The RT9955 generates all the supply rails for thin-film transistor (TFT) liquid-crystal display (LCD) panels in TVs and monitors. It includes boost and buck regulators, VGH and VGL charge pump regulators, gate pulse modulator (GPM) , HV LDO, voltage detector (XAO) and VCOM OP. The RT9955 supports input voltage from 8V to 14V and is optimized for LCD TV panel and LCD monitor applications running directly from 12V supply.
The boost and buck regulators feature internal power MOSFETs and high frequency operation, allowing the use of small inductors and capacitors, for in a compact solution. Both switching regulators use fixed frequency, current mode control architectures, providing fast load-transient response and easy compensation.
The VGH and VGL charge pump regulators provide supply voltages for the TFT gate driver. Both output voltages can be adjusted with external resistive voltage dividers.
The GPM is controlled by frame signals from the timing controller to modulate the Gate-On voltage (VGHM), which acts as a flicker compensation to reduce the coupling effect between gate lines and pixels. It can also delay VGHM while power on to achieve a correct power on sequence for gate driver ICs. The VGHM power on delay time, the falling time and falling stop voltage can all be programmed by an external capacitor, an external resistor and an resistive voltage divider.
The voltage detector (XAO) monitors VIN voltage to issue a reset signal when the VIN voltage is too low. The detecting level is determined by an external resistive voltage divider.
The HV LDO can provide a highly accurate voltage (0.5%) for gamma reference voltage. It has fast transient response and also a wide operation input range.
The VCOM OP can drive the LCD VCOM voltage that features high short circuit current (300mA), fast slew rate (45V/μs), wide bandwidth (20MHz) and rail-to-rail inputs and outputs.
The RT9955 is available in a small WQFN-48L 7x7 package.