Datasheet

ManualsBrandsMaxim ManualsDC / DC ControllersDC/DC Converter PDIP 2-12 V 2 A

_______________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. Order the MAX1771EVKIT-SO.

________________________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

, Step-Up DC-DC Controller

________________________________________________________________

Maxim Integrated Products

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

Call toll free 1-800-998-8800 for free samples or literature.

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 1; 7/95

EVALUATION KIT MANUAL

FOLLOWS DATA SHEET

* Contact factory for dice specifications.

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

Summary of content (16 pages)

PAGE 1
9-0263; Rev 1; 7/95 NUAL KIT MA ATION SHEET A EVALU T A D WS FOLLO 12V or Adjustable, High-Efficiency, Low IQ, Step-Up DC-DC Controller ________________________Applications ____________________________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.
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
12V or Adjustable, High-Efficiency, Low IQ, Step-Up DC-DC Controller MAX1771 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 MAX MAX1771C ±20 MAX1771E ±40 UNITS FB Input Current IFB SHDN Input High Voltage VIH V+ = 2.0V to 16.5V SHDN Input Low Voltage VIL V+ = 2.0V to 16.5V 0.4 V V+ = 16.
PAGE 4
____________________________Typical Operating Characteristics (continued) (TA = +25°C, unless otherwise noted.) 2 SCHOTTKY DIODE LEAKAGE EXCLUDED BOOTSTRAPPED CIRCUIT OF FIGURE 2a 0.6 0.4 0.2 50 75 100 125 CEXT = 100pF 100 6 4 12 10 8 2 REFERENCE OUTPUT RESISTANCE vs. TEMPERATURE 12 10 8 SUPPLY VOLTAGE (V) MAXIMUM SWITCH ON-TIME vs. TEMPERATURE REFERENCE vs. TEMPERATURE 16.5 MAX1771-08 1.506 MAX1771-07 6 4 SUPPLY VOLTAGE (V) 250 1.504 200 10µA 150 100 50µA 1.500 1.498 16.
PAGE 5
12V or Adjustable, High-Efficiency, Low IQ, Step-Up DC-DC Controller HEAVY-LOAD SWITCHING WAVEFORMS MEDIUM-LOAD SWITCHING WAVEFORMS VOUT VOUT A A 0V 0V ILIM ILIM B B 0A 0A C C 2µs/div VIN = 5V, IOUT = 900mA, VOUT = 12V A: EXT VOLTAGE, 10V/div B: INDUCTOR CURRENT, 1A/div C: VOUT RIPPLE, 50mV/div, AC-COUPLED 10µs/div VIN = 5V, IOUT = 500mA, VOUT = 12V A: EXT VOLTAGE, 10V/div B: INDUCTOR CURRENT, 1A/div C: VOUT RIPPLE, 50mV/div, AC-COUPLED LINE-TRANSIENT RESPONSE A LOAD-TRANSIENT RESPONSE 7V 5
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.
PAGE 7
12V or Adjustable, High-Efficiency, Low IQ, Step-Up DC-DC Controller 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 VIN = 5V C1 68µF C2 0.1µF 4 SHDN 2 2 L1 22µH V+ V+ 5 REF C3 0.1µF C2 0.1µF L1 22µH MAX1771 3 FB EXT 6 AGND CS C1 68µF C3 0.1µF D1 1N5817-22 VOUT = 12V @ 0.5A 4 SHDN MAX1771 6 AGND 1 N 8 Si9410DY/ MTD20N03HDL RSENSE 40mΩ GND 5 REF EXT CS FB GND C4 300µF 7 7 R2 = (R1) 1 VOUT = 12V @ 0.
PAGE 9
12V or Adjustable, High-Efficiency, Low IQ, Step-Up DC-DC Controller Low-Voltage Start-Up Oscillator The MAX1771 features a low input voltage start-up oscillator that guarantees start-up with no load down to 2V when operating in bootstrapped mode and using internal feedback resistors. At these low voltages, the supply voltage is not large enough for proper error-comparator operation and internal biasing.
PAGE 10
MAXIMUM OUTPUT CURRENT (A) 3.5 3.5 VOUT = 5V L = 22µH 3.0 MAXIMUM OUTPUT CURRENT (A) MAX1771 12V or Adjustable, High-Efficiency, Low IQ, Step-Up DC-DC Controller 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 3 4 INPUT VOLTAGE (V) 5 Figure 4a. Maximum Output Current vs. Input Voltage (VOUT = 5V) 3.5 2 RSENSE = 35mΩ 2.
PAGE 11
12V or Adjustable, High-Efficiency, Low IQ, Step-Up DC-DC Controller Diode Selection The MAX1771’s high switching frequency demands a high-speed rectifier. Schottky diodes such as the 1N5817–1N5822 are recommended. Make sure the Schottky diode’s average current rating exceeds the peak current limit set by RSENSE, and that its breakdown voltage exceeds V OUT.
PAGE 12
MAX1771 12V or Adjustable, High-Efficiency, Low IQ, Step-Up DC-DC Controller Table 1.
PAGE 13
12V or Adjustable, High-Efficiency, Low IQ, Step-Up DC-DC Controller 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 3.3V: R2 = 100kΩ, R3 = 20kΩ Figure 5.
PAGE 14
MAX1771 12V or Adjustable, High-Efficiency, Low IQ, Step-Up DC-DC Controller VIN 4.5V TO 15V C1 33µF 16V 2 OFF 4 L1† 20µH V+ C2* 1µF SHDN ON MAX1771 EXT CS AGND 5 C5 0.1µF REF R3 28k 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
12V or Adjustable, High-Efficiency, Low IQ, Step-Up DC-DC Controller 4 C5 0.1µF EXT SHDN 5 3 7 CS REF FB GND MAX1771 V+ AGND 1 D1 MBRS1100T3 3 Q1 MTD6N10 2 1 8 +5V 300mA C8 1µF R9 5.1k C7 220pF R7 200Ω Q2 MMBT8099LT1 -48V R6 200k R5 1k R1 0.15Ω C6 10µF 100V R2 47k 1% C1 220µF 10V C2 220µF 10V C3 0.33µF Q3 MMBT8599LT1 D3 CMPSH-3 2 6 MAX1771 L1 D03340 220µH–680µH R4 100k C4 2.2µF 20V R3 16k 1% D2 CMPZ5240/ MMBZ5240BL Figure 7.
PAGE 16
INPUT 2.7V TO 5.5V 22µH EFFICIENCY vs. LOAD CURRENT 150µF 1N5820 EXT OFF 4 CS SHDN 1 100 OUTPUT 5V 1A 90 MTD20N03HDL EFFICIENCY (%) MAX1771 12V or Adjustable, High-Efficiency, Low IQ, Step-Up DC-DC Controller 8 ON 0.04Ω 330µF MAX1771 5 V+ REF 2 0.1µF GND 7 AGND FB 6 0.1µF 80 VIN = 4V VIN = 3V 70 60 232k 100pF 3 50 1m 100k 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.