OPA1611_15 Datasheet, PDF (13/31 Pages) Texas Instruments – SoundPlus High-Performance, Bipolar-Input Audio Operational Amplifiers

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OPA1611, OPA1612
SBOS450C – JULY 2009 – REVISED AUGUST 2014
Feature Description (continued)
Having a good understanding of this basic ESD circuitry and its relevance to an electrical overstress event is
helpful. Figure 30 shows the ESD circuits contained in the OPA161x series (indicated by the dashed line area).
The ESD protection circuitry involves several current-steering diodes connected from the input and output pins
and routed back to the internal power-supply lines, where they meet at an absorption device internal to the
operational amplifier. This protection circuitry is intended to remain inactive during normal circuit operation.
R_F
R_I
-In
+In
I_D
V_IN(1)
+V_S
+V
OPA1611
Op-Amp
Core
ESD Current-
Steering Diodes
Out
Edge-Triggered ESD
Absorption Circuit
R_L
-V
-V_S
(1) V_IN = +V_S + 500 mV.
Figure 30. Equivalent Internal ESD Circuitry and its Relation 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 discharged through a semiconductor device. The ESD protection circuits are designed to
provide a current path around the operational amplifier core to prevent damage to the core. The energy absorbed
by the protection circuitry is then dissipated as heat.
When an ESD voltage develops across two or more of the amplifier device pins, current flows through one or
more of the steering diodes. Depending on the path that the current takes, the absorption device may activate.
The absorption device internal to the OPA1611 triggers when a fast ESD voltage pulse is impressed across the
supply pins. Once triggered, the absorption device quickly activates and clamps the ESD pulse to a safe voltage
level.
When the operational amplifier connects into a circuit such as the one Figure 30 shows, the ESD protection
components are intended to remain inactive and not become involved in the application circuit operation.
However, circumstances may arise where an applied voltage exceeds the operating voltage range of a given pin.
If this condition occurs, some of the internal ESD protection circuits may possibly be biased on, and conduct
current. Any such current flow occurs through steering diode paths and rarely involves the absorption device.
Figure 30 shows a specific example where the input voltage, V_IN, exceeds the positive supply voltage (+V_S) by
500 mV or more. Much of what happens in the circuit depends on the supply characteristics. If +V_S can sink the
current, one of the upper input steering diodes conducts and directs current to +V_S. Excessively high current
levels can flow with increasingly higher V_IN. As a result, the datasheet specifications recommend that applications
limit the input current to 10 mA.
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