ADS9224R: Input Voltage for AVDD, DVDD

Masakazu Adachi

Intellectual 2500 points

Part Number: ADS9224R

Hello team,

I received a question from the customer.

Is it ok to apply such voltage waveforms to AVDD and DVDD?

Applying a power supply with a rising waveform like this often results in no output when CONVST is input to the ADC.

Yellow is AVDD (5V) and green is DVDD (3.3V).

Both are 1.0V/div, 500us/div.

I asked this question because I could not find the sequence of AVDD and DVDD input even after reading the Power Supply Recommendations in Chapter 9. If the customer applies a linearly rising power supply, the system operates fine.

Regards,

Masa

over 2 years ago

0 Ryan Andrews over 2 years ago

TI__Guru 63606 points

Hello Masa-san,

Thank you for your post.

There is no specific sequencing required for the ADS9224R power supplies. However, if these supply waveforms are causing issues, my suggestion would be to pulse the PDn/RSTn pin (pin 26) after both AVDD and DVDD are stable (i.e. after time = T1 on the scope image). Please follow the timing guidelines in section 7.4.3.1 to reset the device after power-up and then configure the device as needed.

Regards,

Ryan

0 Masakazu Adachi over 2 years ago in reply to Ryan Andrews

TI__Intellectual 2500 points

Hello Ryan-san,

Thank you for your suggestion.

Cloud you tell me why the maximum value of the reset pulse is defined?

Regards,

Masa

+1 Ryan Andrews over 2 years ago in reply to Masakazu Adachi

TI__Guru 63606 points

Hi Masa-san,

Pin 26 serves dual functionality and can be used as reset or power-down. The maximum pulse width for reset (tWL-RST) ensures that the pulse is interpreted as a reset signal only. Typically the maximum for reset and the minimum pulse width for power-down are the same in most devices, but in ADS9224R there is more margin between the two pulse widths to ensure reliability.

Regards,

Ryan

0 Masakazu Adachi over 2 years ago in reply to Ryan Andrews

TI__Intellectual 2500 points

Hi Ryan-san,

Thank for the support. I understand.

Regards,

Masa

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ADS9224R: Input Voltage for AVDD, DVDD