RT9921

® RT9921 Integrated Multi-Channel DC/DC Converter for TFT LCD Panels General Description 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 (unitygain OPA), and a VGH charge pump controller for activematrix thin-film transistor (TFT) liquid-crystal displays (LCDs). 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 0.2Ω 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. 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. 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 fa...