Rainbow Electronics MAX5081 User Manual

General Description

The MAX5080/MAX5081 are 250kHz PWM step-down
DC-DC converters with an on-chip, 0.3Ω high-side
switch. The input voltage range is 4.5V to 40V for the
MAX5080 and 7.5V to 40V for the MAX5081. The output
is adjustable from 1.23V to 32V and can deliver up to
1A of load current.

Both devices utilize a voltage-mode control scheme for
good noise immunity in the high-voltage switching envi­ronment and offer external compensation allowing for
maximum flexibility with a wide selection of inductor val­ues and capacitor types. The switching frequency is
internally fixed at 250kHz and can be synchronized to
an external clock signal through the SYNC input. Light
load efficiency is improved by automatically switching
to a pulse-skip mode.

All devices include programmable undervoltage lock­out and soft-start. Protection features include cycle-by­cycle current limit, hiccup-mode output short-circuit
protection, and thermal shutdown. Both devices are
available in a space-saving, high-power (2.7W), 16-pin
TQFN package and are rated for operation over the

-40°C to +125°C temperature range.

Applications

FireWire®Power Supplies Automotive

Distributed Power Industrial

Features

♦ 4.5V to 40V (MAX5080) or 7.5V to 40V (MAX5081)

Input Voltage Range

♦ 1A Output Current

♦ V

OUT

Range From 1.23V to 32V

♦ Internal High-Side Switch

♦ Fixed 250kHz Internal Oscillator

♦ Automatic Switchover to Pulse-Skip Mode at

Light Loads

♦ External Frequency Synchronization

♦ Thermal Shutdown and Short-Circuit Protection

♦ Operates Over the -40°C to +125°C Temperature

Range

♦ Space-Saving (5mm x 5mm) High-Power 16-Pin

TQFN Package

MAX5080/MAX5081

1A, 40V, MAXPower Step-Down

DC-DC Converters

________________________________________________________________ Maxim Integrated Products 1

19-3656; Rev 0; 5/05

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.

Ordering Information

Typical Operating Circuits

FireWire is a registered trademark of Apple Computer, Inc.

Typical Operating Circuits continued at end of data sheet.

*EP = Exposed pad.

Pin Configurations appear at end of data sheet.

PART TEMP RANGE PIN-PACKAGE

MAX5080ATE -40°C to +125°C 16 TQFN-EP*

MAX5081ATE -40°C to +125°C 16 TQFN-EP*

V

IN

4.5V TO 40V

IN

R1

C1

R2

C2

PGND

REG

ON/OFF

SYNC SGND PGND SS COMP

DVREG

C-

MAX5080

D1

C

F

C

BST

C+

LX

FB

C

SS

BST

L1

C6

D2

C8

R5

C5

C7

R3

R6

R4

V

OUT

PGND

MAX5080/MAX5081

1A, 40V, MAXPower Step-Down
DC-DC Converters

2 _______________________________________________________________________________________

ABSOLUTE MAXIMUM RATINGS

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.

IN, ON/OFF to SGND..............................................-0.3V to +45V

LX to SGND .................................................-0.3V to (V

IN

+ 0.3V)

BST to SGND ................................................-0.3V to (V

IN

+ 12V)

BST to LX................................................................-0.3V to +12V

PGND to SGND .....................................................-0.3V to +0.3V

REG, DVREG, SYNC to SGND ...............................-0.3V to +12V

FB, COMP, SS to SGND ...........................-0.3V to (V

REG

+ 0.3V)

C+ to PGND (MAX5080 only)................(V

DVREG

- 0.3V) to +12V

C- to PGND (MAX5080 only)................-0.3V to (V

DVREG

+ 0.3V)
Continuous current through internal power MOSFET (pins 11/12
connected together and pins 13/14 connected together)

T

J

= +125°C.........................................................................3A

T

J

= +150°C.........................................................................2A

Continuous Power Dissipation

*

(TA= +70°C)

16-Pin TQFN (derate 33.3mW/°C above +70°C) ...2666.7mW
16-Pin TQFN (θ

JA

)........................................................30°C/W

16-Pin TQFN (θ

JC

).......................................................1.7°C/W

Operating Temperature Range .........................-40°C to +125°C

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

Storage Temperature Range .............................-60°C to +150°C

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

ELECTRICAL CHARACTERISTICS

(VIN= V

ON/OFF

= 12V, V

REG

= V

DVREG

, V

SYNC

= PGND = SGND, TA= TJ= -40°C to +125°C, unless otherwise noted. Typical values

are at T

A

= + 25°C.) (Note 1)

*As per JEDEC 51 Standard

Input Voltage Range V

Undervoltage Lockout Threshold UVLO

Undervoltage Lockout Hysteresis UVLO

Switching Supply Current (PWM
Operation)

Efficiency

No-Load Supply Current
(PFM Operation)

Shutdown Current I

ON/OFF CONTROL

Input Voltage Threshold V

Input Voltage Hysteresis 0.12 V

Input Bias Current V

ERROR AMPLIFIER/SOFT-START

Soft-Start Current I

Reference Voltage (Soft-Start) V

FB Regulation Voltage V

FB Input Range 0 1.5 V

FB Input Current -250 +250 nA

COMP Voltage Range I

Open-Loop Gain 80 dB

Unity-Gain Bandwidth 1.8 MHz

PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS

MAX5080 4.5 40

IN

MAX5081 7.5 40

VIN rising, MAX5080 3.9 4.2

rising, MAX5081 6.8 7.3

V

IN

MAX5080 0.4

HYST

MAX5081 0.7

I

SW

VFB = 0V, MAX5080 10.5

VFB = 0V, MAX5081 9.5

VIN = 12V, V

= 4.5V, V

V

IN

OUT

OUT

(MAX5080)

MAX5080 1.4 2.5

MAX5081 1.3 2.3

SS

FB

V

I

SHDN

ON/ OFFVON/ OFF

SS

= 0V, VIN = 40V 200 300 µA

ON/OFF

rising 1.20 1.23 1.25 V

= 0 to 40V -250 +250 nA

ON/OFF

= -500µA to +500µA 1.215 1.228 1.240 V

COMP

= -500µA to +500µA 0.25 4.50 V

COMP

= 3.3V, I

= 3.3V, I

= 1A 84

OUT

= 1A

OUT

88

81524µA

1.215 1.228 1.240 V

V

V

V

mA

%

mA

MAX5080/MAX5081

1A, 40V, MAXPower Step-Down

DC-DC Converters

_______________________________________________________________________________________ 3

ELECTRICAL CHARACTERISTICS (continued)

(VIN= V

ON/OFF

= 12V, V

REG

= V

DVREG

, V

SYNC

= PGND = SGND, TA= TJ= -40°C to +125°C, unless otherwise noted. Typical values

are at T

A

= + 25°C.) (Note 1)

FB Offset Voltage I

OSCILLATOR

Frequency f

Maximum Duty Cycle D

SYNC High-Level Voltage 2.2 V

SYNC Low-Level Voltage 0.8 V

SYNC Frequency Range f

PWM Modulator Gain f

Ramp Level Shift (Valley) 0.3 V

POWER SWITCH

Switch On-Resistance V

Switch Gate Charge V

Switch Leakage Current VIN = 40V, VLX = V

BST Leakage Current V

CHARGE PUMP

C- Output Voltage Low MAX5080 only, sinking 10mA 0.1 V

C- Output Voltage High

DVREG to C+ On-Resistance MAX5080 only, sourcing 10mA 10 Ω
LX to PGND On-Resistance Sinking 10mA 12 Ω

CURRENT-LIMIT COMPARATOR

Pulse-Skip Threshold I

Cycle-by-Cycle Current Limit I

Number of Consecutive ILIM
Events to Hiccup

Hiccup Timeout 512

INTERNAL VOLTAGE REGULATOR

Output Voltage V

Line Regulation

Load Regulation I

Dropout Voltage

PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS

SYNC

= -500µA to +500µA -5 +5 mV

COMP

V

SW

MAX

PFM

ILIM

REG

= 0V 225 250 275 kHz

SYNC

V

= 0V, V

SYNC

V

= 0V, VIN = 7.5V, MAX5081 87

SYNC

V

= 0V, VIN ≤ 40V 87

SYNC

= 150kHz to 350kHz 10 V/V

SYNC

- V

BST

LX

- VLX = 6V 6 nC

BST

= VLX = VIN = 40V 10 µA

BST

MAX5080 only, relative to DVREG, sourcing
10mA

MAX5080 4.75 5 5.25

MAX5081 7.6 8 8.4

VIN = 5.5V to 40V, MAX5080 1

V

= 9.0V to 40V, MAX5081 1

IN

= 0 to 20mA 0.25 V

REG

VIN = 4.5V, I

= 7.5V, I

V

IN

= 4.5V, MAX5080 87

IN

150 350 kHz

= 6V 0.3 0.6 Ω

= 0V 10 µA

BST

0.1 V

100 200 300 mA

1.4 2 2.6 A

7

= 20mA, MAX5080 0.5

REG

= 20mA, MAX5081 0.5

REG

periods

%

Clock

V

mV/V

V

MAX5080/MAX5081

1A, 40V, MAXPower Step-Down
DC-DC Converters

4 _______________________________________________________________________________________

ELECTRICAL CHARACTERISTICS (continued)

(VIN= V

ON/OFF

= 12V, V

REG

= V

DVREG

, V

SYNC

= PGND = SGND, TA= TJ= -40°C to +125°C, unless otherwise noted. Typical values

are at T

A

= + 25°C.) (Note 1)

Note 1: 100% production tested at TA= +25°C and TA= TJ= +125°C. Limits at -40°C are guaranteed by design.

Typical Operating Characteristics

(VIN= 12V, see Figure 5 (MAX5080) and Figure 6 (MAX5081), TA= +25°C, unless otherwise noted.)

UNDERVOLTAGE LOCKOUT HYSTERESIS

vs. TEMPERATURE (MAX5080)

MAX5080 toc01

TEMPERATURE (°C)

UNDERVOLTAGE LOCKOUT HYSTERESIS (V)

1108535 6010-15

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

0

-40 135

UNDERVOLTAGE LOCKOUT HYSTERESIS

vs. TEMPERATURE (MAX5081)

MAX5080 toc02

TEMPERATURE (°C)

UNDERVOLTAGE LOCKOUT HYSTERESIS (V)

1108535 6010-15

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

0

-40 135

ON/OFF THRESHOLD HYSTERESIS

vs. TEMPERATURE

MAX5080 toc03

TEMPERATURE (°C )

ON/OFF THRESHOLD HYSTERESIS (V)

11085603510-15

0.05

0.10

0.15

0.20

0

-40 135

SHUTDOWN SUPPLY CURRENT
vs. INPUT VOLTAGE (MAX5080)

MAX5080 toc04

INPUT VOLTAGE (V)

SHUTDOWN SUPPLY CURRENT (µA)

353020 2510 155

25

50

75

100

125

150

175

200

225

250

0

040

TA = +135°C

TA = +25°C

TA = +85°C

TA = -40°C

V

ON/OFF

= 0V

SHUTDOWN SUPPLY CURRENT
vs. INPUT VOLTAGE (MAX5081)

MAX5080 toc05

INPUT VOLTAGE (V)

SHUTDOWN SUPPLY CURRENT (µA)

353020 2510 155

25

50

75

100

125

150

175

200

225

250

275

300

0

040

TA = +135°C

TA = +25°C

TA = +85°C

TA = -40°C

V

ON/OFF

= 0V

NO-LOAD SUPPLY CURRENT

vs. INPUT VOLTAGE (MAX5080)

MAX5080 toc06

INPUT VOLTAGE (V)

SUPPLY CURRENT (mA)

35305 10 15 20 25

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

0

040

TA = +135°C

TA = +25°C

TA = +85°C

TA = -40°C

THERMAL SHUTDOWN

Thermal Shutdown Temperature Temperature rising +160 °C
Thermal Shutdown Hysteresis 20 °C

PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS

OPERATING FREQUENCY

vs. TEMPERATURE

MAX5080 toc07

TEMPERATURE (°C)

OPERATING FREQUENCY (kHz)

1108535 6010-15

242

244

246

248

250

252

254

256

258

260

240

-40 135

VIN = 4.5V

VIN = 40V

MAXIMUM DUTY CYCLE

vs. INPUT VOLTAGE (MAX5080)

MAX5080 toc08

INPUT VOLTAGE (V)

MAXIMUM DUTY CYCLE (%)

353020 2510 155

82

84

86

88

90

92

94

96

98

100

80

040

MAXIMUM DUTY CYCLE

vs. INPUT VOLTAGE (MAX5081)

MAX5080 toc09

INPUT VOLTAGE (V)

MAXIMUM DUTY CYCLE (%)

353020 2510 155

82

84

86

88

90

92

94

96

98

100

80

040

MAX5080/MAX5081

1A, 40V, MAXPower Step-Down

DC-DC Converters

_______________________________________________________________________________________ 5

Typical Operating Characteristics (continued)

(VIN= 12V, see Figure 5 (MAX5080) and Figure 6 (MAX5081), TA= +25°C, unless otherwise noted.)

OPEN-LOOP GAIN/PHASE vs. FREQUENCY

MAX5080 toc10

FREQUENCY (kHz)

GAIN (dB)

PHASE (DEGREES)

10001001010.10.010.001

0

20

40

60

80

100

-20

75

100

125

150

175

50

0 10,000

GAIN

PHASE

OUTPUT CURRENT LIMIT

vs. INPUT VOLTAGE

MAX5080 toc11

INPUT VOLTAGE (V)

OUTPUT CURRENT LIMIT (A)

353020 2510 155

1.6

1.7

1.8

1.9

2.0

2.1

2.2

2.3

2.4

2.5

1.5
040

MAX5080

TA = +135°C

TA = +25°C

TA = +85°C

TA = -40°C

TURN-ON/OFF WAVEFORM

MAX5080 toc12

I

LOAD

= 1A

V

OUT

2V/div

V

ON/OFF

2V/div

2ms/div

TURN-ON/OFF WAVEFORM

MAX5080 toc13

V

ON/OFF

2V/div

V

OUT

2V/div

2ms/div

I

LOAD

= 100mA

Typical Operating Characteristics (continued)

(VIN= 12V, see Figure 5 (MAX5080) and Figure 6 (MAX5081), TA= +25°C, unless otherwise noted.)

MAX5080/MAX5081

1A, 40V, MAXPower Step-Down
DC-DC Converters

6 _______________________________________________________________________________________

OUTPUT VOLTAGE vs. TEMPERATURE

3.40
MAX5080

3.38

3.36

3.34

3.32

3.30

3.28

OUTPUT VOLTAGE (V)

3.26

3.24

3.22

3.20

I

= 0A

LOAD

I

= 1A

LOAD

-40 135
TEMPERATURE (°C)

EFFICIENCY vs. LOAD CURRENT

100

V

= 5V

OUT

90

80

70

60

50

EFFICIENCY (%)

40

30

20

0

0.001 1

VIN = 7.5V

VIN = 12V

LOAD CURRENT (A)

VIN = 40V

0.10.01

1108535 6010-15

VIN = 24V

MAX5081

MAX5080 toc14

MAX5080 toc16

EFFICIENCY vs. LOAD CURRENT

100

V

= 3.3V

OUT

90

80

70

60

50

EFFICIENCY (%)

40

30

20

0

0.001 1

VIN = 7.5V

VIN = 4.5V

VIN = 24V

VIN = 40V

0.10.01

LOAD CURRENT (A)

LOAD-TRANSIENT RESPONSE

0

VIN = 12V, I
MAX5080

= 0.25A TO 1A

OUT

200µs/div

VIN = 12V

MAX5080

MAX5080 toc17

MAX5080 toc15

V

OUT

AC-COUPLED
200mV/div

I

LOAD

500mA/div