Datasheet

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LP3972
SNVS468K –SEPTEMBER 2006–REVISED MAY 2013 www.ti.com
Connection Diagram
Note: Circle marks pin 1 position.
40-Pin WQFN, Package Number RSB0040A
PIN DESCRIPTIONS
Pin No. Name I/O Type
(1)
Description
1 PWR_ON I D This is an active HI push button input which can be used to signal PWR_ON
and PWR_OFF events to the CPU by controlling the ext_wakeup [pin4] and
select contents of register 8H'88
2 nTEST_JIG I D This is an active LOW input signal used for detecting an external HW event. The
response is seen in the ext_wakeup [pin4] and select contents of register 8H'88
3 SPARE I D This is an input signal used for detecting a external HW event. The response is
seen in the ext_wakeup [pin4] and select contents of register 8H'88. The polarity
on this pin is assignable
4 EXT_WAKEUP O D This pin generates a single 10 ms pulse output to CPU in response to input
from pins 1, 2, and 3. Flags CPU to interrogate register 8H'88
5 FB1 I A Buck1 input feedback terminal
6 V
IN
I PWR Battery Input (Internal circuitry and LDO1-3 power input)
7 V
OUT
LDO1 O PWR LDO1 output
8 V
OUT
LDO2 O PWR LDO2 output
9 nRSTI I D Active low Reset pin. Signal used to reset the IC (by default is pulled high
internally). Typically a push button reset.
10 GND1 G G Ground
11 VREF O A Bypass Cap. for the high internal impedance reference.
12 V
OUT
LDO3 O PWR LDO3 output
13 V
OUT
LDO4 O PWR LDO4 output
14 V
IN
LDO4 I PWR Power input to LDO4, this can be connected to either from a 1.8V supply to
main Battery supply.
15 V
IN
BUBATT I PWR Back Up Battery input supply.
16 V
OUT
LDO_RTC O PWR LDO_RTC output supply to the RTC of the application processor.
17 nBATT_FLT O D Main Battery fault output, indicates the main battery is low
(discharged) or the dc source has been removed from the system. This gives
the processor an indicator that the power will shut down. During this time the
processor will operate from the back up coin cell.
18 PGND2 G G Buck2 NMOS Power Ground
19 SW2 O PWR Buck2 switcher output
(1) A: Analog Pin D: Digital Pin G: Ground Pin P: Power Pin I: Input Pin I/O: Input/Output Pin O: Output Pin
Note: In this document, active-low logic items are prefixed with a lowercase "n".
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