Manual

ManualsBrandsRainbow Electronics ManualsSensorsMAX1747

For price, delivery, and to place orders, please contact Maxim Distribution at 1-888-629-4642,

or visit Maxim’s website at www.maxim-ic.com.

General Description

The MAX1747 triple charge-pump DC-DC converter

provides the regulated voltages required by active

matrix thin-film transistor (TFT) liquid-crystal displays

(LCDs) in a low-profile TSSOP package. One high-

power and two low-power charge pumps convert the

+2.7V to +4.5V input supply voltage into three indepen-

dent output voltages.

The primary high-power charge pump generates an

output voltage (V

OUT

) between 4.5V and 5.5V that is

regulated within ±1%. The low-power BiCMOS control

circuitry and the low on-resistance (R

) power

MOSFETs maximize efficiency. The adjustable switch-

ing frequency (200kHz to 2MHz) provides fast transient

response and allows the use of small low-profile ceram-

ic capacitors.

The dual low-power charge pumps independently regu-

late one positive output (V

POS

) and one negative output

NEG

). These additional outputs use external diode

and capacitor multiplier stages (as many stages as

required) to regulate output voltages up to +35V and

-35V.

The constant switching frequency and a proprietary

regulation algorithm minimize output ripple and capaci-

tor sizes for all three charge pumps. The MAX1747 is

available in the ultra-thin TSSOP package (1.1mm max

height).

MAX1747

Triple Charge-Pump TFT LCD

DC-DC Converter

________________________________________________________________ Maxim Integrated Products 1

OUT

CXP

SUPM

CXNFB

RDY

TGND

TOP VIEW

PGND

SUPP

DRVP

SUPNREF

GND

INTG

DRVN

SHDNFBN

FBP

MAX1747

TSSOP

Pin Configuration

19-1788; Rev 0; 10/00

Ordering Information

PART TEMP. RANGE PIN-PACKAGE

MAX1747EUP -40°C to +85°C 20 TSSOP

Features

♦ Adjustable Outputs

Up to +5.5V Main High-Power Output

Up to +35V Positive Charge-Pump Output

Down to -35V Negative Charge-Pump Output

♦ 200kHz to 2MHz Adjustable Switching Frequency

♦ +2.7V to +4.5V Input Supply

♦ Internal Power MOSFETs

♦ 0.1µA Shutdown Current

♦ Internal Soft-Start

♦ Power-Ready Output

♦ Internal Supply Sequencing

♦ Fast Transient Response

♦ Ultra-Thin Solution (No Inductors)

♦ Thin TSSOP Package (1.1mm max)

Applications

TFT Active-Matrix LCDs

Passive-Matrix Displays

Personal Digital Assistants (PDAs)

SUPN

DRVP

FBP

PGND

DRVN

GND

TGND

MAX1747

SHDN

RDY

FBN

REF

INPUT

TO µC

SUPM

MAIN OUTPUT

POSITIVE

OUTPUT

INTG

CXP

CXN

OUT

SUPP

NEGATIVE

OUTPUT

Typical Operating Circuit

EVALUATION KIT

AVAILABLE

Summary of content (13 pages)

PAGE 1
9-1788; Rev 0; 10/00 KIT ATION EVALU LE B A IL A AV Triple Charge-Pump TFT LCD DC-DC Converter Features ♦ Adjustable Outputs The dual low-power charge pumps independently regulate one positive output (VPOS) and one negative output (VNEG). These additional outputs use external diode and capacitor multiplier stages (as many stages as required) to regulate output voltages up to +35V and -35V.
PAGE 2
MAX1747 Triple Charge-Pump TFT LCD DC-DC Converter ABSOLUTE MAXIMUM RATINGS IN, SUPM, OUT, TGND to GND................................-0.3V to +6V SHDN........................................................................-0.3V to +1V PGND to GND.....................................................................±0.3V SUPM to IN .........................................................................±0.3V CXN to PGND.........................................-0.3V to (VSUPM + 0.3V) CXP to PGND ...........
PAGE 3
Triple Charge-Pump TFT LCD DC-DC Converter (VIN = VSUPM = +3.0V, VSUPP = VSUPN = +5V, TGND = PGND = GND, I SHDN = 22µA, COUT = 2 ✕ 4.7µF, CREF = 0.22µF, CINTG = 1500pF, VOUT = +5V, TA = 0°C to +85°C, unless otherwise noted. Typical values are at TA = +25°C.
PAGE 4
MAX1747 Triple Charge-Pump TFT LCD DC-DC Converter ELECTRICAL CHARACTERISTICS (VIN = VSUPM = +3.0V, VSUPP = VSUPN = +5V, TGND = PGND = GND, I SHDN = 22µA, COUT = 2 1500pF, VOUT = +5V, TA = -40°C to +85°C, unless otherwise noted.) (Note 1) PARAMETER Input Supply Range Input Undervoltage Threshold Input Quiescent Supply Current Output Quiescent Supply Current SYMBOL VUVLO IIN + ISUPM IQ(OUT) 4.7µF, CREF = 0.22µF, CINTG = MIN MAX UNITS 2.7 4.5 V 2.2 2.6 V VFB = VFBP = 1.5V, VFBN = -0.
PAGE 5
Triple Charge-Pump TFT LCD DC-DC Converter (VIN = VSUPM = +3.0V, VSUPP = VSUPM = +5V, TGND = PGND = GND, I SHDN = 22µA, COUT = 2 1500pF, VOUT = +5V, TA = -40°C to +85°C, unless otherwise noted.) (Note 1) PARAMETER SYMBOL CONDITIONS ✕ 4.7µF, CREF = 0.22µF, CINTG = MIN MAX UNITS -2µA < IREF < 50µA 1.222 1.269 V VREF rising 0.95 1.18 V 0.
PAGE 6
Typical Operating Characteristics (continued) (Circuit of Figure 1, VIN = VSUPM = +3.3V, TA = +25°C, unless otherwise noted.) SWITCHING FREQUENCY vs. ISHDN 14 12.0 MAX1747 toc05 2.0 MAX1747 toc04 16 NO-LOAD SUPPLY CURRENT vs. TEMPERATURE 1.6 MAX1747 toc06 NO-LOAD SUPPLY CURRENT vs. SWITCHING FREQUENCY 11.5 10 8 6 4 IIN + ISUPM (mA) FREQUENCY (MHz) 1.2 0.8 0.4 9.5 0.5 1.0 1.5 0 2.0 10 20 30 40 -40 50 10 35 60 85 ISHDN (mA) TEMPERATURE (°C) SWITCHING FREQUENCY vs.
PAGE 7
Triple Charge-Pump TFT LCD DC-DC Converter MAXIMUM POSITIVE CHARGE-PUMP OUTPUT VOLTAGE vs. SUPPLY VOLTAGE MAX1747 toc13 VPOS(NOMINAL) = 32V 28 VPOS (V) LOAD TRANSIENT MAX1747 toc14 34 IPOS = 1mA 200mA IOUT 100mA/div 100mA 0 22 IPOS = 10mA 16 5.05V VOUT 50mV/div 5V 10 4.95V 4 3 5 7 9 11 40µs/div VIN = 3.3V, VOUT = 5.
PAGE 8
Triple Charge-Pump TFT LCD DC-DC Converter MAX1747 Pin Description PIN 1, 2 NAME TGND FUNCTION 3 RDY 4 FB 5 INTG 6 IN 7 GND Analog Ground. Connect to power ground (PGND) underneath the IC. 8 REF Internal Reference Bypass Terminal. Connect a 0.22µF capacitor from this terminal to analog ground (GND). External load capability to 50µA. REF is disabled in shutdown. 9 FBP Positive Charge-Pump Feedback Input. Regulates to 1.25V nominal.
PAGE 9
Triple Charge-Pump TFT LCD DC-DC Converter CIN 10µF SUPM R7 100k RFREQ 100k C1 0.1µF CXN IN CX 0.47µF VOUT +5V, 200mA OUT COUT (2) 4.7µF SUPP RDY D3 R1 150k SUPN C11 0.1µF SHDN C12 0.1µF C5 0.1µF R2 49.9k DRVN D4 FB D7 C6 1.0µF C9 0.1µF D1 C3 0.1µF MAX1747 DRVP D8 D2 C10 1.0µF D5 C7 0.1µF FBN VNEG -7V, 10mA MAX1747 CXP VIN = 3.0V R5 280k D6 R6 49.9k CREF 0.22µF C4 1.0µF REF FBP TGND INTG GND PGND VPOS +12V, 5mA CINTG 1500pF R4 49.9k R3 432k C8 1.0µF Figure 1.
PAGE 10
MAX1747 Triple Charge-Pump TFT LCD DC-DC Converter SUPM MAX1747 C1 OSC MAX1747 VSUPM = VIN 2.7V TO 4.5V VOUT OUT OSC CX CXN D4 R1 CINTG INTG PGND VREF 1.25V REF GND VNEG C6 R6 REF R2 CREF R5 FBN VREF 1.25V FB gm D3 C5 DRVN COUT CXP VSUPP = 2.7V TO 13V SUPN GND PGND CREF VNEG = -(R5/R6) ✕ VREF VREF = 1.25V VOUT = [1+ (R1/R2)] ✕ VREF VREF = 1.25V Figure 2. Main Charge-Pump Block Diagram Figure 3.
PAGE 11
Triple Charge-Pump TFT LCD DC-DC Converter VSUPP = 2.7V TO 13V SUPP OSC D2 R3 FBP GND CIN RFREQ OSC DRVP VREF 1.25V VON = VIN IN MAX1747 D1 C3 MAX1747 MAX1747 SHDN VPOS GND R4 C4 PGND VPOS = [1 + (R3/R4)] ✕ VREF VREF = 1.25V RFREQ = kFREQ ✕ (VON - 0.7V)/fOSC RFREQ IS IN kΩ, kFREQ IS 45.5MHz/mA, AND fOSC IS IN MHz. Figure 4. Positive Charge-Pump Block Diagram Figure 5. Frequency Adjustment in the Typical Operating Characteristics).
PAGE 12
MAX1747 Triple Charge-Pump TFT LCD DC-DC Converter Efficiency ≅ VPOS / [VSUPP ✕ (N+1)] for the positive low-power charge pump where N is the number of charge-pump stages. Output Voltage Selection Adjust the main output voltage by connecting a voltage-divider from the output (VOUT) to FB and GND (see Typical Operating Circuit). Adjust the negative lowpower output voltage by connecting a voltage-divider from the output (VNEG) to FBN to REF.
PAGE 13
Triple Charge-Pump TFT LCD DC-DC Converter PC board should feature separate analog and power ground areas connected at only one point under the IC. To maximize output power and efficiency, and minimize output power ripple voltage, use extra-wide power ground traces, and solder the IC’s power ground pin directly to it. Avoid having sensitive traces near the switching nodes and high-current lines. Refer to the MAX1747 evaluation kit for an example of proper board layout.