OPA1678 Datasheet, PDF (15/41 Pages) Texas Instruments – Low-Distortion Audio Operational Amplifiers

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OPA1678, OPA1679
SBOS855 – FEBRUARY 2017
Feature Description (continued)
7.3.2 Electrical Overstress
Designers often ask questions about the capability of an operational amplifier to withstand electrical overstress.
These questions tend to focus on the device inputs, but can involve the supply voltage pins or even the output
pin. Each of these different pin functions have electrical stress limits determined by the voltage breakdown
characteristics of the particular semiconductor fabrication process and specific circuits connected to the pin.
Additionally, internal electrostatic discharge (ESD) protection is built into these circuits to protect them from
accidental ESD events both before and during product assembly.
A good understanding of this basic ESD circuitry and the relevance to an electrical overstress event is helpful.
Figure 32 illustrates the ESD circuits contained in the OPA167x (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 the diodes meet at an absorption device internal to the operational
amplifier. This protection circuitry is intended to remain inactive during normal circuit operation.
TVS
RF
+VS
R1
IN±
RS
IN+
ID
+
VIN
±
250 Ÿ
250 Ÿ
+
Power-Supply
ESD Cell
RL
±VS
TVS
Copyright © 2017, Texas Instruments Incorporated
Figure 32. 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 has a trigger, or threshold voltage, that is above the normal operating voltage of the OPA167x but below
the device breakdown voltage level. When this threshold is exceeded, the absorption device quickly activates
and clamps the voltage across the supply rails to a safe level.
Copyright © 2017, Texas Instruments Incorporated
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