Rainbow Electronics MAX1885 User Manual

General Description

The MAX1778/MAX1880–MAX1885 multiple-output DC-DC converters provide the regulated voltages required by active matrix thin-film transistor (TFT) liquid crystal displays (LCD) in a low-profile TSSOP package. One high-power step-up converter and two low-power charge pumps convert the 2.7V to 5.5V input voltage into three independent output voltages. A built-in linear regulator and VCOM buffer complete the power-supply requirements.

The main step-up converter accurately generates an externally set output voltage up to 13V that can supply the display’s row/column drivers. The converter’s high switching frequency and current-mode PWM architecture provide fast transient response and allow the use of small low-profile inductors and ceramic capacitors. The low-power BiCMOS control circuitry and internal 14V switch (0.35Ω N-channel MOSFET) enable efficiencies up to 91%.

The dual low-power charge pumps (MAX1778/ MAX1880/MAX1881/MAX1882 only) independently regulate one positive output (V

POS

) and one negative out-

put (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

-40V. A unique control scheme minimizes output ripple as well as capacitor sizes for both charge pumps.

A resistor-programmable, 40mA, low-dropout linear regulator (MAX1778/MAX1881/MAX1883/MAX1884 only) provides preregulation or postregulation for any of the supplies. For higher current applications, an external transistor can be added. Additionally, the VCOM buffer provides a high current output that is ideal for driving the capacitive backplane of TFT LCD panels. The VCOM buffer’s output voltage is preset with an internal 50% resistive-divider or can be externally adjusted for other voltages.

The MAX1778/MAX1880–MAX1885 are protected against output undervoltage and thermal overload conditions by a latched fault detection circuit that shuts down the device. All devices are available in the ultrathin TSSOP package (1.1mm max height).

Applications

TFT LCD Notebook Displays

TFT LCD Desktop Monitor Panels

Features

♦ 500kHz/1MHz Current-Mode PWM Step-Up

Regulator

Up to +13V Main High-Power Output ±1% Accurate High Efficiency (91%)

♦ Dual Regulated Charge-Pump Outputs

(MAX1778/MAX1880/MAX1881/MAX1882 only)

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

♦ Low-Dropout 40mA Linear Regulator

(MAX1778/MAX1881/MAX1883/MAX1884 only)

Up to +15V LDO Input

♦ Optional Higher Current with External Transistor

♦ 2.7V to 5.5V Input Supply

♦ Internal Supply Sequencing and Soft-Start

♦ Power-Ready Output

♦ Adjustable Fault-Detection Latch

♦ Thermal Protection (+160°C)

♦ 0.1µA Shutdown Current

♦ 0.7mA IN Quiescent Current

♦ Ultra-Small External Components

♦ Thin TSSOP Package (1.1mm max height)

MAX1778/MAX1880–MAX1885

Quad-Output TFT LCD DC-DC

Converters with Buffer

________________________________________________________________ Maxim Integrated Products 1

19-1979; Rev 0a; 3/01

Ordering Information

Typical Operating Circuit appears at end of data sheet.

Pin Configurations and Selector Guide appear at end of data sheet.

For pricing, delivery, and ordering information, please contact Maxim/Dallas Direct! at 1-888-629-4642, or visit Maxim’s website at www.maxim-ic.com.

PART TEMP. RANGE PIN-PACKAGE

MAX1778EUG -40°C to +85°C 24 TSSOP MAX1880EUG -40°C to +85°C 24 TSSOP MAX1881EUG -40°C to +85°C 24 TSSOP MAX1882EUG -40°C to +85°C 24 TSSOP MAX1883EUP -40°C to +85°C 20 TSSOP MAX1884EUP -40°C to +85°C 20 TSSOP MAX1885EUP -40°C to +85°C 20 TSSOP

MAX1778/MAX1880–MAX1885

Quad-Output TFT LCD DC-DC Converters with Buffer

2 _______________________________________________________________________________________

ABSOLUTE MAXIMUM RATINGS

ELECTRICAL CHARACTERISTICS

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

SUPP

= V

SUPN

= V

SUPB

= V

SUPL

= 10V, LDOOUT = FBL, BUF- = BUFOUT, BUF+ = FLTSET = TGND =

PGND = GND, C

REF

= 0.22µF, C

BUF

= 1µF, TA= 0°C to +85°C. Typical values are at TA= +25°C, unless otherwise noted.)

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, FLTSET 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, SUPB to GND ................................................-0.3V to +14V

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

SUPL to GND..........................................................-0.3V to +18V

LDOOUT to GND ....................................-0.3V to (V

SUPL

+ 0.3V)

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

IN

+ 0.3V)

FBL to GND .............-0.3V to the lower of (V

SUP

L

+ 0.3V) or +6V

BUFOUT, BUF+, BUF- to GND ...............-0.3V to (V

SUPB

+ 0.3V)

Continuous Power Dissipation (T

A

= +70°C)

20-Pin TSSOP (derate 10.9mW/°C above +70°C) ......879mW

24-Pin TSSOP (derate 12.2mW/°C above +70°C) ......975mW

Operating Temperature Range

MAX1778EUG, MAX1883EUP ........................-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

IN

UVLO

IN

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

VFB = V

FBP

= 1.5V, V

FBN

= -0.2V

SUPP Quiescent Current I

SUPN Quiescent Current I

SUPP

SUPN

IN Shutdown Current V

SUPP Shutdown Current

SUPN Shutdown Current

SUPL Shutdown Current

SUPB Shutdown Current V

V

= 1.5V

FBP

V

= -0.2V

FBN

= 0, VIN = 5V 0.1 10 µA

SHDN

V

= 0, V

SHDN

SUPP

MAX1778/MAX1880/MAX1881/MAX1882

V

= 0, V

SHDN

SUPN

MAX1778/MAX1880/MAX1881/MAX1882

V

= 0, V

SHDN

SUPL

MAX1778/MAX1881/MAX1883/MAX1884

= 0, V

SHDN

SUPB

2.7 5.5 V

MAX1778/MAX1880/ MAX1883 (f

OSC

= 1MHz)

0.7 1

MAX1881/MAX1882/ MAX1884/MAX1885 (f

= 500kHz)

OSC

MAX1778/MAX1880 (f

= 1MHz)

OSC

MAX1881/MAX1882 (f

= 500kHz)

OSC

MAX1778/MAX1880 (f

= 1MHz)

OSC

MAX1881/MAX1882 (f

= 500kHz)

OSC

= 13V,

= 13V

0.6 1

0.4 0.7

0.3 0.5

0.4 0.7

0.3 0.5

0.1 10 µA

= 13V 6 13 µA

mA

MAX1778/MAX1880–MAX1885

Quad-Output TFT LCD DC-DC

Converters with Buffer

_______________________________________________________________________________________ 3

ELECTRICAL CHARACTERISTICS (continued)

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

SUPP

= V

SUPN

= V

SUPB

= V

SUPL

= 10V, LDOOUT = FBL, BUF- = BUFOUT, BUF+ = FLTSET = TGND =

PGND = GND, C

REF

= 0.22µF, C

BUF

= 1µF, TA= 0°C to +85°C. Typical values are at TA= +25°C, unless otherwise noted.)

)

PARAMETER SYMBOL

CONDITIONS MIN TYP MAX

UNITS

MAIN STEP-UP CONVERTER

Main Output Voltage Range V

FB Regulation Voltage V

FB Input Bias Current I

Operating Frequency f

Oscillator Maximum Duty Cycle

Load Regulation

MAIN

FB

OSC

Integrator enabled, C

V

IN

= 1000pF 1.234 1.247 1.260

INTG

13

Integrator disabled (INTG = REF) 1.220 1.280

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

MAX1778/MAX1880/MAX1883 0.85 1 1.15

MAX1881/MAX1882/MAX1884/MAX1885 425 500 575

80 85 91 %

I

= 0 to 200mA,

LX

V

= 10V

MAIN

Integrator enabled, C

= 1000pF

INTG

Integrator disabled (INTG = REF)

0.01

0.2

V

nA

MHz

kHz

%

Line Regulation 0.1 %/V

Integrator Transconductance 317 µs

LX Switch On-Resistance R

LX Leakage Current I

LX Current Limit I

LX(ON

LX

LIM

ILX = 100mA 0.35 0.7 Ω

VLX = 13V 0.01 20 µA

Phase I = soft-start (1024/f

Phase II = soft-start (1024/f

Phase III = soft-start (1024/f

Phase IV = fully-on (after 3072/f

) 0.275 0.38 0.5

OSC

) 0.75

OSC

) 1.12

OSC

) 1.15 1.5 1.85

OSC

A

Maximum RMS LX Current 1A

Soft-Start Period t

FB Fault Trip Level

SS

Power-up to the end of Phase III 3072 / f

OSC

Falling edge, FLTSET = GND 1.07 1.1 1.14

Falling edge, FLTSET = 1V 0.955 0.99 1.025

s

V

POSITIVE CHARGE PUMP (MAX1778/MAX1880/MAX1881/MAX1882 ONLY)

SUPP Input Supply Range

Operating Frequency f

FBP Regulation Voltage V

FBP Input Bias Current I

DRVP PCH On-Resistance R

DRVP NCH On-Resistance R

V

SUPP

CHP

FBP

PCH(ON

NCH(ON

V

= 1.5V -50 +50

FBP

V

= 1.2V 2 4

FBP

V

= 1.3V 20

FBP

Maximum RMS DRVP Current 0.1

FBP Power-Ready Trip Level Rising edge 1.09 1.125 1.16

FBP Fault Trip Level

Falling edge, FLTSET = GND 1.08 1.11 1.16

Falling edge, FLTSET = 1V 0.955 0.99 1.025

2.7 13 V

0.5 x f

OSC

1.2 1.25 1.3

510

Hz

V

nA

Ω

kΩ

A

V

MAX1778/MAX1880–MAX1885

Quad-Output TFT LCD DC-DC Converters with Buffer

4 _______________________________________________________________________________________

ELECTRICAL CHARACTERISTICS (continued)

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

SUPP

= V

SUPN

= V

SUPB

= V

SUPL

= 10V, LDOOUT = FBL, BUF- = BUFOUT, BUF+ = FLTSET = TGND =

PGND = GND, C

REF

= 0.22µF, C

BUF

= 1µF, TA= 0°C to +85°C. Typical values are at TA= +25°C, unless otherwise noted.)

)

PARAMETER

NEGATIVE CHARGE PUMP (MAX1778/MAX1880/MAX1881/MAX1882 ONLY)

SUPN Input Supply Range

Operating Frequency

FBN Regulation Voltage

FBN Input Bias Current

DRVN PCH On-Resistance

DRVN NCH On-Resistance R

Maximum RMS DRVN Current

FBN Power-Ready Trip Level

FBN Fault Trip Level

LOW-DROPOUT LINEAR REGULATOR (MAX1778/MAX1881/MAX1883/MAX1884 ONLY)

SUPL Input Supply Range V

SUPL Undervoltage Lockout Rising edge, 50mV hysteresis (typ) 3.8 4 4.3 V

SUPL Quiescent Current I

Dropout Voltage (Note 1) V

FBL Regulation Voltage V

LDO Load Regulation

LDO Line Regulation

FBL Input Bias Current I

LDO Current Limit I

VCOM BUFFER

SUPB Input Supply Range V

SUPB Quiescent Current I

BUFOUT Leakage Current -10 +10

Power-Supply Rejection Ratio PSRR V

Input Common-Mode Voltage Range

Common-Mode Rejection Ratio CMRR VCM = 1.2V to 8.8V 75

Input Bias Current I

Input Offset Current I

Gain Bandwidth Product GBW C

SYMBOL CONDITIONS MIN TYP MAX UNITS

V

SUPN

f

CHP

V

FBN

I

FBN

R

PCH(ON

NCH(ON

V

= 0 -50 +50 nA

FBN

V

= +50mV

FBN

V

= -50mV

FBN

2.7 13 V

0.5 x f

OSC

-50 0 +50 mV

510Ω

24Ω

20 kΩ

0.1 A

Falling edge 80 125 165 mV

Rising edge 80 140 190 mV

SUPL

DROP

FBL

LDOLIMVSUPL

SUPB

V

CM

BIAS

OS

I

LDO

LDO is set to regulate at 9V

V

SUPL

I

LDO

V

SUPL

I

LDO

V

SUPL

I

LDO

V

FBL

V

SUPB

|VOS| < 10mV 1.2 8.8

VCM = 5V -100 -10 +100

VCM = 5V -100 +100

BUF

= 100µA 120 220 µA

I

= 40mA 130 300

LDO

I

= 5mA 70

LDO

= 10V, LDO regulating at 9V,

= 15mA

= 10V, LDO regulating at 9V,

= 100µA to 40mA

= 4.5V to 15V, FBL = LDOOUT,

= 15mA

= 1.25V -0.8 +0.8

= 10V, V

LDOOUT

= 9V, V

= 1.2V 40 130 220

FBL

= 13V 420 850

= 4.5V to 13V, VCM = 2.25V 85 98

= 1µF 13

4.5 15 V

1.235 1.25 1.265 V

4.5 13

Hz

mV

1.2 %

0.02 %/V

µA

mA

V

µA

dB

V

dB

nA

kHz

MAX1778/MAX1880–MAX1885

Quad-Output TFT LCD DC-DC

Converters with Buffer

_______________________________________________________________________________________ 5

ELECTRICAL CHARACTERISTICS (continued)

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

SUPP

= V

SUPN

= V

SUPB

= V

SUPL

= 10V, LDOOUT = FBL, BUF- = BUFOUT, BUF+ = FLTSET = TGND =

PGND = GND, C

REF

= 0.22µF, C

BUF

= 1µF, TA= 0°C to +85°C. Typical values are at TA= +25°C, unless otherwise noted.)

Dual Mode is a registered trademark of Maxim Integrated Products, Inc.

PARAMETER SYMBOL CONDITIONS MIN TYP MAX

Output Voltage V

Input Offset Voltage V

Output Voltage Swing High V

Output Voltage Swing Low V

Peak Buffer Output Current ±150 mA

BUF+ Dual Mode™ Threshold Voltage

REFERENCE

Reference Voltage V

Reference Undervoltage Threshold

LOGIC SIGNALS

SHDN Input Low Voltage 0.9 V SHDN Input High Voltage 2.1 V SHDN Input Current I

FLTSET Input Voltage Range

FLTSET Threshold Voltage Rising edge, 25mV hysteresis (typ) 80 125 170 mV

FLTSET Input Current V

RDY Output Low Voltage I RDY Output High Leakage V

Thermal Shutdown Rising temperature 160 °C

BUFOUT

OS

OH

OL

BUF+ = GND

V

= 4.5V to 13V,

SUPB

V

= 1.2V to

CM

–1.2V) I

(V

SUPB

I

= -45mA, ∆VOS = 1V 9 9.6 V

BUFOUT

= +45mA, ∆VOS = 1V 0.4 1 V

BUFOUT

I

BUFOUT

= 0 4.99 5.01

BUFOUT

= ±5mA 4.97 5.03

BUFOUT

= ±45mA 4.93 5.07

BUFOUT

= ±5mA -30 30

= ±45mA -70 70

Falling edge, 20mV hysteresis (typ) 80 125 170 mV

REF

-2µA < I

< 50µA 1.231 1.25 1.269 V

REF

0.9 1.05 1.2 V

SHDN

0.01 1 µA

0.67 x V

REF

= 1V 0.1 50 nA

FLTSET

= 2mA 0.25 0.5 V

SINK

= 13V 0.01 1 µA

RDY

0.85 x V

REF

UNITS

V

mV

V

MAX1778/MAX1880–MAX1885

Quad-Output TFT LCD DC-DC Converters with Buffer

6 _______________________________________________________________________________________

ELECTRICAL CHARACTERISTICS

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

SUPP

= V

SUPN

= V

SUPB

= V

SUPL

= 10V, LDOOUT = FBL, BUF- = BUFOUT, BUF+ = FLTSET = TGND =

PGND = GND, C

REF

= 0.22µF, C

BUF

= 1µF, TA= -40°C to +85°C, unless otherwise noted.) (Note 2)

)

PARAMETER SYMBOL CONDITIONS MIN MAX UNITS

Input Supply Range V

Input Undervoltage Threshold

IN Quiescent Supply Current

SUPP Quiescent Current I

SUPN Quiescent Current I

IN Shutdown Current V

SUPP Shutdown Current

SUPN Shutdown Current

SUPL Shutdown Current

SUPB Shutdown Current V

MAIN STEP-UP CONVERTER

Main Output Voltage Range V

FB Regulation Voltage V

FB Input Bias Current I

Operating Frequency F

Oscillator Maximum Duty Cycle

LX Switch On-Resistance R

LX Leakage Current I

LX Current Limit I

FB Fault Trip Level Falling edge, FLTSET = GND 1.07 1.14 V

V

IN

UVLO

I

IN

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

VFB = V

FBP

V

FBN

= 1.5V, = -0.2V

MAX1778/MAX1880/ MAX1883 (f

OSC

= 1MHz)

MAX1881/MAX1882/MAX1884/ MAX1885 (f

= 500kHz)

OSC

MAX1778/MAX1880 (f

= 1MHz)

SUPP

V

= 1.5V

FBP

OSC

MAX1881/MAX1882 (f

= 500kHz)

OSC

MAX1778/MAX1880 (f

= 1MHz)

SUPN

V

= -0.2V

FBN

= 0, VIN = 5V 10 µA

SHDN

V

= 0, V

SHDN

OSC

MAX1881/MAX1882 (f

= 500kHz)

OSC

= 13V,

SUPP

MAX1778/MAX1880/MAX1881/MAX1882

V

SHDN

= 0, V

SUPN

= 13V,

MAX1778/MAX1880/MAX1881/MAX1882

V

SHDN

= 0, V

SUPL

= 13V,

MAX1778/MAX1881/MAX1883/MAX1884

MAIN

FB

OSC

LX(ON

LX

LIM

= 0, V

SHDN

Integrator enabled, C

Integrator disabled (INTG = REF) 1.21 1.29

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

MAX1778/MAX1880/MAX1883 0.75 1.25 MHz

MAX1881/MAX1882/MAX1884/MAX1885 375 625 kHz

ILX = 100mA 0.7 Ω

VLX = 13V 20 µA

Phase I = soft-start (1024/f

Phase IV = fully on (after 3072/f

= 13V 13 µA

SUPB

= 1000pF 1.223 1.269

INTG

) 0.275 0.525

OSC

) 1.1 2.05

OSC

2.7 5.5 V

V

IN

79 91 %

1

mA

1

0.7

mA

0.5

0.7

mA

0.5

10 µA

13 V

V

A

MAX1778/MAX1880–MAX1885

Quad-Output TFT LCD DC-DC

Converters with Buffer

_______________________________________________________________________________________ 7

ELECTRICAL CHARACTERISTICS (continued)

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

SUPP

= V

SUPN

= V

SUPB

= V

SUPL

= 10V, LDOOUT = FBL, BUF- = BUFOUT, BUF+ = FLTSET = TGND =

PGND = GND, C

REF

= 0.22µF, C

BUF

= 1µF, TA= -40°C to +85°C, unless otherwise noted.) (Note 2)

)

PARAMETER SYMBOL CONDITIONS MIN MAX UNITS

POSITIVE CHARGE PUMP (MAX1778/MAX1880/MAX1881/MAX1882 ONLY)

SUPP Input Supply Range V

FBP Regulation Voltage V

FBP Input Bias Current I

DRVP PCH On-Resistance R

DRVP NCH On-Resistance R

FBP Power-Ready Trip Level Rising edge 1.09 1.16 V

NEGATIVE CHARGE PUMP (MAX1778/MAX1880/MAX1881/MAX1882 ONLY)

SUPN Input Supply Range V

FBN Regulation Voltage V

FBN Input Bias Current I

DRVN PCH On-Resistance R

DRVN NCH On-Resistance R

FBN Power-Ready Trip Level Falling edge 80 165 mV

LOW DROPOUT LINEAR REGULATOR (MAX1778/MAX1881/MAX1883/MAX1884 ONLY)

SUPL Input Supply Range V

SUPL Undervoltage Lockout Rising edge, 50mV hysteresis (typ) 3.8 4.3 V

SUPL Quiescent Current I

Dropout Voltage (Note 1) V

FBL Regulation Voltage V

LDO Load Regulation

LDO Line Regulation

FBL Input Bias Current I

LDO Current Limit I

VCOM BUFFER

SUPB Input Supply Range V

SUPB Quiescent Current I

BUFOUT Leakage Current -10 +10 µA

Input Common-Mode Voltage

PCH(ON

NCH(ON

PCH(ON

NCH(ON

LDOLIM

SUPP

FBP

V

FBP

SUPN

FBN

SUPL

DROP

FBL

SUPB

V

CM

= 1.5V -50 +50 nA

FBP

V

= 1.2V 4 Ω

FBP

V

= 1.3V 20 kΩ

FBP

V

= 0 -50 +50 nA

FBN

V

= +50mV 4 Ω

FBN

V

= -50mV 20 kΩ

FBN

I

= 100µA 240 µA

LDO

LDO regulating to 9V, I

V

= 10V, LDO regulating to 9V,

SUPL

I

= 15mA

LDO

V

= 10V, LDO regulating to 9V,

SUPL

I

= 100µA to 40mA

LDO

= 4.5V to 15V, FBL = LDOOUT,

V

SUPL

I

= 15mA

LDO

V

= 1.25V -1.2 +1.2 µA

FBL

V

= 10V, V

SUPL

V

= 13V 850 µA

SUPB

LDOOUT

= 40mA 330 mV

LDO

= 9V, V

= 1.2V 40 260 mA

FBL

|VOS| < 10mV 1.2 8.8 V

2.7 13 V

1.2 1.3 V

10 Ω

2.7 13 V

-50 +50 mV

10 Ω

4.5 15 V

1.222 1.265 V

1.2 %

0.02 %/V

4.5 13 V

MAX1778/MAX1880–MAX1885

Quad-Output TFT LCD DC-DC Converters with Buffer

8 _______________________________________________________________________________________

ELECTRICAL CHARACTERISTICS (continued)

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

SUPP

= V

SUPN

= V

SUPB

= V

SUPL

= 10V, LDOOUT = FBL, BUF- = BUFOUT, BUF+ = FLTSET = TGND =

PGND = GND, C

REF

= 0.22µF, C

BUF

= 1µF, TA= -40°C to +85°C, unless otherwise noted.) (Note 2)

Note 1: Dropout Voltage is defined as the V

SUPL

- V

LDOOUT

, when V

SUPL

is 100mV below the set value of V

LDOOUT

.

Note 2: Specifications to -40°C are guaranteed by design, not production tested.

PARAMETER SYMBOL CONDITIONS MIN MAX UNITS

Input Bias Current I

Input Offset Current I

Input Offset Voltage V

Output Voltage Swing High V

Output Voltage Swing Low V

BUF+ Dual Mode Threshold Voltage

REFERENCE

Reference Voltage V

Reference Undervoltage Threshold

LOGIC SIGNALS

SHDN Input Low Voltage 0.9 V SHDN Input High Voltage 2.1 V SHDN Input Current I

FLTSET Input Voltage Range 0.74 x V

FLTSET Threshold Voltage Rising edge, 25mV hysteresis (typ) 80 170 mV

FLTSET Input Current V

RDY Output Low Voltage I RDY Output High Leakage V

BUFOUT

BIAS

OS

OH

OL

VCM = 5V -500 +500 nA

BUF+ = GND

V

= 4.5V to 13V

SUPB

= 1.2V to

V

CM

(V

- 1.2V)

SUPB

I

= -45mA, ∆VOS = 1V 9 V

BUFOUT

= +45mA, ∆VOS = 1V 1 V

BUFOUT

I

= 0 4.988 5.012

BUFOUT

= ±5mA 4.97 5.03Output Voltage V

BUFOUT

= ±45mA 4.93 5.07

BUFOUT

= ±5mA -30 30

BUFOUT

= ±45mA -70 70

BUFOUT

Falling edge, 20mV hysteresis (typ) 80 170 mV

REF

SHDN

-2µA < I

FLTSET

SINK

RDY

< 50µA 1.223 1.269 V

REF

= 1V 50 nA

= 2mA 0.5 V

= 13V 1 µA

0.9 1.2 V

0.85 x V

REF

V

mV

1µA

REF

V

MAX1778/MAX1880–MAX1885

Quad-Output TFT LCD DC-DC

Converters with Buffer

_______________________________________________________________________________________ 9

Typical Operating Characteristics

(Circuit of Figure 1, VIN= +3.3V, SHDN = IN, V

MAIN

= V

SUPP

= V

SUPN

= V

SUPB

= V

SUPL

= 8V, BUF- = BUFOUT,

BUF+ = FLTSET = TGND = PGND = GND, T

A

= +25°C.)

MAIN 8V OUTPUT VOLTAGE

vs. LOAD CURRENT

8.12

8.08

VIN = 3.3V

MAX1778 toc01

100

90

MAIN 8V OUTPUT EFFICIENCY

vs. LOAD CURRENT

VIN = 5V

MAX1778 toc02

12.24

12.16

MAIN 12V OUTPUT VOLTAGE

vs. LOAD CURRENT

MAX1778 toc03

8.04

(V)

8.00

OUT

V

7.96

7.92

7.88 0 200 400 600 800

VIN = 5V

I

OUT

(mA)

R C

C

COMP COMP

INTG

= 470pF

= 24kΩ = 470pF

MAIN 12V OUTPUT EFFICIENCY

vs. LOAD CURRENT

100

V

5V

=

(mA)

IN

FIGURE 8 V

OUT

C

INTG

= 12V

= 470pF

MAX1778 toc04

90

V

3.3V

=

IN

80

70

EFFICIENCY (%)

60

50

40

0 200 300100 400 500 600

I

OUT

POSITIVE CHARGE-PUMP EFFICIENCY

vs. LOAD CURRENT

100

V

= 7V

90

80

70

60

EFFICIENCY (%)

50

40

30

SUPP

01051520

I

NEG

(mA)

V

= 7.5V

SUPP

V

SUPP

POS

MAX1778 toc07

= 8V

= 10V

= 20V

80

VIN = 3.3V

70

EFFICIENCY (%)

60

V

= 8V

OUT

= 24kΩ

R

COMP

50

40

= 470pF

C

COMP

= 470pF

C

INTG

0 200 400 600 800

I

(mA)

OUT

STEP UP CONVERTERS

SWITCHING FREQUENCY vs. INPUT VOLTAGE

1.20

MAX1778

1.15

1.10

1.05

1.00

0.95

0.90

SWITCHING FREQUENCY (MHz)

0.85

0.80

2.5 3.53.0 4.0 4.5 5.0 5.5 VIN (V)

MAXIMUM POSITIVE CHARGE-PUMP

OUTPUT VOLTAGE vs. SUPPLY VOLTAGE

40

35

30

25

(V)

POS

V

20

15

10

5

2684 101214

I

= 1mA

POS

I

= 10mA

POS

V

(V)

SUPP

MAX1778 toc05

MAX1778 toc08

12.08

V

3.3V

=

(V)

12.00

OUT

V

11.92

11.84

11.76

IN

V

5V

=

IN

FIGURE 8

= 470pF

C

INTG

0 200 300100 400 500 600

I

(mA)

OUT

POSITIVE CHARGE-PUMP OUTPUT VOLTAGE

vs. LOAD CURRENT

20.2

= 10V

= 7.5V

MAX1778 toc06

V

SUPP

(mA)

V

= 7V

SUPP

V

SUPP

= 8V

SUPP

20.0

19.8

(V)

POS

V

19.6

19.4

19.2 01051520

I

POS

NEGATIVE CHARGE-PUMP OUTPUT VOLTAGE

vs. LOAD CURRENT

-4.90

-4.92

V

= 7V

V

-4.94

-4.96

(V)

NEG

V

-4.98

-5.00

-5.02

-5.04 0 10203040

SUPN

= 6V

SUPN

V

= 8V

SUPN

I

(mA)

NEG

MAX1778 toc09

MAX1778/MAX1880–MAX1885

Quad-Output TFT LCD DC-DC Converters with Buffer

10 ______________________________________________________________________________________

Typical Operating Characteristics (continued)

(Circuit of Figure 1, VIN= +3.3V, SHDN = IN, V

MAIN

= V

SUPP

= V

SUPN

= V

SUPB

= V

SUPL

= 8V, BUF- = BUFOUT,

BUF+ = FLTSET = TGND = PGND = GND, T

A

= +25°C.)

30

50

40

70

60

90

80

100

NEGATIVE CHARGE-PUMP EFFICIENCY

vs. LOAD CURRENT

MAX1778 toc10

I

NEG

(mA)

EFFICIENCY (%)

0 10203040

V

SUPN

= 7V

V

SUPN

= 8V

V

SUPN

= 6V

V

NEG

= -5V

-14

-10

-12

-6

-8

-4

-2

2684 101214

MAXIMUM NEGATIVE CHARGE-PUMP

OUTPUT VOLTAGE vs. SUPPLY VOLTAGE

MAX1778 toc11

V

SUPN

(V)

V

NEG

(V)

I

NEG

= 10mA

I

NEG

= 1mA

1.23

1.24

1.25

1.26

1.27

0 20406080100

REFERENCE VOLTAGE

vs. REFERENCE LOAD CURRENT

MAX1778 toc12

I

REF

(µA)

V

REF

(V)

STEP-UP CONVERTER LOAD-TRANSIENT

RESPONSE

MAX1778 toc13

200mA

0

8.1V

8.0V

7.9V

1A

0

40µs/div

A. I

MAIN

= 20mA to 200mA, 200mA/div

B. V

MAIN

= 8V, 100mV/div C. INDUCTOR CURRENT, 1A/div C

INTG

= 1000pF

C

B

A

STEP-UP CONVERTER LOAD-TRANSIENT

RESPONSE WITHOUT INTEGRATOR

MAX1778 toc14

200mA

0

8.1V

8.0V

7.9V

1A

0

40µs/div

A. I

MAIN

= 20mA to 200mA, 200mA/div

B. V

MAIN

= 8V, 100mV/div C. INDUCTOR CURRENT, 1A/div INTG = REF

C

B

A

STEP-UP CONVERTER LOAD-TRANSIENT

RESPONSE (1µs PULSES)

MAX1778 toc15

0.5A

0

8.0V

7.9V

1A

0.5A

0

4µs/div

A. I

MAIN

= 0 to 500mA, 500mA/div

B. V

MAIN

= 8V, 100mV/div C. INDUCTOR CURRENT, 500mA/div

C

B

A

MAX1778/MAX1880–MAX1885

Quad-Output TFT LCD DC-DC

Converters with Buffer

______________________________________________________________________________________ 11

Typical Operating Characteristics (continued)

(Circuit of Figure 1, VIN= +3.3V, SHDN = IN, V

MAIN

= V

SUPP

= V

SUPN

= V

SUPB

= V

SUPL

= 8V, BUF- = BUFOUT,

BUF+ = FLTSET = TGND = PGND = GND, T

A

= +25°C.)

RIPPLE VOLTAGE WAVEFORMS

8V

-5V

20V

= 8V, I

A. V

MAIN

= -5V, I

= 20V, I

= 10mA, 20mV/div

NEG

POS

B. V C. V

NEG

POS

POWER-UP SEQUENCE

2V

0

5V

0

20V

10V

0

-10V

= O TO 2V, 2V/div

A. V

SHDN

B. RDY, 5V/div C. POSITIVE CHARGE PUMP = V D. STEP-UP CONVERTER: V E. NEGATIVE CHARGE PUMP: V

1µs/div

= 200mA, 10mV/div

= 5mA, 20mV/div

2ms/div

MAIN

POS

= 8V, R

NEG

MAX1778 toc16

MAX1778 toc19

= 20V, R

LOAD

= -5V, R

= 4kΩ, 10V/div

LOAD

= 40Ω, 10V/div

= 500Ω, 10V/div

LOAD

A

B

C

A

B

C

D

E

2V

0

8V

6V

4V

0.5A

0

A. V

SHDN

B. V

MAIN

C. INDUCTOR CURRENT, 500mA/div R

LOAD

4V

2V

0

20V

10V

0

-5V

A. RDY, 2V/div B. POSITIVE CHARGE PUMP, V C. STEP-UP CONVERTER: V D. NEGATIVE CHARGE PUMP, V

STEP-UP CONVERTER

SOFT-START (LIGHT LOAD)

1ms/div

= O TO 2V, 2V/div

= 8V, 2V/div

= 400

Ω

POWER-UP SEQUENCE

(CIRCUIT OF FIG.10)

1ms/div

POS(SYS)

MAIN(SYS)

NEG

MAX1778 toc17

MAX1778 toc20

= 20V, 10V/div

= 8V, 10V/div

= -5V, -5V/div

A

B

C

A

B

C

D

SOFT-START (HEAVY LOAD)

2V

0

8V

6V

4V

1.0A

0.5A

0

= O TO 2V, 2V/div

A. V

SHDN

= 8V, 2V/div

B. V

MAIN

C. INDUCTOR CURRENT, 500mA/div

= 20

R

LOAD

POWER-UP INTO SHORT-CIRCUIT

4V

2V

0

5V

0

10V

5V

0

A. RDY, 2V/div B. GATE OF N-CH MOSFET, 5V/div C. STEP-UP CONVERTER, V

V

MAIN(SYS)

STEP-UP CONVERTER

MAX1778 toc18

1ms/div

Ω

(CIRCUIT OF FIG. 10)

100µs/div

= GND

MAIN(START)

MAX1778 toc21

= 8V, 5V/div

A

B

C

A

B

C

MAX1778/MAX1880–MAX1885

Quad-Output TFT LCD DC-DC Converters with Buffer

12 ______________________________________________________________________________________

Typical Operating Characteristics (continued)

(Circuit of Figure 1, VIN= +3.3V, SHDN = IN, V

MAIN

= V

SUPP

= V

SUPN

= V

SUPB

= V

SUPL

= 8V, BUF- = BUFOUT,

BUF+ = FLTSET = TGND = PGND = GND, T

A

= +25°C.)

LDO OUTPUT VOLTAGE

vs. LDO INPUT VOLTAGE

(INTERNAL LINEAR REGULATOR)

5.05

I

= 0

(V)

LDOOUT

I

LDOOUT

MAX1778 toc22

= 40mA

5.00

4.95

(V)

4.90

LDOOUT

V

4.85

4.80

4.75

4861012

V

SUPL

5.04

5.02

5.00

(V)

4.98

LDOOUT

4.96

V

4.94

4.92

4.90

0.01 0.1 10 100

LDO OUTPUT VOLTAGE

vs. LDO OUTPUT CURRENT

(INTERNAL LINEAR REGULATOR)

1

I

(mA)

LDOOUT

DROPOUT VOLTAGE

vs. LDO LOAD CURRENT

(INTERNAL LINEAR REGULATOR)

200

V

= 5V

LDOOUT

160

(mV)

120

LDOOUT

- V 80

SUPL

V

40

0

02010 30 40

I

(mA)

LDOOUT

MAX1778 toc25

LDO OUTPUT VOLTAGE vs. TEMPERATURE

(INTERNAL LINEAR REGULATOR)

5.10

5.08

MAX1778 toc23

5.06

5.04

5.02

(V)

5.00

LDO

V

4.98

4.96

4.94

4.92

4.90

-40 10-15 35 60 85 TEMPERATURE (°C)

LDO SUPPLY CURRENT

vs. LDO OUTPUT CURRENT

(INTERNAL LINEAR REGULATOR)

4.0

V

= 5V

LDOOUT

3.5

3.0

(mA)

2.5

2.0

LDOOUT

- I

1.5

SUPL

I

1.0

0.5

0

0 10203040

I

(mA)

LDOOUT

I

LDOOUT

I

LDOOUT

MAX1778 toc24

= 0

= 40mA

MAX1778 toc26