OPA171 datasheet(21/58 Pages) TI2

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Power-Supply

ESD Cell

2.5 NŸ

IN±

IN+

TVS

VIN

±VS

TVS

+VS

Figure 7-1. Equivalent Internal ESD Circuitry Relative to a Typical Circuit Application

An ESD event produces a short duration, high-voltage pulse that is transformed into a short duration, high-

current pulse when discharging through a semiconductor device. The ESD protection circuits are designed to

provide a current path around the operational amplifier core to prevent damage. The energy absorbed by the

protection circuitry is then dissipated as heat.

When an ESD voltage develops across two or more amplifier device pins, current flows through one or

more steering diodes. Depending on the path that the current takes, the absorption device can activate. The

absorption device contains a trigger (or threshold voltage) that is above the normal operating voltage of the

OPAx171 but below the device breakdown level. When this threshold is exceeded, the absorption device quickly

activates and clamps the voltage across the supply rails to a safe level.

When the operational amplifier connects into a circuit (as shown in Figure 7-1), the ESD protection components

are intended to remain inactive and do not become involved in the application circuit operation. However,

circumstances may arise when an applied voltage exceeds the operating voltage of a given pin. If this condition

occurs, there is a risk that some internal ESD protection circuits can turn on and conduct current. Any such

current flow occurs through steering-diode paths and rarely involves the absorption device.

Figure 7-1 shows a specific example where the input voltage (VIN) exceeds the positive supply voltage (V+) by

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

current, one of the upper steering diodes conducts and directs current to V+. 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 begins 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.

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OPA171, OPA2171, OPA4171

SBOS516H – SEPTEMBER 2010 – REVISED JUNE 2024

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OPA171 Datasheet(PDF) 21 Page - Texas Instruments