Rainbow Electronics MAX15038 User Manual

General Description

The MAX15038 high-efficiency switching regulator
delivers up to 4A load current at output voltages from

0.6V to 90% of VIN. The IC operates from 2.9V to 5.5V,
making it ideal for on-board point-of-load and postregu­lation applications. Total output error is less than ±1%
over load, line, and temperature ranges.

The MAX15038 features fixed-frequency PWM mode
operation with a switching frequency range of 500kHz
to 2MHz set by an external resistor. The MAX15038
provides the option of operating in a pulse-skip mode
to improve light-load efficiency. High-frequency opera­tion allows for an all-ceramic capacitor design. The
high operating frequency also allows for small-size
external components.

The low-resistance on-chip nMOS switches ensure high
efficiency at heavy loads while minimizing critical induc­tances, making the layout a much simpler task with
respect to discrete solutions. Following a simple layout
and footprint ensures first-pass success in new designs.

The MAX15038 comes with a high bandwidth (28MHz)
voltage-error amplifier. The voltage-mode control archi­tecture and the voltage-error amplifier permit a type III
compensation scheme to be utilized to achieve maxi­mum loop bandwidth, up to 20% of the switching fre­quency. High loop bandwidth provides fast transient
response, resulting in less required output capacitance
and allowing for all-ceramic-capacitor designs.

The MAX15038 provides two three-state logic inputs to
select one of nine preset output voltages. The preset
output voltages allow customers to achieve ±1% out­put-voltage accuracy without using expensive 0.1%
resistors. In addition, the output voltage can be set to
any customer value by either using two external resis­tors at the feedback with a 0.6V internal reference or
applying an external reference voltage to the REFIN
input. The MAX15038 offers programmable soft-start
time using one capacitor to reduce input inrush current.

Applications

Server Power Supplies
POLs
ASIC/CPU/DSP Core and I/O Voltages
DDR Power Supplies
Base-Station Power Supplies
Telecom and Networking Power Supplies
RAID Control Power Supplies

Features

o Internal 31mΩ R

DS(ON)

High-Side and 24mΩ

R

DS(ON)

Low-Side MOSFETs

o Continuous 4A Output Current Over Temperature
o ±1% Output Accuracy Over Load, Line, and

Temperature

o Operates from 2.9V to 5.5V V

IN

Supply

o Adjustable Output from 0.6V to (0.9 x VIN)
o Soft-Start Reduces Inrush Supply Current
o 500kHz to 2MHz Adjustable Switching Frequency
o Compatible with Ceramic, Polymer, and

Electrolytic Output Capacitors

o Nine Preset and Adjustable Output Voltages

0.6V, 0.7V, 0.8V, 1.0V, 1.2V, 1.5V, 1.8V, 2.0V,

2.5V, and Adjustable

o Monotonic Startup for Safe-Start into Prebiased

Outputs

o Selectable Forced PWM or Skip Mode for Light

Load Efficiency

o Overcurrent and Overtemperature Protection
o Output Current Sink/Source Capable with Cycle-

by-Cycle Protection

o Open-Drain Power-Good Output
o Lead-Free, 4mm x 4mm, 24-Pin Thin QFN Package

MAX15038

4A, 2MHz Step-Down Regulator

with Integrated Switches

________________________________________________________________

Maxim Integrated Products

1

Typical Operating Circuit

Ordering Information

19-4320; Rev 0; 10/08

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

+

Denotes a lead-free/RoHS-compliant package.

*

EP = Exposed pad.

Pin Configuration appears at end of data sheet.

EVALUATION KIT

AVAILABLE

PART TEMP RANGE PIN-PACKAGE

MAX15038ETG+ -40°C to +85°C 24 Thin QFN-EP*

INPUT

2.9V TO 5.5V
IN

EN

V

DD

CTL2

CTL1

FREQ

REFIN

SS

MODE

MAX15038

GND

BST

OUT

PGND

COMP

PWRGD

OUTPUT

V

1.8V, 4A

DD

LX

FB

MAX15038

4A, 2MHz Step-Down Regulator
with Integrated Switches

2 _______________________________________________________________________________________

ABSOLUTE MAXIMUM RATINGS

ELECTRICAL CHARACTERISTICS

(VIN= VEN= 5V, C

VDD

= 2.2µF, TA= TJ= -40°C to +85°C, typical values are at TA= +25°C, circuit of Figure 1, unless otherwise

noted.) (Note 3)

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, PWRGD to GND..................................................-0.3V to +6V

V

DD

to GND..................-0.3V to the lower of +4V or (VIN+ 0.3V)

COMP, FB, MODE, REFIN, CTL1, CTL2, SS,

FREQ to GND ..........................................-0.3V to (V

DD

+ 0.3V)

OUT, EN to GND ......................................................-0.3V to +6V

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

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

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

LX to PGND ..................-0.3V to the lower of +6V or (V

IN

+ 0.3V)

LX to PGND ..........-1V to the lower of +6V or (V

IN

+ 1V) for 50ns

I

LX(RMS)

(Note 1) ......................................................................4A

V

DD

Output Short-Circuit Duration .............................Continuous

Converter Output Short-Circuit Duration ....................Continuous

Continuous Power Dissipation (T

A

= +70°C)

24-Pin TQFN (derate 27.8mW/°C above +70°C) ........2222mW

Thermal Resistance (Note 2)

θ

JA

.................................................................................36°C/W

θ

JC

..................................................................................6°C/W

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

Note 1: LX has internal clamp diodes to PGND and IN. Applications that forward bias these diodes should take care not to exceed

the IC’s package power dissipation limits.

Note 2: Package thermal resistances were obtained using the method described in JEDEC specification JESD51-7, using a four-

layer board. For detailed information on package thermal considerations, refer to www.maxim-ic.com/thermal-tutorial

.

IN

IN Voltage Range 2.9 5.5 V

IN Supply Current fS = 1MHz, no load

Total Shutdown Current from IN

3.3V LDO (VDD)

VDD Undervoltage Lockout
Threshold

VDD Output Voltage VIN = 5V, I

VDD Dropout VIN = 2.9V, I

V

DD

BST

BST Supply Current V

PWM COMPARATOR

PWM Comparator Propagation
Delay

PWM Peak-to-Peak Ramp
Amplitude

PWM Valley Amplitude 0.8 V

PARAMETER CONDITIONS MIN TYP MAX UNITS

Current Limit VIN = 5V, VDD = 0 25 40 mA

VIN = 5V, VEN = 0 10 20

= VDD = 3.3V, VEN = 0 45

V

IN

LX starts/stops switching

= 0 to 10mA 3.1 3.3 3.5 V

VDD

= 10mA 0.08 V

VDD

= VIN = 5V, VLX = 0 or 5V, VEN = 0 0.025 µA

BST

10mV overdrive 20 ns

VIN = 3.3V 4.7 8

= 5V 5 8.5

V

IN

VDD rising 2.6 2.8

VDD falling 2.35 2.55

Minimum glitch-width
rejection

10 µs

1V

mA

µA

V

MAX15038

4A, 2MHz Step-Down Regulator

with Integrated Switches

_______________________________________________________________________________________ 3

ELECTRICAL CHARACTERISTICS (continued)

(VIN= VEN= 5V, C

VDD

= 2.2µF, TA= TJ= -40°C to +85°C, typical values are at TA= +25°C, circuit of Figure 1, unless otherwise

noted.) (Note 3)

PARAMETER CONDITIONS MIN TYP MAX UNITS

ERROR AMPLIFIER

COMP Clamp Voltage, High VIN = 2.9V to 5V, VFB = 0.5V, V

COMP Clamp Voltage, Low VIN = 2.9V to 5V, VFB = 0.7V, V

COMP Slew Rate VFB step from 0.5V to 0.7V in 10ns 1.6 V/µs

COMP Shutdown Resistance

Internally Preset Output Voltage
Accuracy

FB Set Point Value CTL1 = CTL2 = GND, MODE = GND 0.594 0.6 0.606 V
FB to OUT Resistor All VID settings except CTL1 = CTL2 = GND 5.5 8 10.5 kΩ

Open-Loop Voltage Gain 115 dB

Error-Amplifier Unity-Gain
Bandwidth

Error-Amplifier Common-Mode
Input Range

Error-Amplifier Maximum Output
Current

FB Input Bias Current CTL1 = CTL2 = GND -125 nA

CTL_

CTL_ Input Bias Current

CTL_ Input Threshold

Hysteresis All VID transitions 50 mV

REFIN

REFIN Input Bias Current V

REFIN Offset Voltage V

LX (All Pins Combined)

LX On-Resistance, High-Side ILX = -2A

LX On-Resistance, Low-Side ILX = 2A

LX Leakage Current VIN = 5V, VEN = 0

= 0.6V 2 V

REFIN

= 0.6V 0.7 V

REFIN

From COMP to GND, V
V

= VSS = 0

EN

V

= VSS, MODE = GND -1 +1 %

REFIN

V

= 2.9V to 3.5V 0 V

DD

V

= 1V,

COMP

V

= 0.6V

REFIN

V

= 0 -7.2

CTL_

= V

V

CTL_

Low, falling 0.8

Float VDD/2

High, rising

REFIN

REFIN

High-side sourcing 5.7 7

Low-side sinking 7LX Current-Limit Threshold

Zero-crossing current threshold, MODE = V

DD

= 0.6V -185 nA

= 0.9V, FB shorted to COMP -4.5 +4.5 mV

= 3.3V, V

IN

VFB = 0.7V, sinking 1

V

= 0.5V, sourcing -1

FB

VIN = V

V

IN

VIN = 3.3V 30

V

IN

- VLX = 3.3V 42

BST

= V

- VLX = 5V 31 54

BST

= 5V 24 42

= 100mV,

COMP

DD

VLX = 0 -0.01

= 5V +0.01

V

LX

6 Ω

28 MHz

+7.2

V

-

DD

0.8

0.2

- 2 V

DD

mA

µA

V

mΩ

mΩ

A

µA

MAX15038

4A, 2MHz Step-Down Regulator
with Integrated Switches

4 _______________________________________________________________________________________

ELECTRICAL CHARACTERISTICS (continued)

(VIN= VEN= 5V, C

VDD

= 2.2µF, TA= TJ= -40°C to +85°C, typical values are at TA= +25°C, circuit of Figure 1, unless otherwise

noted.) (Note 3)

LX Switching Frequency V

Switching Frequency Range 500 2000 kHz

LX Minimum Off-Time 78 ns

LX Maximum Duty Cycle R

LX Minimum Duty Cycle R

Average Short-Circuit IN Supply
Current

RMS LX Output Current 4A

ENABLE

EN Input Logic-Low Threshold EN falling 0.9 V

EN Input Logic-High Threshold EN rising 1.5 V

EN Input Current VEN = 0 or 5V, VIN = 5V 0.01 µA

MODE

MODE Input-Logic Hysteresis MODE falling 5 % V

MODE Input Bias Current

SS

SS Current VSS = 0.45V, V

THERMAL SHUTDOWN

Thermal-Shutdown Threshold Rising 165 °C

Thermal-Shutdown Hysteresis 25 °C

POWER-GOOD (PWRGD)

Power-Good Threshold Voltage

Power-Good Edge Deglitch VFB rising or falling 48

PWRGD Output Voltage Low I

PWRGD Leakage Current VIN = V

HICCUP OVERCURRENT LIMIT

Current-Limit Startup Blanking 112

Autoretry Restart Time 896

PARAMETER CONDITIONS MIN TYP MAX UNITS

R

= 49.9kΩ 0.9 1 1.1

= 2.9V to 5V

IN

= 49.9kΩ 92 95 %

FREQ

= 49.9kΩ 515%

FREQ

OUT connected to GND, V

Logic-low, falling 26

Logic VDD/2 or floating, rising 50MODE Input-Logic Threshold

Logic-high, rising 74

MODE = GND -5

MODE = V

VFB falling, V

V

FB

PWRGD

DD

= 0.6V, sourcing 6.7 8 9.3 µA

REFIN

= 0.6V 88 90 92

REFIN

rising, V

= 4mA 0.03 0.1 V

PWRGD

= 0.6V 92.5

REFIN

= 5V, VFB = 0.7V, V

= 5V 0.15 A

IN

FREQ

= 23.6kΩ 1.8 2 2.2

R

FREQ

5

= 0.6V 0.01 µA

REFIN

MHz

% V

DD

DD

µA

%

V

REFIN

Clock

cycles

Clock

cycles

Clock

cycles

MAX15038

4A, 2MHz Step-Down Regulator

with Integrated Switches

_______________________________________________________________________________________

5

Typical Operating Characteristics

(Typical values are VIN= VEN= 5V, V

OUT

= 1.8V, R

FREQ

= 49.9kΩ, I

OUT

= 4A, TA= +25°C, circuit of Figure 1, unless otherwise noted.)

ELECTRICAL CHARACTERISTICS (continued)

(VIN= VEN= 5V, C

VDD

= 2.2µF, TA= TJ= -40°C to +85°C, typical values are at TA= +25°C, circuit of Figure 1, unless otherwise

noted.) (Note 3)

Note 3: Specifications are 100% production tested at TA= +25°C. Limits over the operating temperature range are guaranteed by design.

PARAMETER CONDITIONS MIN TYP MAX UNITS

FB Hiccup Threshold VFB falling 70

Hiccup Threshold Blanking Time VFB falling 28 µs

V

REFIN

%

EFFICIENCY

vs. OUTPUT CURRENT

100

90

80

70

EFFICIENCY (%)

60

50

40

0.1 10.0
OUTPUT CURRENT (A)

V

= 2.5V

OUT

V

= 1.8V

OUT

V

= 1.2V

OUT

1.0

MAX15038 toc01

EFFICIENCY

vs. OUTPUT CURRENT

100

90

80

70

EFFICIENCY (%)

60

50

VIN = 3.3V

40

0.1 10.0
OUTPUT CURRENT (A)

V

= 2.5V

OUT

V

= 1.8V

OUT

V

= 1.2V

OUT

1.0

MAX15038 toc02

FREQUENCY (MHz)

FREQUENCY

vs. INPUT VOLTAGE

2.20

2.15

2.10

2.05

2.00

1.95

1.90

1.85

1.80

2.5 5.5

TA = -40°C

INPUT VOLTAGE (V)

TA = +25°C

R

TA = +85°C

FREQ

= 23.2k

5.04.53.0 3.5 4.0

Ω

MAX15038 toc03

FREQUENCY

vs. INPUT VOLTAGE

1.20

1.15

1.10

1.05

1.00

0.95

FREQUENCY (MHz)

0.90

0.85

0.80

2.5 5.5

TA = +25°C

TA = -40°C

INPUT VOLTAGE (V)

R

FREQ

TA = +85°C

= 49.9k

5.04.53.0 3.5 4.0

Ω

0

-0.05

-0.10

MAX15038 toc04

-0.15

-0.20

V

-0.25

-0.30

-0.35

OUTPUT-VOLTAGE CHANGE (%)

-0.40

-0.45

-0.50

OUT

04

LOAD REGULATION

= 1.2V

V

= 1.8V

OUT

LOAD CURRENT (A)

LINE REGULATION (LOAD = 4A)

0

-0.02

MAX15038 toc05a

-0.04

-0.06

V

= 2.5V

OUT

321

-0.08

OUTPUT-VOLTAGE CHANGE (%)

-0.10

-0.12

2.5 5.5
INPUT VOLTAGE (V)

V

= 2.5V

OUT

= 1.8V

5.04.54.03.53.0

MAX15038 toc05b

V

OUT

V

= 1.2V

OUT

MAX15038

4A, 2MHz Step-Down Regulator
with Integrated Switches

6 _______________________________________________________________________________________

Typical Operating Characteristics (continued)

(Typical values are VIN= VEN= 5V, V

OUT

= 1.8V, R

FREQ

= 49.9kΩ, I

OUT

= 4A, TA= +25°C, circuit of Figure 1, unless otherwise noted.)

LOAD TRANSIENT

MAX15038 toc06

40µs/div

V

OUT

AC-COUPLED
100mV/div

2A

I

OUT

0A

SWITCHING WAVEFORMS
(FORCED PWM, 2A LOAD)

MAX15038 toc07

400ns/div

AC-COUPLED
50mV/div

V

OUT

I

LX

V

LX

2A/div

0A

5V/div

SWITCHING WAVEFORMS

(SKIP MODE, NO LOAD)

MAX15038 toc08

2µs/div

AC-COUPLED
100mV/div

V

OUT

I

LX

V

LX

1A/div

0A

0V

5V/div

SOFT-START WAVEFORM

(R

LOAD

= 0.5Ω)

MAX15038 toc09

400µs/div

V

EN

5V/div

0V

V

OUT

1V/div

SHUTDOWN WAVEFORM

(R

LOAD

= 0.5Ω)

MAX15038 toc10

10µs/div

V

EN

5V/div

0V

V

OUT

1V/div

INPUT SHUTDOWN CURRENT

vs. INPUT VOLTAGE

MAX15038 toc11

INPUT VOLTAGE (V)

INPUT SHUTDOWN CURRENT (µA)

5.04.54.03.53.0

6

7

8

9

10

11

12

5

2.5 5.5

VEN = 0V

MAXIMUM OUTPUT CURRENT

vs. OUTPUT VOLTAGE

MAX15038 toc12

OUTPUT VOLTAGE (V)

MAXIMUM OUTPUT CURRENT (A)

2.01.51.0

3

4

5

6

7

8

9

10

2

0.5 2.5