AD7849: critical item for power supplies

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Q 
 Is there any critical item for power supplies of AD7849 which could result in behaviour as described above ? Or do you have any other idea what happens with the converters. We are using this devices in other applications for years and there we do not have problems like this. So it seems that there is an application dependent reason. 
 
 A 
 Firstly, I would like to make sure that the part is not going into latchup. The fact that the part is drawing too much current could suggest that the part is latching up and this DAC is particularly vulnerable to latchup. It is absolutely critical that you respect the absolute maximum ratings for the AD7849 at all times, even during power up. Any digital input should never be allowed to be more than 0.4V outside the digital supply voltage, even during power up. If the circuitry driving the digital pins of the AD7849 is powered separately and is likely to power up before the AD7849, you can protect the digital inputs using Schottky diodes to Vcc and Dgnd. For extra protection, you can also add a series resistance prior to the digital inputs. Vcc(digital supply) must never exceed Vdd(analog supply) by more than 0.4V. If the digital supply is likely to power up before the analog supply, you should protect the AD7849 using the circuit shown on page 4 of the datasheet. ROFS and the DAC output pins must never have a voltage applied to them which is outwith the analog supplies. All analog and digital pins on an IC are protected by parasitic ESD protection diodes. These diodes will turn on when the voltage applied to a given pin exceeds the supply voltage. You must limit the current through these protection diodes to less then 10mA otherwise there is a danger of them shorting out and blowing the part. It's probably worth while examining the power supplies in your system to ensure that they turn on in the correct order i.e. so that the Absolute maximum ratings are respected during power-up.

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AD7849: FAQ