THV6520 Datasheet, PDF (8/11 Pages) THine Electronics, Inc. – THV6520 is a controller IC power supply system with

THV6520_Rev.1.00_E
The delay time is programmable by an external capacitor
as equation. For example, setting DC = 100nF can
generate around 12ms delay for reset signal.
T_D = 120K x DC.
VLS
VGH_OUT
VGH
Vext
VDIN
V_DETH
(V_DIN+V_DIN)
V_DETL
V_DIN
R6
VGH_FB
R5
V_PC
T_D
DOUT
Fig. 3 Detector timing chart
Positive charge pump (VGH)
The positive charge pump is used to generate the TFT
LCD gate on voltage. The output voltage, VGH, can be
set by an external resistive divider.
Voltage V_{VGH_FB} is typically 1.24V. A single stage
charge pump can produce an output voltage less than
approximately twice the charge pump input voltage VLS.
The charge pump can deliver up to 20mA of current. The
maximum voltage VGH should not exceed 38V if it is
used to supply the Gate slope circuit. The output voltage
VGH is regulated as the following equation.
VGH
 V_{VGH _ FB}

R₅  R₆
R₅
Fig. 4 VGH setup
Gate slope
The Gate slope is a flicker compensation circuit to
reduce the coupling effect of gate lines, and is controlled
by timing controller to modulate GOUT, the Gate-On
voltage. This block is not activated until the below 3
conditions are satisfied: 1) The input voltage exceeds its
UVLO, 2) No fault condition is detected, and 3)
GDELAY exceeds its turn-on threshold. Once Gate slope
activates and GIN is high, the internal switch between
V_VGH and GOUT turns on and the switch between
GOUT and GR turns off. If GIN is low, the internal
switch between V_VGH and GOUT turns off and the
switch between GOUT and GR turns on. At that time,
the falling time and delay time of the Gate-On voltage
are programmable by an external resistor connected
between GR and GND.
VCOM buffer
The VCOM buffer generates the bias supply for the back
plane of an LCD screen which is capacitively coupled to
the pixel drive voltage. The purpose of the VCOM buffer
is to hold the bias voltage steady while pixel voltage
changes dynamically. The buffer is designed to sustain
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