Low-Cost Multiple-Output Power Supply for LCD Monitors/TVs

The MAX8728 generates all the supply rails for thin-film transistor (TFT) liquid-crystal display (LCD) panels in TVs and monitors. It includes step-down and step-up regulators, positive and negative charge pumps, and a dual-mode, logic-controlled, high-voltage switch control block. The MAX8728 can operate from input voltages from 7V to 13.2V and is optimized for LCD TV panel and LCD monitor applications running directly from 12V supplies.

The step-up and step-down regulators feature internal power MOSFETs and high-frequency operation allowing the use of small inductors and capacitors, resulting in a compact solution. Both switching regulators use fixed-frequency, current-mode control architectures, providing fast load-transient response and easy compensation. The positive and negative charge-pump regulators provide TFT gate driver supply voltages. Both output voltages can be adjusted with external resistive voltage-dividers.

The MAX8728 is available in a small (5mm x 5mm), low-profile (0.8mm), 32-pin thin QFN package and operates over the -40°C to +85°C temperature range.

Applications

* LCD Monitors * LCD TVs

* Optimized for 10.8V to 13.2V Input Supply

* 7V to 13.2V Input Supply Range

* Selectable Frequency (500kHz/1MHz/1.5MHz)

* Current-Mode Step-Down Regulator

* 14V Internal n-Channel MOSFET

* 1.5% Accurate Output

* Current-Mode Step-Up Regulator

* 15V Internal n-Channel MOSFET

* 1% Accurate Output

* True Shutdown (Output Goes to Zero)

* 180° Out-of-Phase Switching

* Adjustable Positive/Negative Charge Pumps

* Soft-Start and Timer Delay Fault Latch for All Outputs

* Logic-Controlled, High-Voltage Switches

* Power-Up and Power-Down Sequences

* Thermal-Overload Protection