MC34653EFSLASHR2 datasheet(12/24 Pages) FREESCALE

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Analog Integrated Circuit Device Data

Freescale Semiconductor

34653

FUNCTIONAL DEVICE OPERATION

OPERATIONAL MODES

Figure 9. Overcurrent Mode for More Than 3.0 ms

Figure 10. Overcurrent Mode for Less Than 3.0 ms

DISABLING AND ENABLING THE 34653

When a negative voltage (< 1.8 V below VPWR) is applied

to the DISABLE pin for more than 1.0 ms (Point A in

Figure 11), the 34653 is disabled, the Power MOSFET turns

off, and the power good output signals deactivate. The 34653

stays in this state until the voltage on the DISABLE pin is

brought to within ±1.2 V of VPWR 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 10. Applying a

positive voltage (> 1.8 V above VPWR) would also disable the

34653 in the same manner.

Figure 11. Disabling and Enabling the 34653

Figure 12 demonstrates that the 34653 must be enabled

for the length of the start-up timer to start turning on the

Power MOSFET. After the fourth disable signal, the 34653

was enabled for the length of the start-up timer. And because

the retry counter is less than 10, the 34653 turns on the

Power MOSFET and starts the charging process (refer to

Charging Process, pages 10–11).

Figure 12. Start-Up Timer Versus Disable

BOARD REMOVAL

When the board is removed, its power ramps down. As

soon as the 34653’s input voltage reaches the undervoltage

turn-off threshold, the undervoltage detection circuit activates

and the Power MOSFET turns off for having violated one of

the start-up conditions (list on page 10).

MC34653EF/R2 Datasheet(PDF) 12 Page - Freescale Semiconductor, Inc