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General Description

The MAX8784 evaluation kit (EV kit) is a fully assembled

and tested surface-mount PCB that provides the volt-

ages and features required for active-matrix, thin-film

transistor (TFT) liquid-crystal display (LCD) panels in

LCD monitors and LCD TVs. The EV kit contains a step-

up switching regulator, a two-stage positive charge

pump for the TFT gate-on supply, a single-stage nega-

tive charge pump for the TFT gate-off supply, and three

high-current op amps. Two capacitor-control delays are

available: one to control the initial startup of the step-

up, and the other to control the delay between the neg-

ative and positive charge pumps. Also included is a

logic-controlled, high-voltage switch for the positive-

gate driver supply. A high-voltage stress (HVS) mode is

provided to increase the step-up and the positive

charge-pump output voltages for stress testing the dis-

play panel during production. A capacitive dummy load

is provided at the high-voltage switch output for ease of

testing without a panel attached.

The EV kit operates from a DC supply voltage of +4.5V

to +5.5V, as configured. The step-up switching regula-

tor is configured for a +14V output providing at least

700mA. The positive charge pump is configured for a

+28V output providing at least 50mA. The negative

charge pump is configured for a -9V output providing at

least 50mA. The three high-current op amps are each

configured for a +7V output that can source or sink

180mA. The high-voltage switch can be controlled by

external logic. The EV kit’s input voltage range can be

lowered to +4V at slightly lower load currents.

The MAX8784 step-up switching regulator operates at

1.2MHz, allowing the use of tiny surface-mount compo-

nents. The MAX8784 thin QFN package (0.8mm max

height), with low-profile external components, allows

this circuit to be less than 3mm high.

Features

♦ +4.5V to +5.5V Input-Voltage Range

♦ Output Voltages

+14V Output at 700mA (Step-Up

Switching Regulator)

+28V Output at 50mA (Positive

Charge Pump)

-9V Output at 50mA (Negative

Charge Pump)

Three High-Current Op Amps (±180mA)

♦ 1.2MHz Switching Frequency

♦ All Output Voltages are Resistor Adjustable

♦ Logic-Controlled, High-Voltage Switch

♦ High-Voltage Stress Mode for the Step-Up and

Positive Charge-Pump Output Voltages

♦ Capacitor-Controlled Initial Startup Delay and

Positive Charge-Pump Delay

♦ Low-Profile Surface-Mount Components

♦ Fully Assembled and Tested

Evaluates: MAX8784

MAX8784 Evaluation Kit

________________________________________________________________

Maxim Integrated Products

19-0787; Rev 0; 3/07

For pricing, delivery, and ordering information, please contact Maxim/Dallas Direct! at

1-888-629-4642, or visit Maxim’s website at www.maxim-ic.com.

Ordering Information

PART TEMP RANGE IC PACKAGE

MAX8784EVKIT+ 0°C to +70°C* 40 Thin QFN-EP**

Denotes a lead-free and RoHS-compliant EV kit.

This limited temperature range applies to the EV kit PCB only.

The MAX8784 IC temperature range is -40°C to +85°C.

EP = Exposed paddle.

Component List

DESIGNATION QTY DESCRIPTION

C1, C2 2

10µF ±20%, 6.3V X5R ceramic

capacitors (0603)

TDK C1608X5R0J106M

C3, C4 2

10µF ±20%, 16V X5R ceramic

capacitors (1206)

TDK C3216X5R1C106M

C5 1

1µF ±10%, 6.3V X5R ceramic

capacitor (0402)

TDK C1005X5R0J105K

C6 0 Not installed, capacitor (0402)

C7 1

330pF ±10%, 50V X7R

ceramic capacitor (0402)

Murata GRM155R71H331K

Summary of content (11 pages)

PAGE 1
9-0787; Rev 0; 3/07 MAX8784 Evaluation Kit The MAX8784 evaluation kit (EV kit) is a fully assembled and tested surface-mount PCB that provides the voltages and features required for active-matrix, thin-film transistor (TFT) liquid-crystal display (LCD) panels in LCD monitors and LCD TVs. The EV kit contains a stepup switching regulator, a two-stage positive charge pump for the TFT gate-on supply, a single-stage negative charge pump for the TFT gate-off supply, and three high-current op amps.
PAGE 2
MAX8784 Evaluation Kit Evaluates: MAX8784 Component List (continued) DESIGNATION QTY C8 1 C9, C13, C14, C15 4 C10 1 C11, C16 2 C12 1 C17 1 DESCRIPTION DESIGNATION QTY JU1, JU2, JU4, JU5 4 JU3 1 3-pin header L1 1 3µH, 3ADC inductor Sumida CDRH6D28-3R0 205kΩ ±1% resistor (0603) 0.01µF ±10%, 10V X5R ceramic capacitor (0402) TDK C1005X5R1A103K 0.1µF ±10%, 25V X5R ceramic capacitors (0402) TDK C1005X5R1E104K 0.22µF ±10%, 6.
PAGE 3
MAX8784 Evaluation Kit Recommended Equipment • +4.5V to +5.5V, 5A DC power supply • One voltmeter Procedure The MAX8784 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) Verify that a shunt is installed across jumper JU1 (EV kit ON). 2) Verify that no shunt is installed across jumper JU2 (VGON internally connected to DRN).
PAGE 4
Evaluates: MAX8784 MAX8784 Evaluation Kit The MAX8784 features a HVS mode that can increase the output voltages of the step-up switching regulator and the positive charge pump to stress test the display panel during production. The step-up switching-regulator’s output is increased to +17V in HVS mode, set by resistor R21 (refer to the HVS Mode section in the MAX8784 data sheet). The positive charge-pump output is set to +30V in HVS mode and is not adjustable.
PAGE 5
MAX8784 Evaluation Kit The MAX8784 EV kit features a capacitive dummy load of 1500pF (C17) at the VGON output pad to simulate a panel load to test the switch matrix. When testing with an LCD panel, disconnect the dummy load. Jumper JU4 connects and disconnects the dummy load. Table 4 lists the selectable JU4 jumper options. Table 4.
PAGE 6
HVS Figure 1. MAX8784 EV Kit Schematic _______________________________________________________________________________________ BGND VGOFF -9V, 50mA R12 10kΩ R11 10kΩ AVDD R13 100kΩ JU5 R10 10kΩ R9 10kΩ VIN AVDD C11 1μF 50V R6 187kΩ 1% R5 20kΩ 1% R8 10kΩ VIN L D2 C10 0.22μF OUT3 OUT2 OUT1 C5 1μF 6.3V R20 SHORT (PC TRACE) 2 R 1 AGND AVDD R7 10kΩ PGND VIN 4.5V-5.5V 3 REF C12 0.
PAGE 7
MAX8784 Evaluation Kit Evaluates: MAX8784 Figure 2.
PAGE 8
Evaluates: MAX8784 MAX8784 Evaluation Kit Figure 3.
PAGE 9
MAX8784 Evaluation Kit Evaluates: MAX8784 Figure 4.
PAGE 10
Evaluates: MAX8784 MAX8784 Evaluation Kit Figure 5.
PAGE 11
MAX8784 Evaluation Kit Evaluates: MAX8784 Figure 6. MAX8784 EV Kit PCB Layout—Solder Side Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are implied. Maxim reserves the right to change the circuitry and specifications without notice at any time.