Low-Power Triple-Output TFT LCD DC-DC Converter

 

Part Number	Replacement	Explanation

Description

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The MAX1779 triple-output DC-DC converter provides highly efficient regulated voltages required by small active matrix, thin-film transistor (TFT) liquid-crystal displays (LCDs). One high-power DC-DC converter and two low-power charge pumps convert the +2.7V to +5.5V input supply voltage into three independent output voltages.

The primary high-power DC-DC converter generates a boosted output voltage (V_MAIN) up to 13V that is regulated within ±1%. The low-power BiCMOS control circuitry and the low on-resistance (1 ohm) of the integrated power MOSFET allows efficiency up to 91%. The 250kHz current-mode pulse-width modulation (PWM) architecture provides fast transient response and allows the use of ultra-small inductors and ceramic capacitors.

The dual charge pumps independently regulate one positive output (V_POS) and one negative output (V_NEG). These low-power outputs use external diode and capacitor stages (as many stages as required) to regulate output voltages up to +40V and down to -40V. A proprietary regulation algorithm minimizes output ripple, as well as capacitor sizes for both charge pumps.

The MAX1779 is available in the ultra-thin TSSOP package (1.1mm max height).

MAX1779: Typical Operating Circuit Enlarge+

Key Features

• Three Integrated DC-DC Converters
• 250kHz Current-Mode PWM Boost Regulator
  • Up to +13V Main High-Power Output
  • ±1% Accuracy
  • High Efficiency (91%)
• Dual Charge-Pump Outputs
  • Up to +40V Positive Charge-Pump Output
  • Down to -40V Negative Charge-Pump Output
• Internal Supply Sequencing
• Internal Power MOSFETs
• +2.7V to +5.5V Input Supply
• 0.1µA Shutdown Current
• 0.5mA Quiescent Current
• Internal Soft-Start
• Power-Ready Output
• Ultra-Small External Components
• Thin TSSOP Package (1.1mm max)

Applications/Uses

• Camcorders
• Digital Still Cameras
• Passive-Matrix LCD Displays
• PDAs
• TFT Active-Matrix LCD Displays