MAX8798ETX+ Maxim Integrated Products, MAX8798ETX+ Datasheet

IC INTERNAL-SW BOOST REG 36-TQFN

MAX8798ETX+

Manufacturer Part Number
MAX8798ETX+
Description
IC INTERNAL-SW BOOST REG 36-TQFN
Manufacturer
Maxim Integrated Products
Datasheet
1.MAX8798ETX.pdf (31 pages)

Specifications of MAX8798ETX+

Applications
LCD Monitor, Notebook Display
Current - Supply
400µA
Voltage - Supply
1.8 V ~ 6 V
Operating Temperature
-40°C ~ 85°C
Mounting Type
Surface Mount
Package / Case
36-TQFN Exposed Pad
Operating Supply Voltage
1.8 V to 5.5 V
Maximum Operating Temperature
- 40 C
Mounting Style
SMD/SMT
Maximum Power Dissipation
2179.8 mW
Minimum Operating Temperature
+ 85 C
Supply Current
4 uA
Input Voltage
4V
Output Current
400mA
Output Voltage
18V
No. Of Outputs
2
Power Dissipation Pd
2.18W
Supply Voltage Range
1.8V To 5.5V
No. Of Pins
36
Operating Temperature Range
-40°C To +85°C
Rohs Compliant
Yes
Lead Free Status / RoHS Status
Lead free / RoHS Compliant
The MAX8798 includes a high-performance, step-up
regulator; a high-speed operational amplifier; a digitally
adjustable VCOM calibration device with nonvolatile
memory; an I
ing scan driver. The device is optimized for thin-film
transistor (TFT) liquid-crystal display (LCD) applications.
The step-up DC-DC converter provides the regulated
supply voltage for panel source driver ICs. The high
switching frequency allows the use of ultra-small induc-
tors and ceramic capacitors. The current-mode control
architecture provides fast transient response to pulsed
loads typical of source driver loads. The step-up regu-
lator features soft-start and current limit.
The high-current operational amplifier is designed to
drive the LCD backplane (VCOM). The amplifier fea-
tures high output current (±150mA), fast slew rate
(45V/µs), wide bandwidth (20MHz), and rail-to-rail
inputs and outputs.
The programmable VCOM calibrator is externally
attached to the VCOM amplifier’s resistive voltage-divider
and sinks a programmable current to adjust the VCOM
output-voltage level. An internal 7-bit digital-to-analog
converter (DAC) controls the sink current. The DAC is
ratiometric relative to BOOST and is guaranteed to be
monotonic over all operating conditions. The calibrator IC
includes an EEPROM to store the desired VCOM voltage
level. The 2-wire I
and the programming circuit minimizes panel connector
lead count and simplifies production equipment.
The high-voltage, level-shifting scan driver is designed
to drive the TFT panel gate drivers. Its three outputs
swing 65V (maximum) between +45V (maximum) and
-25V (minimum) and can swiftly drive capacitive loads.
To save power, the two complementary outputs are
designed to allow charge sharing during state changes.
The MAX8798 is available in a 36-pin, thin QFN pack-
age with a maximum thickness of 0.8mm for ultra-thin
LCD panels.
19-0971; Rev 1; 6/08
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.
MAX8798ETX+ -40°C to +85°C
Integrated 3-Channel Scan Driver for TFT LCDs
PART
Notebook Computer Displays
LCD Monitor Panels
2
C interface; and a high-voltage, level-shift-
TEMP RANGE
________________________________________________________________ Maxim Integrated Products
2
C interface between the LCD panel
Ordering Information
General Description
Internal-Switch Boost Regulator with
PIN-
PACKAGE
36 Thin QFN
6mm x 6mm
Applications
T-3666M-1
CODE
PKG
♦ 1.8V to 5.5V IN Supply Voltage Range
♦ 1.8V to 4.0V V
♦ 1.2MHz Current-Mode Step-Up Regulator
♦ High-Speed (20MHz) Operational Amplifier
♦ High-Voltage Drivers with Scan Logic
♦ Programmable VCOM Calibrator
♦ Thermal-Overload Protection
BUS
SYSTEM
I
2
PANEL
C
V
V IN
IN
Fast Transient Response
Built-In 20V, 1.9A, 150mΩ MOSFET
±150mA Output Current
+45V to -25V Outputs
65V (maximum) Swing
Output Charge Sharing
7-Bit Adjustable Current-Sink Output
I
EEPROM Setting Memory
VN
2
C Interface
Simplified Operating Circuit
DISH
CPV
OE
STV
OECON
CKVCS
CKVB
CKVBCS
GOFF
STVP
CKV
VL
V
GND
SDA
SCL
SCLS
DD
50kΩ
DD
WPP
Input Voltage Range
1kΩ
GATE DRIVERS
VN
SCAN DRIVER
VCOM CALIBRATOR
LOGIC
WPN
SHDN
AND
7
LINEAR
3.3V
REG
IN
STEP-UP
1.9A
REG
SET
BOOST
COMP
VCOM
BGND
PGND
AGND
GON
NEG
POS
OUT
LX
FB
Features
VP
TO VCOM
BACKPLANE
V
MAIN
VP
1

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MAX8798ETX+ Summary of contents

Page 1

... Ordering Information PIN- PART TEMP RANGE PACKAGE 36 Thin QFN MAX8798ETX+ -40°C to +85°C 6mm x 6mm ________________________________________________________________ Maxim Integrated Products 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. ♦ 1.8V to 5.5V IN Supply Voltage Range ♦ ...

Page 2

Internal-Switch Boost Regulator with Integrated 3-Channel Scan Driver for TFT LCDs ABSOLUTE MAXIMUM RATINGS IN, VL, SHDN to AGND .........................................-0.3V to +7. SDA, SCL, SCLS, WPN, WPP, SET to GND...-0.3V to +4.0V DD OECON, CPV, OE, STV to ...

Page 3

Internal-Switch Boost Regulator with Integrated 3-Channel Scan Driver for TFT LCDs ELECTRICAL CHARACTERISTICS (continued +3V, circuit of Figure 2, V SHDN 0°C to +85°C, unless ...

Page 4

Internal-Switch Boost Regulator with Integrated 3-Channel Scan Driver for TFT LCDs ELECTRICAL CHARACTERISTICS (continued +3V, circuit of Figure 2, V SHDN 0°C to +85°C, unless ...

Page 5

Internal-Switch Boost Regulator with Integrated 3-Channel Scan Driver for TFT LCDs ELECTRICAL CHARACTERISTICS (continued +3V, circuit of Figure 2, V SHDN 0°C to +85°C, unless ...

Page 6

Internal-Switch Boost Regulator with Integrated 3-Channel Scan Driver for TFT LCDs ELECTRICAL CHARACTERISTICS (continued +3V, circuit of Figure 2, V SHDN -40°C to +85°C, unless ...

Page 7

Internal-Switch Boost Regulator with Integrated 3-Channel Scan Driver for TFT LCDs ELECTRICAL CHARACTERISTICS (continued +3V, circuit of Figure 2, V SHDN -40°C to +85°C, unless ...

Page 8

Internal-Switch Boost Regulator with Integrated 3-Channel Scan Driver for TFT LCDs ELECTRICAL CHARACTERISTICS (continued +3V, circuit of Figure 2, V SHDN -40°C to +85°C, unless ...

Page 9

Internal-Switch Boost Regulator with Integrated 3-Channel Scan Driver for TFT LCDs (Circuit of Figure 3V +25°C, unless otherwise noted STEP-UP REGULATOR EFFICIENCY vs. LOAD CURRENT 100 ...

Page 10

Internal-Switch Boost Regulator with Integrated 3-Channel Scan Driver for TFT LCDs (Circuit of Figure 3V +25°C, unless otherwise noted STEP-UP REGULATOR PULSED LOAD TRANSIENT RESPONSE (20mA TO 1A 3.6μ ...

Page 11

Internal-Switch Boost Regulator with Integrated 3-Channel Scan Driver for TFT LCDs (Circuit of Figure 3V +25°C, unless otherwise noted OPERATIONAL AMPLIFIER LOAD TRANSIENT RESPONSE MAX8798 toc16 V VCOM (AC-COUPLED) 200mV/div 0mV I VCOM ...

Page 12

Internal-Switch Boost Regulator with Integrated 3-Channel Scan Driver for TFT LCDs (Circuit of Figure 3V +25°C, unless otherwise noted CALIBRATOR SIGNAL LSB DOWNWARD STEP RESPONSE 0V 0V 0mV 0mV 40μs/div CALIBRATOR FULL-SCALE UPWARD ...

Page 13

Internal-Switch Boost Regulator with Integrated 3-Channel Scan Driver for TFT LCDs PIN NAME High-Voltage, Gate-Pulse Output. When enabled, CKV toggles between its high state (connected to GON) and its low state (connected to GOFF) on each falling edge of the ...

Page 14

Internal-Switch Boost Regulator with Integrated 3-Channel Scan Driver for TFT LCDs PIN NAME 20 BGND Amplifier Ground Operational Amplifier Supply Input. Connect BOOST greater ceramic capacitor. Adjustable Sink-Current Output. OUT connects to the resistive voltage-divider at the ...

Page 15

Internal-Switch Boost Regulator with Integrated 3-Channel Scan Driver for TFT LCDs -12V, 20mA V IN 2.2V TO 3.6V 10μF 0.1μ SYSTEM 20kΩ 3nF 200Ω PANEL 200Ω VL 0.22μF 0.1μF 20kΩ 20kΩ BUS Figure ...

Page 16

Internal-Switch Boost Regulator with Integrated 3-Channel Scan Driver for TFT LCDs V IN 1.8V TO 5.5V DISH CPV OE SYSTEM STV OECON GOFF VN STVP CKVCS PANEL CKVB CKVBCS CKV GND V IN SDA SCL I ...

Page 17

Internal-Switch Boost Regulator with Integrated 3-Channel Scan Driver for TFT LCDs Typical Application Circuit The MAX8798 typical application circuit (Figure 2) gener- ates a +8V source-driver supply and approximately +20V and -12V gate-driver supplies for TFT displays. The input- voltage ...

Page 18

Internal-Switch Boost Regulator with Integrated 3-Channel Scan Driver for TFT LCDs Figure 4 shows the block diagram of the step-up regu- lator. An error amplifier compares the signal 1.24V and changes the COMP output. The voltage at ...

Page 19

Internal-Switch Boost Regulator with Integrated 3-Channel Scan Driver for TFT LCDs Linear Regulator (VL) The MAX8798 includes an internal 3.3V linear regulator. BOOST is the input of the linear regulator. The input volt- age range is between 5V and 18V. ...

Page 20

Internal-Switch Boost Regulator with Integrated 3-Channel Scan Driver for TFT LCDs SYSTEM VIDEO TIMING Figure 5. Scan Driver System Diagram High-Voltage Level-Shifting Scan Driver The MAX8798 includes a 3-channel high-voltage (60V) level-shifting scan driver that includes logic functions necessary to ...

Page 21

Internal-Switch Boost Regulator with Integrated 3-Channel Scan Driver for TFT LCDs GOFF Rapid Discharge Function The DISH input controls a switch between GOFF and GND. When DISH is pulled below ground by at least 1V, GOFF is rapidly discharged to ...

Page 22

Internal-Switch Boost Regulator with Integrated 3-Channel Scan Driver for TFT LCDs Design Procedure Main Step-Up Regulator The minimum inductance value, peak current rating, and series resistance are factors to consider when selecting the inductor. These factors influence the converter’s effi- ...

Page 23

Internal-Switch Boost Regulator with Integrated 3-Channel Scan Driver for TFT LCDs Choosing an LIR of 0.5 and estimating efficiency of 85% at this operating point: 2 − ⎛ ⎞ ⎛ ⎞ ...

Page 24

Internal-Switch Boost Regulator with Integrated 3-Channel Scan Driver for TFT LCDs Setting the VCOM Adjustment Range The external resistive voltage-divider sets the maximum value of the VCOM adjustment range. R full-scale sink current which determines the mini- OUT ...

Page 25

Internal-Switch Boost Regulator with Integrated 3-Channel Scan Driver for TFT LCDs VCOM Calibrator Interface The MAX8798 is a slave-only device with 9Eh. The 2-wire I C-bus-like serial interface (SCL and SDA) is designed to attach to ...

Page 26

Internal-Switch Boost Regulator with Integrated 3-Channel Scan Driver for TFT LCDs The data byte follows successful transmission of the MAX8798’s slave address (Figure 8). For a read opera- tion, the MAX8798 outputs the 7 bits corresponding to the current DAC ...

Page 27

Internal-Switch Boost Regulator with Integrated 3-Channel Scan Driver for TFT LCDs PCB Layout and Grounding Careful PCB layout is important for proper operation. Use the following guidelines for good PCB layout: • Minimize the area of high-current loops by placing ...

Page 28

Internal-Switch Boost Regulator with Integrated 3-Channel Scan Driver for TFT LCDs Pin Configuration TOP VIEW PGND 30 PGND MAX8798 COMP 33 AGND 34 GOFF ...

Page 29

Internal-Switch Boost Regulator with Integrated 3-Channel Scan Driver for TFT LCDs (The package drawing(s) in this data sheet may not reflect the most current specifications. For the latest package outline information go to www.maxim-ic.com/packages.) ______________________________________________________________________________________ Package Information 29 ...

Page 30

Internal-Switch Boost Regulator with Integrated 3-Channel Scan Driver for TFT LCDs (The package drawing(s) in this data sheet may not reflect the most current specifications. For the latest package outline information go to www.maxim-ic.com/packages.) 30 ______________________________________________________________________________________ Package Information (continued) ...

Page 31

... 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. Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600 ____________________ 31 © 2008 Maxim Integrated Products DESCRIPTION is a registered trademark of Maxim Integrated Products, Inc ...

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