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OPA202, OPA2202, OPA4202

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SBOS812 – OCTOBER 2017

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Copyright © 2017, Texas Instruments Incorporated

8.3.6 Phase-Reversal Protection

The OPA202, OPA2202, and OPA4202 family has internal phase-reversal protection. Many FET- and bipolar-

input op amps exhibit a phase reversal when the input is driven beyond its linear common-mode range. This

condition is most often encountered in noninverting circuits when the input is driven beyond the specified

common-mode voltage range, causing the output to reverse into the opposite rail. The input circuitry of the

OPA202, OPA2202, and OPA4202 prevents phase reversal with excessive common-mode voltage; instead, the

output limits into the appropriate rail (see Figure 29).

8.3.7 Thermal Protection

The OPAx202 series of op amps are capable of driving 2-kΩ loads with power-supply voltages of up to ±18 V

over the specified temperature range. In a single-supply configuration, where the load is connected to the

negative supply voltage, the minimum load resistance is 1.1 kΩ at a supply voltage of 36 V. For lower supply

voltages (either single-supply or symmetrical supplies), a lower load resistance may be used as long as the

output current does not exceed 35 mA; otherwise, the device short circuit current protection circuit may activate.

Internal power dissipation increases when operating at high supply voltages. Copper leadframe construction

used in the OPA202, OPA2202, and OPA4202 devices improves heat dissipation. Printed-circuit-board (PCB)

layout can help reduce a possible increase in junction temperature. Wide copper traces help dissipate the heat

by acting as an additional heat sink. An increase in temperature is further minimized by soldering the devices

directly to the PCB rather than using a socket.

Although the output current is limited by internal protection circuitry, accidental shorting of one or more output

channels of a device can result in excessive heating. For instance, when an output is shorted to midsupply, the

typical short-circuit current of 35 mA leads to an internal power dissipation of over 600 mW at a supply of ±18 V.

To prevent excessive heating, the OPAx202 series has an internal thermal shutdown circuit, which shuts down

the device if the die temperature exceeds approximately 135°C. When this thermal shutdown circuit activates, a

built-in hysteresis of 10°C ensures that the die temperature must drop to approximately 125°C before the device

switches on again. Additional consideration must be given to the combination of maximum operating voltage,

maximum operating temperature, load, and package type.

8.3.8 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 the relevance to an electrical overstress

event. See Figure 44 for an illustration of the ESD circuits contained in the OPAx202 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 the pulse discharges through a semiconductor device. The ESD protection circuits are designed

to provide a current path around the operational amplifier core to protect the core from damage. 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

OPAx202 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.