OPA192 Datasheet, PDF (17/35 Pages) Texas Instruments – High Voltage, Rail-to-Rail Input/Output, Precision Operational Amplifiers, e-trim Series

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OPA192
OPA2192
OPA4192
SBOS620A – DECEMBER 2013 – REVISED JANUARY 2014
ELECTRICAL OVERSTRESS
Designers often ask questions about the capability of an operational amplifier to withstand electrical overstress
(EOS). 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 42 for an illustration of the ESD circuits contained in the OPAx192 (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 or
the power-supply ESD cell, internal to the operational amplifier. This protection circuitry is intended to remain
inactive during normal circuit operation.
TVS
RF
R1
IN-
RS
IN+
ID
+
VIN
±
100 Ÿ
100 Ÿ
+VS
VDD
OPA192
Power-Supply
RL
ESD Cell
VSS
-VS
TVS
Figure 42. Equivalent Internal ESD Circuitry Relative to a Typical Circuit Application
An ESD event is very short in duration and very high voltage (for example, 1 kV, 100 ns), whereas an EOS event
is long duration and lower voltage (for example, 50 V, 100 ms). The ESD diodes are designed for out-of-circuit
ESD protection (that is, during assembly, test, and storage of the device before it is soldered to the PCB). During
an ESD event, the ESD signal is passed through the ESD steering diodes to an absorption circuit (labeled ESD
power-supply circuit). The ESD absorption circuit clamps the supplies to a safe level.
While this behavior is necessary for out-of-circuit protection, it causes excessive current and damage if activated
in-circuit. A transient voltage suppressors (TVS) can be used to prevent against damage caused by turning on
the ESD absorption circuit during an in-circuit ESD event. Using the appropriate current limiting resistors and
TVS diodes allows for the use of device ESD diodes to protect against EOS events.
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