OPA140_15 Datasheet, PDF (20/44 Pages) Texas Instruments – High-Precision, Low-Noise, Rail-to-Rail Output,11-MHz JFET Op Amp

OPA140, OPA2140, OPA4140
SBOS498B – JULY 2010 – REVISED NOVEMBER 2015
Feature Description (continued)
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TSSOP Quad
SOIC Quad
MSOP Dual
SOIC Dual
90 100 110 120 130 140 150 160
Ambient Temperature (°C)
Figure 35. Maximum Supply Voltage vs Temperature
(OPA2140 and OPA4140), Quiescent Condition
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8
6
4
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0
80
TSSOP Quad
SOIC Quad
MSOP Dual
SOIC Dual
90 100 110 120 130 140 150 160
Ambient Temperature (°C)
Figure 36. Maximum Supply Voltage vs Temperature
(OPA2140 and OPA4140), Maximum DC Load
7.3.8 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.
It is helpful to have a good understanding of this basic ESD circuitry and its relevance to an electrical overstress
event. See Figure 37 for an illustration of the ESD circuits contained in the OPAx140 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.
An ESD event produces a short duration, high-voltage pulse that is transformed into a short duration, high-
current pulse as it discharges through a semiconductor device. The ESD protection circuits are designed to
provide a current path around the operational amplifier core to prevent it from being damaged. 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 has a trigger, or threshold voltage, that is above the normal operating voltage of the
OPAx140 but below the device breakdown voltage level. Once 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 such as the one Figure 37 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.
Should this condition occur, there is a risk that some of the internal ESD protection circuits may be biased on,
and conduct current. Any such current flow occurs through steering diode paths and rarely involves the
absorption device.
Figure 37 depicts 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 may 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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