LP3910SQ-AN Datasheet, PDF (29/60 Pages) National Semiconductor (TI) – Power Management IC for Hard Drive Based Portable Media Players

Power up sequence:
30101205
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
T1
Delay for LDO1 and LDO2
5
T2
Delay to BUCK1
15
T3
Delay for BUCK2
20
T4
Delay for BUCK-Boost
25
T5
Delay for NRST
60
Units
ms
ms
ms
ms
ms
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
T1
Delay for LDO1 and LDO2
58
ms
T2
Delay to BUCK1
48
ms
T3
Delay for BUCK2
43
ms
T4
Delay for BUCK-Boost
38
ms
T5
Delay for NRST
3
ms
Transitioning from Standby to Active Mode (Power Up)
Battery Power Present Only
When only battery power is present and the battery voltage
V_BATT > V_BATTLOW, the LP3910SQ-AN 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 USBP-
WR. 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 con-
verters 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 POW-
ERACK pin to keep the LP3910SQ-AN in the Active mode.
These serve as a Power Acknowledgement, 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 se-
quencer, then the LP3910SQ-AN 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 con-
nected is NOT permitted.
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