AN2229

1 Explanation of 2 possible Startup Behaviors

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Explanation of 2 possible Startup Behaviors

Starting condition: the device is disconnected from the battery.

startup states:

a)

Gate of high side driver is internally switched to ground (Fig. 1).

b)

Gate of high side driver is internally switched to CBx (Fig. 2).

After the first VS ramp up the outputs will enter one of the explained states.

If the device enters state 2 and the threshold of the external MOSFET is below 3.5V, the Sx pin will raise

and the charging of the bootstrap capacitor will be stopped. This state will persist until the L9903/04 will

be enabled by the EN pin. The only consequence of entering state 2 is an increased leakage current.

There is no influence on the standard application suggested inside datasheet. There is no influence on

operating condition (EN=HIGH). If the application requires a startup behavior like in figure 1, an

initialization is needed (see sections 3 and 4).

Figure 1.

Startup behavior internal switched

to ground (state 1)

Figure 2.

Startup behavior internal switch to

CBx (state 2.