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AD5422 - Transient voltage protection

Hello,

we want to use the AD5422 in single supply mode (AVDD=17VDC) with voltage and current output on same terminal.

There is a input protection example in the datasheet of the AD5422 (page 37, figure 76).

Right at the input terminal we want to use a bi-directional TVS SMBJ18CA. We also use a current limiting resistor 18 Ohm.

At the input of the AD5422 we have two protection diodes to AVDD and GND.

 

What kind of diodes should be used there (type and power rating) ?

Do I have to use schottky diodes or can I use normal silicon diodes, e.g. LL4148 ?

Should I take care of the higher reverse current when using schottky diodes ?

What is the clamping voltage of the AD5422 internal ESD protection diodes ?

Is another resistor necessary between external clamping diodes and the AD5422 input ?

 

Regards

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  • Any leakage from the TVS or diode will generate some error on the output, so it's important to keep these leakages small in relation to your output. Another option for diode is the BAV199, this device is a standard diode but has lower leakage.

    In either case, the extra resistor inside the diode to limit current on chip provides an additional level of protection to the part.

    The level of transient protection in any given design will depend on the environment in which it is operating and so it is difficult to give a specific recommendatioin which covers all cases.

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  • Any leakage from the TVS or diode will generate some error on the output, so it's important to keep these leakages small in relation to your output. Another option for diode is the BAV199, this device is a standard diode but has lower leakage.

    In either case, the extra resistor inside the diode to limit current on chip provides an additional level of protection to the part.

    The level of transient protection in any given design will depend on the environment in which it is operating and so it is difficult to give a specific recommendatioin which covers all cases.

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