Maxim MAX1729EUB Datasheet

EVALUATION KIT

FOLLOWS DATA SHEET

ECB and LCD Display Bias Supply with Accurate

Output Voltage and Temperature Compensation

General Description

The MAX1729 micropower step-up/step-down DC-DC
converter is ideally suited for electrically controlled bire­fringence (ECB) and liquid-crystal-display (LCD) bias­supply generation. It provides step-up/step-down
voltage conversion and reduces output ripple by using
a step-up DC-DC converter followed by a linear regula­tor. This architecture permits a physically smaller induc­tor than those used in competing SEPIC and flyback
topologies. This device features low quiescent current
(67µA typical). A logic-controlled shutdown mode fur­ther reduces quiescent current to 0.4µA typical.

The MAX1729 features an input that dynamically
adjusts the output voltage to control display color or
contrast. It offers two feedback modes: internal and
external. Internal feedback mode allows output volt­ages between 2.5V and 16V, and is specifically
designed to hold temperature drift to ±11ppm/°C.
External feedback mode allows the MAX1729 output
voltage range to be tailored for various displays.

An on-chip temperature sensor with a positive tempera­ture coefficient provides compensation for LCD/ECB
display temperature characteristics. In internal feed­back mode, the buffered temperature sensor output is
read and used to adjust the output voltage via a digital
control signal. External feedback mode features an
additional compensation method in which the tempera­ture output is summed directly into the feedback net­work to provide first-order negative temperature
compensation of the output voltage. The MAX1729 is
available in the space-saving 10-pin µMAX package.

Applications

ECB Display Bias & Color Adjustment
LCD Display Bias & Contrast Adjustment
Cellular Phones
Personal Digital Assistants

Features

♦ High-Accuracy Reference Voltage (±1%)
♦ ±11ppm/°C Output Voltage Drift
♦ On-Chip Temperature Sensor Output
♦ Accurate Voltage and Temperature Provide:

Consistent ECB Colors
Consistent LCD Gray-Scale Contrast

♦ +2.7V to +5.5V Input Voltage Range
♦ Output Voltage Range

+2.5V to +16V in Internal Feedback Mode
Programmable in External Feedback Mode

♦ Dynamic Control of the Output Voltage
♦ 67µA Supply Current
♦ 0.4µA Shutdown Current
♦ 10-Pin µMAX Package (1.09mm max height)
♦ Evaluation Kit Available (MAX1729EVKIT)

MAX1729

________________________________________________________________

Maxim Integrated Products

1

PS

OUT

FB

COMP

LX

TC

CTLIN

V

OUT

+2.5V to +16V

DIGITAL

PWM

CONTROLLER

GND

IN

V

IN

2.7V to 5.5V

MAX1729

REF

ADC

Typical Operating Circuit

19-1406; Rev 1; 1/99

PART

MAX1729EUB -40°C to +85°C

TEMP. RANGE PIN-PACKAGE

10 µMAX

Ordering Information

Pin Configuration

1
2
3
4
5

10

9
8
7
6

GND
LX
PS
OUTCOMP

REF

TC

IN

MAX1729

µMAX

TOP VIEW

CTLINFB

For free samples & the latest literature: http://www.maxim-ic.com, or phone [phone].
For small orders, phone [phone].

MAX1729

ECB and LCD Display Bias Supply with Accurate
Output Voltage and Temperature Compensation

2 _______________________________________________________________________________________

ABSOLUTE MAXIMUM RATINGS

ELECTRICAL CHARACTERISTICS

(VIN= +3V, CTLIN = IN, FB = GND, TA= -40°C to +85°C, unless otherwise noted. Typical values are at TA= +25°C.) (Note 1)

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 to GND.................................................................-0.3V to +6V

LX, PS, OUT to GND...............................................-0.3V to +20V

CTLIN, FB, REF, COMP, TC to GND ...........-0.3V to (V

IN

+ 0.3V)

LX to PS..................................................................-20V to +1.0V

LX, PS, OUT Current...........................................................60mA

Continuous Power Dissipation (T

A

= +70°C)

10-pin µMAX (derate 5.6mW/°C above +70°C)..........444mW

Operating Temperature Range ...........................-40°C to +85°C

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

Storage Temperature Range.............................-65°C to +160°C

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

CONDITIONS

V2.7 5.5V

IN

Operating Voltage Range

UNITSMIN TYP MAXSYMBOLPARAMETER

V2.0 2.6V

LO

Undervoltage Lockout
Threshold (Note 2)

µA37 50I

IN

IN Supply Current

µA30 40I

PS

PS Supply Current

µA0.4 2I

SHDN

Shutdown Supply Current CTLIN = GND, I

SHDN

= IIN+ I

PS

I

REF

= 0 V

1.215 1.228 1.241

V

REF

Reference Output Voltage

TA= +25°C

1.200 1.256TA= -40°C to +85°C

FB = GND, CTLIN =

0.1% duty cycle,
I

OUT

= 0 to 0.5mA

V

V

OUT

(MIN)

Minimum Output Voltage

2.35 2.45 2.5

TA= -40°C to +85°C

I

OUT

= 0 to 0.5mA V16 16.40

V

OUT

(MAX)

Maximum Output Voltage

FB = GND, CTLIN =

0.1% to 100% duty
cycle, I

OUT

= 0

V/100%CTLIN to V

OUT

Gain

13.90 13.95 14.00TA= 0°C to +85°C

VPS= +18V (Note 3) ppm/°C

±11 ±30

TC

OUT

Output Voltage
Temperature Coefficient

TA= 0°C to +85°C

±18 ±65TA= -40°C to +85°C

mA0.5 2.5I

OUT

Maximum Output Current

V1.178 1.228 1.278V

TC

TC Output Voltage TA= +25°C

mV/°C

15.5 16.5 17.5

TC

TC

TC Output Temperature
Coefficient (Note 3)

TA= 0°C to +85°C

14.5 16.5 18.5TA= -40°C to +85°C
µA±50I

TC

TC Output Current

TA= 0°C to +85°C

2.35 2.52

TA= -40°C to +85°C 13.60 14.20

V

1.215 1.228 1.241

V

FB

Feedback Set Voltage (FB)

TA= +25°C

1.200 1.256TA= -40°C to +85°C
mV90 122 150V

MODE

FB Mode Threshold

nA550I

FB

FB Bias Current VFB= +1.25V

V

2

V

IH

CTLIN High Voltage

VIN= +5.5V

1.3VIN= +2.7V

MAX1729

ECB and LCD Display Bias Supply with Accurate

Output Voltage and Temperature Compensation

_______________________________________________________________________________________ 3

Note 1: Specifications to -40°C are guaranteed by design, not production tested.
Note 2: When V

IN

is below this level, the boost and LDO outputs are disabled.

Note 3: Guaranteed by design.
Note 4: Minimum time to hold CTLIN low to invoke shutdown. If CTLIN is held low for less than t

OFF

, device does not enter shutdown.

Note 5: Switching regulator regulates this voltage to keep LDO from dropping out.

ELECTRICAL CHARACTERISTICS

(VIN= +3V, CTLIN = IN, FB = GND, TA= -40°C to +85°C, unless otherwise noted. Typical values are at TA= +25°C.) (Note 1)

VFB= 0, Internal Feedback Mode

V0.4 0.6 1.0

VIN= +5.5V, CTLIN = GND or IN

VIN= +2.7V to +5.5V

PS to OUT Voltage (Note 5)

TA= +25°C

I

DIODE

= 30mA

(Note 4)

ILX= 30mA

ns25

CONDITIONS

511

V-µs

6810

KPFM On-Time Constant

t

CTLIN

CTLIN Minimum Pulse Width
for V

OUT

Control

VFB= +1.25V ns

Ω

60 150

R

COMP

COMP Impedance

µA±1I

IHL

V0.4V

IL

CTLIN Low Voltage
CTLIN Bias Current

20tR/t

F

COMP Rise/Fall Time

VIN= +5.5V 1.5

mV700 970V

LX-PS

LX to PS Diode Forward
Voltage

µs700 1250 2400t

OFF

CTLIN Minimum Pulse Width
for Shutdown

Ω

2.5 5.0

R

ON

Switch On-Resistance

UNITSMIN TYP MAXSYMBOLPARAMETER

VIN= +2.7V

VLX= 18V µA0.1 1I

LX(OFF)

Switch Off-Leakage Current

V

FB =

+1.25V, External Feedback Mode

33

kΩ

TA= -40°C to +85°C

MAX1729

ECB and LCD Display Bias Supply with Accurate
Output Voltage and Temperature Compensation

4 _______________________________________________________________________________________

Typical Operating Characteristics

(Circuit of Figure 2, TA = +25°C, unless otherwise noted.)

0

0.01 1010.1

EFFICIENCY vs. OUTPUT CURRENT

V

OUT

= 9.4 (CTLIN AT 50% DUTY CYCLE)

20

10

30

60

50

40

MAX1729 toc 01

OUTPUT CURRENT (mA)

EFFICIENCY (%)

VIN = 5.5V

VIN = 2.7V

0

0.01 1010.1

EFFICIENCY vs. OUTPUT CURRENT

V

OUT

= 16.4 (CTLIN = IN)

20

10

30

60

50

40

MAX1729 toc 02

OUTPUT CURRENT (mA)

EFFICIENCY (%)

VIN = 5.5V

VIN = 2.7V

0.05

0.15

0.10

0.25

0.20

0.35

0.30

0.40

2.5 3.5 4.03.0 4.5 5.0 5.5 6.0

NO-LOAD SUPPLY CURRENT vs.

SUPPLY VOLTAGE

MAX1729 toc 03

SUPPLY VOLTAGE (V)

SUPPLY CURRENT (mA)

V

OUT

= 16.4V

V

OUT

= 9.4V

V

OUT

= 2.5V

0

2

1

4

3

6

5

7

2.5 3.5 4.03.0 4.5 5.0 5.5 6.0

MAXIMUM OUTPUT CURRENT vs.

SUPPLY VOLTAGE

MAX1729 toc 04

SUPPLY VOLTAGE (V)

MAXIMUM OUTPUT CURRENT (mA)

V

OUT

= +2.5V

V

OUT

= 9.4V

V

OUT

= 16.4V

0

4
2

8
6

10

12

16
14

18

0 20304010 50 60 70 80 90 100

OUTPUT VOLTAGE vs.

DUTY CYCLE

MAX1729 toc 07

DUTY CYCLE (%)

OUTPUT VOLTAGE (V)

0

-100
1 10 100 1k 10k 100k

PS TO OUT (LDO)

POWER-SUPPLY REJECTION RATIO

-80

MAX1729 toc 05

FREQUENCY (Hz)

PSRR (dB)

-60

-40

-20

0

1.0

0.5

2.0

1.5

2.5

3.0

2.5 4.0 4.53.0 3.5 5.0 5.5 6.0

SHUTDOWN SUPPLY CURRENT

MAX1729 toc 06

INPUT VOLTAGE (V)

SHUTDOWN CURRENT (µA)

20ms/div

START-UP DELAY FROM SHUTDOWN

V

CTLIN

5V/div

V

REF

1V/div

V

TC

1V/div

V

OUT

10V/div

MAX1729 toc 08

V

IN

= 5V

I

O

= 0.5mA

500ms/div

DELAY TO SHUTDOWN

V

CTLIN

5V/div

V

REF

1V/div

V

TC

1V/div

V

OUT

10V/div

MAX1729 toc 09a

V

IN

= 5V

I

O

= 0.5mA