Datasheet

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AVAILABLE

EVALUATION KIT AVAILABLE

Functional Diagrams

Pin Configurations appear at end of data sheet.

Functional Diagrams continued at end of data sheet.

UCSP is a trademark of Maxim Integrated Products, Inc.

For pricing, delivery, and

ordering information, please contact Maxim Direct

at 1-888-629-4642, or visit Maxim’s website at www.maximintegrated.com.

General Description

The MAX1771 step-up switching controller provides

90% efficiency over a 30mA to 2A load. A unique cur-

rent-limited pulse-frequency-modulation (PFM) control

scheme gives this device the benefits of pulse-width-

modulation (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 sur-

face-mount magnetics of 5mm height and 9mm diame-

ter. 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

12V or Adjustable, High-Efficiency,

Low I

, Step-Up DC-DC Controller

GND

AGND

REF

SHDN

V+

EXT

TOP VIEW

MAX1771

DIP/SO

Pin Configuration

FB AGND GND

V+

EXT

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

* Contact factory for dice specifications.

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

MAX1771

Summary of content (16 pages)

PAGE 1
EVALUATION KIT AVAILABLE MAX1771 LE AVAILAB 12V or Adjustable, High-Efficiency, Low IQ, Step-Up DC-DC Controller 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).
PAGE 2
MAX1771 12V or Adjustable, High-Efficiency, Low IQ, Step-Up DC-DC Controller 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 (TA = +70°C) Plastic DIP (derate 9.09mW/°C above +70°C) ............727mW SO (derate 5.88mW/°C above +70°C) ......................
PAGE 3
MAX1771 12V or Adjustable, High-Efficiency, Low IQ, Step-Up DC-DC Controller ELECTRICAL CHARACTERISTICS (continued) (V+ = 5V, ILOAD = 0mA, TA = TMIN to TMAX, unless otherwise noted. Typical values are at TA = +25°C.) PARAMETERS SYMBOL CONDITIONS MIN TYP MAX1771C ±20 MAX1771E ±40 FB Input Current IFB SHDN Input High Voltage VIH V+ = 2V to 16.5V SHDN Input Low Voltage VIL V+ = 2V to 16.5V MAX1771M SHDN Input Current VCS UNITS nA ±60 1.6 V V+ = 16.
PAGE 4
MAX1771 12V or Adjustable, High-Efficiency, Low IQ, Step-Up DC-DC Controller Typical Operating Characteristics (continued) (TA = +25°C, unless otherwise noted.) ENTIRE CIRCUIT 2 SCHOTTKY DIODE LEAKAGE EXCLUDED 0 25 50 75 100 125 CEXT = 2200pF CEXT = 1000pF 150 CEXT = 446pF CEXT = 100pF 100 NON-BOOTSTRAPPED CIRCUIT OF FIGURE 2b 0 2 6 4 12 10 8 2 6 4 12 10 8 TEMPERATURE (°C) SUPPLY VOLTAGE (V) SUPPLY VOLTAGE (V) REFERENCE OUTPUT RESISTANCE vs. TEMPERATURE REFERENCE vs.
PAGE 5
MAX1771 12V or Adjustable, High-Efficiency, Low IQ, Step-Up DC-DC Controller Typical Operating Characteristics (continued) (Circuit of Figure 2a, TA = +25°C, unless otherwise noted.
PAGE 6
MAX1771 12V or Adjustable, High-Efficiency, Low IQ, Step-Up DC-DC Controller Typical Operating Characteristics (continued) (Circuit of Figure 2a, TA = +25°C, unless otherwise noted.) ENTERING/EXITING SHUTDOWN A 0V B 5V 0V 2ms/div IOUT = 500mA, VIN = 5V A: SHDN, 5V/div B: VOUT, 5V/div Pin Description 6 PIN NAME FUNCTION 1 EXT Gate Drive for External N-Channel Power Transistor 2 V+ Power-Supply Input. Also acts as a voltage-sense point when in bootstrapped mode.
PAGE 7
MAX1771 12V or Adjustable, High-Efficiency, Low IQ, Step-Up DC-DC Controller range of load currents; and 3) the maximum supply current is only 110µA. The device has a shutdown mode that reduces the supply current to 5µA max. Detailed Description The MAX1771 is a BiCMOS, step-up, switch-mode power-supply controller that provides a preset 12V output, in addition to adjustable-output operation.
PAGE 8
MAX1771 12V or Adjustable, High-Efficiency, Low IQ, Step-Up DC-DC Controller VIN = 5V C1 68µF C2 0.1µF C2 0.1µF 2 2 L1 22µH V+ V+ 5 REF C3 0.1µF VIN = 5V L1 22µH MAX1771 4 SHDN 3 FB EXT 6 AGND CS 5 REF C1 68µF D1 1N5817-22 VOUT = 12V AT 0.5A 1 N 8 Si9410DY/ MTD20N03HDL MAX1771 4 SHDN EXT 6 AGND CS FB GND C4 300µF RSENSE 40mΩ GND C3 0.1µF 7 7 R2 = (R1) VOUT (V REF -1 1 VOUT = 12V AT 0.
PAGE 9
MAX1771 12V or Adjustable, High-Efficiency, Low IQ, Step-Up DC-DC Controller The control circuitry allows the IC to operate in continuous-conduction mode (CCM) while maintaining high efficiency with heavy loads. When the power switch is turned on, it stays on until either 1) the maximum ontime one-shot turns it off (typically 16µs later), or 2) the switch current reaches the peak current limit set by the current-sense resistor.
PAGE 10
MAX1771 12V or Adjustable, High-Efficiency, Low IQ, Step-Up DC-DC Controller 3.5 VOUT = 5V L = 22µH 3.0 MAXIMUM OUTPUT CURRENT (A) MAXIMUM OUTPUT CURRENT (A) 3.5 RSENSE = 20mΩ 2.5 RSENSE = 25mΩ 2.0 RSENSE = 35mΩ 1.5 1.0 RSENSE = 50mΩ 0.5 VOUT = 12V L = 22µH 3.0 RSENSE = 20mΩ RSENSE = 25mΩ 2.5 RSENSE = 35mΩ 2.0 1.5 1.0 RSENSE = 50mΩ 0.5 RSENSE = 100mΩ 0 2 3 4 INPUT VOLTAGE (V) 5 Figure 4a. Maximum Output Current vs. Input Voltage (VOUT = 5V) 3.5 2 RSENSE = 20mΩ RSENSE = 35mΩ 2.
PAGE 11
MAX1771 12V or Adjustable, High-Efficiency, Low IQ, Step-Up DC-DC Controller Power Transistor Selection Diode Selection Use an N-channel MOSFET power transistor with the MAX1771. To ensure the external N-channel MOSFET (N-FET) is turned on hard, use logic-level or low-threshold N-FETs when the input drive voltage is less than 8V. This applies even in bootstrapped mode, to ensure start-up. N-FETs provide the highest efficiency because they do not draw any DC gate-drive current.
PAGE 12
MAX1771 12V or Adjustable, High-Efficiency, Low IQ, Step-Up DC-DC Controller Table 1.
PAGE 13
MAX1771 12V or Adjustable, High-Efficiency, Low IQ, Step-Up DC-DC Controller Layout Considerations C1 2.2µF VIN* 3V TO 11V D2 1N5817 2 4 V+ SHDN L1 20µH 1 CTX20-4 3V = OFF C4 5 REF 0.1µF MAX1771 EXT CS GND AGND 6 7 C2 Q1** 47µF 16V 1 8 L2 VOUT 5V 500mA C3 220µF 10V R1 0.1Ω FB 3 D1 1N5817 R3† R2† C5 47pF SEE TEXT FOR FURTHER COMPONENT INFO **VIN MAY BE LOWER THAN INDICATED IF THE SUPPLY IS NOT **REQUIRED TO START UNDER FULL LOAD **MOTOROLA MMFT3055ELT1 † FOR 5V: R2 = 200kΩ, R3 = 470kΩ 3.
PAGE 14
MAX1771 12V or Adjustable, High-Efficiency, Low IQ, Step-Up DC-DC Controller VIN 4.5V TO 15V C1 33µF 2 16V OFF 4 L1 20µH V+ C2* 1µF SHDN ON MAX1771 EXT CS AGND 5 C5 0.1µF REF R3 28kΩ 1% GND FB 3 1 Q1** L2* 20µH 8 6 7 D2* 1N4148 NOTE: KEEP ALL TRACES CONNECTED TO PIN 3 AS SHORT AS POSSIBLE VOUT 12V 250mA D1 1N5819 R1 0.
PAGE 15
MAX1771 12V or Adjustable, High-Efficiency, Low IQ, Step-Up DC-DC Controller L1 D03340 220µH–680µH 4 C5 0.1µF EXT SHDN 5 3 7 MAX1771 V+ +5V 300mA C8 1µF R9 5.1kΩ 1 C7 220pF R7 200Ω Q2 MMBT8099LT1 -48V 6 R6 200kΩ R5 1kΩ R1 0.15Ω C6 10µF 100V R2 47kΩ 1% C1 220µF 10V C2 220µF 10V C3 0.33µF Q3 MMBT8599LT1 D3 CMPSH-3 2 AGND GND 3 Q1 MTD6N10 2 8 CS REF FB 1 D1 MBRS1100T3 R4 100kΩ C4 2.2µF 20V R3 16kΩ 1% D2 CMPZ5240/ MMBZ5240BL Figure 7.
PAGE 16
MAX1771 12V or Adjustable, High-Efficiency, Low IQ, Step-Up DC-DC Controller INPUT 2.7V TO 5.5V 22µH EFFICIENCY vs. LOAD CURRENT 150µF 1N5820 OFF 4 CS SHDN 90 1 MTD20N03HDL EFFICIENCY (%) EXT 100 OUTPUT 5V 1A 8 ON 330µF 0.04Ω MAX1771 5 V+ REF 2 0.1µF GND 7 AGND FB 6 0.1µF 232kΩ 80 VIN = 4V VIN = 3V 70 60 100pF 3 50 1m 100kΩ 10m 100m 1 LOAD CURRENT (A) Figure 9. 5V/1A Boost Converter ___________________Chip Topography EXT V+ CS 0.126" (3.200mm) GND AGND FB SHDN 0.