Multi-Output Power Supplies with VCOM Amplifier and High-Voltage Gamma Reference for LCD TVs

Active: In Production.

The MAX17126B generates all the supply rails for thin-film transistor liquid-crystal display (TFT LCD) TV panels operating from a regulated 12V input. They include a step-down and a step-up regulator, a positive and a negative charge pump, an operational amplifier, a high-accuracy high-voltage gamma reference, and a high-voltage switch control block. The MAX17126B can operate from input voltages from 8V to 16.5V and is optimized for an LCD TV panel running directly from 12V supplies.

The step-up and step-down switching regulators feature internal power MOSFETs and high-frequency operation allowing the use of small inductors and capacitors, resulting in a compact solution. The step-up regulator provides TFT source driver supply voltage, while the step-down regulator provides the system with logic supply voltage. Both regulators use fixed-frequency current-mode control architectures, providing fast load-transient response and easy compensation. A current-limit function for internal switches and output-fault shutdown protects the step-up and step-down power supplies against fault conditions. The MAX17126B provides soft-start functions to limit inrush current during startup. In addition, the MAX17126B integrates a control block that can drive an external p-channel MOSFET to sequence power to source drivers.

The positive and negative charge-pump regulators provide TFT gate-driver supply voltages. Both output voltages can be adjusted with external resistive voltage-dividers. A logic-controlled, high-voltage switch block allows the manipulation of the positive gate-driver supply.

The MAX17126B includes one high-current operational amplifier designed to drive the LCD back-plane (VCOM). The amplifier features high output current (±200mA), fast slew rate (45V/µs), wide bandwidth (20MHz), and rail-to-rail outputs.

Also featured in the MAX17126B is a high-accuracy, high-voltage adjustable reference for gamma correction.

The MAX17126B is available in a small (7mm x 7mm), ultra-thin (0.8mm), 48-pin TQFN package and operate over the -40°C to +85°C temperature range.

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