OPA2171-EP_16 Datasheet, PDF (16/28 Pages) Texas Instruments – 36-V, Single-Supply, SOT553, General-Purpose Operational Amplifiers

OPA2171-EP
SBOS735 – SEPTEMBER 2015
8 Application and Implementation
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NOTE
Information in the following applications sections is not part of the TI component
specification, and TI does not warrant its accuracy or completeness. TI’s customers are
responsible for determining suitability of components for their purposes. Customers should
validate and test their design implementation to confirm system functionality.
8.1 Application Information
8.1.1 Electrical Overstress
Designers often ask 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.
These ESD protection diodes also provide in-circuit, input overdrive protection, as long as the current is limited to
10 mA as stated in Absolute Maximum Ratings. Figure 38 shows how a series input resistor may be added to the
driven input to limit the input current. The added resistor contributes thermal noise at the amplifier input and its
value should be kept to a minimum in noise-sensitive applications.
I_OVERLOAD
10mA max
V_IN
5kW
V+
OPA171
V_OUT
Figure 38. Input Current Protection
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 the operational amplifier connects into a circuit, 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. If this condition occurs, 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 ESD cells and rarely involves the absorption device.
If there is uncertainty about the ability of the supply to absorb this current, external Zener diodes may be added
to the supply pins. Select the Zener voltage such that the diode does not turn on during normal operation.
However, its Zener voltage should be low enough so that the Zener diode conducts if the supply pin begins to
rise above the safe operating supply voltage level.
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