego UA&A

Part Number: TAS2770

Hi, E2E Team!

We are using the TAS2770 in one of our client's products, and as part of a Speaker Health communication system, we report VBAT from the amplifier to the host device.

In the system, we use a VBAT voltage of +16V, but when reading registers 0x27 and 0x28, the result is always 0xE0C (~+14V). This has been replicated on different systems and the readings are about the same (0xE0E, 0xE0F, and similar)

We isolated VBAT net on one system and connected an external power supply to validate the behavior of the SAR ADC in the amplifier. The readings we obtained from the SAR ADC are correct with any value below +14V, however, with any voltage higher than 14V, the result from the SAR ADC conversion is always around +14V (0xE0C, 0xE0F, and similar).

Is this a limitation of the SAR ADC for VBAT?

Is there any configuration required in the TAS2770 to enable the SAR ADC to read voltages up-to +16V?

Thanks!

-Diego Melendez Lopez

over 3 years ago

0 Atiq Rahman over 3 years ago

TI__Expert 5110 points

Hi Diego,

Do you also see the same behavior on TAS2770 EVM?

Regards,

Atiq

0 Diego UA&A over 3 years ago in reply to Atiq Rahman

Prodigy 120 points

Hi, Atiq,

Thanks for your email, yes, we see the same behavior on the EVM.

Best regards,

-Diego Melendez Lopez

0 Atiq Rahman over 3 years ago

TI__Expert 5110 points

Hi Diego,

We have tried the SAR ADC measurement for VBAT on EVM too and it works well up to 14V and saturates above that. I would suggest using it upto 14V in your application.

Thanks,

Atiq

0 Diego UA&A over 3 years ago

Prodigy 120 points

Hi, Atiq,

Thanks for your confirmation. Do you have any additional information about the reason for the SAR ADC to saturate?, I would like to understand if this is an expected behavior for the device. If so, can we asume that the SAR ADC does not work with values above 14V?

Thanks!

-Diego Melendez Lopez

0 Atiq Rahman over 3 years ago in reply to Diego UA&A

TI__Expert 5110 points

Hi Diego,

I am checking with team for some more details on this SAR ADC measurement and would keep you posted early next week.

Thanks,

Atiq

+1 Atiq Rahman over 3 years ago in reply to Atiq Rahman

TI__Expert 5110 points

Hi Diego,

Current design implementation of SAR ADC for VBAT is targeted for 14V and hence the measurement you got is correct. We are working internally so that next update of datasheet would reflect this change.

Thanks,

Atiq

0 Diego UA&A over 3 years ago

Prodigy 120 points

Hi, Atiq,

Got it, we will consider this for future designs with the TAS2770.

Thanks for your help!

-Diego Meléndez López

0 Atiq Rahman over 3 years ago in reply to Diego UA&A

TI__Expert 5110 points

Hi Diego,

Thanks for using TI Audio products in your designs.

Regards,

Atiq

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TAS2770: SAR ADC measure of VBAT above 14V