Datasheet

ManualsBrandsMAXIM INTEGRATED ManualsPMICsPMIC - DC/DC voltage regulator Holder SOIC 8

__________________General Description

The MAX748A/MAX763A are 3.3V-output CMOS, step-

down switching regulators. The MAX748A accepts

inputs from 3.3V to 16V and delivers up to 500mA. The

MAX763A accepts inputs between 3.3V and 11V and

delivers up to 500mA. Typical efficiencies are 85% to

90%. Quiescent supply current is 1.4mA (MAX763A),

and only 0.2µA in shutdown.

Pulse-width-modulation (PWM) current-mode control pro-

vides precise output regulation and excellent transient

responses. Output voltage accuracy is guaranteed to be

±5% over line, load, and temperature variations.

Fixed-frequency switching allows easy filtering of output

ripple and noise, as well as the use of small external

components. A 22µH inductor works in most applica-

tions, so no magnetics design is necessary.

The MAX748A/MAX763A also feature cycle-by-cycle cur-

rent limiting, overcurrent limiting, undervoltage lockout,

and programmable soft-start protection. The MAX748A

is available in 8-pin DIP and 16-pin wide SO packages;

the MAX763A comes in 8-pin DIP and SO packages.

___________________________Applications

5V-to-3.3V Converters

Cellular Phones

Portable Instruments

Hand-Held Computers

Computer Peripherals

________________________________Features

♦ Up to 500mA Load Currents

♦ Guaranteed 159kHz to 219.5kHz Current-Mode

PWM

♦ 85% to 90% Efficiencies

♦ 1.7mA Quiescent Current (MAX748A)

1.4mA Quiescent Current (MAX763A)

♦ 0.2µA Shutdown Supply Current

♦ 22µH Preselected Inductor Value;

No Component Design Required

♦ Overcurrent, Soft-Start, and Undervoltage

Lockout Protection

♦ Cycle-by-Cycle Current Limiting

♦ 8-Pin DIP/SO Packages (MAX763A)

_________________Ordering Information

PART TEMP. RANGE PIN-PACKAGE

MAX748ACPA 0°C to +70°C 8 Plastic DIP

MAX748ACWE 0°C to +70°C 16 Wide SO

MAX748AC/D 0°C to +70°C Dice*

MAX748AEPA -40°C to +85°C 8 Plastic DIP

MAX748AEWE -40°C to +85°C 16 Wide SO

MAX748AMJA -55°C to +125°C 8 CERDIP

MAX748A/MAX763A

3.3V, Step-Down,

Current-Mode PWM DC-DC Converters

_______________________________________________________________________

Maxim Integrated Products

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

19-0190; Rev 0; 9/93

Ordering Information continued on last page.

* Contact factory for dice specifications.

____________________Pin Configurations

MAX748A



INPUT

3.3V TO 16V

V+

OUT

GNDSS

REF

SHDNON/OFF

22µH

OUTPUT

3.3V

100µF

____________Typical Operating Circuit

TOP VIEW

V+

GND

OUT

REF

MAX748A

MAX763A



DIP

SHDN

Pin Configurations continued on last page.

Summary of content (12 pages)

PAGE 1
9-0190; Rev 0; 9/93 3.3V, Step-Down, Current-Mode PWM DC-DC Converters ________________________________Features ♦ Up to 500mA Load Currents The MAX748A/MAX763A also feature cycle-by-cycle current limiting, overcurrent limiting, undervoltage lockout, and programmable soft-start protection. The MAX748A is available in 8-pin DIP and 16-pin wide SO packages; the MAX763A comes in 8-pin DIP and SO packages. ___________________________Applications 5V-to-3.
PAGE 2
MAX748A/MAX763A 3.3V, Step-Down, Current-Mode PWM DC-DC Converters ABSOLUTE MAXIMUM RATINGS Pin Voltages: V+ (MAX748A) ......................................................+17V, -0.3V V+ (MAX763A) ......................................................+12V, -0.3V LX (MAX748A) .................................(V+ - 21V) to (V+ + 0.3V) LX (MAX763A) .................................(V+ - 12V) to (V+ + 0.3V) OUT .................................................................................
PAGE 3
.3V, Step-Down, Current-Mode PWM DC-DC Converters (Circuit of Figure 3, V+ = 5V, ILOAD = 0mA, TA = TMIN to TMAX, unless otherwise noted.) PARAMETER CONDITIONS Efficiency V+ = 5V MIN MAX748A TYP MAX MIN MAX763A TYP MAX ILOAD = 300mA 88 88 ILOAD = 100mA 90 90 UNITS % Supply Current Includes switch current 1.7 3.0 1.4 2.5 mA Shutdown Current SHDN = 0V (Note 1) 0.2 100.0 0.2 100.0 µA Shutdown Input Threshold VIH 2.0 2.0 VIL 0.25 1.0 1.
PAGE 4
____________________________Typical Operating Characteristics (continued) (Circuit of Figure 3, TA = +25°C, VOUT = 3.3V, unless otherwise noted.) MAX763A QUIESCENT SUPPLY CURRENT vs. SUPPLY VOLTAGE MAX748A QUIESCENT SUPPLY CURRENT vs. SUPPLY VOLTAGE 1000 IOUT = OmA IOUT = 0mA 3.5 TA = +125°C 3.0 2.5 2.0 TA = -55°C 1.5 TA = +25°C 1.0 PEAK INDUCTOR CURRENT (mA) 4.0 QUIESCENT SUPPLY CURRENT (mA) QUIESCENT SUPPLY CURRENT (mA) PEAK INDUCTOR CURRENT vs. OUTPUT CURRENT 5.0 4.5 4.0 TA = -55°C 3.
PAGE 5
3.
PAGE 6
MAX748A/MAX763A 3.3V, Step-Down, Current-Mode PWM DC-DC Converters _______________________________________________________________________Pin Description PIN # 16-PIN WIDE SO 8-PIN DIP/SO (MAX748A) NAME FUNCTION Shutdown—active low. Connect to ground to power down chip; tie to V+ for normal operation. Output voltage falls to 0V when SHDN is low. 1 2 SHDN 2 3 REF 3 7 SS Soft-Start. Capacitor between SS and GND provides soft-start and short-circuit protection.
PAGE 7
3.3V, Step-Down, Current-Mode PWM DC-DC Converters SHDN MAX748A/MAX763A MAX748A 3.3V to 16.0V MAX763A 3.3V to 11.0V VIN C3 150µF C2 1.0µF V+ OVERCURRENT COMPARATOR SLOPE COMPENSATION BIAS GEN RAMP GEN Σ OUT C5 330pF RSENSE ERROR AMP CURRENT SENSE AMP F/F CC R Q S 1.23V BANDGAP LX PWM COMPARATOR REF C6 1000pF 200kHz OSC 1M ±35% L1 22µH VOUT 3.3V D1 1N5817 C4 150µF MAX748A MAX763A SS CLAMP UNDERVOLTAGE LOCKOUT SS C1 0.047µF VUVLO GND Figure 1.
PAGE 8
MAX748A/MAX763A 3.3V, Step-Down, Current-Mode PWM DC-DC Converters Table 3.
PAGE 9
3.3V, Step-Down, Current-Mode PWM DC-DC Converters C2 1.0µF C3 150µF 8 1 V+ SHDN LX 7 D1 1N5817 MAX748A MAX763A OUT 3 SS C1 0.047µF CC GND 6 MAX748A/MAX763A INPUT MAX748A 3.3V TO 16.0V V MAX763A 3.3V TO 11.0V IN 5 4 L1 22µH OUTPUT 3.3V C5 330pF OPTIONAL 21kHz LOWPASS OUTPUT FILTER L2 25µH OUTPUT FILTER OUTPUT C7 2.2µF C4 150µF REF 2 C6 1000pF Figure 3. Standard 3.3V Step-Down Application Circuit Using Through-Hole Components (commercial temperture range) Table 2.
PAGE 10
MAX748A/MAX763A 3.3V, Step-Down, Current-Mode PWM DC-DC Converters INPUT MAX748A 3.3V TO 16.0V MAX763A 3.3V TO 11.0V 1 VIN C2 1.0µF 8 C3* 150µF (16V) V+ SHDN LX OUT SS C1 0.047µF CC GND 6 C3* 68µF (16V) 5 4 V+ SHDN LX MAX748A MAX763A OUT OUTPUT 3.3V SS C1 0.047µF CC GND 6 C6 1000pF *OS-CON Series (very low ESR) 5 C5 330pF 3 C4* 220µF (10V) 7 D1 1N5817 L1 22µH REF 2 8 1 C5 330pF 3 C2 1.0µF 7 D1 1N5817 MAX748A MAX763A INPUT MAX748A 3.3V TO 16.0V V MAX763A 3.3V TO 11.
PAGE 11
3.3V, Step-Down, Current-Mode PWM DC-DC Converters Figure 7. DIP PC Layout, Component Side (1X Scale) Figure 8. DIP PC Layout, Solder Side (1X Scale) Figure 9. DIP PC Layout, Drill Guide (1X Scale) ______________________________________________________________________________________ MAX748A/MAX763A Figure 6.
PAGE 12
MAX748A/MAX763A 3.3V, Step-Down, Current-Mode PWM DC-DC Converters _____Pin Configurations (continued) ____________________Chip Topographies 0.131" TOP VIEW 3.327mm SHDN 1 REF 2 SS 3 MAX748A MAX763A CC 4 8 V+ 7 LX 6 GND 5 OUT SS REF CC SHDN 0.116" SO V+ 2.946mm V+ V+ 1 16 V+ SHDN 2 15 V+ REF 3 14 LX OUT 13 LX GND N.C. 4 MAX748A N.C. 5 12 LX N.C.