LM7321, LM7322

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SNOSAW8D – MAY 2008 – REVISED MARCH 2013

OUTPUT SHORT CIRCUIT CURRENT AND DISSIPATION ISSUES

The LM7321/LM7321Q/LM7322/LM7322Q output stage is designed for maximum output current capability. Even

though momentary output shorts to ground and either supply can be tolerated at all operating voltages, longer

lasting short conditions can cause the junction temperature to rise beyond the absolute maximum rating of the

device, especially at higher supply voltage conditions. Below supply voltage of 6V, the output short circuit

condition can be tolerated indefinitely.

With the op amp tied to a load, the device power dissipation consists of the quiescent power due to the supply

current flow into the device, in addition to power dissipation due to the load current. The load portion of the

power itself could include an average value (due to a DC load current) and an AC component. DC load current

would flow if there is an output voltage offset, or the output AC average current is non-zero, or if the op amp

operates in a single supply application where the output is maintained somewhere in the range of linear

operation.

Therefore:

Op Amp Quiescent Power Dissipation

DC Load Power

AC Load Power

where:

Table 1 shows the maximum AC component of the load power dissipated by the op amp for standard Sinusoidal,

Triangular, and Square Waveforms:

Table 1. Normalized AC Power Dissipated in the Output Stage for Standard Waveforms

Sinusoidal

Triangular

Square

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Product Folder Links: LM7321 LM7322