Maxim 公司的MAX8784是TV和監(jiān)視器的TFT-LCD電源解決方案，包括升壓穩(wěn)壓器，調(diào)整的正和負(fù)電荷泵，三個(gè)大電流運(yùn)輸放大器，以及雙模式邏輯控制高壓開(kāi)關(guān)控制區(qū)塊。輸入電壓4V-5.5V。效率高達(dá)90%，開(kāi)關(guān)頻率1.2MHz，主要用在LCD TV和LCD 監(jiān)視器。本文介紹了MAX8784主要特性，方框圖，典型工作電路圖和所用元件列表，MAX8784評(píng)估板主要特性，電路圖和評(píng)估板元件列表。

　　在生產(chǎn)過(guò)程中測(cè)試顯示面板MAX8784工作輸入電壓為4V 5 5V，并且針對(duì)液晶電桃而板和液品顯示器的應(yīng)J}j進(jìn)行了優(yōu)化。該升壓DC—DC穩(wěn)壓器為T(mén)FT僳驅(qū)動(dòng)器提供丁一種穩(wěn)壓電源電壓。該升壓捌節(jié)器是一個(gè)高頻率（1 2MHz）、高效率電{ifc模式穩(wěn)壓器該升壓調(diào)節(jié)器有一個(gè)內(nèi)臂110m高開(kāi)關(guān)頻率。允許使}}I超小型電感和陶瓷電容。該電流模式架構(gòu)提供r快速的瞬態(tài)響應(yīng)和方便的補(bǔ)償升￡芷調(diào)節(jié)器其有輸出欠壓保護(hù)高帶寬（20MHz的）。以及高輸出短路電流（200mA） 每個(gè)運(yùn)算放大器都縣有軌到軌流入和軌軌輸出正電荷泵穩(wěn)壓器和負(fù)電荷泵淵節(jié)器為T(mén)FT柵極驅(qū)動(dòng)提供穩(wěn)定的電源電雎正電荷泵是一個(gè)兩階段的電荷泉，它無(wú)需外部二板管l兩個(gè)電荷泵輸出的電眶可通過(guò)電阻調(diào)整其中的邏輯控制高壓開(kāi)關(guān)可以控制正TFT柵極驅(qū)動(dòng)電源MAX8784封裟為小型（5mm X5ram）。簿型（0.

　　The MAX8784 generates supply rails for the thin-film transistor （TFT） liquid-crystal display （LCD） panels in TVs and monitors. It includes a step-up regulator, a regulated positive and a negative charge-pump, three high-current operational amplifiers, and Dual Mode?, logic-controlled, high-voltage switch control block. HVS mode automatically increases the output voltages of the boost regulator and the positive charge-pump to stress test display panels during production. The MAX8784 can operate from input voltages of 4V to 5.5V and is optimized for LCD TV panel and LCD monitor applications.

　　The step-up DC-DC regulator provides a regulated supply voltage for TFT source drivers. The step-up regulator is a high-frequency （1.2MHz）， high-efficiency, currentmode regulator. The step-up regulator has a built-in 110m??（typ） power MOSFET. The high-switching frequency allows the use of ultra-small inductors and ceramic capacitors. The current-mode architecture provides fast transient response and easy compensation.

　　The step-up regulator features output undervoltage protection, soft-start, internal current limit, and adjustable output voltage by an external resistive pider.

　　The three operational amplifiers drive the LCD backplane and the gamma-correction-pider string. Each operational amplifier has a fast slew rate （45V/μs）， a wide bandwidth （20MHz）， and a high-output short-circuit current （200mA）。 Each op amp has rail-to-rail input and rail-to-rail output operation.

　　The positive charge-pump regulator and the negative charge-pump regulator provide regulated supply voltages for the TFT gate drivers. The positive charge pump is a two-stage charge pump, which requires no external diodes. The output voltages of both charge pumps are resistor adjustable. The logic-controlled high-voltage switch allows the manipulation of the positive TFT gate-driver supply.

　　The MAX8784 is available in a small （5mm x 5mm）， lowprofile （0.8mm）， 40-pin TQFN package and operates over the -40℃ to +85℃ temperature range.

　　MAX8784主要特性：

　　_ Step-Up Regulator Supply for LCD Panel Source Driver

　　Fast Transient Response to Pulsed Load

　　Built-In 18V, 4A, 0.11??n-Channel Power MOSFET with Lossless Current Sensing

　　Cycle-by-Cycle Current-Limit Comparator 90% Efficiency （5V In to 15V Out）

　　1.2MHz Switching Frequency

　　_ Three High-Current 19V Operational Amplifiers

　　180mA Output Short-Circuit Current

　　45V/μs Slew Rate

　　20MHz Bandwidth

　　Rail-to-Rail Input and Output Operation

　　_ Regulated Charge-Pump Tripler with Integrated Diodes for TFT Gate-On Supply

　　_ Regulated Charge Pump for TFT Gate-Off Supply

　　_ Built-In Sequencing Internal Digital Soft-Start

　　36V Gate-On Switch

　　Startup Timing Capacitors for AVDD and GON

　　_ Undervoltage and Thermal Protection

　　_ 4V to 5.5V Input Operating Range

　　MAX8784應(yīng)用：

　　LCD TVs and LCD Monitors

　　圖1。MAX8784功能方框圖

　　圖2。MAX8784簡(jiǎn)化工作電路圖

　　圖3。MAX8784典型工作電路圖

　　工作電路元件列表：

圖4。MAX8784 HVS模式工作電路圖

　　MAX8784評(píng)估板

　　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. Two capacitor-control delays are available: one to control the initial startup of the stepup, and the other to control the delay between the negative and positive charge pumps. Also included is a logic-controlled, high-voltage switch for the positivegate 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 display panel during production. A capa

　　citive 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 regulator 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 components.

　　The MAX8784 thin QFN package （0.8mm max height）， with low-profile external components, allows this circuit to be less than 3mm high.

　　MAX8784評(píng)估板主要特性：

　　1.+4.5V to +5.5V Input-Voltage Range

　　2. Output Voltages

　　+14V Output at 700mA

　　+28V Output at 50mA

　　-9V Output at 50mA

　　Three High-Current Op Amps

　　3. 1.2MHz Switching Frequency

　　4. All Output Voltages are Resistor Adjustable

　　5.Logic-Controlled, High-Voltage Switch

　　6. High-Voltage Stress Mode for the Step-Up and

　　Positive Charge-Pump Output Voltages

　　7. Capacitor-Controlled Initial Startup Delay and Positive Charge-Pump Delay

　　8.Low-Profile Surface-Mount Components

　　9.Fully Assembled and Tested

　　圖5。MAX8784評(píng)估板電路圖

　　MAX8784評(píng)估板元件列表：