Rainbow Electronics MAX15020 User Manual

General Description

The MAX15020 high-voltage step-down DC-DC con­verter operates over an input voltage range of 7.5V to
40V. The device integrates a 0.2Ω high-side switch and
is capable of delivering 2A load current with excellent
load and line regulation. The output is dynamically
adjustable from 0.5V to 36V through the use of an exter­nal reference input (REFIN). The MAX15020 consumes
only 6µA in shutdown mode.

The device utilizes feed-forward voltage-mode architec­ture for good noise immunity in the high-voltage switch­ing environment and offers external compensation for
maximum flexibility. The switching frequency is selec­table to 300kHz or 500kHz and can be synchronized to
an external clock signal of 100kHz to 500kHz by using
the SYNC input. The IC features a maximum duty cycle
of 95% (typ) at 300kHz.

The device includes configurable undervoltage lockout
(UVLO) and soft-start. Protection features include
cycle-by-cycle current limit, hiccup-mode for output
short-circuit protection, and thermal shutdown. The
MAX15020 is available in a 20-pin TQFN 5mm x 5mm
package and is rated for operation over the

-40°C to +125°C temperature range.

Applications

Printer Head Driver Power Supply

Automotive Power Supply

Industrial Power Supply

Step-Down Power Supply

Features

o Wide 7.5V to 40V Input Voltage Range

o 2A Output Current, Up to 96% Efficiency

o Dynamic Programmable Output Voltage (0.5V to

36V)

o Maximum Duty Cycle of 95% (typ) at 300kHz

o 100kHz to 500kHz Synchronizable SYNC

Frequency Range

o Configurable UVLO and Soft-Start

o Low-Noise, Voltage-Mode Step-Down Converter

o Programmable Output-Voltage Slew Rate

o Lossless Constant Current Limit with Fixed

Timeout to Hiccup Mode

o Extremely Low-Power Consumption (< 6µA typ) in

Shutdown Mode

o 20-Pin (5mm x 5mm) Thin QFN Package

MAX15020

2A, 40V Step-Down DC-DC Converter with

Dynamic Output-Voltage Programming

________________________________________________________________

Maxim Integrated Products

1

Ordering Information

MAX15020

ON/OFF

IN

DVREG

V

OUT

(0.5V TO 36V)

LX

REFOUT

REFIN

EP

SS

PWM

INPUT

V

IN

(7.5V TO 40V)

BST

FB

COMP

SYNC GND FSEL

PGND

REG

Typical Operating Circuit

19-0811; Rev 0; 4/07

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.

+

Denotes a lead-free package.

*

EP = Exposed pad.

PART

TEMP RANGE

PIN­PACKAGE

PKG

CODE

MAX15020ATP+

T2055-5

Pin Configuration appears at end of data sheet.

EVALUATION KIT

AVAILABLE

-40°C to +125°C

20 TQFN-EP*
(5mm x 5mm)

MAX15020

2A, 40V Step-Down DC-DC Converter with
Dynamic Output-Voltage Programming

2 _______________________________________________________________________________________

ABSOLUTE MAXIMUM RATINGS

ELECTRICAL CHARACTERISTICS

(VIN= 36V, V

REG

= V

DVREG

, V

PGND

= V

GND

= VEP= 0V, V

SYNC

= 0V, C

REFOUT

= 0.1µF, TA= TJ= -40°C to +125°C, FSEL = REG,

unless otherwise noted. Typical values are at T

A

= +25°C.) (Note 1)

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 GND........…....................................-0.3V to +45V

LX to GND................................................-0.715V to (V

IN

+ 0.3V)

BST to GND ..................................................-0.3V to (V

IN

+ 12V)

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

PGND, EP to GND .................................................-0.3V to +0.3V

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

FB, COMP, FSEL, REFIN, REFOUT,

SS to GND .............................................-0.3V to (V

REG

+ 0.3V)

Continuous Current through Internal Power MOSFET

T

J

= +125°C..........................................................................4A

T

J

= +150°C.......................................................................2.7A

Continuous Power Dissipation (T

A

= +70°C)
20-Pin Thin QFN, single-layer board (5mm x 5mm)

(derate 21.3mW/°C above +70°C)...........................1702.1mW

20-Pin Thin QFN, multilayer board (5mm x 5mm)

(derate 34.5mW/°C above +70°C)...........................2758.6mW

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

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

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

Input Voltage Range V

UVLO Rising Threshold UVLO

UVLO Falling Threshold UVLO

UVLO Hysteresis UVLO

Quiescent Supply Current VIN = 40V, VFB = 1.3V 1.6 2.8 mA

Switching Supply Current VIN = 40V, VFB = 0V 14.5 mA

Shutdown Current I

ON/OFF CONTROL

Input-Voltage Threshold V

Input-Voltage Threshold
Hysteresis

Input Bias Current V

Shutdown Threshold Voltage V

INTERNAL VOLTAGE REGULATOR (REG)

Output Voltage I

OSCILLATOR

Frequency f

Maximum Duty Cycle D

SYNC/FSEL High-Level Voltage 2 V

SYNC/FSEL Low-Level Voltage 0.8 V

SYNC Frequency Range f

PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS

IN

RISING

FALLING

HYST

SHDN

ON/OFF

SD

SW

MAX

SYNC

V

V

V

V

V

V

V

= 0.2V, VIN = 40V 6 15 µA

ON/OFF

rising 1.200 1.225 1.270 V

ON/OFF

= 0V to V

ON/OFF

= 0 to 20mA 7.1 8.3 V

REG

= 0V 450 550

FSEL

= V

FSEL

FSEL

FSEL

FSEL

REG

= 0V 85

= V

REG

= V

REG

IN

7.5 40.0 V

6.80 7.20 7.45 V

6.0 6.5 7.0 V

0.7 V

120 mV

-250 +250 nA

0.2 V

270 330

90

100 550 kHz

kHz

%

MAX15020

2A, 40V Step-Down DC-DC Converter with

Dynamic Output-Voltage Programming

_______________________________________________________________________________________ 3

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

ELECTRICAL CHARACTERISTICS (continued)

(VIN= 36V, V

REG

= V

DVREG

, V

PGND

= V

GND

= VEP= 0V, V

SYNC

= 0V, C

REFOUT

= 0.1µF, TA= TJ= -40°C to +125°C, FSEL = REG,

unless otherwise noted. Typical values are at T

A

= +25°C.) (Note 1)

SOFT-START/REFIN/REFOUT/FB

Soft-Start Current I

REFOUT Output Voltage 0.97 0.98 1.01 V

REFIN Input Range 0 3.6 V

FB Accuracy

FB Input Current VSS = 0.2V, VFB = 0V -250 +250 nA

Open-Loop Gain 80 dB

Unity-Gain Bandwidth 1.8 MHz

PWM Modulator Gain (VIN /
V

)

RAMP

CURRENT-LIMIT COMPARATOR

Cycle-by-Cycle Switch Current
Limit

Number of ILIM Events to Hiccup 4

Hiccup Timeout 512

POWER SWITCH

Switch On-Resistance V

BST Leakage Current V

Switch Leakage Current VIN = 40V, VLX = V

Switch Gate Charge V

THERMAL SHUTDOWN

Thermal Shutdown Temperature T

Thermal Shutdown Hysteresis 20 °C

PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS

SS

I

ILIM

SHDN

REFIN = REFOUT 0.97 0.98 1.01 V

FB = COMP, V

f

= 100kHz, VIN = 7.5V 9.4

SYNC

f

= 500kHz, VIN = 40V 8.9

SYNC

- VLX = 6V 0.18 0.35 Ω

BST

= VLX = VIN = 40V 10 µA

BST

- VLX = 6V 10 nC

BST

= 0.2V to 3.6V

REFIN

BST

81526µA

V

REFIN

- 5mV

= 0V 10 µA

V

REFIN

2.5 3.5 4.5 A

+160 °C

V

REFIN

+ 5mV

mV

V/V

—

Clock

periods

MAX15020

2A, 40V Step-Down DC-DC Converter with
Dynamic Output-Voltage Programming

4 _______________________________________________________________________________________

Typical Operating Characteristics

(VIN= 36V, Circuit of Figure 2, TA= +25°C, unless otherwise noted.)

UNDERVOLTAGE LOCKOUT HYSTERESIS

vs. TEMPERATURE

MAX15020 toc01

TEMPERATURE (°C)

UNDERVOLTAGE LOCKOUT HYSTERESIS

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

MAX15020 toc02

TEMPERATURE (°C)

ON/OFF THRESHOLD HYSTERESIS (V)

1108535 6010-15

0.05

0.10

0.15

0.20

0

-40 135

SHUTDOWN SUPPLY CURRENT

vs. INPUT VOLTAGE

MAX15020 toc03

INPUT VOLTAGE (V)

SUPPLY CURRENT (µA)

302010

1

2

3

4

5

6

7

0

040

NO-LOAD SUPPLY CURRENT

vs. INPUT VOLTAGE

MAX15020 toc04

INPUT VOLTAGE (V)

SUPPLY CURRENT (mA)

302010

2

4

8

6

10

12

14

16

0

040

OPERATING FREQUENCY

vs. TEMPERATURE

MAX15020 toc05

TEMPERATURE (°C)

OPERATING FREQUENCY (kHz)

1108535 6010-15

290

292

294

296

298

300

302

304

306

308

288

-40 135

MAXIMUM DUTY CYCLE

vs. INPUT VOLTAGE

MAX15020 toc06

INPUT VOLTAGE (V)

DUTY CYCLE (%)

302010

86

88

82

84

90

92

94

96

98

100

80

040

LOOP GAIN/PHASE

vs. FREQUENCY

MAX15020 toc07

FREQUENCY (kHz)

GAIN (dB)

PHASE (DEGREES)

100101

-40

-30

-20

-10

0

10

20

30

40

50

-50

-144

-108

-72

-36

0

36

72

108

144

180

-180

0.1 1000

PHASE

VIN = 37V, V

OUT

= 15V,

I

OUT

= 2.02A

GAIN

MAXIMUM LOAD CURRENT

vs. INPUT VOLTAGE

MAX15020 toc08

INPUT VOLTAGE (V)

LOAD CURRENT (A)

353020 2510 155

2.6

2.7

2.8

2.9

3.0

3.1

3.2

3.3

3.4

3.5

2.5
040

TA = -45°C

TA = +25°C

TA = +85°C

MAX15020

2A, 40V Step-Down DC-DC Converter with

Dynamic Output-Voltage Programming

_______________________________________________________________________________________

5

Typical Operating Characteristics (continued)

(VIN= 36V, Circuit of Figure 2, TA= +25°C, unless otherwise noted.)

LOAD TRANSIENT

MAX15020 toc14

200µs/div

50mV/div
AC-COUPLED

2A

1A

I

OUT

V

OUT

VIN = 12V, V

OUT

= 3.3V

LOAD TRANSIENT

MAX15020 toc15

200µs/div

50mV/div
AC-COUPLED

1.2A

0.2A

V

OUT

I

OUT

VIN = 12V, V

OUT

= 3.3V

TURN-ON/TURN-OFF WAVEFORM

V

OUT

VIN = 40V, R

MAX15020 toc12

V

ON/OFF

TURN-ON/TURN-OFF WAVEFORM

V

OUT

VIN = 12V, R

= 27Ω

LOAD

100

90

80

70

60

50

40

EFFICIENCY (%)

30

20

10

0

MAX15020 toc09

5V/div

V

ON/OFF

0V

1V/div

0V

10ms/div

EFFICIENCY vs. LOAD CURRENT

VIN = 7.5V

VIN = 12V

VIN = 24V

VIN = 40V

0.01 10
OUTPUT CURRENT (A)

fS = 500kHz
V

10.1

OUT

= 3.3V

LOAD

= 27Ω

10ms/div

MAX15020 toc10

REFOUT VOLTAGE vs. TEMPERATURE

1.05

5V/div

0V

1V/div

0V

1.03

1.01

0.99

REFOUT VOLTAGE (V)

0.97

0.95

-40 135

TEMPERATURE (°C)

EFFICIENCY vs. LOAD CURRENT

100

90

80

70

60

50

40

EFFICIENCY (%)

30

20

10

0

0.01 10
OUTPUT CURRENT (A)

10.1

fS = 500kHz

= 40V

V

IN

= 30V

V

OUT

MAX15020 toc11

11085603510-15

MAX15020 toc13

MAX15020

2A, 40V Step-Down DC-DC Converter with
Dynamic Output-Voltage Programming

6 _______________________________________________________________________________________

Typical Operating Characteristics (continued)

(VIN= 36V, Circuit of Figure 2, TA= +25°C, unless otherwise noted.)

HEAVY-LOAD

SWITCHING WAVEFORMS

MAX15020 toc20

1µs/div

20V/div

0V

1A/div

0A

I

LX

V

LX

I

LOAD

= 2A

FEEDBACK VOLTAGE

vs. REFIN INPUT VOLTAGE

MAX15020 toc21

REFIN INPUT VOLTAGE (V)

FEEDBACK VOLTAGE (V)

321

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

0

04

LOAD TRANSIENT

V

OUT

I

OUT

VIN = 40V, V

LIGHT-LOAD SWITCHING WAVEFORMS

V

LX

OUT

= 30V

200µs/div

MAX15020 toc16

MAX15020 toc18

50mV/div
AC-COUPLED

2A

1A

20V/div

0V

LOAD TRANSIENT

V

OUT

I

OUT

VIN = 40V, V

OUT

= 30V

200µs/div

SWITCHING WAVEFORMS

V

LX

MAX15020 toc17

50mV/div
AC-COUPLED

1.1A

0.25A

MAX15020 toc19

20V/div

0V

I

LX

I

= 40mA

LOAD

1µs/div

1A/div

0A

I

LX

I

= 500mA

LOAD

1µs/div

1A/div

0A