®
RT9921
Integrated Multi-Channel DC/DC Converter for TFT LCD
Panels
General Description
The VGH charge pump controller provides regulated TFT
Gate-On voltage. The regulation of the positive charge
pump is generated by the internal comparator that senses
the output voltage and compares it with an internal
reference.
The RT9921 includes a high-performance boost regulator,
a low dropout linear regulator (LDO), a gate pulse
modulator (GPM), a voltage detector, a VCOM buffer (unity-
gain OPA), and a VGH charge pump controller for active-
matrix thin-film transistor (TFT) liquid-crystal displays
(LCDs).
Features
2.5V to 5.5V Input Supply Voltage
640kHz/1.2MHz Current-Mode Boost Regulator
Fast Transient Response to Pulsed Load
Adjustable Output Voltage ( 1%)
Built-In 16V, 2A, 0.2Ω N-MOSFET
High Efficiency Up to 90%
The boost converter provides the regulated supply voltage
for the panel source driver ICs. The converter is a high
switching frequency (640kHz or 1.2MHz) current-mode
regulator with an integrated 16VN-Channel 0.2Ω MOSFET
that allows the use of ultra-small inductors and ceramic
capacitors. It provides fast transient response to pulsed
loading while achieving efficiency over 90%. The device
can produce output voltage as high as 15V from an input
as low as 2.5V. Soft-Start is programmed by external
capacitor, which sets the input-current ramp-rate.
Programmable Soft-Start
Over-Current Protection
Output Under-Voltage Protection
Low Dropout Voltage Linear Regulator
Adjustable Output Voltage : 1.5V to VIN − 0.5V
( 1.5%)
The low-dropout (LDO) linear regulator can supply up to
350mA current while input voltage is 3.3V. It uses an
internal P-MOSFET as the pass device. It is suitable for
the supply voltage of the timing controller.
Maximum Output Current : 350mA
On-Chip GPM Controller with Adjustable
Falling Time and Power-On Delay
Flicker Compensator
The GPM is controlled by frame signals from timing
controller to modulate theGate-On voltage, VGHM, which
acts a flicker compensation circuit to reduce the coupling
effect between gate lines and pixels. It also can delay the
Gate-On voltage while power-on for achieving a corrected
power-on sequence for gate driver ICs. Both of power-on
delay time and the falling time of theGate-On voltage are
programmable by external capacitor and resistor.
Power-On Sequence Control
Low Voltage Detector
Programmable Detecting Voltage ( 2%) and Delay
Time
Unity-Gain Operation Amplifier for VCOM Buffer
Charge Pump for VGH regulation
Over-Temperature Protection
Thin 24 Lead VQFN Package
RoHS Compliant and 100% Lead (Pb)-Free
The voltage detector monitors the supply voltage to issue
a reset signal while the detected voltage is too low. The
detecting level is decided by an external resistor divider
and the delay time is programmable by an external
capacitor.
Marking Information
For marking information, contact our sales representative
directly or through a Richtek distributor located in your
area.
The VCOM buffer can drive the LCD VCOM voltage that
features high short-circuit current (140mA), fast slew rate
(12V/μs), wide bandwidth (12MHz) and rail-to-rail inputs
and outputs.
Copyright 2014 Richtek Technology Corporation. All rights reserved.
©
is a registered trademark of Richtek Technology Corporation.
DS9921-04 May 2014
www.richtek.com
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