MAXIM MAX1966, MAX1967 User Manual

General Description

The MAX1966/MAX1967 are voltage-mode pulse-width­modulated (PWM), step-down DC-DC controllers that
are ideal for a variety of cost-sensitive applications.
They drive low-cost N-MOSFETs for both the high-side
switch and synchronous rectifier and require no external
Schottky power diode or current-sense resistor. Short­circuit and current-limit protection is provided by sens­ing the drain-to-source voltage on the low-side FET.
Both devices can supply outputs as low as 0.8V and are
well suited for DSP cores and other low-voltage logic.

The MAX1966 has an input range of 2.7V to 5.5V while
the MAX1967 has an input range of 2.7V to 28V. In
ultra-low-cost designs, the MAX1966/MAX1967 can
provide efficiency exceeding 90% and can achieve
95% efficiency with optimized component selection.

The MAX1966/MAX1967 operate at 100kHz and ac­commodate aluminum electrolytic capacitors and pow­dered-iron core magnetics in minimum-cost designs.
They also provide excellent performance with high-per­formance surface-mount components. The MAX1966 is
available in a low-cost 8-pin SO package. The MAX1967
is available in a 10-pin µMAX package.

Applications

Features

♦ Cost-Optimized Design

♦ No Schottky Diode or Current-Sense Resistor

Required

♦ >95% Efficiency

♦ Low-Cost External Components

♦ All N-Channel FET Design

♦ 2.7V to 5.5V Input Range (MAX1966)

♦ 2.7V to 28V Input Range (MAX1967)

♦ 0.8V Feedback for Low-Voltage Outputs

♦ 100kHz Switching Frequency Accommodates

Low-Cost Components

♦ Thermal Shutdown

♦ Output Current-Limit and Short-Circuit Protection

MAX1966/MAX1967

Low-Cost Voltage-Mode PWM

Step-Down Controllers

________________________________________________________________ Maxim Integrated Products 1

Pin Configurations

Ordering Information

MAX1966

V

OUT

2.7V TO

5.5V INPUT

VIN

COMP/EN

GND

BST

DH

LX

DL

FB

Typical Operating Circuit

19-2286; Rev 1; 9/03

For pricing, delivery, and ordering information, please contact Maxim/Dallas Direct! at
1-888-629-4642, or visit Maxim’s website at www.maxim-ic.com.

Pin Configurations continued at end of data sheet.

Set-Top Boxes
Graphic Card Supplies
xDSL Modems and

Routers
Cable Modems and

Routers

Telecom Power Supplies
Networking Power

Supplies
Termination Supplies

PART TEMP RANGE PIN-PACKAGE

MAX1966ESA -40°C to +85°C 8 SO

MAX1967EUB -40°C to +85°C 10 µMAX

TOP VIEW

1

BST

2

MAX1966

3

FB

4

SO

87DH

6

5

LXCOMP/EN

GND

DLVIN

MAX1966/MAX1967

Low-Cost Voltage-Mode PWM
Step-Down Controllers

2 _______________________________________________________________________________________

ABSOLUTE MAXIMUM RATINGS

ELECTRICAL CHARACTERISTICS

(VIN = VL = VCC = 5V (MAX1967), VIN = 5V (MAX1966), TA= -40°C to +85°C (Note 1), unless otherwise noted. Typical values are at
T

A

= +25°C.)

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.

(All Voltages Referenced to GND, Unless Otherwise Noted)

VIN to GND (MAX1966)............................................-0.3V to +6V

VIN to GND (MAX1967)..........................................-0.3V to +30V

VCC to GND (MAX1967)..........-0.3V, lower of 6V or (VIN+ 0.3V)

FB to GND ................................................................-0.3V to +6V

DL, COMP/EN to GND (MAX1966) ................-0.3V to V

IN

+ 0.3V

VL, DL, COMP/EN to GND (MAX1967).........-0.3V to V

CC

+ 0.3V

BST to LX..................................................................-0.3V to +6V

DH to LX........................................................-0.3V to BST + 0.3V

VL Short to GND (MAX1967) ....................................................5s

RMS Input Current (any pin).............................................±50mA

Continuous Power Dissipation (T

A

= +70°C)

8-Pin SO (derate 5.88mW/°C above +70°C)................471mW

10-Pin µMAX (derate 5.6mW/°C above +70°C) ...........444mW

Operating Temperature Range ...........................-40°C to +85°C

Junction Temperature......................................................+150°C

Storage Temperature Range .............................-65°C to +150°C

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

MAX1967 VIN Operating Range 4.9 28 V

MAX1967 Operating Range with
VIN = VL

MAX1966 VIN Operating Range 2.7 5.5 V

MAX1967 VL Undervoltage
Lockout (UVLO) Trip Level

MAX1966 VIN UVLO
Trip Level

Operating Supply Current FB = 0.88V, no switching 0.7 3 mA

V L Outp ut V ol tag e ( M AX 1967 Onl y)

Thermal Shutdown (Note 1) Rising temperature, typical hysteresis = 10°C 160 °C

OSCILLATOR

Frequency f

Minimum Duty Cycle 10 %

Maximum Duty Cycle 90 95 %

SOFT-START

Digital Ramp Period

Soft-Start Levels

ERROR AMPLIFIER

FB Regulation Voltage
(MAX1967)

FB Regulation Voltage
(MAX1966)

FB to COMP/EN Gain 4000 V/V

PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS

Rising and falling edge, hysteresis = 2% 2.35 2.53 2.66 V

Rising and falling edge, hysteresis = 2% 2.35 2.53 2.66 V

5.5V < VIN < 28V, 1mA < I
FB = 0.88V

OSC

0°C to +85°C 82 102 124

-40°C to +85°C 79 102 127

Internal 6-bit DAC for converter to ramp from

0 to full output voltage

2.7V < VCC < 5.5V, 0°C to +85°C 0.787 0.800 0.815

2.7V < VCC < 5.5V, -40°C to +85°C 0.782 0.800 0.815

2.7V < VIN < 5.5V, 0°C to +85°C 0.787 0.800 0.815

2.7V < VIN < 5.5V, -40°C to +85°C 0.782 0.800 0.815

< 25mA,

VL

2.7 5.5 V

4.67 5 5.3 V

1024 /

f

OSC

V

/

OUT

64

kHz

s

V

V

V

MAX1966/MAX1967

Low-Cost Voltage-Mode PWM

Step-Down Controllers

_______________________________________________________________________________________ 3

ELECTRICAL CHARACTERISTICS (continued)

(VIN = VL = VCC = 5V (MAX1967), VIN = 5V (MAX1966), TA= -40°C to +85°C, unless otherwise noted. Typical values are at
T

A

= +25°C.)

Note 1: Specifications to -40°C are guaranteed by design and not production tested.
Note 2: Thermal shutdown disables the buck regulator when the die reaches this temperature. Soft-start is reset and COMP/EN is

discharged to zero. In the MAX1967, the VL regulator remains on during thermal shutdown.

FB to COMP/EN
Transconductance

FB Input Bias Current V

COMP/EN Source Current V

Current-Limit Threshold Voltage
(Across Low-Side NFET)

MOSFET DRIVERS

Break-Before-Make Time 30 ns

DH On-Resistance in Low State V

DH On-Resistance in High State V

DH Peak Source and Sink
Current

DL On-Resistance in Low State I

DL On-Resistance in High State I

DL Source Current VDL = 2.5V 1 A

DL Sink Current VDL = 2.5V 2 A

Maximum Total (DH + DL)
Average Source Current

BST Leakage Current V

LX Leakage Current V

PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS

-5µA < I

COMP/EN

= 0.880V 3 100 nA

FB

COMP/EN

LX to GND -340 -305 -270 mV

= 5V, VLX = 0, I

BST

= 5V, VLX = 0, I

BST

V

= 5V, VLX = 0, DH = 2.5V 1 A

BST

= -50mA 1.1 2.5 Ω

DL

= 50mA 2.5 5.5 Ω

DL

= 5V, VLX = 0 25 mA

V

BST

= 33V, V

BST

= 33V, V

BST

< 5µA 70 108 160 µS

= 0 15 46 100 µA

= -50mA 1.6 4 Ω

DH

= 50mA 2.5 5.5 Ω

DH

= 28V 0 50 µA

LX

= 28V 33 100 µA

LX

MAX1966/MAX1967

Low-Cost Voltage-Mode PWM
Step-Down Controllers

4 _______________________________________________________________________________________

Typical Operating Characteristics

(TA = +25°C, unless otherwise noted.)

100

50

0.01 0.1 1 10

EFFICIENCY vs. LOAD CURRENT

(1.2V/3A)

60

MAX1966 toc01

LOAD CURRENT (A)

EFFICIENCY (%)

70

80

90

VIN = 5.0V

VIN = 3.3V

MAX1966
FIGURE 1

100

50

0.01 0.1 1 10

EFFICIENCY vs. LOAD CURRENT (1.8V/3A)

MAX1966

60

MAX1966 toc02

LOAD CURRENT (A)

EFFICIENCY (%)

70

80

90

VIN = 5.0V

VIN = 3.3V

MAX1966
FIGURE 1

100

50

0.01 0.1 1 10

EFFICIENCY vs. LOAD CURRENT (1.2V/5A)

MAX1966

60

MAX1966 toc03

LOAD CURRENT (A)

EFFICIENCY (%)

70

80

90

VIN = 5.0V

VIN = 5.0V

VIN = 3.3V

VIN = 3.3V

MAX1966
FIGURE 1

100

50

0.01 0.1 1 10

EFFICIENCY vs. LOAD CURRENT (1.8V/5A)

MAX1966

60

MAX1966 toc04

LOAD CURRENT (A)

EFFICIENCY (%)

70

80

90

VIN = 5.0V

VIN = 3.3V

MAX1966
FIGURE 1

100

50

0.01 0.1 1 10

EFFICIENCY vs. LOAD CURRENT (1.2V/3A)

MAX1967

60

MAX1966 toc05

LOAD CURRENT (A)

EFFICIENCY (%)

70

80

90

VIN = 5V

VIN = 12V

MAX1967
FIGURE 2

100

50

0.01 0.1 1 10

EFFICIENCY vs. LOAD CURRENT (1.8V/3A)

MAX1967

60

MAX1966 toc06

LOAD CURRENT (A)

EFFICIENCY (%)

70

80

90

VIN = 5V

VIN = 12V

MAX1967
FIGURE 2

100

50

0.01 0.1 1 10

EFFICIENCY vs. LOAD CURRENT (3.3V/3A)

MAX1967

60

MAX1966 toc07

LOAD CURRENT (A)

EFFICIENCY (%)

70

80

90

VIN = 5V

V

IN

= 12V

MAX1967
FIGURE 2

100

50

0.01 0.1 1 10

EFFICIENCY vs. LOAD CURRENT (1.2V/5A)

MAX1967

60

MAX1966 toc08

LOAD CURRENT (A)

EFFICIENCY (%)

70

80

90

VIN = 5V

VIN = 5V

VIN = 12V

VIN = 20V

MAX1967
FIGURE 2

100

50

0.01 0.1 1 10

EFFICIENCY vs. LOAD CURRENT (1.8V/5A)

MAX1967

60

MAX1966 toc09

LOAD CURRENT (A)

EFFICIENCY (%)

70

80

90

VIN = 5V

VIN = 12V

VIN = 20V

MAX1967
FIGURE 2

MAX1966/MAX1967

Low-Cost Voltage-Mode PWM

Step-Down Controllers

_______________________________________________________________________________________ 5

Typical Operating Characteristics (continued)

(TA = +25°C, unless otherwise noted.)

0

2

4

6

8

10

41491924

MAX1967 SUPPLY CURRENT

vs. INPUT VOLTAGE

MAX1966 toc14

INPUT VOLTAGE (V)

SUPPLY CURRENT (mA)

MAX1967
V

OUT

= 3.3V

0

2

4

6

8

10

2.5 4.03.53.0 4.5 5.55.0

MAX1966 SUPPLY CURRENT

vs. INPUT VOLTAGE

MAX1966 toc13

INPUT VOLTAGE (V)

SUPPLY CURRENT (mA)

MAX1966
V

OUT

= 1.8V

EFFICIENCY vs. LOAD CURRENT (3.3V/5A)

MAX1967

100

90

80

70

EFFICIENCY (%)

60

50

VIN = 5V

VIN = 12V

VIN = 24V

MAX1967
FIGURE 2

0.01 0.1 1 10
LOAD CURRENT (A)

MAX1966 toc10

FREQUENCY (kHz)

FREQUENCY vs. INPUT VOLTAGE

104

MAX1966

= 1.8V

V

OUT

102

100

98

2.5 7.0 16.011.5 20.5 25.0
INPUT VOLTAGE (V)

MAX1967

V

OUT

= 3.3V

MAX1966 toc11

FREQUENCY (kHz)

FREQUENCY vs. TEMPERATURE

130

120

110

100

90

80

-40 -25 20 355-10 50 8065
TEMPERATURE (°C)

MAX1966 toc12

LOAD STEP RESPONSE

VIN = 5.0V, V
L = 22µH

= 0.1 TO 3A

I

LOAD

V

OUT

I

OUT

INDUCTOR

CURRENT

OUT

= 1.8V

400ms/div

MAX1966 toc15

200mV/div

2A/div

2A/div

V

OUT

INDUCTOR

CURRENT

START-UP WAVEFORM

MAX1966 toc16

V

IN

NO LOAD

2ms/div

2V/div

1V/div

1A/div