LP3971_16 Datasheet, PDF (37/52 Pages) Texas Instruments – Power Management Unit for Advanced Application Processors

LP3971
www.ti.com
SNVS432V – JANUARY 2006 – REVISED MAY 2013
WAKE-UP FUNCTIONALITY (PWR_ON, nTEST_JIG, SPARE AND EXT_WAKEUP)
Three input pins can be used to assert wakeup output for 10 ms for application processor notification to wakeup.
SPARE Input can be programmed through I²C compatible interface to be active low or high (SPARE bit, Default
is active low ‘1’). A reason for wakeup event can be read through I²C compatible interface also. Additionally
wakeup inputs have 30 ms de-bounce filtering. Furthermore PWR_ON have distinguishing between short and
long (∼1s) pulses (push button input). LP3971 also has an internal Thermal Shutdown early warning that
generates a wakeup to the system also. This is generated usually at 125°C.
PWR_ON
nTEST_JIG
OR
SPARE
EXT_WAKEUP
PWR_ON
nTEST_JIG
SPARE
EXT_WAKEUP
10 ms
Internal Thermal Early Warning
WAKEUP register bits
WUP0
WUP1
WUP2
WUP3
TSD_EW
Reason for WAKEUP
SPARE
TEST_JIG
PWR_ON short pulse
PWR_ON long pulse
TSD Early Warning
INTERNAL THERMAL SHUTDOWN PROCEDURE
Thermal shutdown is build to generate early warning (typ. 125°C) which triggers the EXT_WAKEUP for the
processor acknowledge. When a thermal shutdown triggers (typ. 160°C) the PMU will reset the system until the
device cools down.
BATTERY SWITCH AND BACK UP BATTERY CHARGER
When Back-Up battery is connected but the main battery has been removed or its supply voltage too low,
LP3971 uses Back-Up Battery for generating LDO_RTC voltage. When Main Battery is available the battery fet
switches over to the main battery for LDO_RTC voltage. When Main battery voltage is too low or removed
nBATT_FLT is asserted. If no back up battery exists, the battery switch to back up can be switched off by
nBU_BAT_EN bit. User can set the battery fault determination voltage and battery charger current via I²C
compatible interface. Enabling of back up battery charger can be done via serial interface (nBAT_CHG_EN) or
external charger enable pin (nCHG_EN). Pin 29 is set as external charger enable input by default. A
SHUTBKUPBAT register bit can be used to avoid discharging back up battery during storage etc. By setting this
bit before removing main battery the back up battery connection will not draw any current and stays like this until
the bit is set to default or the system is reset.
GENERAL PURPOSE I/O FUNCTIONALITY (GPIO1 AND GPIO2)
LP3971 has 2 general purpose I/Os for system control. I²C compatible interface will be used for setting any of the
pins to input, output or hi-Z mode. Inputs value can be read via serial interface (GPI1,2 bits). The pin 29
functionality needs to be set to GPIO by serial interface register bit nEXTCHGEN. (GPIO/CHG)
GPIO<1>
X
X
1
Controls
GPIO<1>
Nextchgen_sel
X
1
X
1
0
1
bucen
0
0
X
Port Function
GPIO1
Input = 0
Input = 1
X
Reg
Gpin 1
0
0
0
batmonchg
Function
Enabled
Not Enabled
Copyright © 2006–2013, Texas Instruments Incorporated
Product Folder Links: LP3971
Submit Documentation Feedback
37