OPA172IDR Datasheet, PDF (17/29 Pages) Texas Instruments – 36-V Single-Supply 10-MHz Rail-to-Rail Output Operational Amplifiers

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OPA172
OPA2172
OPA4172
SBOS618 – DECEMBER 2013
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 may 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.
Having a good understanding of this basic ESD circuitry and its relevance to an electrical overstress event is
helpful. See Figure 45 for an illustration of the ESD circuits contained in the OPAx172 (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
R_F
R₁
IN-
R_S
IN+
I_D
+
V_IN ±
250Ÿ
250Ÿ
+V_S
V_DD
OPA172
Power supply
ESD cell
R_L
V_SS
-V_S
TVS
Figure 45. 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 while 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 may activate. The
absorption device has a trigger, or threshold voltage, that is above the normal operating voltage of the OPAx172
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 © 2013, Texas Instruments Incorporated
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