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General Description

The MAX774/MAX775/MAX776 inverting switching

regulators deliver high efficiency over three decades of

load current. A unique current-limited, pulse-

frequency modulated (PFM) control scheme provides

the benefits of pulse-width modulation (high efficiency

with heavy loads), while using less than 100µA of supply

current (vs. 2mA to 10mA for PWM converters). The result

is high efficiency over a wide range of loads.

These ICs also use tiny external components; their high

switching frequency (up to 300kHz) allows for less than

5mm diameter surface-mount magnetics.

The MAX774/MAX775/MAX776 accept input voltages from

3V to 16.5V, and have preset output voltages of

-5V, -12V, and -15V, respectively. Or, the output voltage

can be user-adjusted with two resistors. Maximum

- V

OUT

differential voltage is limited only by the break-

down voltage of the chosen external switch transistor.

These inverters use external P-channel MOSFET switches,

allowing them to power loads up to 5W. If less power is

required, use the MAX764/MAX765/MAX766 inverting

switching regulators with on-board MOSFETs.

Applications

LCD-Bias Generators

High-Efficiency DC-to-DC Converters

Battery-Powered Applications

Data Communicators

Features

♦ 85% Efficiency for 5mA to 1A Load Currents

♦ Up to 5W Output Power

♦ 100µA (max) Supply Current

♦ 5µA (max) Shutdown Current

♦ 3V to 16.5V Input Range

♦ -5V (MAX774), -12V (MAX775), -15V (MAX776),

or Adjustable Output Voltage

♦ Current-Limited PFM Control Scheme

♦ 300kHz Switching Frequency

Ordering Information

*Contact factory for dice specifications.

MAX774/MAX775/MAX776

-5V/-12V/-15V or Adjustable, High-Efficiency,

Low I

Inverting DC-to-DC Controllers

________________________________________________________________ Maxim Integrated Products 1

MAX774

MAX775

MAX776

DIP/SO

TOP VIEW

GND

EXT

V+

OUT

SHDN

REF

Pin Configuration

MAX774

OUTPUT

-5V

REF

SHDN

GND

V+

EXT

OUT

ON/OFF

INPUT

3V TO 16V

Typical Operating Circuit

PART TEMP RANGE PIN-PACKAGE

MAX774CPA

0°C to +70°C 8 Plastic DIP

MAX774CSA 0°C to +70°C 8 SO

MAX774C/D 0°C to +70°C Dice*

MAX774EPA -40°C to +85°C 8 Plastic DIP

MAX774ESA -40°C to +85°C 8 SO

MAX774MJA -55°C to +125°C 8 CERDIP

19-0191; Rev 2; 12/02

EVALUATION KIT

AVAILABLE

Ordering Information continued on last page.

Summary of content (16 pages)

PAGE 1
9-0191; Rev 2; 12/02 TION KIT EVALUA ABLE IL A AV -5V/-12V/-15V or Adjustable, High-Efficiency, Low IQ Inverting DC-to-DC Controllers Features ♦ 85% Efficiency for 5mA to 1A Load Currents The MAX774/MAX775/MAX776 accept input voltages from 3V to 16.5V, and have preset output voltages of -5V, -12V, and -15V, respectively. Or, the output voltage can be user-adjusted with two resistors. Maximum VIN - VOUT differential voltage is limited only by the breakdown voltage of the chosen external switch transistor.
PAGE 2
MAX774/MAX775/MAX776 -5V/-12V/-15V or Adjustable, High-Efficiency, Low IQ Inverting DC-to-DC Controllers ABSOLUTE MAXIMUM RATINGS Supply Voltages V+ to OUT ...........................................................................21V V+ to GND ..............................................................-0.3V, +17V OUT to GND ........................................................-0.3V, to -17V REF, SHDN, FB, CS...................................-0.3V to (V+ + 0.3V) EXT .................................
PAGE 3
-5V/-12V/-15V or Adjustable, High-Efficiency, Low IQ Inverting DC-to-DC Controllers MAX774/MAX775/MAX776 ELECTRICAL CHARACTERISTICS (continued) (V+ = 5V, ILOAD = 0mA, CREF = 0.1µF, TA = TMIN to TMAX, unless otherwise noted. Typical values are at TA = +25°C.) PARAMETER SYMBOL Efficiency (Circuit of Figure 2— Bootstrapped) MIN MAX775, V+ = 5V, ILOAD = 500mA MAX776, V+ = 5V, ILOAD = 400mA SHDN Input Current SHDN Input Voltage High CONDITIONS MAX774, V+ = 5V, ILOAD = 1A VIH V+ = 16.
PAGE 4
__________________________________________Typical Operating Characteristics (TA = +25°C, unless otherwise noted.) MAX774 EFFICIENCY vs. LOAD CURRENT VOUT = -5V (NONBOOTSTRAPPED) VIN = 15V 70 ILOAD = 100mA 80 80 EFFICIENCY (%) VIN = 3V VIN = 5V 60 VIN = 4V EFFICIENCY (%) 80 90 MA774/5/6--1b VIN = 5V EFFICIENCY (%) 90 MAX1774/5/6-01a 90 MAX774 EFFICIENCY vs. TEMPERATURE MAX774/5/6-2 MAX774 EFFICIENCY vs.
PAGE 5
-5V/-12V/-15V or Adjustable, High-Efficiency, Low IQ Inverting DC-to-DC Controllers 4.5 3.5 VOUT = -5V 3.0 4.0 VOUT = -24V 3.5 3.0 2.5 1000 100 10 EXT RISE AND FALL TIMES vs. TEMPERATURE EXT RISE AND FALL TIMES vs. TEMPERATURE 110 80 5V FALL 70 60 12V RISE 50 CEXT = 5nF 4 6 8 10 12 14 16 INPUT VOLTAGE (V) SWITCH ON-TIME vs.
PAGE 6
_____________________________Typical Operating Characteristics (continued) (TA = +25°C, unless otherwise noted.) OPERATING SUPPLY CURRENT vs. TEMPERATURE REFERENCE TEMPERATURE COEFFICIENT 76 1.504 74 72 V+ = 3V 68 1.500 1.498 1.496 1.494 1.
PAGE 7
-5V/-12V/-15V or Adjustable, High-Efficiency, Low IQ Inverting DC-to-DC Controllers INDUCTOR CURRENT NEAR FULL LOAD OPERATING WAVEFORMS A 1A/div B 0A C 20µs/div 10µs/div CIRCUIT OF FIGURE 2 VOUT = -5V, V+ = 4.7V ILOAD = 1.05A (1A/div) CIRCUIT OF FIGURE 2 V+ = 6.
PAGE 8
MAX774/MAX775/MAX776 -5V/-12V/-15V or Adjustable, High-Efficiency, Low IQ Inverting DC-to-DC Controllers Typical Operating Characteristics (continued) (TA = +25°C, unless otherwise noted.
PAGE 9
-5V/-12V/-15V or Adjustable, High-Efficiency, Low IQ Inverting DC-to-DC Controllers MAX774/MAX775/MAX776 V+ FB MODE COMPARATOR REF MAX774 MAX775 MAX776 50mV SHDN ERROR COMPARATOR OUT N 1.5V REFERENCE Q TRIG ONE-SHOT FROM V+ S TRIG Q EXT Q R ONE-SHOT FROM OUT CURRENT COMPARATOR CS 0.1V (HALF CURRENT) CURRENTCONTROL CIRCUITS 0.2V (FULL CURRENT) FROM V+ GND Figure 1.
PAGE 10
MAX774/MAX775/MAX776 -5V/-12V/-15V or Adjustable, High-Efficiency, Low IQ Inverting DC-to-DC Controllers VIN VIN C1 150µF C2 0.1µF 1 OUT 3 2 4 V+ 1 5 MAX774 SHDN MAX775 CS 6 MAX776 FB R2 R1 0.07Ω EXT Q1 Si9435 P 7 C1 150µF VOUT REF GND 8 C3 0.1µF 1N5822/ MBR340 L1 22µH C4* * MAX774 = 330µF, 10V MAX775, MAX776 = 120µF, 20V OUTPUT VOLTAGE (V) INPUT VOLTAGE (V) MAX774 -5 3 to 15 1 MAX775 -12 3 to 8 0.5 MAX776 -15 3 to 5 0.
PAGE 11
-5V/-12V/-15V or Adjustable, High-Efficiency, Low IQ Inverting DC-to-DC Controllers VOUT RZ 1 OUT GND 8 R2 2 FB R1 4 MAX774 MAX775 MAX776 REF 0.1µF 6V ≤ VZ + VIN ≤ 10V VOUT – VZ > IZ RZ IZ = ZENER BREAKDOWN CURRENT VZ = ZENER BREAKDOWN VOLTAGE VIN = INPUT SUPPLY VOLTAGE Figure 5. Connection Using Zener Diode to Boost Base Drive connected to the output voltage (-5V, -12V, -15V). In nonbootstrapped operation, OUT is connected to ground, and EXT now swings from V+ to ground.
PAGE 12
RSENSE = 0.06Ω 2000 1500 1000 RSENSE = 0.07Ω RSENSE = 0.08Ω 500 0 RSENSE = 0.09Ω VOUT = -5V 3 4 5 6 1000 VOUT = -12V 800 RSENSE = 0.05Ω RSENSE = 0.06Ω RSENSE = 0.07Ω 600 MAX775-FIG07 RSENSE = 0.05Ω MAXIMUM OUTPUT CURRENT (mA) MAX775-fig6 2500 MAXIMUM OUTPUT CURRENT (mA) MAX774/MAX775/MAX776 -5V/-12V/-15V or Adjustable, High-Efficiency, Low IQ Inverting DC-to-DC Controllers 400 RSENSE = 0.08Ω RSENSE = 0.
PAGE 13
600 500 400 300 RSENSE = 0.08Ω RSENSE = 0.09Ω 200 600 MAX776-FIG09 RSENSE = 0.05Ω RSENSE = 0.06Ω RSENSE = 0.07Ω 800 MAXIMUM OUTPUT CURRENT (mA) MAXIMUM OUTPUT CURRENT (mA) VOUT = -15V VOUT = -24V RSENSE = 0.05Ω RSENSE = 0.06Ω RSENSE = 0.07Ω 400 200 RSENSE = 0.08Ω RSENSE = 0.09Ω 0 100 3 4 5 6 INPUT VOLTAGE (V) 7 3 4 5 6 7 8 9 10 11 12 13 14 15 INPUT VOLTAGE (V) Figure 8. MAX776 Maximum Output Current vs. Input Voltage (VOUT = -15V) Figure 9. MAX774/MAX775/MAX776 Maximum Output Current vs.
PAGE 14
MAX774/MAX775/MAX776 -5V/-12V/-15V or Adjustable, High-Efficiency, Low IQ Inverting DC-to-DC Controllers Table 1.
PAGE 15
-5V/-12V/-15V or Adjustable, High-Efficiency, Low IQ Inverting DC-to-DC Controllers TEMP RANGE PIN-PACKAGE MAX775CPA PART 0°C to +70°C 8 Plastic DIP MAX775CSA MAX775C/D MAX775EPA MAX775ESA MAX775MJA MAX776CPA MAX776CSA MAX776C/D MAX776EPA MAX776ESA MAX776MJA 0°C to +70°C 0°C to +70°C -40°C to +85°C -40°C to +85°C -55°C to +125°C 0°C to +70°C 0°C to +70°C 0°C to +70°C -40°C to +85°C -40°C to +85°C -55°C to +125°C 8 SO Dice* 8 Plastic DIP 8 SO 8 CERDIP 8 Plastic DIP 8 SO Dice* 8 Plastic DIP 8 SO 8 CER
PAGE 16
MAX774/MAX775/MAX776 -5V/-12V/-15V or Adjustable, High-Efficiency, Low IQ Inverting DC-to-DC Controllers Package Information (continued) (The package drawing(s) in this data sheet may not reflect the most current specifications. For the latest package outline information, go to www.maxim-ic.com/packages.) DIM D1 A A1 A2 A3 B B1 C D D1 E E1 e eA eB L α E E1 D A3 A A2 L A1 INCHES MIN MAX – 0.200 0.015 – 0.125 0.175 0.055 0.080 0.016 0.022 0.050 0.065 0.008 0.012 0.348 0.390 0.005 0.035 0.300 0.