34652 datasheet(23/26 Pages) FREESCALE

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Analog Integrated Circuit Device Data

Freescale Semiconductor

34652

TYPICAL APPLICATIONS

SHORT CIRCUIT DETECTION

If the current going through the load becomes >5.0 A, the

Power MOSFET is discharged very fast (in less than 10

µs)

to try to regulate the current, and the 34652 is in the

overcurrent mode for 3.0 ms. Then it follows the pattern

outlined in the Overcurrent Limit paragraph above.

POWER MOSFET ENERGY CAPABILITY

Figure 24 shows a projected energy capability of the

device’s internal Power MOSFET under a drain to source

voltage of 82 V and an ambient temperature of 90°C. It is

compared to the energy levels required for the capacitive

loads of 100

µF, 200 µF, and 400 µF at 80 V for the

discharge periods of 16 ms, 32 ms, and 64 ms, respectively.

It is clear that the Power MOSFET well exceeds the required

energy capability for all three cases with a sufficient margin.

For example, the 400

µF capacitor load with a 64 ms

discharge time requires an energy capability of about

1540 mJ, which is well below the Power MOSFET capability

of about 3500 mJ. As a result of this analysis, the 33652 is

expected to more than meet all energy capability

requirements for the possible capacitive loads.

Figure 24. Projected Energy Capability of the Power

MOSFET Compared to the Required Energy Levels of

400

µF

200

µF

100

µF

Estimated for Area =1.7 mm2

500

1000

1500

2000

2500

3000

3500

Time (ms)

020

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