MIC4423/4424/4425

Micrel

MIC4423/4424/4425

10

January 1999

= 12 x [(0.5 x 0.0035) + (0.5 x 0.0003)]

= 0.0228W

Total power dissipation, then, is:

= 0.2454W

Assuming an SOIC package, with an

result in the junction running at:

0.2454 x 120 = 29.4

°C

above ambient, which, given a maximum ambient temperature

of 60

°C, will result in a maximum junction temperature of

89.4

°C.

EXAMPLE 2: A MIC4424 operating on a 15V input, with one

driver driving a 50

Ω resistive load at 1MHz, with a duty cycle

of 67%, and the other driver quiescent, in a maximum ambient

temperature of 40

°C:

and:

= 0.174W

(because only one side is operating)

= 0.025 W

and:

(1 x 0.000125)]

(this assumes that the unused side of the driver has its input

grounded, which is more efficient)

= 0.015W

then:

= 0.213W

In a ceramic package with an

power results in a junction temperature given the maximum

40

°C ambient of:

(0.213 x 100) + 40 = 61.4

°C

The actual junction temperature will be lower than calculated

both because duty cycle is less than 100% and because the

Definitions

D = Duty Cycle expressed as the fraction of time the input

to the driver is high.

f = Operating Frequency of the driver in Hertz

inputs are high and neither output is loaded.

inputs are low and neither output is loaded.

in Watts.

states (“shoot-through current”) in Watts. NOTE: The

“shoot-through” current from a dual transition (once

up, once down) for both drivers is stated in the graph

on the following page in ampere-nanoseconds. This

figure must be multiplied by the number of repetitions

per second (frequency to find Watts).