7.3.5 Thermal Protection

The OPAx202 family of op amps is capable of driving 2-kΩ loads with power-supply voltages of up to ±18 V across 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 OPAx202 devices improves heat dissipation. Printed-circuit-board (PCB) layout helps 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 have an internal thermal shutdown circuit that 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 makes sure that the die temperature drops 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.