AD5413 on the same line as a switching output

Question

Hello everyone, 
 we have an application where we need to use a single line as either a digital output or an analog output. The digital output has a voltage range of 10V to 30V (+Ub) and the used AD5413 has a supply of 12V. We need that seperate 12V supply for the AD5413 because of the needed Headroom for the 0-10V interface. Since the absolut maximum ratings only allows AVDD1 + 0.3 V at the VIOut-Pin we have some trouble with the digital output and the internal protective circuit responds, resulting in a short circuit on the digital output. Therefore we used two diodes at the AD5413 supply as shown. 
 Is there any reason against this approach? 
 I know the ADG5401F but unfortunately this device is too expensive for this price sensitive project. 
 Thanks a lot.

RGrau · Accepted Answer

Hi Tim, 
 I understand. The above setup should work. Consider that the diodes will introduce a forward voltage drop which needs to be considered for the AD5413 headroom. The reverse current of the diodes and maximum reverse voltage also needs to be considered when selecting the diodes. 
 To protect the AD5413 output from a reverse overvoltage, a TVS diode between the VIOUT and AVDD1 pins is recommended as the AD5413 does not have an internal output fault protection, and if the voltage in VIOUT is higher than AVDD1 the current goes into the device which can damage the device. 
 Regards, 
 Raquel.)

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AD5413 on the same line as a switching output

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