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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). <p align="justify">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 16V N-Channel 0.2W 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. </p><p align="justify">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. </p><p align="justify">The GPM is controlled by frame signals from timing controller to modulate the Gate-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 the Gate-On voltage are programmable by external capacitor and resistor. </p><p align="justify">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. </p><p align="justify">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. </p><p align="justify">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. </p>
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<li class="mv5"> 2.5V to 5.5V Input Supply Voltage<br /></li><li class="mv5"> 640kHz/1.2MHz Current-Mode Boost Regulator<br />► Fast Transient Response to Pulsed Load<br />► Adjustable Output Voltage (±1%)<br />► Built-In 16V, 2A, 0.2Ω N-MOSFET<br />► High Efficiency Up to 90% <br />► Programmable Soft-Start<br />► Over-Current Protection<br />► Output Under-Voltage Protection<br /></li><li class="mv5"> Low Dropout Voltage Linear Regulator<br />► Adjustable Output Voltage : 1.5V to V<sub>IN</sub> - 0.5V <br />( ±1.5%)<br />► Maximum Output Current : 350mA <br /></li><li class="mv5"> On-Chip GPM Controller with Adjustable <br />► Falling Time and Power-On Delay<br />► Flicker Compensator<br />► Power-On Sequence Control<br /></li><li class="mv5"> Low Voltage Detector<br />► Programmable Detecting Voltage (±2%) and Delay Time<br /></li><li class="mv5"> Unity-Gain Operation Amplifier for VCOM Buffer<br /></li><li class="mv5"> Charge Pump for VGH regulation<br /></li><li class="mv5"> Over-Temperature Protection<br /></li><li class="mv5"> Thin 24 Lead VQFN Package<br /></li><li class="mv5"> RoHS Compliant and 100% Lead (Pb)-Free</li>
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