EC9223

Multi-Channel TFT LCD Supply

E-CMOS Corp. (www.ecmos.com.tw)

5E26N-Rev. F001

10/13

Positive Charge Pump (VGH)

The positive charge pump is used to generate the TFT LCD gate on voltage. The output voltage, VGH, can be set by an

approximately twice the charge pump input voltage AVDD. The output voltage VGH is regulated as the following equation.

The negative charge pump is used to generate the TFT LCD gate off voltage. The output voltage, VGL, is set

with an external resistive divider from its output to REF with the midpoint connected to FBN. The error amplifier

compares the feedback signal from FBN with an internal reference 240mV. The output voltage VGL is regulated

VCOM Buffer

changes dynamically. The buffer is designed to sustain up to ±75mA of output current. In transients, it can

deliver up to 150mA at which point the over current protection circuit limits the output current. Excessive current

draw over a period of time may cause the chip temperature to rise and set off the over temperature protection

circuit.