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Dear team:
Consult Figure 82 in the AD5422 data sheet. How the Schottky diodes D2 and D1 are selected (can you give a recommendation)? Operating voltage is 24V. Here's what D2 and D1 do.

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• Hi lijie,

0336.e8bbbd9ea9e2a594d9624d720052a224.jpg

Looking at figure 78 on the data sheet, the power diodes and Rp help protect the IOUT pin from overvoltages.

The power diodes that you should choose should have a low forward voltage so that it would have a faster turn-on time.

Rp will limit the current flowing through the power diode, hence preventing it from getting damaged due to high dissipation.

Lets say you have a 0.3V forward voltage for the selected power diode and AVDD=15V. You can compute for the resistor by this equation:

Rp= (VOUT-0.3V-AVDD)/Id

Consider Id based on the maximum power dissipation you want on the power diode.

Don't use an Rp that is very large as this would affect the compliance voltage (AVDD-2.5V) of the IOUT during normal operation.

Refer to INDUSTRIAL ANALOG OUTPUT MODULE section (page 41)  and figure 83 for the recommended TVS diodes.

Best regards,

Rainier

• Hi lijie,

0336.e8bbbd9ea9e2a594d9624d720052a224.jpg

Looking at figure 78 on the data sheet, the power diodes and Rp help protect the IOUT pin from overvoltages.

The power diodes that you should choose should have a low forward voltage so that it would have a faster turn-on time.

Rp will limit the current flowing through the power diode, hence preventing it from getting damaged due to high dissipation.

Lets say you have a 0.3V forward voltage for the selected power diode and AVDD=15V. You can compute for the resistor by this equation:

Rp= (VOUT-0.3V-AVDD)/Id

Consider Id based on the maximum power dissipation you want on the power diode.

Don't use an Rp that is very large as this would affect the compliance voltage (AVDD-2.5V) of the IOUT during normal operation.

Refer to INDUSTRIAL ANALOG OUTPUT MODULE section (page 41)  and figure 83 for the recommended TVS diodes.

Best regards,

Rainier

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