34652_07 Datasheet, PDF (14/26 Pages) Freescale Semiconductor, Inc – 2.0 A Negative Voltage Hot Swap Controller with Enhanced Programmability

FUNCTIONAL DEVICE OPERATION
OPERATIONAL MODES
Figure 10. Overcurrent Mode for Less Than 3.0 ms
Short Circuit Mode
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 at the I_LIM value, and the 34652
is in the overcurrent mode for 3.0 ms. Then it follows the
pattern outlined in the Overcurrent Mode paragraph above.
DISABLING AND ENABLING THE 34652
When a negative voltage (< 1.8 V below V_PWR) is applied
to the DISABLE pin for more than 1.0 ms (Point A in
Figure 11), the 34652 is disabled, the Power MOSFET turns
off, and the power good output signals deactivate. The 34652
stays in this state until the voltage on the DISABLE pin is
brought to within ± 1.2 V of V_PWR for more than 1.0 ms to
enable the device (Point B in Figure 11). Then a new start-up
sequence initiates as described on page 12. Applying a
positive voltage (> 1.8 V above V_PWR) would also disable the
34652 in the same manner.
Figure 11. Disabling and Enabling the 34652
Figure 12 demonstrates that the 34652 must be enabled
for the length of the start-up timer to start turning on the
Power MOSFET. After the fourth disable signal, the 34652
was enabled for the length of the start-up timer. And because
the retry counter is less than 10, the 34652 turns on the
Power MOSFET and starts the charging process (refer to the
Charging Process section, pages 12–13).
Figure 12. Start-Up Timer Versus Disable
34652
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Analog Integrated Circuit Device Data
Freescale Semiconductor