MAX8784ETL+ Maxim Integrated Products, MAX8784ETL+ Datasheet

IC REG STP UP W/AMP 40-TQFN

MAX8784ETL+

Manufacturer Part Number
MAX8784ETL+
Description
IC REG STP UP W/AMP 40-TQFN
Manufacturer
Maxim Integrated Products
Datasheet
1.MAX8784ETL.pdf (24 pages)

Specifications of MAX8784ETL+

Applications
LCD TV/Monitor
Voltage - Supply
4 V ~ 5.5 V
Operating Temperature
-40°C ~ 85°C
Mounting Type
Surface Mount
Package / Case
40-TQFN Exposed Pad
Operating Supply Voltage
4 V to 5.5 V
Maximum Operating Temperature
- 40 C
Mounting Style
SMD/SMT
Maximum Power Dissipation
2857 mW
Minimum Operating Temperature
+ 85 C
Supply Current
4 mA
Lead Free Status / RoHS Status
Lead free / RoHS Compliant
Current - Supply
-
Lead Free Status / Rohs Status
Lead free / RoHS Compliant
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-con-
trolled, 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 opti-
mized for LCD TV panel and LCD monitor applications.
The step-up DC-DC regulator provides a regulated sup-
ply voltage for TFT source drivers. The step-up regulator
is a high-frequency (1.2MHz), high-efficiency, current-
mode regulator. The step-up regulator has a built-in
110mΩ (typ) power MOSFET. The high-switching fre-
quency allows the use of ultra-small inductors and
ceramic capacitors. The current-mode architecture pro-
vides fast transient response and easy compensation.
The step-up regulator features output undervoltage pro-
tection, soft-start, internal current limit, and adjustable
output voltage by an external resistive divider.
The three operational amplifiers drive the LCD back-
plane and the gamma-correction-divider string. Each
operational amplifier has a fast slew rate (45V/µs), a
wide bandwidth (20MHz), and a high-output short-cir-
cuit 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 volt-
ages 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 posi-
tive TFT gate-driver supply.
The MAX8784 is available in a small (5mm x 5mm), low-
profile (0.8mm), 40-pin TQFN package and operates
over the -40°C to +85°C temperature range.
19-0737; Rev 0; 1/07
+ Denotes a lead(Pb)-free/RoHS-compliant package.
Dual Mode is a trademark of Maxim Integrated Products, Inc.
For pricing, delivery, and ordering information, please contact Maxim Direct at 1-888-629-4642,
or visit Maxim’s website at www.maxim-ic.com.
Step-Up Regulator, Internal Charge Pumps, Switch
MAX8784ETL+
PART
LCD TVs and LCD Monitors
Control, and Operational Amplifier for TFT LCDs
-40°C to +85°C
TEMP RANGE
________________________________________________________________ Maxim Integrated Products
Ordering Information
General Description
PIN-
PACKAGE
40 TQFN
5mm x 5mm
Applications
PKG CODE
T4055-1
o Step-Up Regulator Supply for LCD Panel Source
o Three High-Current 19V Operational Amplifiers
o Regulated Charge-Pump Tripler with Integrated
o Regulated Charge Pump for TFT Gate-Off Supply
o Built-In Sequencing
o Undervoltage and Thermal Protection
o 4V to 5.5V Input Operating Range
VGOFF
Driver
Diodes for TFT Gate-On Supply
STEP-UP
VIN
OUTPUT
Fast Transient Response to Pulsed Load
Built-In 18V, 4A, 0.11Ω n-Channel Power
Cycle-by-Cycle Current-Limit Comparator
90% Efficiency (5V In to 15V Out)
1.2MHz Switching Frequency
180mA Output Short-Circuit Current
45V/µs Slew Rate
20MHz Bandwidth
Rail-to-Rail Input and Output Operation
Internal Digital Soft-Start
36V Gate-On Switch
Startup Timing Capacitors for AVDD and GON
MOSFET with Lossless Current Sensing
VCOM
VCOM
VCOM
TO
TO
TO
VIN
Simplified Operating Circuit
STEP-UP
OUTPUT
V
POS1
NEG1
OUT1
POS2
OUT2
POS3
OUT3
FBN
PGND
NEG2
HVS
REF
AGND
DRVN
CC
SUP
C1N
MAX8784
C1P
C2N
C2P
COMP
PGND
GDEL
SHDN
POUT
ADEL
RSET
GON
DRN
CTL
FBP
LX
FB
TCON
ON/OFF
Features
STEP-UP
OUTPUT
VGON
STEP-UP
OUTPUT
1

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MAX8784ETL+ Summary of contents

Page 1

... Ordering Information PIN- PART TEMP RANGE PACKAGE 40 TQFN MAX8784ETL+ -40°C to +85°C 5mm x 5mm + Denotes a lead(Pb)-free/RoHS-compliant package. Dual Mode is a trademark of Maxim Integrated Products, Inc. ________________________________________________________________ Maxim Integrated Products For pricing, delivery, and ordering information, please contact Maxim Direct at 1-888-629-4642, or visit Maxim’ ...

Page 2

Step-Up Regulator, Internal Charge Pumps, Switch Control, and Operational Amplifier for TFT LCDs ABSOLUTE MAXIMUM RATINGS , CTL, HVS, SHDN, ADEL, GDEL to AGND ....-0.3V to +7. REF, COMP, FB, FBN, FBP to AGND .........-0. POS1, ...

Page 3

Step-Up Regulator, Internal Charge Pumps, Switch Control, and Operational Amplifier for TFT LCDs ELECTRICAL CHARACTERISTICS (continued +5V, Circuit of Figure 1, AVDD = SUP = +14V PARAMETER FB Transconductance LX Current Limit LX On-Resistance Current-Sense Transresistance ...

Page 4

Step-Up Regulator, Internal Charge Pumps, Switch Control, and Operational Amplifier for TFT LCDs ELECTRICAL CHARACTERISTICS (continued +5V, Circuit of Figure 1, AVDD = SUP = +14V PARAMETER OPERATIONAL AMPLIFIERS SUP Supply Range SUP Overvoltage Fault Threshold ...

Page 5

Step-Up Regulator, Internal Charge Pumps, Switch Control, and Operational Amplifier for TFT LCDs ELECTRICAL CHARACTERISTICS (continued +5V, Circuit of Figure 1, AVDD = SUP = +14V PARAMETER REFERENCE REF Output Voltage REF Load Regulation REF Sink ...

Page 6

Step-Up Regulator, Internal Charge Pumps, Switch Control, and Operational Amplifier for TFT LCDs ELECTRICAL CHARACTERISTICS (continued +5V, Circuit of Figure 1, AVDD = SUP = +14V PARAMETER POSITIVE GATE-DRIVER TIMING AND CONTROL SWITCHES CTL Input-Low Voltage ...

Page 7

Step-Up Regulator, Internal Charge Pumps, Switch Control, and Operational Amplifier for TFT LCDs (Circuit of Figure 5V, AVDD = 14V STEP-UP REGULATOR EFFICIENCY vs. LOAD CURRENT 1.2MHz OSC VIN = 5.0V 91 ...

Page 8

Step-Up Regulator, Internal Charge Pumps, Switch Control, and Operational Amplifier for TFT LCDs (Circuit of Figure 5V, AVDD = 14V TIMER-DELAY LATCH RESPONSE TO OVERLOAD 10ms/div AVDD: 10V/div LX: 10V/div I : 5A/div L REFERENCE ...

Page 9

Step-Up Regulator, Internal Charge Pumps, Switch Control, and Operational Amplifier for TFT LCDs (Circuit of Figure 5V, AVDD = 14V HIGH-VOLTAGE SWITCH CONTROL FUNCTION C = 1.5nF GON R = 1kΩ TO AVDD DRN 10µs/div ...

Page 10

Step-Up Regulator, Internal Charge Pumps, Switch Control, and Operational Amplifier for TFT LCDs PIN NAME 1 C1N Negative Terminal of Flying Capacitor C1 2 C1P Positive Terminal of Flying Capacitor C1 3 BGND Operational Amplifier and Charge-Pump Supply Ground Operational ...

Page 11

Step-Up Regulator, Internal Charge Pumps, Switch Control, and Operational Amplifier for TFT LCDs PIN NAME 31 AGND Analog GND 32 RSET Open-Drain HVS Mode Output. For details, see the HVS Mode section. 33 COMP Error-Amplifier Output. Connect a series RC ...

Page 12

Step-Up Regulator, Internal Charge Pumps, Switch Control, and Operational Amplifier for TFT LCDs VIN = 4.5V TO 5.5V C1 1µF VCOM AVDD VCOM R1 10kΩ VCOM R2 10kΩ C2 0.22µF R3 20kΩ 187kΩ C4 VGOFF 1µF -9V, 20mA ...

Page 13

Step-Up Regulator, Internal Charge Pumps, Switch Control, and Operational Amplifier for TFT LCDs Table 2. Component Suppliers SUPPLIER Fairchild Semiconductor Sumida TDK Toshiba VIN VGOFF Figure 2. Functional Diagram and TVs. It has a step-up switching regulator to gener- ate ...

Page 14

Step-Up Regulator, Internal Charge Pumps, Switch Control, and Operational Amplifier for TFT LCDs Step-Up Regulator The step-up regulator employs a current-mode, fixed- frequency PWM architecture to maximize loop band- width and to provide fast-transient response to pulsed loads typical of ...

Page 15

Step-Up Regulator, Internal Charge Pumps, Switch Control, and Operational Amplifier for TFT LCDs Positive Charge-Pump Regulator The positive charge-pump regulator is typically used to generate the positive supply rail for the TFT LCD gate driver ICs. The positive charge pump ...

Page 16

Step-Up Regulator, Internal Charge Pumps, Switch Control, and Operational Amplifier for TFT LCDs Negative Charge-Pump Regulator The negative charge-pump regulator (see Figure 5) generates the negative supply rail for the TFT LCD gate driver ICs. The output voltage is set ...

Page 17

Step-Up Regulator, Internal Charge Pumps, Switch Control, and Operational Amplifier for TFT LCDs When CTL is logic-high, Q1 turns on and Q2 and Q3 turn off, connecting GON to POUT. When CTL is logic- low, Q1 turns off and Q2 ...

Page 18

Step-Up Regulator, Internal Charge Pumps, Switch Control, and Operational Amplifier for TFT LCDs HVS mode is designed as a special operating mode for end-of-line panel testing. In HVS mode, higher than normal voltages are forced to the power-supply outputs to ...

Page 19

Step-Up Regulator, Internal Charge Pumps, Switch Control, and Operational Amplifier for TFT LCDs Design Procedure Step-Up Regulator The inductance value, peak-current rating, and series resistance are factors to consider when selecting the inductor. These factors influence the converter’s effi- ciency, ...

Page 20

Step-Up Regulator, Internal Charge Pumps, Switch Control, and Operational Amplifier for TFT LCDs Output-Capacitor Selection The total output-voltage ripple has two components: the capacitive ripple caused by the charging and dis- charging of the output capacitance, and the ohmic ripple ...

Page 21

Step-Up Regulator, Internal Charge Pumps, Switch Control, and Operational Amplifier for TFT LCDs Increasing the pump capacitor value (C4, C6, and C7) lowers the effective source impedance and increases the output-current capability. Increasing the capaci- tance indefinitely has a negligible ...

Page 22

Step-Up Regulator, Internal Charge Pumps, Switch Control, and Operational Amplifier for TFT LCDs • Place V pin and REF pin bypass capacitors as CC close as possible to the device. The ground con- nection of the V bypass capacitor should ...

Page 23

Step-Up Regulator, Internal Charge Pumps, Switch Control, and Operational Amplifier for TFT LCDs For the latest package outline information and land patterns www.maxim-ic.com/packages. Note that a “+”, “#”, or “-” in the package code indicates RoHS status only. ...

Page 24

... 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. 24 ____________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600 © 2007 Maxim Integrated Products Package Information (continued) Maxim is a registered trademark of Maxim Integrated Products ...

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