ADG453: Power Up Sequence

Q

Why some microcircuits ADG452 and ADG453, at submission supply voltage Vdd = +
15 V, Vss =-15 V, VL = + 5 V start to be heated up strongly, the current of
consumption up to several tens ma increases, at changeover by other copies of
the same microcircuits all works normally. Whether there is a restriction on
the order of submission a supply voltage +15 V,-15 V, and +5 V.

A

By powering on the VL before the VDD of the ADG452/ADG453 you are exceeding the
absolute max ratings for the part and will result in part failure, if this
occurs quiet often it will lead to part failure, using external schottky diodes
and a series limiting resistor will protect the part from latch up should this
occur. Refer to page 5 of the datasheet for more details on the max ratings
where you will note that you need to apply VDD prior to VL, and all analog and
digital inputs are referenced to VDD.

A simple solution is to include a Schottky diode between VL and VDD. Connect
the cathode to VL and the anode to VDD. Under normal operating conditions the
diode is reverse biased. When VDD collapses and VL remains high, the Schottky
diode conducts and ensures that there is never more than a 0.3V voltage drop
between VL and VDD.

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