TFT-LCD DC-DC Converter with Operational Amplifiers

The MAX8795A includes a high-performance step-up regulator, two linear-regulator controllers, and five high-current operational amplifiers for active-matrix, thin-film transistor (TFT), liquid-crystal displays (LCDs). Also included is a logic-controlled, high-voltage switch with adjustable delay.

The step-up DC-DC converter provides the regulated supply voltage for the panel source driver ICs. The converter is a high-frequency (1.2MHz) current-mode regulator with an integrated 20V n-channel MOSFET that allows the use of ultra-small inductors and ceramic capacitors. It provides fast transient response to pulsed loads while achieving efficiencies over 85%.

The gate-on and gate-off linear-regulator controllers provide regulated TFT gate-on and gate-off supplies using external charge pumps attached to the switching node. The MAX8795A includes five high-performance operational amplifiers. These amplifiers are designed to drive the LCD backplane (VCOM) and/or the gamma-correction divider string. The device features high output current (±130mA), fast slew rate (45V/µs), wide bandwidth (20MHz), and rail-to-rail inputs and outputs.

The MAX8795A is available in a lead-free, 32-pin, thin QFN package with a maximum thickness of 0.8mm for ultra-thin LCD panels, as well as in a 32-pin LQFP package with 0.8mm pin pitch.

Applications

* Automotive Displays * LCD Monitor Panels * Notebook Computer Displays

* 2.5V to 5.5V Input Supply Range

* 1.2MHz Current-Mode Step-Up Regulator

* Fast Transient Response to Pulsed Load

* High-Accuracy Output Voltage (1%)

* Built-In 20V, 3A, 0.16Ω n-Channel MOSFET

* High Efficiency (85%)

* Linear-Regulator Controllers for VGON and VGOFF

* High-Performance Operational Amplifiers

* ±130mA Output Short-Circuit Current

* 45V/µs Slew Rate

* 20MHz, -3dB Bandwidth

* Rail-to-Rail Inputs/Outputs

* Logic-Controlled, High-Voltage Switch with Adjustable Delay

* Timer-Delay Fault Latch for All Regulator Outputs

* Thermal-Overload Protection

* 0.6mA Quiescent Current