Simplified Block Diagram
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- 500kHz/1MHz Current-Mode PWM Step-Up Regulator
- Up to +13V Main High-Power Output
- ±1% Accurate
- High Efficiency (91%)
- Dual Regulated Charge-Pump Outputs (MAX1778/MAX1880–MAX1882 only)
- Up to +40V Positive Charge-Pump Output
- Up to -40V Negative Charge-Pump Output
- Low-Dropout 40mA Linear Regulator (MAX1778/MAX1881/MAX1883/MAX1884 only)
- Up to +15V LDO Input
- Optional Higher Current with External Transistor
- 2.7V to 5.5V Input Supply
- Internal Supply Sequencing and Soft-Start
- Power-Ready Output
- Adjustable Fault-Detection Latch
- Thermal Protection (+160°C)
- 0.1µA Shutdown Current
- 0.7mA IN Quiescent Current
- Ultra-Small External Components
- Thin TSSOP Package (1.1mm max height)
- TFT LCD Desktop Monitor Panels
- TFT LCD Notebook Displays
The main step-up converter accurately generates an externally set output voltage up to 13V that can supply the display's row/column drivers. The converter's high switching frequency and current-mode PWM architecture provide fast transient response and allow the use of small low-profile inductors and ceramic capacitors. The low-power BiCMOS control circuitry and internal 14V switch (0.35≈ N-channel MOSFET) enable efficiencies up to 91%.
The dual low-power charge pumps (MAX1778/ MAX1880/MAX1881/MAX1882 only) independently regulate one positive output (VPOS) and one negative output (VNEG). These low-power outputs use external diode and capacitor stages (as many stages as required) to regulate output voltages up to +40V and -40V. A unique control scheme minimizes output ripple as well as capacitor sizes for both charge pumps.
A resistor-programmable, 40mA, low-dropout linear regulator (MAX1778/MAX1881/MAX1883/MAX1884 only) provides preregulation or postregulation for any of the supplies. For higher current applications, an external transistor can be added. Additionally, the VCOM buffer provides a high current output that is ideal for driving the capacitive backplane of TFT LCD panels. The VCOM buffer's output voltage is preset with an internal 50% resistive-divider or can be externally adjusted for other voltages.
The MAX1778/MAX1880MAX1885 are protected against output undervoltage and thermal overload conditions by a latched fault detection circuit that shuts down the device. All devices are available in the ultra-thin TSSOP package (1.1mm max height).