34652 datasheet(14/26 Pages) FREESCALE

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Analog Integrated Circuit Device Data

Freescale Semiconductor

34652

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 ILIM 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 VPWR) 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 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 12. Applying a

positive voltage (> 1.8 V above VPWR) 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

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