TPS65142
SLVSAX5 –JULY 2011
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Power Down Sequence and LCD Discharge Function
The power down sequence of the bias section is as following. When the input voltage VIN falls below a
predefined threshold set by V(DET_THRESHOLD), XAO is driven low and the VGHM output is driven to VGH. (Note
that when VIN falls below the UVLO threshold, all IC functions are disabled except XAO and VGHM outputs).
Since VGHM is connected to VGH, it tracks the output of the positive charge pump as it decays. This feature,
together with XAO, can be used to discharge the panel by turning on all the pixel TFTs and discharging them into
the gradually decaying VGHM voltage. VHGM is held low during power-up.
The REF regulator will be disabled when VIN falls below the UVLO threshold, hence, the WLED boost converter
as well.
VDET threshold
VIN UVLO
VIN
VIN UVLO
Internal Device
Enable
Power Good of VS
VS
Power Good of VREF
VREF
VCOM
VGH
VGL
VREF
VDPM
Unknown state
Unknown state
Connect to
VFLK
VGHM
VGH
VBAT UVLO
VBAT
VO
EN
Figure 32. Power Up/Down Sequence
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