STPMIC25 datasheet(45/145 Pages) STMICROELECTRONICS

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Refer to Section 6.6

5.4.2

VBUS monitoring

VBUS is monitored permanently by the PMIC state machine. VBUS monitoring is filtered by the tVBUSDB debounce

timer for both rising and falling voltages as shown in Figure 14

Figure 14. VBUS debounce filter behavior

Christophe Belet

VBUS_Fall

VBUS voltage

VBUS_Rise

tVBUSDB

VBUS internal signal

rising edge detection

falling edge detection

tVBUSDB

5.4.3

Turn-on conditions

A turn-on condition is required to power-up the PMIC and to reach the POWER_ON state. A turn-on condition is

only valid from the OFF state, or alternatively from the NO_SUPPLY state (the PMIC has no VIN initially).

The PMIC manages several turn-on conditions:

•

PONKEYn pin assertion

•

VBUS voltage presence

•

WAKEUPn pin assertion

•

AUTO turn-on (AUTO_TURN_ON bit set in the NVM)

•

Fail-safe restart condition

Note:

A fail-safe restart condition is not a real turn-on condition, but rather an allowed restart condition following a

failure event triggering a turn-off event. See Section 5.4.5.

5.4.3.1

PONKEYn / VBUS / WAKEUPn turn-on detection conditions

A turn-on condition can be triggered by 3 external signal sources:

PONKEYn is tied low initially. The PMIC is in a NO_SUPPLY state. When the VIN voltage rises and crosses the

VINPOR_Rise threshold, the PMIC goes into the INIT&LOAD state (transition A), and then it goes into the

CHECK&LOAD state (transition C).

PONKEYn is initially released. The PMIC is in the OFF state. When the PONKEYn is asserted, a turn-on

condition occurs.

WAKEUPn asserted low is always a turn-on condition.

VBUS is tied high initially (VBUS > VBUS_Rise). The PMIC is in the NO_SUPPLY state. When the VIN voltage rises

and crosses the VINPOR_Rise threshold, the PMIC goes into the INIT&LOAD state (transition A), and then it goes

into the CHECK&LOAD state (transition C).

VBUS is initially < VBUS_Fall. The PMIC is in the OFF state. When the VBUS voltage rises and crosses VBUS_Rise,

a turn-on condition occurs.

STPMIC25

Feature descriptions

DS14278 - Rev 3

page 45/145

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