ADM8839:  Charge Pump Regulator for Color TFT Panel

The ADM8839 is a charge pump regulator, used for colour TFT (Thin Film Transistor) LCD’s (Liquid Crystal Displays). The device can be used to generate 3 output voltages (+5 V ±2%, +15 V, -15 V) from a single 2.7V - 4.2V (li-ion) input supply, using charge pump technology. These voltages are then used to provide supplies for the LCD controller (5 V ±2%), and the gate drives for the transistors in the panel (+15 V and -15 V). Only a few external capacitors are needed for the charge pumps. An efficient low dropout voltage regulator also ensures that the power efficiency is high and provides a low ripple 5 V output. This LDO can be shutdown and an external LDO used to regulate the 5 V doubler output and to drive the input to the charge pump section which generates the +15 V and -15 V outputs if so required by the user.

The ADM8839 has a power save shutdown feature. The 5 V output consumes the most power, so Power Efficiency is also maximised on this output with an oscillator enabling scheme (Green Idle™). This effectively senses the load current that is flowing and turns on the charge pump only when charge needs to be delivered to the 5 V pump doubler output.

The ADM8839 is fabricated using CMOS technology for minimal power consumption. The part is packaged in a 20- lead LFCSP (Lead Frame Chip Scale Package) with a tiny 4mm x 4mm footprint.