Maxim MAX746C-D, MAX746CPE, MAX746CSE, MAX746EPE, MAX746ESE Datasheet

_______________General Description

The MAX746 is a high-efficiency, high-current, step-down
DC-DC power-supply controller that drives external N-chan­nel FETs. It provides 93% to 96% efficiency from a 6V supply
voltage with load currents ranging from 50mA up to 3A. It
uses a pulse-width-modulating (PWM) current-mode control
scheme to provide precise output regulation and low output
noise. The MAX746's 4V to 15V input voltage range, fixed
5V/adjustable (Dual-ModeTM) output, and adjustable current
limit make this device ideal for a wide range of applications.

High efficiency is maintained with light loads due to a propri­etary automatic pulse-skipping control (Idle-ModeTM) scheme
that minimizes switching losses by reducing the switching fre­quency at light loads. The low 950µA quiescent current and
ultra-low 1.4µA shutdown current further extend battery life.

External components are protected by the MAX746's cycle­by-cycle current limit. The MAX746 also features a 2V ±1.5%
reference, a comparator for low-battery detection or level
translating, and soft-start and shutdown capability.

The MAX747—discussed in aseparatedata sheet—
functions similarly to the MAX746, but drives P-channel logic
level FETs.

________________________Applications

5V-to-3.3V Green PC Applications
Notebook/Laptop Computers
Personal Digital Assistants
Battery-Operated Equipment
Cellular Phones

____________________________Features

♦ 93% to 96% Efficiency for 50mA to 3A

Output Currents

♦ 4V to 15V Input Voltage Range
♦ Low 950µA Supply Current
♦ 1.4µA Shutdown Current
♦ Drives External N-Channel FETs
♦ Fixed-Frequency Current-Mode PWM (Heavy Loads)
♦ Idle-Mode PFM (Light Loads)
♦ Cycle-by-Cycle Current Limiting
♦ 2V ±1.5% Accurate Reference Output
♦ Adjustable Soft-Start
♦ Undervoltage Lockout
♦ Precision Comparator for Power-Fail or

Low-Battery Warning

______________Ordering Information

* Contact factory for dice specifications.

MAX746

High-Efficiency, PWM, Step-Down,

N-Channel DC-DC Controller

________________________________________________________________

Maxim Integrated Products

1

16
15
14
13
12
11
10

9

1
2
3
4
5
6
7
8

GND
V+
CP
HIGH

REF

SS

LBI

LBO

TOP VIEW

MAX746

EXT
AGND
CS
OUT

AV+

CC

FB

SHDN

DIP/SO

__________________Pin Configuration

CP
HIGH
SHDN

LBI
REF

EXT

OUT

V+

AV+

CS

OUTPUT

5V

LOW-BATTERY
DETECTOR OUTPUT

LBO

GND

AGND

FB

CC

SS

ON/OFF

LOW-BATTERY

DETECTOR INPUT

INPUT 6V TO 15V

40mΩ

39µH

440µF

MAX746

__________Typical Operating Circuit

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

PART TEMP. RANGE PIN-PACKAGE

MAX746CPE 0°C to +70°C 16 Plastic DIP
MAX746CSE 0°C to +70°C 16 Narrow SO
MAX746C/D 0°C to +70°C Dice*

MAX746MJE -55°C to +125°C 16 CERDIP

MAX746ESE -40°C to +85°C 16 Narrow SO

MAX746EPE -40°C to +85°C 16 Plastic DIP

19-0192; Rev 1; 11/93

™Dual-Mode and Idle-Mode are trademarks of Maxim Integrated Products.

MAX746

High-Efficiency, PWM, Step-Down,
N-Channel DC-DC Controller

2 _______________________________________________________________________________________

ABSOLUTE MAXIMUM RATINGS

Supply Voltage V+, AV+ to GND..............................-0.3V to 17V

HIGH, EXT to GND....................................................-0.3V to 21V

AGND to GND..........................................................-0.3V to 0.3V

All Other Pins................................................-0.3V to (V+ + 0.3V)

Reference Current (I

REF

)....................................................±2mA

Continuous Power Dissipation (T

A

= +70°C)

Plastic DIP (derate 10.53mW/°C above +70°C) ..........842mW

Narrow SO (derate 8.70mW/°C above +70°C) ............696mW

CERDIP (derate 10.00mW/°C above +70°C)...............800mW

Operating Temperature Ranges:

MAX746C_E........................................................0°C to +70°C

MAX746E_E.....................................................-40°C to +85°C

MAX746MJE ..................................................-55°C to +125°C

Junction Temperatures:

MAX746C_E/E_E..........................................................+150°C

MAX746MJE.................................................................+175°C

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

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

ELECTRICAL CHARACTERISTICS

(V+ = 10V, I

LOAD

= 0A, I

REF

= 0µA, TA= T

MIN

to T

MAX

, unless otherwise noted.)

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.

PARAMETER SYMBOL MIN TYP MAX UNITS

Efficiency 94 %

Load Regulation 1.3 2.5 %

Line Regulation

0.1

%/V

OUT Leakage Current 50 80

µA

FB Input Logic Low 40 mV

Output Voltage

Input Voltage 415V

V

OUT

4.85 5.08 5.25 V

Feedback Voltage V

FB

V

Reference Voltage V

REF

1.96 2.00 2.04
Reference Load Regulation 920mV
Soft-Start Source Current 0.5 1.0 1.5

µA

Soft-Start Fault Current (Note 1) 100 500

µA

Supply Current (Note 2) I

SUPP

1.7

mA

0.95

1.4 20

µA

Oscillator Frequency f

OSC

80 100 120

kHz

CONDITIONS

I

REF

= 0µA to 100µA

0V < (V+ - CS) < 0.125V

V+ = 4V to 15V, external feedback mode

V

OUT

= 5V

For dual-mode switchover

SS = 0V
SS = 2V

Operating, V+ = 15V

Operating, V+ = 10V
Shutdown mode

(V+ - CS) = 0V,
external feedback mode

FB Input Leakage Current 1 100 nAFB = 2V

I

REF

= 0µA

MAX746E/M

MAX746E/M 1.95 2.00 2.05

MAX746C

V+

V+ = 6V to 15V, 0V < (V+ - CS) < 0.125V,
FB = 0V (includes line and load regulation)

MAX746C 1.96 2.00 2.04

V+ = 6V to 15V, FB = 0V 0.05

Circuit of Figure 1, I

LOAD

= 0.5A to 2.5A,

V+ = 6V

1.97 2.00 2.03

V

MAX746E/M

MAX746C 1.1 1.4

MAX746E/M

85 100 115MAX746C

MAX746

High-Efficiency, PWM, Step-Down,

N-Channel DC-DC Controller

_______________________________________________________________________________________ 3

Note 1: The soft-start fault current is the current sink capability of SS when V

REF

< 1V or when the device is in shutdown.

Note 2: I

SUPP

is the supply current drawn by V+, which includes the current drawn by the charge pump. The charge pump

doubles the current drawn by HIGH from the V+ input, so I

SUPP

= IV++ 2I

HIGH

.

ELECTRICAL CHARACTERISTICS (continued)

(V+ = 10V, I

LOAD

= 0A, I

REF

= 0µA, TA= T

MIN

to T

MAX

, unless otherwise noted.)

PARAMETER

SHDN Input Leakage Current

SYMBOL MIN TYP MAX UNITS

LBO Output Voltage Low V

OL

nA

0.4 V

LBI Threshold Voltage

1.96 2.00 2.04

V

Compensation Pin Impedance 24

kΩ

EXT Source Current 270 mA

LBI Input Leakage Current nA
LBO Output Leakage Current 1

µA

SHDN Input Voltage Low V

IL

0.4 V

SHDN Input Voltage High V

IH

2.0 V

EXT Output Low

EXT Output High V

HIGH

- 0.1 V

0.25 V

EXT Sink Current 160 mA

MAX746E/M

CONDITIONS

SHDN = 10V

I

SINK

= 0.5mA

LBI falling

V

HIGH

= 15V, V

EXT

= 2.5V

LBI = 2.5V
V+ = 15V, LBO = 15V, LBI = 2.5V

V

HIGH

forced to 15V, I

EXT

= -1mA

V

HIGH

forced to 15V, I

EXT

= 1mA

V

HIGH

= 15V, V

EXT

= 12.5V

MAX746C 1.97 2.00 2.03

100

0.1 100

Charge-Pump Output Voltage

Maximum Duty Cycle 91 96 %

V

HIGH

V+ + 4 V+ + 5 V+ + 6 V

V

LIMIT

125 150 175 mV

V+ = 6V
I

HIGH

= 0mA to 10mA

V+ – CS

Current-Sense Amplifier
Current-Limit Threshold

MAX746

High-Efficiency, PWM, Step-Down,
N-Channel DC-DC Controller

4 _______________________________________________________________________________________

N0-LOAD SUPPLY CURRENT

vs. SUPPLY VOLTAGE

NO-LOAD SUPPLY CURRENT (mA)

0.8

0.9

1.0

1.1

1.2

579111315

SUPPLY VOLTAGE (V)

MAX746-01

0

-75



NO-LOAD SUPPLY CURRENT 

vs. TEMPERATURE

MAX746-02

TEMPERATURE (°C)

NO-LOAD SUPPLY CURRENT (mA)

3

1

4

2

-50 -25 0 25 50 75 100 125

V+ = 9V
V

OUT

= 5V

ENTIRE
CIRCUIT

SCHOTTKY DIODE
LEAKAGE EXCLUDED

4

0

0.01

PEAK INDUCTOR CURRENT

vs. OUTPUT CURRENT

1

2

MAX746-03

OUTPUT CURRENT (A)

PEAK INDUCTOR CURRENT (A)

3

0.1 1 10

VIN = 12V

VIN = 9V

VIN = 6V

CIRCUIT OF FIGURE 1a
V

OUT

= 5V

1.5

0

0.01

PEAK INDUCTOR CURRENT

vs. OUTPUT CURRENT

0.5

MAX746-03

OUTPUT CURRENT (A)

PEAK INDUCTOR CURRENT (A)

1.0

0.1 1

CIRCUIT OF FIGURE 1c
V

OUT

= 5V

VIN = 12V

VIN = 6V

10

100

70

0.01



EFFICIENCY vs. OUTPUT CURRENT

80

MAX746-07

OUTPUT CURRENT (A)

EFFICIENCY (%)

90

0.1 1 10

VIN = 12V

VIN = 9V

VIN = 6V

CIRCUIT OF FIGURE 1a
V

OUT

= 5V

4

0

0.01

PEAK INDUCTOR CURRENT

vs. OUTPUT CURRENT

1

2

MAX746-05

OUTPUT CURRENT (A)

PEAK INDUCTOR CURRENT (A)

3

0.1 1 10

CIRCUIT OF FIGURE 1b

V

OUT

= 3.3V

V+ = 5V

100

70

0.01



EFFICIENCY vs. OUTPUT CURRENT

80

MAX746-06

OUTPUT CURRENT (A)

EFFICIENCY (%)

90

0.1 1 10

CIRCUIT OF FIGURE 1c

VIN = 12V

VIN = 6V

V

OUT

= 5V

100

70

0.01



EFFICIENCY vs. OUTPUT CURRENT

80

MAX746-08

OUTPUT CURRENT (A)

EFFICIENCY (%)

90

0.1 1 10

CIRCUIT OF FIGURE 1b
V

OUT

= 3.3V

V+ = 5V

CONTINUOUS-CONDUCTION MODE
BOUNDARY AND CORRESPONDING

PEAK INDUCTOR CURRENT

SUPPLY VOLTAGE (V)

5

7

9

11

13

0.7

OUTPUT CURRENT (A)

15

MAX746-09

0.9 1.1 1.3 1.5 1.7

DISCONTINUOUS-

CONDUCTION REGION

CONTINUOUS-

CONDUCTION

REGION

PEAK

INDUCTOR

CURRENT

__________________________________________Typical Operating Characteristics

(Circuit of Figure 1a, TA = +25°C, unless otherwise noted.)

MAX746

High-Efficiency, PWM, Step-Down,

N-Channel DC-DC Controller

_______________________________________________________________________________________

5

A: LOAD CURRENT, 0.1A TO 1.5A, 1A/div
B: V

OUT

RIPPLE, 50mV/div, AC-COUPLED

V+ = 10V

LOAD-TRANSIENT RESPONSE

A

B

200µs/div

A: EXT VOLTAGE, 10V/div
B: INDUCTOR CURRENT, 500mA/div
C: V

OUT

RIPPLE, 50mV/div, AC-COUPLED

V+ = 6V, I

OUT

= 480mA

A

B

MODERATE-LOAD, IDLE-MODE

WAVEFORMS

20µs/div

C

A: LOAD CURRENT, 0.1A TO 1.5A, 1A/div
B: V

OUT

RIPPLE, 50mV/div, AC COUPLED

V+ = 10V

LOAD-TRANSIENT RESPONSE

A

B

1ms/div

A : EXT VOLTAGE, 20V/div
B : INDUCTOR CURRENT 1A/div
C : V

OUT

RIPPLE, 50mV/div

V+ = 10V, I

OUT

= 3A

CONTINUOUS-CONDUCTION MODE

WAVEFORMS

A

B

C

5µs/div

0V

8V

A: V+ = 8V TO 10V, 2V/div
B: V

OUT

RIPPLE, 100mV/div

I

OUT

= 3A

LINE-TRANSIENT RESPONSE

A

B

10V

500ms/div

A: EXT VOLTAGE, 10V/div
B: INDUCTOR CURRENT, 500mA/div
C: V

OUT

RIPPLE, 50mV/div, AC-COUPLED

V+ = 10V, I

OUT

= 75mA

DISCONTINUOUS-CONDUCTION

IDLE-MODE WAVEFORMS

A

B

20µs/div

C

____________________________Typical Operating Characteristics (continued)

(Circuit of Figure 1a, TA = +25°C, unless otherwise noted.)