LM137JAN

SNVS332B – DECEMBER 2010 – REVISED MARCH 2013

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Thermal Regulation

When power is dissipated in an IC, a temperature gradient occurs across the IC chip affecting the individual IC

circuit components. With an IC regulator, this gradient can be especially severe since power dissipation is large.

Thermal regulation is the effect of these temperature gradients on output voltage (in percentage output change)

per Watt of power change in a specified time. Thermal regulation error is independent of electrical regulation or

temperature coefficient, and occurs within 5 ms to 50 ms after a change in power dissipation. Thermal regulation

depends on IC layout as well as electrical design. The thermal regulation of a voltage regulator is defined as the

specification is 0.02%/W, max.

Vertical sensitivity, 5 mV/div

Figure 4.

10 ms. This performance is thus well inside the specification limit of 0.02%/W × 10W = 0.2% max. When the

10W pulse is ended, the thermal regulation again shows a 3 mV step as the LM137 chip cools off. Note that the

load regulation error of about 8 mV (0.08%) is additional to the thermal regulation error. In Figure 5, when the

10W pulse is applied for 100 ms, the output drifts only slightly beyond the drift in the first 10 ms, and the thermal

error stays well within 0.1% (10 mV).

Horizontal sensitivity, 20 ms/div

Figure 5.

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