Rainbow Electronics MAX1748 User Manual

General Description

The MAX1748 triple-output DC-DC converter in a low­profile TSSOP package provides the regulated voltages
required by active matrix, thin-film transistor (TFT) liquid
crystal displays (LCDs). One high-power DC-DC con­verter and two low-power charge pumps convert the
+3.3V to +5V input supply voltage into three independent
output voltages.

The primary high-power DC-DC converter generates a
boosted output voltage (V

MAIN

) up to 13V that is regu­lated within ±1%. The low-power BiCMOS control cir­cuitry and the low on-resistance (0.35Ω) of the
integrated power MOSFET allows efficiency up to 93%.
The 1MHz current-mode PWM architecture provides
fast transient response and allows the use of ultra-small
inductors and ceramic capacitors.

The dual charge pumps independently regulate one
positive output (V

POS

) and one negative output (V

NEG

).
These low-power outputs use external diode and
capacitor stages (as many stages as required) to regu­late output voltages up to +40V and down to -40V. A
proprietary regulation algorithm minimizes output rip­ple, as well as capacitor sizes for both charge pumps.

The MAX1748 is available in the ultra-thin TSSOP pack­age (1.1mm max height).

________________________Applications

TFT Active Matrix LCD Displays

Passive Matrix LCD Displays

PDAs

Digital Still Cameras

Camcorders

Features

♦ Three Integrated DC-DC Converters
♦ 1MHz Current-Mode PWM Boost Regulator

Up to +13V Main High-Power Output
±1% Accuracy
High Efficiency (93%)

♦ Dual Charge-Pump Outputs

Up to +40V Positive Charge-Pump Output
Down to -40V Negative Charge-Pump Output

♦ Internal Supply Sequencing
♦ Internal Power MOSFETs
♦ +2.7V to +5.5V Input Supply
♦ 0.1µA Shutdown Current
♦ 0.6mA Quiescent Current
♦ Internal Soft-Start
♦ Power-Ready Output
♦ Ultra-Small External Components
♦ Thin TSSOP Package (1.1mm max)

MAX1748

Triple-Output TFT LCD DC-DC Converter

________________________________________________________________ Maxim Integrated Products 1

Pin Configuration

19-1740; Rev 0; 6/00

For free samples and the latest literature, visit www.maxim-ic.com or phone [phone].
For small orders, phone [phone].

Ordering Information

Typical Operating Circuit appears at end of data sheet.

16 TSSOP

PIN-PACKAGETEMP. RANGE

-40°C to +85°CMAX1748EUE

PART

TOP VIEW

1

RDY TGND

FB

2

INTG

3

MAX1748

4

IN

GND

5

REF

6

FBP

7

FBN

8

TSSOP

16

15

LX

14

PGND

13

SUPP

12

DRVP

SUPN

11

10

DRVN

9

SHDN

MAX1748

Triple-Output TFT LCD DC-DC Converter

2 _______________________________________________________________________________________

ABSOLUTE MAXIMUM RATINGS

ELECTRICAL CHARACTERISTICS

(VIN= +3.0V, SHDN = IN, V

SUPP

= V

SUPN

= 10V, TGND = PGND = GND, C

REF

= 0.22µF, C

INTG

= 470pF, TA= 0°C to +85°C, unless

otherwise noted. Typical values are at T

A

= +25°C.)

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, SHDN, TGND to GND .........................................-0.3V to +6V

DRVN to GND .........................................-0.3V to (V

SUPN

+ 0.3V)

DRVP to GND..........................................-0.3V to (V

SUPP

+ 0.3V)

PGND to GND.....................................................................±0.3V

RDY to GND ...........................................................-0.3V to +14V

LX, SUPP, SUPN to PGND .....................................-0.3V to +14V

INTG, REF, FB, FBN, FBP to GND...............-0.3V to (V

IN

+ 0.3V)

Continuous Power Dissipation (T

A

= +70°C)

16-Pin TSSOP (derate 9.4mW/°C above +70°C) ..........755mW

Operating Temperature Range

MAX1748EUE .................................................-40°C to +85°C

Junction Temperature......................................................+150°C

Storage Temperature Range .............................-65°C to +150°C

Lead Temperature (soldering, 10s) .................................+300°C

)

)

PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS

Input Supply Range V

Input Undervoltage Threshold V

IN Quiescent Supply Current I

SUPP Quiescent Current I

SUPN Quiescent Current I

IN Shutdown Current V

SUPP Shutdown Current V

SUPN Shutdown Current V

MAIN BOOST CONVERTER

Output Voltage Range V

FB Regulation Voltage V

FB Input Bias Current I

Operating Frequency f

Oscillator Maximum Duty Cycle 78 85 90 %

Load Regulation I

Line Regulation 0.1 % / V

Integrator Gm 320 µmho

LX Switch On-Resistance R

LX Leakage Current I

LX Current Limit I

Maximum RMS LX Current 1A

Soft-Start Period t

FB Fault Trip Level 1.07 1.1 1.14 V

POSITIVE CHARGE PUMP

V

Input Supply Range V

SUPP

IN

UVLO

IN

SUPP

SUPN

MAIN

FB

FB

OSC

LX(ON

LX

VIN rising, 40mV hysteresis (typ) 2.2 2.4 2.6 V

VFB = V

V

FBP

V

FBN

SHDN

SHDN

SHDN

= 1.5V, V

FBP

= 1.5V 0.4 0.8 mA

= -0.1V 0.4 0.8 mA

= 0, V

IN

= 0, V

SUPP

= 0, V

SUPN

TA = 0°C to +85°C 1.235 1.248 1.261 V

VFB = 1.25V, INTG = GND -50 50 nA

= 0 to 200mA, V

MAIN

ILX = 100mA 0.35 0.7 Ω

VLX = 13V 0.01 20 µA

Phase I = soft-start (1.0ms) 0.275 0.380 0.500

Phase II = soft-start (1.0ms) 0.75

LX(MAX

Phase III = soft-start (1.0ms) 1.12

Phase IV = fully on (after 3.0ms) 1.1 1.5 2.0

SS

SUPP

Power-up to the end of Phase III

= -0.2V 0.6 1 mA

FBN

= 5V 0.1 10 µA

= 13V 0.1 10 µA

= 13V 0.1 10 µA

= 10V 0.2 %

MAIN

2.7 5.5 V

V

IN

13 V

0.85 1 1.15 MHz

A

3072 /

f

OSC

s

2.7 13 V

MAX1748

Triple-Output TFT LCD DC-DC Converter

_______________________________________________________________________________________ 3

ELECTRICAL CHARACTERISTICS (continued)

(VIN= +3.0V, SHDN = IN, V

SUPP

= V

SUPN

= 10V, TGND = PGND = GND, C

REF

= 0.22µF, C

INTG

= 470pF, TA= 0°C to +85°C, unless

otherwise noted. Typical values are at T

A

= +25°C.)

PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS

Operating Frequency

FBP Regulation Voltage V

FBP Input Bias Current I

DRVP PCH On-Resistance

DRVP NCH On-Resistance

FBP Power-Ready Trip Level Rising edge 1.091 1.125 1.159 V

FBP Fault Trip Level Falling edge 1.11 V

Maximum RMS DRVP Current 0.1 A

NEGATIVE CHARGE PUMP

V

Input Supply Range V

SUPN

Operating Frequency

FBN Regulation Voltage V
FBN Input Bias Current I

DRVN PCH On-Resistance

DRVN NCH On-Resistance

FBN Power-Ready Trip Level Rising edge 80 110 165 mV

FBN Fault Trip Level Falling edge 130 mV

Maximum RMS DRVN Current 0.1 A

REFERENCE

Reference Voltage V

Reference Undervoltage
Threshold

LOGIC SIGNALS

SHDN Input Low Voltage 0.4V hysteresis (typ) 0.9 V
SHDN Input High Voltage 2.1 V
SHDN Input Current I

RDY Output Low Voltage I
RDY Output High Voltage V

FBP

V

FBP

SUPN

FBN

FBN

REF

SHDN

= 1.5V -50 50 nA

FBP

V

= 1.213V 1.5 4 Ω

FBP

V

= 1.275V 20 kΩ

FBP

V

= -0.05V -50 50 nA

FBN

V

= 0.035V 1.5 4 Ω

FBN

= -0.025V 20 kΩ

V

FBN

-2µA < I

V

REF

SINK

RDY

< 50µA 1.231 1.25 1.269 V

REF

rising 0.9 1.05 1.2 V

= 2mA 0.25 0.5 V

= 13V 0.01 1 µA

0.5 ×
f

OSC

1.20 1.25 1.30 V

310Ω

2.7 13 V

0.5 ×
f

OSC

-50 0 50 mV

310Ω

0.01 1 µA

Hz

Hz

MAX1748

Triple-Output TFT LCD DC-DC Converter

4 _______________________________________________________________________________________

)

)

ELECTRICAL CHARACTERISTICS (continued)

(VIN= +3.0V, SHDN = IN, V

SUPP

= V

SUPN

= 10V, TGND = PGND = GND, C

REF

= 0.22µF, C

INTG

= 470pF, TA= -40°C to +85°C,

unless otherwise noted.) (Note 1)

PARAMETER SYMBOL CONDITIONS MIN MAX UNITS

Input Supply Range V

Input Undervoltage Threshold V

IN Quiescent Supply Current I

SUPP Quiescent Current I

SUPN Quiescent Current I

IN Shutdown Current V

SUPP Shutdown Current V

SUPN Shutdown Current V

MAIN BOOST CONVERTER

Output Voltage Range V

FB Regulation Voltage V

FB Input Bias Current I

Operating Frequency F

Oscillator Maximum Duty Cycle 78 90 %

LX Switch On-Resistance R

LX Leakage Current

LX Current Limit I

FB Fault Trip Level 1.07 1.14 V

POSITIVE CHARGE PUMP

SUPP Input Supply Range V

FBP Regulation Voltage V

FBP Input Bias Current I

DRVP PCH On-Resistance 10 Ω

DRVP NCH On-Resistance

FBP Power-Ready Trip Level Rising edge 1.091 1.159 V

NEGATIVE CHARGE PUMP

SUPN Input Supply Range V

FBN Regulation Voltage V

FBN Input Bias Current

DRVN PCH On-Resistance

DRVN NCH On-Resistance

FBN Power-Ready Trip Level Rising edge 80 165 mV

REFERENCE

Reference Voltage V

Reference Undervoltage

LX(MAX

IN

UVLO

IN

SUPP

SUPN

MAIN

FB

OSC

LX(ON

I

LX

VIN rising, 40mV hysteresis (typ) 2.2 2.6 V

FB

VFB = V

V

FBP

V

FBN

SHDN

SHDN

SHDN

= 1.5V, V

FBP

= 1.5V 0.8 mA

= -0.1V 0.8 mA

= 0, VIN = 5V 10 µA

= 0, V

SUPP

= 0, V

SUPN

VFB = 1.25V, INTG = GND -50 50 nA

I

= 100mA 0.7 Ω

LX

VLX = 13V 20 µA

Phase I = soft-start (1.0ms) 0.275 0.500

Phase IV = fully on (after 3.0ms) 1.1 2.0

SUPP

FBP

V

FBP

SUPN

FBN

I

FBN

REF

= 1.5V -50 50 nA

FBP

V

= 1.213V 4 Ω

FBP

= 1.275V 20 kΩ

V

FBP

V

= -0.05V -50 50 nA

FBN

V

= 0.035V 4 Ω

FBN

= -0.025V 20 kΩ

V

FBN

-2µA < I

V

REF

< 50µA 1.223 1.269 V

REF

rising 0.9 1.2 V

2.7 5.5 V

= -0.2V 1 mA

FBN

= 13V 10 µA

= 13V 10 µA

V

IN

1.225 1.271 V

0.75 1.25 MHz

2.7 13 V

1.20 1.30 V

2.7 13 V

-50 50 mV

13 V

A

10 Ω

MAX1748

Triple-Output TFT LCD DC-DC Converter

_______________________________________________________________________________________ 5

V

(V)

Typical Operating Characteristics

(Circuit of Figure 5, VIN= 3.3V, TA= +25°C, unless otherwise noted.)

ELECTRICAL CHARACTERISTICS (continued)

(VIN= +3.0V, SHDN = IN, V

SUPP

= V

SUPN

= 10V, TGND = PGND = GND, C

REF

= 0.22µF, C

INTG

= 470pF, TA= -40°C to +85°C,

unless otherwise noted.) (Note 1)

Note 1: Specifications from 0°C to -40°C are guaranteed by design, not production tested.

PARAMETER SYMBOL CONDITIONS MIN MAX UNITS

LOGIC SIGNALS

SHDN Input Low Voltage 0.45V hysteresis (typ) 0.9 V
SHDN Input High Voltage 2.1 V

Input Current I

SHDN
RDY Output Low Voltage I
RDY Output High Leakage V

SHDN

= 2mA 0.5 V

SINK

= 13V 1 µA

RDY

1 µA

MAIN OUTPUT VOLTAGE

vs. LOAD CURRENT

10.04

10.02

10.00

9.98

9.96

(V)

9.94

MAIN

V

9.92

9.90

9.88

9.86

9.84
0 200100 300 400 500 600

VIN = 3.3V

I

(mA)

MAIN

VIN = 5.0V

100

MAX1748 toc01

EFFICIENCY (%)

MAIN STEP-UP CONVERTER

EFFICIENCY vs. LOAD CURRENT

(BOOST ONLY)

V

= 10V

MAIN

95

90

85

80

75

70

65

60

0 200100 300 400 500 600

VIN = 3.3V

I

MAIN

(mA)

VIN = 5.0V

100

MAX1748toc02

EFFICIENCY (%)

MAIN STEP-UP CONVERTER

EFFICIENCY vs. LOAD CURRENT

(BOOST ONLY)

V

= 8V

MAIN

95

VIN = 3.3V

I

MAIN

VIN = 5.0V

(mA)

90

85

80

75

70

65

60

0 200100 300 400 500 800600 700

MAX1748toc03

EFFICIENCY vs. LOAD CURRENT

(BOOST CONVERTER AND CHARGE PUMPS)

90

V

= 8V

= 10V

= -5V WITH I

NEG

= 15V WITH I

POS

I

(mA)

MAIN

MAIN

NEG

POS

= 10mA
= 5mA

MAX1748toc04

85

80

75

70

65

EFFICIENCY (%)

60

55

50

0 10050 150 200 250 400300 350

V

MAIN

VIN = 3.3V
V
V

NEGATIVE CHARGE-PUMP OUTPUT

VOLTAGE vs. LOAD CURRENT

-4.60
V

= -5V

NEG

-4.65

-4.70

V

= 6V

-4.75

-4.80

NEG

-4.85

-4.90

-4.95

-5.00

-5.05

015205 10 25303540

SUPN

V

= 8V

SUPN

V

= 10V

SUPN

I

(mA)

NEG

MAX1748toc05

NEGATIVE CHARGE-PUMP EFFICIENCY

vs. LOAD CURRENT

80

70

60

50

EFFICIENCY (%)

40

30

20

015205 10 25303540

I

NEG

(mA)

V

V

SUPN

SUPN

V

= 8V

= 10V

SUPN

V

NEG

= 6V

MAX1748toc06

= -5V