OPA202IDBVT datasheet(23/47 Pages) TI1

23 / 47 page

Op Amp

Core

(1)

OUT

ESD Current-

Steering Diodes

V+

TVS

(2)

Edge-Triggered ESD

Absorption Circuit

V±

TVS

(2)

100

+IN

(3)

OPA202, OPA2202, OPA4202

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SBOS812D – OCTOBER 2017 – REVISED DECEMBER 2019

Product Folder Links: OPA202 OPA2202 OPA4202

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Figure 43 shows a specific example where the input voltage, VIN, exceeds the positive supply voltage (+VS) by

500 mV or more. Much of what happens in the circuit depends on the supply characteristics. If +VS can sink the

current, one of the upper input steering diodes conducts and directs current to +VS. Excessively high current

levels can flow with increasingly higher VIN. As a result, the data sheet specifications recommend that

applications limit the input current to 10 mA.

If the supply is not capable of sinking the current, VIN may begin sourcing current to the operational amplifier, and

then take over as the source of positive supply voltage. The danger in this case is that the voltage can rise to

levels that exceed the operational amplifier absolute maximum ratings.

Another common question involves what happens to the amplifier if an input signal is applied to the input while

the power supplies +VS or –VS are at 0 V.

It depends on the supply characteristic while at 0 V, or at a level below the input signal amplitude. If the supplies

appear as high impedance, then the operational amplifier supply current may be supplied by the input source

through the current steering diodes. This state is not a normal bias condition; the amplifier most likely does not

operate normally. If the supplies are low impedance, then the current through the steering diodes can become

quite high. The current level depends on the ability of the input source to deliver current, and any resistance in

the input path.

If there is an uncertainty about the ability of the supply to absorb this current, external Zener diodes may be

added to the supply pins as shown in Figure 43. The Zener voltage must be selected such that the diode does

not turn on during normal operation.

However, the Zener voltage must be low enough so that the Zener diode conducts if the supply pin rises above

the safe operating supply voltage level.

(1)

VIN = +VS + 500 mV.

(2)

TVS: +VS(max) > VTVSBR (Min) > +VS

(3)

Suggested value is approximately 5 kΩ in overvoltage conditions.

Figure 43. Equivalent Internal ESD Circuitry in a Typical Application Circuit

OPA202IDBVT Datasheet(PDF) 23 Page - Texas Instruments

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