MAX1543ETP+-MAX1543ETP+T Fast Delivery |IC PHOENIX CO.,LIMITED

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MAX1543ETP+-MAX1543ETP+T
TFT LCD DC-to-DC Converter with Operational Amplifiers
General Description
The MAX1542/MAX1543 include a high-performance
boost regulator and two high-current operational ampli-
fiers for active matrix, thin-film transistor (TFT), liquid-
crystal displays (LCDs). Also included is a logic-
controlled, high-voltage switch with adjustable delay.
The MAX1543 includes an additional high-voltage load
switch and features pin-selectable boost regulator
switching frequency.
The step-up DC-to-DC converter is a high-frequency
640kHz (MAX1543)/1.2MHz (MAX1542/MAX1543) cur-
rent-mode regulator with a built-in power MOSFET that
allows the use of ultra-small inductors and ceramic
capacitors. It provides fast transient response to pulsed
loads while producing efficiencies over 85%.
The two easy-to-use, high-performance operational
amplifiers can drive the LCD backplane (VCOM) and/or
the gamma correction divider string. The devices fea-
ture high short-circuit current (150mA), fast slew rate
(7.5V/µs), wide bandwidth (12MHz), and Rail-to-Rail®
inputs and outputs.
The MAX1542/MAX1543 are available in 20-pin thin
QFN packages with a maximum thickness of 0.8mm for
ultra-thin LCD panel design.
Applications
Notebook Computer Displays
LCD Monitor Panels
PDAs
Car Navigation Displays
FeaturesUltra-High-Performance Step-Up Regulator
Fast Transient Response to Pulsed Load Using
Current-Mode Control Architecture
High-Accuracy Output Voltage (1.3%)
Built-In 14V, 1.2A, 0.2ΩN-Channel Power
MOSFET with Lossless Current-Sensing
High Efficiency (85%)
8-Step Current-Controlled Digital Soft-StartTwo High-Performance Operational Amplifiers
150mA Output Short-Circuit Current
7.5V/µs Slew Rate
12MHz -3dB Bandwidth
Rail-to-Rail Inputs/Outputs
Unity Gain StableLogic-Controlled High-Voltage Switch with
Adjustable DelayTimer Delay Latch FB Fault ProtectionThermal Protection2.6V to 5.5V Input Operating Voltage Range3.6mA (Switching), 0.45mA (Not Switching)
Quiescent CurrentUltra-Thin 20-Pin Thin QFN Package
(5mm x 5mm x 0.8mm)
MAX1542/MAX1543
TFT LCD DC-to-DC Converter with
Operational Amplifiers19181716
DRNCTLDELCOMPFB789
POS1NEG1OUT1OUT2NEG2
POS2
SUP
FREQ
AGND
PGND
I.C.
COM
SRC
MAX1543
THIN QFN (5mm x 5mm)
TOP VIEW
Pin ConfigurationsOrdering Information
19-2741; Rev 0; 4/03
EVALUATION KIT
AVAILABLE
PARTTEMP RANGEPIN-PACKAGE
MAX1542ETP-40°C to +85°C20 Thin QFN (5mm x 5mm)
MAX1543ETP-40°C to +85°C20 Thin QFN (5mm x 5mm)
Rail-to-Rail is a registered trademark of Nippon Motorola, Ltd.Pin Configurations continued at end of data sheet.
MAX1542/MAX1543
TFT LCD DC-to-DC Converter with
Operational Amplifiers
ABSOLUTE MAXIMUM RATINGS
Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress ratings only, and functional
operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to
absolute maximum rating conditions for extended periods may affect device reliability.
IN, CTL, COMP, FB, DEL, FREQ (MAX1543)
to AGND...............................................................-0.3V to +6V
COMP, FB, DEL to AGND.............................-0.3V to (IN + 0.3V)
PGND to AGND..................................................................±0.3V
LX to PGND............................................................-0.3V to +14V
SUP, POS1, NEG1, OUT1, POS2,
NEG2, OUT2 to AGND.......................................-0.3V to +14V
POS1, NEG1, OUT1, POS2, NEG2,
OUT2 to AGND......................................-0.3V to (SUP + 0.3V)
SRC, COM to AGND...............................................-0.3V to +30V
SRC to COM...........................................................-0.3V to +30V
SRC to DRN (MAX1543).........................................-0.3V to +30V
COM to AGND...........................................-0.3V to (SRC + 0.3V)
DRN (MAX1543) to AGND.........................-0.3V to (SRC + 0.3V)
DRN (MAX1543) to COM.........................................-30V to +30V
MAX1542 COM RMS Output Current...............................+75mA
MAX1543 COM RMS Output Current...............................±50mA
OUT1, OUT2 Continuous Output Current.........................±75mA
Continuous Power Dissipation (TA= +70°C)
20-Pin Thin QFN 5mm x 5mm
(derate 20.8mW/°C above +70°C).............................1667mW
Operating Temperature Range...........................-40°C to +85°C
Junction Temperature .....................................................+150°C
Storage Temperature Range.............................-65°C to +150°C
Lead Temperature (soldering, 10s).................................+300°C
ELECTRICAL CHARACTERISTICS
(VIN= 3V, VSUP= 8V, VSRC= 28V, FREQ = IN (MAX1543), PGND = AGND = 0, TA= 0°C to +85°C, typical values at TA= +25°C,
unless otherwise noted.)
PARAMETERSYMBOLCONDITIONSMINTYPMAXUNITS
IN Supply RangeVIN2.65.5V
VIN rising2.32.52.7IN Undervoltage Lockout
ThresholdVUVLOVIN falling2.22.352.5V
VFB = 1.3V, LX not switching0.450.65IN Quiescent CurrentIINVFB = 1.1V, LX switching3.66.5mA
MAX154255
FREQ = AGND51Duration to Trigger Fault
ConditionMAX1543FREQ = IN55
Rising edge160Thermal ShutdownHysteresis15°C
MAIN STEP-UP REGULATOR
Output Voltage RangeVMAINVIN13V
MAX1542102012001380
MAX1543FREQ = AGND512600768Operating FrequencyfOSC
FREQ = IN102012001380
kHz
Oscillator Maximum Duty Cycle828792%
FREQ Input Low VoltageMAX1543, VIN = 2.6V to 5.5V0.3 x VINV
FREQ Input High VoltageMAX1543, VIN = 2.6V to 5.5V0.7 x
VINV
FREQ Pulldown CurrentMAX1543, VFREQ = 1.0V3.556.5µA
TA = +85°C1.2241.2401.256FB Regulation VoltageVFBNo loadTA = 0°C to +85°C1.2221.2401.258V
FB Fault Trip LevelVFB falling0.9611.04V
FB Load Regulation0 ≤ IMAIN ≤ full load-1%
FB Line RegulationVIN = 2.6V to 5.5V-0.08±0.15%/V
MAX1542/MAX1543
TFT LCD DC-to-DC Converter with
Operational Amplifiers
ELECTRICAL CHARACTERISTICS (continued)
(VIN= 3V, VSUP= 8V, VSRC= 28V, FREQ = IN (MAX1543), PGND = AGND = 0, TA= 0°C to +85°C, typical values at TA= +25°C,
unless otherwise noted.)
PARAMETERSYMBOLCONDITIONSMINTYPMAXUNITS
FB Input Bias CurrentVFB = 1.5V-40+40nA
FB TransconductanceΔICOMP = 5µA75160280µS
FB Voltage GainFB to COMP700V/V
LX On-ResistanceRLX(ON)210400mΩ
LX Leakage CurrentILXVLX = 13V0.0120µA
LX Current LimitILIMVFB = 1V, duty cycle = 65%1.21.51.8A
Current-Sense Transresistance0.300.500.65Ω
MAX154214
FREQ = AGND13Soft-Start PeriodtSSMAX1543FREQ = IN14
Soft-Start Step SizeILIM / 8A
OPERATIONAL AMPLIFIERS
SUP Supply RangeVSUP4.513.0V
SUP Supply CurrentISUPBuffer configuration, VPOS_ = 4V, no load1.31.9mA
Input Offset VoltageVOSVCM = VSUP/2, TA = +25°C012mV
Input Bias CurrentIBIASNEG1, NEG2, POS1, POS2+1±50nA
Input Common-Mode Voltage
RangeVCM0VSUPV
Common-Mode Rejection RatioCMRR0 ≤ VNEG_, VPOS_ ≤ VSUP5090dB
Open-Loop Gain125dB
IOUT_ = 100µAVSUP -
VSUP -
Output Voltage Swing HighVOH
IOUT_ = 5mAVSUP -
VSUP -
IOUT_ = -100µA215Output Voltage Swing LowVOLIOUT_ = -5mA80150mV
Source50150Short-Circuit CurrentTo VSUP/2Sink50140mA
Output Source-and-Sink CurrentBuffer configuration, VPOS_ = 4V,
|ΔVOS| < 10mV40mA
Power-Supply Rejection RatioPSRRDC, 6V ≤ VSUP ≤ 13V, VNEG_, VPOS_ =
VSUP/260100dB
Slew Rate7.5V/µs
-3dB BandwidthRL = 10kΩ, CL =10pF, buffer configuration12MHz
Gain-Bandwidth ProductGBWBuffer configuration8MHz
POSITIVE GATE-DRIVER TIMING AND CONTROL SWITCHES
DEL Capacitor Charge CurrentDuring startup, VDEL = 1V456µA
MAX1542/MAX1543
TFT LCD DC-to-DC Converter with
Operational Amplifiers
ELECTRICAL CHARACTERISTICS
(VIN= 3V, VSUP= 8V, VSRC= 28V, FREQ = IN (MAX1543), PGND = AGND = 0, TA= -40°C to +85°C,unless otherwise noted.)
PARAMETERSYMBOLCONDITIONSMINTYPMAXUNITS
DEL Turn-On ThresholdVTH(DEL)1.1781.2401.302V
DEL Discharge Switch On-
ResistanceDuring UVLO, VIN = 2.2V20Ω
CTL Input Low VoltageVIN = 2.6V to 5.5V0.6V
CTL Input High VoltageVIN = 2.6V to 5.5V2V
CTL Input Leakage CurrentCTL = AGND or IN-1+1µA
CTL-to-SRC Propagation Delay100ns
SRC Input Voltage Range28V
MAX154270130V D RN = 8V , C TL = IN ,D E L = 1.5V MAX1543100180SRC Input CurrentISRC
VDRN = 8V, CTL = AGND, VDEL = 1.5V1530
DRN Input CurrentIDRCVDRN = 8V, CTL = AGND, VDEL = 1.5V,
MAX154390150µA
MAX1542510SRC to COM Switch On-
ResistanceRSRC(ON)VDEL = 1.5V,
CTL = INMAX15431530Ω
DRN to COM Switch On-
Resistance (MAX1543)RDRN(ON)VDEL = 1.5V, CTL = AGND3060Ω
COM to PGND Switch On-
Resistance (MAX1543)RCOM(ON)VDEL = 1.1V35010001800Ω
PARAMETERSYMBOLCONDITIONSMINTYPMAXUNITS
IN Supply RangeVIN2.65.5V
VIN rising2.32.7IN Undervoltage Lockout
ThresholdVUVLOVIN falling2.22.5V
VFB = 1.3V, LX not switching0.65IN Quiescent CurrentIINVFB = 1.1V, LX switching6.5mA
MAIN STEP-UP REGULATOR
Output Voltage RangeVMAINVIN13V
MAX154210001400
FREQ = AGND512768Operating FrequencyfOSCMAX1543FREQ = IN10001400
kHz
FB Regulation VoltageVFBNo load1.2151.260V
FB Fault Trip LevelVFB falling0.961.04V
FB Line RegulationVIN = 2.6V to 5.5V0.15%/V
FB TransconductanceΔICOMP = 5µA75300µS
LX On-ResistanceRLX(ON)400mΩ
ELECTRICAL CHARACTERISTICS (continued)
(VIN= 3V, VSUP= 8V, VSRC= 28V, FREQ = IN (MAX1543), PGND = AGND = 0, TA= 0°C to +85°C, typical values at TA= +25°C,
unless otherwise noted.)
MAX1542/MAX1543
TFT LCD DC-to-DC Converter with
Operational Amplifiers
PARAMETERSYMBOLCONDITIONSMINTYPMAXUNITS
LX Current LimitILIMVFB = 1V, duty cycle = 65%1.21.8A
Current-Sense Transresistance0.300.65Ω
OPERATIONAL AMPLIFIERS
SUP Supply RangeVSUP4.513.0V
SUP Supply CurrentISUPBuffer configuration, VPOS_ = 4V, no load2.1mA
Input Offset VoltageVOSVCM = VSUP/2, TA = +25ºC12mV
Input Bias CurrentIBIASNEG1, NEG2, POS1, POS2±50nA
Input Common-Mode Voltage
RangeVCM0VSUPV
IOUT_ = 100µAVSUP -
Output Voltage Swing HighVOH
IOUT_ = 5mAVSUP -
IOUT_ = -100µA15Output Voltage Swing LowVOLIOUT_ = -5mA150mV
Source50Short-Circuit CurrentTo VSUP/2Sink50mA
Output Source-and-Sink CurrentBuffer configuration, VPOS_ = 4V,
| ΔVOS | < 10mV40mA
POSITIVE GATE-DRIVER TIMING AND CONTROL SWITCHES
DEL Capacitor Charge CurrentDuring startup, VDEL = 1.0V46µA
DEL Turn-On ThresholdVTH (DEL)1.1781.302V
CTL Input Low VoltageVIN = 2.6V to 5.5V0.6V
CTL Input High VoltageVIN = 2.6V to 5.5V2V
SRC Input Voltage Range28V
MAX1542130VDRN = 8V, CTL = IN,
VDEL = 1.5VMAX1543180SRC Input CurrentISRC
VDRN = 8V, CTL = AGND, VDEL = 1.5V30
DRN Input CurrentIDRNVDRN = 8V, CTL = AGND, VDEL = 1.5V,
MAX1543150µA
MAX154210SRC to COM Switch On-
ResistanceRSRC(ON)VDEL = 1.5V, CTL = INMAX154330Ω
DRN to COM Switch On-
Resistance (MAX1543)RDRN(ON)VDEL = 1.5V, CTL = AGND60Ω
COM to PGND Switch On-
Resistance (MAX1543)RCOM(ON)VDEL = 1.1V3501800Ω
ELECTRICAL CHARACTERISTICS (continued)
(VIN= 3V, VSUP= 8V, VSRC= 28V, FREQ = IN (MAX1543), PGND = AGND = 0, TA= -40°C to +85°C,unless otherwise noted.)
MAX1542/MAX1543
TFT LCD DC-to-DC Converter with
Operational Amplifiers
Typical Operating Characteristics
(VIN= 3.3V, VMAIN= 8V, fOSC= 1.2MHz, TA= +25°C, unless otherwise noted.)1000100
STEP-UP REGULATOR EFFICIENCY
vs. LOAD CURRENT (VMAIN = 8V)
MAX1542 toc01
LOAD CURRENT (mA)
EFFICIENCY (%)
MAX1543
fOSC = 1.2MHz
L = 4.7μH
VIN = 3.3V
VIN = 2.7V
VIN = 5V100010010
STEP-UP REGULATOR EFFICIENCY
vs. LOAD CURRENT (VMAIN = 8V)
MAX1542 toc02
LOAD CURRENT (mA)
EFFICIENCY (%)
MAX1543
fOSC = 640kHz
L = 10μH
VIN = 3.3V
VIN = 2.7V
VIN = 5V
VIN = 5V
STEP-UP REGULATOR OUTPUT VOLTAGE
vs. LOAD CURRENT (VMAIN = 8V)
MAX1542 toc03
LOAD CURRENT (mA)
OUTPUT VOLTAGE (V)100
VIN = 3.3V
fOSC = 1.2MHz
MAX1542 toc04
VIN (V)
SUPPLY CURRENT (mA)
STEP-UP REGULATOR SUPPLY CURRENT
vs. SUPPLY VOLTAGE
NO LOAD
fOSC = 1.2MHz
R1 = 75kΩ
R2 = 13.7kΩ
SUP DISCONNECTED
CURRENT INTO INDUCTOR
CURRENT INTO IN PIN
STEP-UP REGULATOR SUPPLY CURRENT
vs. TEMPERATURE
MAX1542 toc05
TEMPERATURE (°C)
SUPPLY CURRENT (mA)3510-15
NO LOAD
VIN = 3.3V
fOSC = 1.2MHz
R1 = 75kΩ
R2 = 13.7kΩ
SUP DISCONNECTED
CURRENT INTO INDUCTOR
CURRENT INTO IN PIN
MAX1542 toc06
VIN (V)
SWITCHING FREQUENCY (kHz)
SWITCHING FREQUENCY
vs. INPUT VOLTAGE
MAX1543
IMAIN = 200mA
FREQ = IN
FREQ = AGND
SUP SUPPLY CURRENT
vs. SUP VOLTAGE
MAX1542 toc07
VSUP (V)
ISUP
(mA)
NO LOAD
BUFFER CONFIGURATION
POS_ = VSUP/2
SUP SUPPLY CURRENT
vs. TEMPERATURE
MAX1542 toc08
TEMPERATURE (°C)
ISUP
(mA)3510-15
NO LOAD
BUFFER CONFIGURATION
VPOS = VSUP/2
VSUP = 13V
VSUP = 8V
VSUP = 5V
MAX1542/MAX1543
TFT LCD DC-to-DC Converter with
Operational Amplifiers
100100k10k1k
OPERATIONAL AMPLIFIER FREQUENCY
RESPONSE FOR VARIOUS CLOAD
MAX1542 toc09
FREQUENCY (Hz)
MAGNITUDE (dB)
VSUP = 8V
AV = 1
RL = 10kΩ
1000pF
15pF
56pF
100pF
OPERATIONAL AMPLIFIER OVERSHOOT
vs. LOAD CAPACITANCE
MAX1542 toc10
LOAD CAPACITANCE (pF)
OVERSHOOT (%)40
VSUP = 8V
RL = 10kΩ
AV = 1
POS_ = 4V ±50mV
FALLING EDGE
RISING EDGE
Typical Operating Characteristics (continued)
(VIN= 3.3V, VMAIN= 8V, fOSC= 1.2MHz, TA= +25°C, unless otherwise noted.)
OPERATIONAL AMPLIFIER
OUTPUT LOW VOLTAGE vs. LOAD
MAX1542 toc12
IOUT_ (mA)
(mV)642
VSUP = 8V
AV = 1
OPERATIONAL AMPLIFIER
OUTPUT HIGH VOLTAGE vs. LOAD
MAX1542 toc11
IOUT_ (mA)
SUP
- V
OUT
(mV)642
VSUP = 8V
AV = 1
POWER-SUPPLY REJECTION RATIO
vs. FREQUENCY
MAX1542 toc13
FREQUENCY (Hz)
PSRR (dB)100101
0.110k
VSUP = 8V
OPERATIONAL AMPLIFIER
SETTLING TIME vs. STEP SIZE
MAX1542 toc14
STEP SIZE (V)
SETTLING TIME (ns)
VSUP = 8V
AV = +1
RL = 10kΩ
CL = 10pF
VCM = 4V
RISING EDGE
FALLING EDGE
STEP-UP REGULATOR
LOAD-TRANSIENT RESPONSE
MAX1542 toc15
40μs/div
IMAIN
200mA/div
500mA/div
200mA
20mA
VMAIN
AC-COUPLED
100mV/divL = 4.7μH
RCOMP = 120kΩ
CCOMP = 470pF
MAX1542/MAX1543
TFT LCD DC-to-DC Converter with
Operational Amplifiers
Typical Operating Characteristics (continued)
(VIN= 3.3V, VMAIN= 8V, fOSC= 1.2MHz, TA= +25°C, unless otherwise noted.)
STEP-UP REGULATOR
PULSED LOAD-TRANSIENT RESPONSE
MAX1542 toc16
10μs/div
IMAIN
1A/div
500mA/div
VMAIN
100mV/div
AC-COUPLEDL = 4.7μH
RCOMP = 120kΩ
CCOMP = 470pF
STARTUP SEQUENCE
MAX1542 toc17
1ms/div
VIN
2V/div
VMAIN
8V/div
VGOFF
5V/div
VCOM
10V/div
HEAVY-LOAD
SOFT-START WAVEFORMS
MAX1542 toc18
2ms/div
RLOAD = 10Ω
VIN
5V/div
VMAIN
5V/div
500mA/div
TIMER DELAY LATCH
RESPONSE TO OVERLOAD
MAX1542 toc19
10ms/div
2A/div
VMAIN
5V/div
VOUT1
5V/div
VCOM
20V/div
OPERATIONAL AMPLIFIER
RAIL-TO-RAIL I/O PERFORMANCE
MAX1542 toc20
100μs/div
VPOS1
5V/div
VOUT1
5V/div
VSUP = 8V
BUFFER CONFIGURATION
OPERATIONAL AMPLIFIER
LOAD-TRANSIENT RESPONSE
MAX1542 toc21
1μs/div
VOUT1
1V/div
AC-COUPLED4V
+50
IOUT1
50mA/div
BUFFER CONFIGURATION
OPERATIONAL AMPLIFIER
LARGE-SIGNAL STEP RESPONSE
MAX1542 toc22
1μs/div
VPOS1
500mV/div
AC-COUPLED4V
VOUT1
2V/divVSUP = 8V
AV = 10
MAX1542/MAX1543
TFT LCD DC-to-DC Converter with
Operational Amplifiers
Typical Operating Characteristics (continued)
(VIN= 3.3V, VMAIN= 8V, fOSC= 1.2MHz, TA= +25°C, unless otherwise noted.)
OPERATIONAL AMPLIFIER
SMALL-SIGNAL STEP RESPONSE
MAX1542 toc24
200ns/div
POS_
50mV/div
AC-COUPLED
OUT_
50mV/div
AC-COUPLED
VSUP = 8V, AV = 1
CH2 + OVER
6.234%
CH2 - OVER
2.352%
OPERATIONAL AMPLIFIER
LARGE-SIGNAL STEP RESPONSE
MAX1542 toc23
1μs/div
VOUT_
1V/div
CHI AMPL
4.86V
CHI + OVER
4.970%
AV = 1
Pin Description
PIN
MAX1542MAX1543NAMEFUNCTION1COMInternal High-Voltage MOSFET Switch Common Terminal. Do not allow the voltage on
COM to exceed VSRC.2SRCSwitch Input. Source of the internal high-voltage P-channel MOSFET. Bypass SRC to
PGND with a minimum of 0.1µF close to the pins.
3, 15, 20—N.C.No Connection. Not internally connected.3I.C.Internal Connection. Make no connection to this pin.4PGND
Power Ground. PGND is the source of the main boost N-channel power MOSFET. Connect
PGND to the output capacitor ground terminals through a short, wide PC board trace.
Connect to analog ground (AGND) underneath the IC.5AGNDAnalog Ground. Connect to power ground (PGND) underneath the IC.6POS1Operational Amplifier 1 Noninverting Input7NEG1Operational Amplifier 1 Inverting Input8OUT1Operational Amplifier 1 Output9OUT2Operational Amplifier 2 Output10NEG2Operational Amplifier 2 Inverting Input11POS2Operational Amplifier 2 Noninverting Input12SUPOperational Amplifier Power Input. Positive supply rail for the OUT1 and OUT2 amplifiers.
Typically connected to VMAIN. Bypass SUP to AGND with a 0.1µF capacitor.13LXPower MOSFET N-Channel Drain and Switching Node. Connect the inductor and catch
diode to LX and minimize the trace area for lowest EMI.
MAX1542/MAX1543
TFT LCD DC-to-DC Converter with
Operational Amplifiers
Pin Description (continued)
PIN
MAX1542MAX1543NAMEFUNCTION14INSupply Voltage. IN can range from 2.6V to 5.5V.15FREQ
Oscillator Frequency Select Input. Pull FREQ low or leave it unconnected for 640kHz
operation. Connect FREQ high for 1.2MHz operation. This input has a 5µA pulldown
current.16FB
Step-Up Converter Feedback Input. Regulates to 1.24V (nominal). Connect a resistor-
divider from the output (VMAIN) to FB to analog ground (AGND). Place the resistor-divider
within 5mm of FB.17COMPStep-Up Regulator Error Amplifier Compensation Point. Connect a series RC from COMP
to AGND. See the Loop Compensation section for component selection guidelines.18DEL
High-Voltage Switch Delay Input. Connect a capacitor from DEL to AGND to set the high-
voltage switch startup delay. A 5µA current source charges CDEL.
For the MAX1542, the high-voltage switch between SRC and COM is disabled until VDEL
exceeds 1.24V. Following the delay period, CTL controls the state of the high-voltage
switch.
For the MAX1543, the switches between SRC, COM, and DRN are disabled and a 1kΩ
pulldown between COM and PGND is enabled until VDEL exceeds 1.24V. Following the
delay period, the 1kΩ pulldown is released and CTL controls the state of the high-voltage
switches (see the Delay Control Circuit section).19CTL
High-Voltage Switch Control Input. When CTL is high, the high-voltage switch between
COM and SRC is on and the high-voltage switches between COM and DRN (MAX1543)
are off. When CTL is low, the high-voltage switch between COM and SRC is off and the
high-voltage switches between COM and DRN (MAX1543) are on. CTL is inhibited by the
undervoltage lockout and when VDEL is less than 1.24V.20DRNSwitch Input. Drain of the internal high-voltage back-to-back P-channel MOSFETs
connected to COM.
Typical Application Circuits
The MAX1542 typical application circuit (Figure 1) and
the MAX1543 typical application circuit (Figure 2) gen-
erate an +8V source driver supply and approximately
+22V and -7V gate driver supplies for TFT displays. The
input voltage is from +2.6V to +5.5V. Table 1 lists rec-
ommended components and Table 2 lists contact infor-
mation for component suppliers.
Detailed Description
The MAX1542/MAX1543 include a high-performance
step-up regulator, two high-current operational ampli-
fiers, and startup timing and level-shifting functionality
useful for active matrix TFT LCDs. Figure 3 shows the
MAX1542/MAX1543 functional diagram.
Main Step-Up Converter
The MAX1542/MAX1543 main step-up converter
switches at 1.2MHz or 640kHz (MAX1543 only) (see the
Oscillator Frequency(FREQ)section). The devices
employ a current-mode, fixed-frequency, pulse-width
modulation (PWM) architecture to maximize loop band-
width providing fast transient response to pulsed loads
found in source drivers for TFT LCD panels. The high-
switching frequency also allows the use of low-profile
inductors and capacitors to minimize the thickness of
LCD panel designs. The integrated high-efficiency
MOSFET and the IC’s built-in digital soft-start function
reduce the number of external components required
while controlling inrush current. The output voltage of
the main step-up converter (VMAIN) can be set from VIN
to 13V with an external resistive voltage-divider at FB.

Partno	Mfg	Dc	Qty	Available	Descript
MAX1543ETP+	MAXIM	N/a	338	avai	TFT LCD DC-to-DC Converter with Operational Amplifiers
MAX1543ETP+T	MAXIM	N/a	20000	avai	TFT LCD DC-to-DC Converter with Operational Amplifiers