Internal-Switch Boost Regulator and High-Voltage, Low-Dropout Linear Regulator for TFT LCDs

The MAX17115 includes a high-performance step-up regulator, a high-accuracy, high-voltage, low-dropout linear regulator (LDO), a high-performance buffer ampifier, and a logic-controlled high-voltage switch block.

The DC-DC converter is a high-frequency (1.2MHz/640kHz) current-mode step-up regulator with a built-in power MOSFET. It provides fast-transient response to pulsed loads while producing efficiencies over 88%. The built-in power MOSFET allows output voltages as high as 18V from inputs from 2.5V to 5.5V. A programmable soft-start function controls startup inrush currents.

The operational amplifier, typically used to drive the LCD backplane (VCOM), features high-output short-circuit current (200mA), fast slew rate (45V/µs), and wide bandwidth (20MHz). Its rail-to-rail input and output maximize application flexibility. The high-voltage LDO is adjustable and has a high accuracy of ±0.5%. It is typically used to drive a gamma reference divider string. The high-voltage switch control block modulates the shape of the gate-on supply and provides an adjustable delay for power-up sequencing.

The high-voltage stress (HVS) function is used to temporarily increase the source-driver supply voltage of the LCD panel for aging tests. The HVS digital input controls an open-drain internal switch, which is typically used to change the feedback divider of the step-up regulator.

The MAX17115 is available in a lead-free, 32-pin, thin QFN package. The package is a 5mm x 5mm square with a maximum thickness of 0.8mm for thin LCD panel design.

Applications

* LCD Monitors * LCD TVs

* 2.5V to 5.5V Input Supply Range

* Pin-Programmable 640kHz/1.2MHz Switching Frequency

* Current-Mode Step-Up Converter

* Fast-Transient Response to Pulsed Load

* High-Accuracy Output Voltage (0.8%)

* Built-In 20V, 4.6A, 0.1Ω n-Channel Power MOSFET

* Cycle-by-Cycle Current Limit

* High Efficiency (88%)

* Programmable Soft-Start

* High-Performance Operational Amplifier

* 200mA Output Short-Circuit Current

* 45V/µs Slew Rate

* 20MHz -3dB Bandwidth

* Rail-to-Rail Input and Output

* High-Voltage LDO

* High ±0.5% Accuracy

* 40mA Guaranteed Output Current

* Logic-Controlled High-Voltage Switch with Adjustable Delay

* High-Voltage Stress Mode

* Built-In Sequencing

* Thermal-Overload Protection

* Gate Driver for Input-Side True Shutdown™ Switch

* Logic-Level Shutdown Input

* Timer-Delayed Fault Shutdown for Boost-Regulator Output