ADS8689: AVDD and DVDD Power-Up Sequence

Hiroaki Yuyama TED

Part Number: ADS8689

Tool/software:

Dear, Data converters Support team.

According to the datasheet, the Absolute Maximum Ratings of the ADS8689 are +7V for both AVDD and DVDD.
The Recommended Operating Conditions for DVDD are up to AVDD.

Are there any restrictions on the power-up sequence and order of AVDD and DVDD? At this time, no analog input signal is applied.

Our customer supplies both AVDD and DVDD from 5V.
In this case, should the ADS8689's digital power supply be separated from the analog power supply?

Would there be any problems with an RC filter with a resistor of a few ohms?
If you have any good ideas for power supply when both AVDD and DVDD are 5V, please let me know.

Best Regards,
Hiroaki Yuyama

5 months ago

0 Tom Hendrick 5 months ago

TI__Guru**** 181021 points

Yuyama-san,

There is no special sequence requirement for the power supplies of the ADS8689, using the same 5V source for both is fine.

0 Hiroaki Yuyama TED 4 months ago in reply to Tom Hendrick

Expert 1740 points

Hi Hendrick-san,

Thank you for your advice.
We told the customer to provide +5V from a clean analog supply to power both the ADS8969's VADD and DVDD.
If the customer has any questions, please advise again.

Best Regards,
Hiroaki Yuyama

0 Hiroaki Yuyama TED 4 months ago in reply to Hiroaki Yuyama TED

Expert 1740 points

Hi Hendrick-san,

In the datasheet, section 6.3 Recommended Operating Conditions states that the MAX value of DVDD is up to AVDD,but are there any problems if DVDD exceeds AVDD?

Our customer is concerned that if DVDD is supplied from the digital power supply, ripple noise will exceed AVDD.

Best Regards,

Hiroaki Yuyama

0 Tom Hendrick 4 months ago in reply to Hiroaki Yuyama TED

TI__Guru**** 181021 points

Yuyama-san,

Please review the top of the pages in section 6.5. All performance data is based on AVDD of 5V and DVDD of 3.3V using the internal reference. Please point that out to your customer and have them use the recommended NOM voltage sources.

0 Hiroaki Yuyama TED 4 months ago in reply to Tom Hendrick

Expert 1740 points

Hi Hendrick-san,

Thank you for your reply.

In the datasheet, 6.1 Absolute Maximum Ratings states that both AVDD and DVDD range from -0.3V to +7.0V.
The customer is concerned that when DVDD exceeds the AVDD voltage, will there be any device problems such as latch-up?
The customer made this inquiry because some systems have a 3V digital interface, but some also have a 5V interface.

Best Regards,

Hiroaki Yuyama

0 Tom Hendrick 4 months ago in reply to Hiroaki Yuyama TED

TI__Guru**** 181021 points

As originally noted, there is no issue if AVDD and DVDD are both 5V

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ADS8689: AVDD and DVDD Power-Up Sequence