MAX8795A Evaluation Kit

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3

Quick Start

Recommended Equipment

• 4.5V to 5.5VDC, 5A power supply

• Digital multimeters

Procedure

The MAX8795A EV kit is fully assembled and tested.

Follow the steps below to verify board operation.

Caution: Do not turn on the power supply until all

connections are completed.

1) Connect the positive terminal of the DC power sup-

ply to the VIN pad. Connect the negative terminal of

the DC power supply to the PGND pad.

2) Verify that a shunt is placed across jumper JU1.

Verify that there is no shunt placed across jumper

JU2.

3) Turn on the power supply and verify that the step-

up regulator output (VMAIN) is approximately +14V.

4) Verify that the positive linear-regulator output

(VPOS) is approximately +25V.

5) Verify that the negative linear-regulator output

(VNEG) is approximately -10V.

6) Verify that all buffer outputs (OUT1–OUT 5) are

approximately +7V.

Detailed Description

The MAX8795A EV kit includes a high-performance

boost converter, two linear-regulator controllers, and

five high-current op amps optimized for complete TFT

LCD power requirements. The main supply step-up

switching circuit, which is powered from a +5V supply

and switches at 1.2MHz, provides a +14V output with at

least 500mA.

For regulated TFT gate-on supply, the EV kit employs a

positive single-stage charge pump and a linear

postregulator that provides +25V output (VPOS) and

supplies at least 20mA. For regulated TFT gate-off sup-

ply, the EV kit employs a negative single-stage charge

pump and a linear postregulator that provides -10V out-

put and supplies at least 50mA.

The EV kit also features five high-current op amps that

are ideal for driving the capacitive backplane of TFT

LCD panels. Each buffer is set to one-half of the main

supply output through external resistor-dividers.

Jumper Selection

Dummy Load for the High-Voltage

Switch Output (COM)

The MAX8795A EV kit features a capacitive dummy

load of 1.5nF (C22) at the COM output pad to simulate

a panel load to test the switch matrix. Jumper JU1

selects and deselects the dummy load. Table 1 lists

jumper JU1 options.

High-Voltage Switch Control Input (CTL)

Using a 2-pin jumper (JU2), the MAX8795A EV kit fea-

tures an option to control the high-voltage switches

between SRC, COM, and DRN. The switch between the

SRC and COM pins, and the switch between the COM

and DRN pins can also be controlled by an external

TTL logic source connected to the CTL pad. See Table

2 for switch states and refer to the

Switch-Control Block

section in the MAX8795A IC data sheet for further infor-

mation about the high-voltage switches connected to

the COM pin.

Table 2. Jumper JU2 Functions

SHUNT

POSITION

CTL PIN

MAX8795A

COM OUTPUT

Installed

Connected to VIN

COM connected to SRC

(+25V)

Not installed*

Connected to

GND through

resistor R10

COM connected to DRN

(+14V)

TTL = logic-low

(COM connected to DRN)

Not installed

Connected to

external TTL

source

TTL = logic-high

(COM connected to SRC)

*

Default position.

Table 1. Jumper JU1 Functions

SHUNT

POSITION

DUMMY LOAD

(C22)

EV KIT FUNCTION

Installed

Connected to

COM

Testing mode

(no panel)

Not installed*

Unconnected

Normal operation

(panel load)

*

Default position.