OPA172-Q1 Datasheet, PDF (20/36 Pages) Texas Instruments – 36-V, Single-Supply, 10-MHz, Rail-to-Rail Output Automotive Grade Operational Amplifiers

OPA172-Q1, OPA2172-Q1, OPA4172-Q1
SBOS809 – NOVEMBER 2016
RF
TVS
+VS
www.ti.com
R1
IN±
RS
IN+
ID
+
VIN
±
250 Ÿ
250 Ÿ
+
Power-Supply
ESD Cell
RL
Copyright © 2016, Texas
Instruments Incorporated
±VS
TVS
Figure 46. 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 terminals, 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 OPAx172-Q1 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.
When the operational amplifier connects into a circuit (as shown in Figure 46), the ESD protection components
are intended to remain inactive and do not become involved in the application circuit operation. However,
circumstances can arise where an applied voltage exceeds the operating voltage range of a given terminal. 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 46 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 data sheet specifications recommend that
applications limit the input current to 10 mA.
If the supply is not capable of sinking the current, V_IN can begin 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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