LP3913 datasheet(29/70 Pages) TI1

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LP3913

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SNVS489I – NOVEMBER 2006 – REVISED SEPTEMBER 2013

Power On Timing

Each timeout T1 thru to T5 are factory programmed from 0 ms to 63 ms. The following defaults are shown below.

Symbol

Description

Time

Units

Programmable Delay for LDO1 and

LDO2

Programmable Delay to Buck1

Programmable Delay for Buck2

Programmable Delay for Buck3

Programmable Delay for NRST

Power Off Timing

The timing delays during a power off sequence are equal to 63 ms minus the timing delay during the power on

sequence.

Symbol

Description

Time

Units

Programmable delay for LDO1 and LDO2

Programmable delay to Buck1

Programmable delay for Buck2

Programmable delay for Buck3

Programmable delay for NRST

Transitioning from Standby to Active Mode (Power Up) Battery Power Present Only

When only battery power is present and the battery voltage VBATT > VBATTLOW, the LP3913 is waiting for one of

three valid wakeup signals. The first is the ONOFF pin. The second and third wakeups are the Wall Adapter and

USBPWR. The ONOFF pin is factory programmable wakeup source. It can be a rising edge, a falling edge, a

level high, or a level low event. Regardless of the mode, the signal requires a 32 ms deglitch time. A deglitched

version of the ONOFF pin is output on the open-drain output pin ONSTAT. ONOFF is usually connected to a

push button. Asserting the ONOFF pin starts the power on sequencer. This enables the DC/DC converters

including the Buck1 DC/DC converter that supplies power to the system processor. The system processor then

needs to set bit D4 (PACK bit) in the Power On Event Register through the I2C interface or apply a logic high to

the POWERACK pin to keep the LP3913 in the Active mode. These serve as a Power Acknowledgment,

confirming the power on request initiated by the ONOFF pin. If neither the PACK bit (D4) in the PON register or

the POWERACK pin is set within 128 ms (max) of the start of the power-up sequencer, then the LP3913 will

automatically turn off, as the system failed to acknowledge the power on request. Connecting the battery will be

considered a Power on event. However hot insertion of the battery with the adapter connected is NOT permitted.

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