34652_07 Datasheet, PDF (23/26 Pages) Freescale Semiconductor, Inc – 2.0 A Negative Voltage Hot Swap Controller with Enhanced Programmability

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.
3500
3000
2500
2000
Estimated for Area =1.7 mm²
400 µF
200 µF
100 µF
1500
1000
500
0
0
20
40
60
Time (ms)
Figure 24. Projected Energy Capability of the Power
MOSFET Compared to the Required Energy Levels of
Analog Integrated Circuit Device Data
Freescale Semiconductor
34652
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