DVDDIO below 3V, can work or no?

Hi,

  Kindly note that, for correct operation of the ADV7282A-M, the DVDDIO supply must be from 2.97 V to 3.63 V.  However, it can operate with a nominal DVDDIO voltage of 1.8 V. In this case, apply the power-up sequences described in the Optimal Power-Up Sequence section according to ADV728x datasheet.

 As per expert comment, DVDDIO must be greater than the 1.8V rails.  Else you will have current flow from 1.8V rail through the chip to the 3.3V rail possibly causing damage to the chip at Digital Inputs logic "1" voltage is higher than DVDDIO and digital input logic "0" voltage is lower than 0V on ADV7182&ADV7182A digital input pins - Q&A - Video - EngineerZone

2. If it cannot, then the DVDDIO must be increased to at least 3V. According to the datasheet, VIH 2B with DVDDIO 3.3V. Will VIH decrease to 1.8V if DVDDIO 3V?

    From the Data sheet it is observed that, VIH is approximately equals to 60% of DVDDIO. According to this 1.8V is 60% of 3V. So, you can decrease V_IH to 1.8V when DVDDIO is 3V.

  Also note that, when DVDDIO is 1.8V, do not pull any pin of the ADV7282A up to 3.3 V. For example, the I2C pins of the ADV7282A (SCLK and SDATA) must also be pulled up to 1.8 V instead of 3.3 V.

Thanks,

Poornima

Thanks for answer! 

We are talking about ADV7282A-M, which according to the documentation is not required to work at DVDDIO=1.8V, but it actually works. It is clear that there should be no overflow from the 1.8V line to the 3.3V line. And for this, the voltage on the 3.3V line should be supplied no later than the voltage on the 1.8V line and be no less than it.
If we supply 1.8V simultaneously to the all power 1.8V and DVDDIO lines, will there be a dangerous overflow from 1.8V power lines to the DVDDIO? We have not had a single chip fail with this type of operation.
But I was more interested in whether rare color and synchronization failures are possible given  DVDDIO=1.8V. And if such failures are possible, then how can this be avoided  given the control processor is at 1.8V. 

Best regards, 

Serge

Hi,

  We don't face such rare color and synchronization failures in our eval board when using DVDDIO at 1.8V So could you please check the same in our evaluation board.

   We can power up the 1.8V SUPPLIES at any stage as long as they can ensure that the 1.8V SUPPLIES do not go to a higher voltage than the 3.3V SUPPLIES during power-up.

   According to simplified power-up sequence of ADV7282A , the ADV7282A can be powered up by asserting all supplies and the PWRDWN pin simultaneously. But make sure lower rated supply should not exceed a higher rated supply.
  We will not get any problems when 1.8V is supplied to DVDDIO, if you follow the instructions mentioned under 'DVDDIO SUPPLY VOLTAGE' in Data sheet.
  It is possible to have DVDDIO at 1.8V (reset and power down will have to be pulled up to 1.8V) but in this state drive strength of all digital outputs to the maximum values.

Note: As per expert comment, In general for all ICs absolute maximum ratings are dependent on

• Gate oxide breakdown threshold
• ESD protection activation limits
• Thermal limitations

Hello, I am a colleague of Fatus.

As you have recommended, we use ADV7282A-M with AVDD = DVDD = DVDDIO = MVDD = PVDD = 1.8V.

Also, we have set up PWRDWN and RESET pins according to simplified power-up sequence from datasheet.

In a result we still have random color and synchronization issues with likelihood at 1/100 reboots. (please see attachments)

Note: we use ADV7282A-M with 1.8V, which according to the datasheet is not required to work at DVDDIO=1.8V

Can you suggest any recommendations to find out the causes of such issues, thanks

Hi,

   Could you please check the same observation in our evaluation board?

Thanks,

Poornima

Hi,

Evaluation board utilizes 3.3V to DVDDIO, so there will be different case.

Other question is, can 1.8V to DVDDIO be a cause of such issues, because the datasheet says to use 3.3V DVDDIO ADV7282A-M

Hi,

   As per specification, "For correct operation of the ADV7282A-M, the DVDDIO supply must be from 2.97 V to 3.63 V. The ADV7282A, however, can operate with a nominal DVDDIO voltage of 1.8 V". 

  Other question is, can 1.8V to DVDDIO be a cause of such issues, because the datasheet says to use 3.3V DVDDIO ADV7282A-M

    We are not sure about what might be the cause of such issues, Better please try to follow as per our evaluation board voltage utilization.

Thanks,

Poornima

Hi,

Can Damping resistor on quartz be cause of such behavior? We currently do not use any damping resistor, what is it's purpose?

Hi,

   As per specification, A damping resistor (RDAMP) is required on the output of the ADV7282A XTAL amplifier (XTALP). The purpose of this damping resistor is to limit the current flowing through the XTAL and to limit the voltage across the XTAL amplifier. To define the appropriate value of the damping resistor RDAMP (see the Typical Circuit Connections section), consult the accompanying calculator tool (visit the design resources section at www.analog.com/ADV7282A to download).