L99VR02XP datasheet(32/50 Pages) STMICROELECTRONICS

32 / 50 page

Tracking mode = 0 → If V(IN_TRK) and all the other conditions are correct OR if V(IN_TRK) is in UV condition but

softstart in ongoing on LDO, the LDO2 is powered un in tracking. Otherwise the power-up is in standalone

regulation mode.

Figure 50. Finite state machine

RAMP in

tracking mode

Stand alone

reg.

RAMP

in stand alone

reg.

LDO2

OFF

Detrack

procedure

Tracking

mode reg.

en LDO2 discharge & wait

for LDO2_UV=1

LDO2_UV=1

ramp elapsed

EN=0 OR UVLO

TRK_COND=F

TRK_COND=T

TRK_COND=F

TRK_COND:

*(UV masked during LDO1 soft start)

EN_LDO2=1 &

1) TRK_MODE=1 &

IN_TRK_UV/OV=0

2) TRK_MODE=0 &

SEL_LDO1=SEL_LDO2 &

TSD_LDO1=0 &UVLO VS_LDO1=0 &

IN_TRK_UV/OV=0*

In tracking mode, by LDO1 or an external regulator, in case of thermal shutdown which occurs on L99VR02XP or

LDO1 or undervoltage or overvoltage events detected on IN_TRK pin, LDO2 automatically goes in detracking

mode. In such case LDO2 is switched-off (VO_LDO2 = 0 V) in T_detrk time and resumes with soft start and works

as an independent regulator.

To activate the tracking functionality of the LDO2 again, it is necessary to reactivate the device with the EN.

Before activating LDO2 for tracking functionality, it is important that the reference to be tracked is stable, to avoid

detracking.

Figure 51. Power-up when LDO2 is tracker of LDO1

VO1

VO2

Tracking

L99VR02XP

Application information

DS14686 - Rev 1

page 32/50

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