TFT- LCD DC-DC Converters with Operational Amplifiers

EC9219

P 2 / 14

2009/09/29

NAME

Function

OUT Operational-Amplifier Output

IN + Operational-Amplifier Non-inverting Input

SGND Analog ground.

Comp

Compensation pin. Output of the internal error amplifier. Capacitor and resistor from COMP pin to ground.

FB

Voltage feedback pin. Internal reference is 1.228V nominal. Connect a resistor divider from VOUT. VOUT =1.228V (1 + R3 / R8). See Typical

Application Circuit.

/SD

Shutdown control pin. Pull SHDN low to turn off the device, and Soft-start Internal reference voltage control pin, Connect RC Delay circuit.

PGND Power ground.

LX

Switch Pin. Connect the inductor/catch diode to LX and minimize the trace area for lowest EMI.

Vin

Analog power supply input pin.

Freq

Frequency Select Input. When FREQ is low, the oscillator frequency is set to 640kHz. When FREQ is high the frequency is 1.2MHz.

SS

Soft-start control pin. Connect a capacitor to control the converter start-up.

Operational-Amplifier Power Input. Positive supply rail for the operational amplifiers.

SUP

Typically connected to DC-DC converter Output. Bypass SUP to SGND with a 0.1µF capacitor.

NC

IN -

Operational-Amplifier Inverting Input