Datasheet

flag2
flag1
flag3
flag4
flag5
flag6
2) Binary coded thermal management flags in status registers, bct<2:0>:
Temp 125
o
C
Warning flag
1) Thermal warning flag @ Temp ~ > ~125
o
C is issued at the wakeup port:
~30
o
C hysteresis
17
o
C
cool
20
o
C 43
o
C 46
o
C 62
o
C 65
o
C 83
o
C 86
o
C
Temp
106
o
C108
o
C 128
o
C 130
o
C
LP3972
SNVS468K –SEPTEMBER 2006–REVISED MAY 2013 www.ti.com
Figure 29.
Application Note - LP3972 Reset Sequence
INITIAL COLD START POWER ON SEQUENCE
1. The Back up battery is connected to the PMU, power is applied to the back-up battery pin, the LDO_RTC
turns on and supplies a stable output voltage to the V
CC
_BATT pin of the Applications processor (initiating
the power-on reset event) with nRSTO asserted from the LP3972 to the processor.
2. nRSTO de-asserts after a minimum of 50 mS.
3. The Applications processor waits for the de-assertion of nBATT_FLT to indicate system power (V
IN
) is
available.
4. After system power (V
IN
) is applied, the LP3972 de-asserts nBATT_FLT. Note that BOTH nRSTO and
nBATT_FLT need to be de-asserted before SYS_EN is enabled. The sequence of the two signals is
independent of each other.
5. The Applications processor asserts SYS_EN, the LP3972 enables the system high-voltage power supplies.
The Applications processor starts its countdown timer set to 125 mS.
6. The LP3972 enables the high-voltage power supplies.
– LDO1 power for V
CC
_MVT (Power for internal logic and I/O Blocks), BG (Bandgap reference voltage),
OSC13M (13 MHz oscillator voltage) and PLL enabled first, followed by others if delay is on.
7. Countdown timer expires; the Applications processor asserts PWR_EN to enable the low-voltage power
supplies. The processor starts the countdown timer set to 125 mS period.
8. The Applications processor asserts PWR_EN (ext. pin or I
2
C), the LP3972 enables the low-voltage
regulators.
9. Countdown timer expires; If enabled power domains are OK (I
2
C read) the power up sequence continues by
enabling the processors 13 MHz oscillator and PLL’s.
10. The Applications processor begins the execution of code.
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