Rainbow Electronics MAX1771 User Manual

General Description

The MAX1771 step-up switching controller provides
90% efficiency over a 30mA to 2A load. A unique cur­rent-limited pulse-frequency-modulation (PFM) control
scheme gives this device the benefits of pulse-width­modulation (PWM) converters (high efficiency at heavy
loads), while using less than 110µA of supply current (vs.
2mA to 10mA for PWM converters).

This controller uses miniature external components. Its
high switching frequency (up to 300kHz) allows sur­face-mount magnetics of 5mm height and 9mm diame­ter. It accepts input voltages from 2V to 16.5V. The
output voltage is preset at 12V, or can be adjusted
using two resistors.

The MAX1771 optimizes efficiency at low input voltages
and reduces noise by using a single 100mV current-limit
threshold under all load conditions. A family of similar
devices, the MAX770–MAX773, trades some full-load
efficiency for greater current-limit accuracy; they provide
a 200mV current limit at full load, and switch to 100mV
for light loads.

The MAX1771 drives an external N-channel MOSFET
switch, allowing it to power loads up to 24W. If less power
is required, use the MAX756/MAX757 or MAX761/MAX762
step-up switching regulators with on-board MOSFETs. An
evaluation kit is available.

Applications

Positive LCD-Bias Generators

Flash Memory Programmers

High-Power RF Power-Amplifier Supply

Palmtops/Hand-Held Terminals

Battery-Powered Applications

Portable Communicators

Features

♦ 90% Efficiency for 30mA to 2A Load Currents

♦ Up to 24W Output Power

♦ 110µA (max) Supply Current

♦ 5µA (max) Shutdown Current

♦ 2V to 16.5V Input Range

♦ Preset 12V or Adjustable Output Voltage

♦ Current-Limited PFM Control Scheme

♦ Up to 300kHz Switching Frequency

♦ Evaluation Kit Available

Ordering Information

MAX1771

12V or Adjustable, High-Efficiency,

Low I

Q

, Step-Up DC-DC Controller

________________________________________________________________ Maxim Integrated Products 1

1

2

3

4

8

7

6

5

CS

GND

AGND

REF

SHDN

FB

V+

EXT

TOP VIEW

MAX1771

DIP/SO

Pin Configuration

FB AGND GND

V+

CS

EXT

N

REF

SHDN

ON/OFF

OUTPUT

12V

INPUT

2V TO V

OUT

MAX1771

Typical Operating Circuit

PART TEMP RANGE PIN-PACKAGE

MAX1771CPA 0°C to +70°C 8 Plastic DIP

MAX1771CSA 0°C to +70°C 8 SO

MAX1771C/D 0°C to +70°C Dice*
MAX1771EPA -40°C to +85°C 8 Plastic DIP
MAX1771ESA -40°C to +85°C 8 SO
MAX1771MJA -55°C to +125°C 8 CERDIP**

19-0263; Rev 2; 3/02

EVALUATION KIT MANUAL

AVAILABLE

* Contact factory for dice specifications.
** Contact factory for availability and processing to MIL-STD-883B.

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.

MAX1771

12V or Adjustable, High-Efficiency,
Low I

Q

, Step-Up DC-DC Controller

2

_______________________________________________________________________________________

ABSOLUTE MAXIMUM RATINGS

Supply Voltage

V+ to GND ...............................................................-0.3V, 17V

EXT, CS, REF, SHDN, FB to GND ...................-0.3V, (V+ + 0.3V)

GND to AGND.............................................................0.1V, -0.1V

Continuous Power Dissipation (T

A

= +70°C)

Plastic DIP (derate 9.09mW/°C above +70°C) ............727mW

SO (derate 5.88mW/°C above +70°C).........................471mW

CERDIP (derate 8.00mW/°C above +70°C).................640mW

Operating Temperature Ranges

MAX1771C_A .....................................................0°C to +70°C

MAX1771E_A ..................................................-40°C to +85°C

MAX1771MJA ................................................-55°C to +125°C

Junction Temperatures

MAX1771C_A/E_A.......................................................+150°C

MAX1771MJA ..............................................................+175°C

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

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

ELECTRICAL CHARACTERISTICS

(V+ = 5V, I

LOAD

= 0mA, TA= T

MIN

to T

MAX

, unless otherwise noted. Typical values are at TA= +25°C.)

PARAMETER

SYMBOL CONDITIONS MIN TYP MAX UNITS

Supply Current 85 110 µA

Standby Current

25

µA

4

Output Voltage (Note 1) V

V+ = 2V to 12V, over full load range,
Circuit of Figure 2a

11.52 12.0 12.48

V+ = 5V to 7V, V

OUT

= 12V

I

LOAD

= 700mA, Circuit of Figure 2a

5 mV/V

V+ = 6V, V

OUT

= 12V, I

LOAD

= 0mA to

500mA, Circuit of Figure 2a

20 mV/A

Maximum Switch On-Time tON(max) 12 16 20 µs

Minimum Switch Off-Time t

OFF

(min) 1.8 2.3 2.8 µs

%

Reference Voltage V

REF

I

REF =

0µA

MAX1771C 1.4700 1.5 1.5300

V

MAX1771E 1.4625 1.5 1.5375

MAX1771M 1.4550 1.5 1.5450

Output Voltage Line Regulation
(Note 2)

Output Voltage Load Regulation
(Note 2)

V+ = 5V, V

OUT

= 12V, I

LOAD

= 500mA,

Circuit of Figure 2a

V+ = 10V, SHDN ≥ 1.6V (shutdown)

V+ = 16.5V, SHDN ≥ 1.6V (shutdown)

V+ = 16.5V, SHDN = 0V (normal operation)

Minimum Start-Up Voltage 1.8 2.0 V

MAX1771 (internal feedback resistors) 2.0 12.5

MAX1771C/E (external resistors) 3.0 16.5

MAX1771MJA (external resistors) 3.1 16.5

Input Voltage Range V

Efficiency 92

REF Load Regulation 0µA ≤ I

REF

≤ 100µA

MAX1771C/E 410

mV

MAX1771M 415

3V ≤ V+ ≤ 16.5V 40 100

FB Trip Point Voltage V

FB

MAX1771C 1.4700 1.5 1.5300

V

MAX1771E 1.4625 1.5 1.5375

MAX1771M 1.4550 1.5 1.5450

µV/VREF Line Regulation

MAX1771

12V or Adjustable, High-Efficiency,

Low I

Q

, Step-Up DC-DC Controller

_______________________________________________________________________________________

3

ELECTRICAL CHARACTERISTICS (continued)

(V+ = 5V, I

LOAD

= 0mA, TA= T

MIN

to T

MAX

, unless otherwise noted. Typical values are at TA= +25°C.)

PARAMETERS

SYMBOL CONDITIONS MIN TYP MAX UNITS

FB Input Current I

FB

MAX1771C ±20

nAMAX1771E ±40

MAX1771M ±60

SHDN Input High Voltage V

IH

V+ = 2V to 16.5V 1.6 V

SHDN Input Low Voltage V

IL

V+ = 2V to 16.5V 0.4 V

SHDN Input Current ±1 µAV+ = 16.5V, SHDN = 0V or V+

Current-Limit Trip Level V

CS

V+ = 5V to 16V

85 100 115

mV

CS Input Current 0.01 ±1 µA

EXT Rise Time V+ = 5V, 1nF from EXT to ground 55 ns

EXT Fall Time V+ = 5V, 1nF from EXT to ground 55 ns

Note 1: Output voltage guaranteed using preset voltages. See Figures 4a–4d for output current capability versus input voltage.
Note 2: Output voltage line and load regulation depend on external circuit components.

75 100 125

Typical Operating Characteristics

(TA = +25°C, unless otherwise noted.)

60

65

75

70

80

85

90

95

100

1

10

100

10,000

1000

EFFICIENCY vs. LOAD CURRENT

(BOOTSTRAPED MODE)

LOAD CURRENT (mA)

EFFICIENCY (%)

VIN = 5V

VIN = 3V

VIN = 8V

VIN = 10V

V

OUT

= 12V
CIRCUIT OF
FIGURE 2a

MAX1771–01

60

65

75

70

80

85

90

95

100

1

10

100

10,000

1000

EFFICIENCY vs. LOAD CURRENT

(NON-BOOTSTRAPED MODE)

LOAD CURRENT (mA)

EFFICIENCY (%)

VIN = 5V

VIN =10V

VIN = 8V

V

OUT

= 12V
CIRCUIT OF
FIGURE 2b

MAX1771–02

0

2.00

LOAD CURRENT vs.

MINIMUM START-UP INPUT VOLTAGE

MAX1771-TOC3

MINIMUM START-UP INPUT VOLTAGE (V)

LOAD CURRENT (mA)

100

200

300

400

500

600

700

2.25 2.50 2.75 3.00 3.25 3.50

EXTERNAL FET THRESHOLD
LIMITS FULL-LOAD START-UP
BELOW 3.5V

V

OUT

= 12V, CIRCUIT OF FIGURE 2a

MAX1771C/E

MAX1771M

250

0

-60 -20 60 140

REFERENCE OUTPUT RESISTANCE vs.

TEMPERATURE

50

MAX1771-07

TEMPERATURE (°C)

REFERENCE OUTPUT RESISTANCE (Ω)

20 100

150

-40 0 8040 120

100

200

100µA

50µA

10µA

1.502

-60 -20 60 140

REFERENCE vs. TEMPERATURE

MAX1771-08

TEMPERATURE (°C)

REFERENCE (V)

20 100-40 0 8040 120

1.500

1.498

1.496

1.494

1.492

1.504

1.506

15.5

16.0

16.5

-60

-30 0 30 60

90

120 150

MAXIMUM SWITCH ON-TIME vs.

TEMPERATURE

TEMPERATURE (°C)

t

ON(MAX) (µs)

MAX1771-09

MAX1771

12V or Adjustable, High-Efficiency,
Low I

Q

, Step-Up DC-DC Controller

4

_______________________________________________________________________________________

4.0

-60 -20 60 140

SHUTDOWN CURRENT vs. TEMPERATURE

MAX1771-10

TEMPERATURE (°C)

SHUTDOWN CURRENT (µA)

20 100-40 0 8040 120

3.5

3.0

2.5

2.0

1.5

1.0

0.5

0

V+ = 15V

V+ = 4V

V+ = 8V

2.20

2.25

2.30

-60

-30 0 30 60

90

120 150

MINIMUM SWITCH OFF-TIME vs.

TEMPERATURE

TEMPERATURE (°C)

t

OFF(MIN) (µs)

MAX1771-11

6.0

7.0

8.0

-60

-30 0 30 60

90

120 150

MAXIMUM SWITCH ON-TIME/

MINIMUM SWITCH OFF-TIME RATIO

vs. TEMPERATURE

TEMPERATURE (°C)

t

ON(MAX)/

t

OFF(MIN) RATIO

MAX1771-12

7.5

6.5

Typical Operating Characteristics (continued)

(TA = +25°C, unless otherwise noted.)

0

1

2

3

4

-75

-50 -25 0

25 50 75 100 125

SUPPLY CURRENT vs. TEMPERATURE

TEMPERATURE (°C)

SUPPLY CURRENT (mA)

V

OUT

= 12V, VIN = 5V
CIRCUIT OF FIGURE 2a
BOOTSTRAPPED MODE

ENTIRE
CIRCUIT

SCHOTTKY DIODE
LEAKAGE EXCLUDED

MAX1771-04

0

0.2

0.4

0.6

0.8

2

4

68

10

12

SUPPLY CURRENT vs. SUPPLY VOLTAGE

SUPPLY VOLTAGE (V)

SUPPLY CURRENT (mA)

V

OUT

= 12V

NON-BOOTSTRAPPED
CIRCUIT OF FIGURE 2b

BOOTSTRAPPED
CIRCUIT OF
FIGURE 2a

MAX1771-05

0

100

150

200

250

50

2

4

68

10

12

EXT RISE/FALL TIME vs. SUPPLY VOLTAGE

SUPPLY VOLTAGE (V)

EXT RISE/FALL TIME (ns)

C

EXT

= 2200pF

C

EXT

= 1000pF

C

EXT

= 446pF

C

EXT

= 100pF

MAX1771-06

MAX1771

12V or Adjustable, High-Efficiency,

Low I

Q

, Step-Up DC-DC Controller

_______________________________________________________________________________________

5

2µs/div

V

IN

= 5V, I

OUT

= 900mA, V

OUT

= 12V
A: EXT VOLTAGE, 10V/div
B: INDUCTOR CURRENT, 1A/div
C: V

OUT

RIPPLE, 50mV/div, AC-COUPLED

A

B

C

V

OUT

0V

I

LIM

0A

HEAVY-LOAD SWITCHING WAVEFORMS

Typical Operating Characteristics (continued)

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

10µs/div

V

IN

= 5V, I

OUT

= 500mA, V

OUT

= 12V
A: EXT VOLTAGE, 10V/div
B: INDUCTOR CURRENT, 1A/div
C: V

OUT

RIPPLE, 50mV/div, AC-COUPLED

A

B

C

V

OUT

0V
I

LIM

0A

MEDIUM-LOAD SWITCHING WAVEFORMS

5ms/div

I

OUT

= 700mA, V

OUT

= 12V

A: V

IN

, 5V to 7V, 2V/div

B: V

OUT

RIPPLE, 100mV/div, AC-COUPLED

A

B

5V

7V

0V

LINE-TRANSIENT RESPONSE

5ms/div

V

IN

= 6V, V

OUT

= 12V
A: LOAD CURRENT, 0mA to 500mA, 500mA/div
B: V

OUT

RIPPLE, 100mV/div, AC-COUPLED

A

B

500mA

0A

LOAD-TRANSIENT RESPONSE