ADSY8401

Rev. 0 | Page 11 of 16

APPLICATIONS

The ADSY8401 is designed as part of a DecDriver® based LCD

driver platform. The level shifters provide an interface between

the image processor and a timing loop, operating at 3.3 V, and

the LCD with high voltage timing input levels. The edge

detecting level shifter provides an interface between the LCD

monitor output at high voltage and a timing loop such as the

AD8389 at 3.3 V. Low offset buffers, AMP and MUX, are

capable of driving high capacitive loads such as VCOM and

NRS without additional buffering. The high current buffer BFR

is capable of 100 mA output current, providing high slew rates

into large capacitive loads, which are often required for the

precharge input, NRS of LCDs.

AMP CHANNEL

The AMP channel is a low offset unity gain buffer designed to

drive a wide range of capacitive loads with a clean settling

response. In LCD panel applications, it is most frequently used

as a VCOM buffer.

MUX CHANNEL

The MUX channel is a 2-input, buffered analog multiplexer. The

overall performance of its buffered output is very similar to that

of the AMP channel. It is ideally suited for driving a wide range

of capacitive loads, from very small up to several nF.

DRIVING NRS

Analog voltage switching capability is provided by the MUX

channel. To achieve rapid settling while driving the capacitive

NRS input, the output of the MUX is buffered by the high

current drive BFR channel.

BFR CHANNEL

The BFR channel comprises a high output current buffer. It can

be used to increase the output drive capability of either the

AMP or MUX channels. The BFR channel is most often used in

series with the MUX channel output to realize a high current

drive NRS switch.

GROUNDED OUTPUT MODE

In certain designs it is desirable to pull the amplifier and buffer

outputs to near ground during power-down. When the voltage

on the GSW pin is tied to DGND, the AMPO, MUXO, and

BFRO outputs are pulled to near AGND. When the GSW input

is left unconnected or tied to DVCC, all outputs operate

normally. The level shifters are not affected by the GSW input.

DRIVING VCOM

The AMP channel comprises a low offset, unity gain buffer. It

can be used to drive a large capacitive load, such as VCOM,

directly with low overshoot. In certain systems, it might be

desirable for a single ADSY8401 to drive the VCOM inputs of

more than one LCD panel. In such cases, the MUX channel can

be used to drive VCOM directly. The MUX’s switching function

is not used, and its output is tied directly to VCOM without the

use of the BFR channel. Offset errors and pulse response are the

same as that of the AMP channel.

6

DB(0:9/11)

STSQ, XFR,

CLK, R/L, INV

DX, DY, DIRY, NRG

DY, DIRY, NRG

DIRX, CLX,CLY

IMAGE

PROCESSOR

LCD

ENBX(1–4)

CLX, CLXN

CLY, CLYN

DIRX

MONITOR

NRS

DO1–DO4

DO5–DO8

DO9T–DO11T,

DO9C–DO11C

DTCTI

AMPO

BFRO

MUXO

VRH, VRL,

V1, V2

VCOM

DXI, CLXI,

ENBX(1–4)I

CLK

DI1–DI8

DTCTO

BFRI

AMPI

VCOM

MONITxI

DI9–DI11

CLXxO

ENBX(1–4)xO

DXxO

MUXA

MUXB

NRS1

NRS2

SEL

INV

ADSY8401

AD8381/AD8382/AD8383

VID(0:6)

10/12

REFERENCE

VOLTAGES

1/3 AD8389

Figure 10. Typical Application—One ADSY8401 per Color