Rainbow Electronics MAX15046B User Manual

19-4719; Rev 0; 7/09

Typical Operating Circuit

40V, High-Performance, Synchronous

General Description

The MAX15046 synchronous step-down controller oper­ates from a 4.5V to 40V input voltage range and gener­ates an adjustable output voltage from 85% of the input
voltage down to 0.6V, supporting loads up to 25A. The
device allows monotonic startup into a prebiased bus
without discharging the output and features adaptive
internal digital soft-start.

The MAX15046 offers the ability to adjust the switching
frequency from 100kHz to 1MHz with an external resis­tor. The MAX15046’s adaptive synchronous rectifica­tion eliminates the need for an external freewheeling
Schottky diode. The device also utilizes the external
low-side MOSFET’s on-resistance as a current-sense
element, eliminating the need for a current-sense resis­tor. This protects the DC-DC components from damage
during output overloaded conditions or output short­circuit faults without requiring a current-sense resistor.
Hiccup-mode current limit reduces power dissipation
during short-circuit conditions. The MAX15046 includes
a power-good output and an enable input with precise
turn-on/turn-off threshold, which can be used for input
supply monitoring and for power sequencing.

Additional protection features include sink-mode current
limit, and thermal shutdown. Sink-mode current limit pre­vents reverse inductor current from reaching dangerous
levels when the device is sinking current from the output.

Buck Controller

Features

S Input Voltage Ranges from 4.5V to 40V or 5V

Q10%

S Adjustable Outputs from 0.85 x V
S Adjustable Switching Frequency (100kHz to 1MHz)

with Q10% (1MHz) Accuracy

S Adaptive Internal Digital Soft-Start
S Up to 25A Output Capability
S Cycle-by-Cycle Valley-Mode Current Limit with

Adjustable, Temperature-Compensated Threshold
(30mV to 300mV)

S Monotonic Startup into Prebiased Output
S Q1% Accurate Voltage Reference
S 3A-Peak Gate Drivers
S Hiccup-Mode Short-Circuit Protection (Patent-

Pending Architecture)

S Overtemperature Shutdown
S Power-Good (PGOOD) Output and Enable Input

(EN) with Q5% Accurate Threshold

S Thermally Enhanced 16-Pin QSOP Package

Applications

Industrial Power Supplies (PLC, Industrial
Computers, Fieldbus Components, Fieldbus
Couplers)

Telecom Power Supplies
Base Stations

Ordering Information

Down to 0.6V

IN

MAX15046

The MAX15046 is available in a 16-pin QSOP or 16-pin
QSOP-EP package and operates over the -40NC to +125NC
temperature range.

Pin Configurations appear at end of data sheet.

4.5V TO 40V
V

IN

ON

OFF

R4

C1

IN

MAX15046

V

CC

PGOOD

EN

LIM

C5

R3

C6

C7

R1

COMP

FB

RT

R3

+
*EP = Exposed pad.

CSP

DH

LX

BST

DL

DRV

PGND

GND

R2

PART TEMP RANGE PIN-PACKAGE

MAX15046AAEE+ -40°C to +125°C 16 QSOP
MAX15046BAEE+ -40°C to +125°C 16 QSOP-EP*

Denotes a lead(Pb)-free/RoHS-compliant package.

Q1

C3

0.6V TO 0.85V x V
V

OUT

IN

L1

C2

D1

C4

R5

Q2

_______________________________________________________________ Maxim Integrated Products 1

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.

40V, High-Performance, Synchronous
Buck Controller

ABSOLUTE MAXIMUM RATINGS

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

VCC to GND ..................... -0.3V to lower of (VIN + 0.6V) and 6V

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

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

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

DL to PGND .............................................-0.3V to (V

BST to PGND .......................................................-0.3V to +50V

LX and CSP to PGND ...............................................-1V to +45V

LX and CSP to PGND ............................-2V (50ns max) to +45V

MAX15046

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

CSP to LX .............................................................-0.3V to +0.3V

DH to LX .................................................. -0.3V to (V

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

VCC Short Circuit to GND ..........................................Continuous

PGOOD Maximum Sink Current .........................................20mA

Note 1: Package thermal resistances were obtained using the method described in JEDEC specification JESD51-7, using a four-lay-

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

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.

DRV

BST

+ 0.3V)

+ 0.3V)

ELECTRICAL CHARACTERISTICS

(VIN = 24V, VEN = 5V, V
noted. Typical values are at TA = +25NC.) (Note 2)

GND

= V

= 0V, CIN = 1FF, C

PGND

VCC

Continuous Power Dissipation (TA = +70NC):

16-Pin QSOP (derate 9.6mW/NC above +70NC) .......771.5mW

16-Pin QSOP-EP (derate 22.7mW/NC above +70NC) 1818.2mW
Junction-to-Case Thermal Resistance (θJC) (Note 1)

16-Pin QSOP ................................................................37NC/W

16-Pin QSOP-EP ............................................................6NC/W

Junction-to-Ambient Thermal Resistance (θJA) (Note 1)

16-Pin QSOP ...........................................................103.7NC/W

16-Pin QSOP-EP ..........................................................44NC/W

Operating Temperature Range ........................ -40NC to +125NC

Junction Temperature .....................................................+150NC

Storage Temperature Range ............................ -65NC to +150NC

Lead Temperature (soldering, 10s) ................................+300NC

= 4.7FF, RRT = 49.9kI, TA = TJ = -40NC to +125NC, unless otherwise

PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS

SYSTEM SPECIFICATIONS

Input-Voltage Range V

Quiescent Supply Current I

Shutdown Supply Current I

VCC REGULATOR

Output Voltage V
VCC Regulator Dropout VIN = 4.5V, I
VCC Short-Circuit Output Current VIN = 5V 30 55 90 mA
VCC Undervoltage Lockout V

VCC Undervoltage Lockout
Hysteresis

ERROR AMPLIFIER (FB, COMP)

FB Input-Voltage Set Point V
FB Input Bias Current I
FB to COMP Transconductance g
Open-Loop Gain 80 dB

Unity-Gain Bandwidth

IN

IN_Q

IN_SBY

VCC

CCUVLO

FB

FB

M

VIN = VCC = V
VIN = 24V, VFB = 0.9V, no switching 2 3 mA

VIN = 24V, VEN = 0V, I
PGOOD = unconnected

6V ≤ VIN ≤ 40V, I

V

rising 3.8 4 4.2 V

VCC

VFB = 0.6V -250 +250 nA
I

= Q20FA

COMP

Capacitor from COMP to GND =
47pF

DRV

= 0,

VCC

= 6mA 5 5.25 5.5 V

LOAD

= 25mA 0.18 0.45 V

LOAD

4.5 40

4.5 5.5

0.35 0.55 mA

400 mV

584 590 596 mV

600 1200 1800

5 MHz

V

FS

2 ______________________________________________________________________________________

40V, High-Performance, Synchronous

Buck Controller

ELECTRICAL CHARACTERISTICS (continued)

(VIN = 24V, VEN = 5V, V
noted. Typical values are at TA = +25NC.) (Note 2)

PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS

V

COMP-RAMP

COMP Source/Sink Current I

ENABLE (EN)

EN Input High V
EN Input Low V
EN Input Leakage Current I

OSCILLATOR

Switching Frequency (100kHz) f
Switching Frequency (300kHz) f
Switching Frequency (1MHz) f

Switching Frequency Adjustment
Range

RT Voltage V

PWM MODULATOR

PWM Ramp Peak-to-Peak
Amplitude

PWM Ramp Valley V
Minimum Controllable On-Time 70 125 ns
Maximum Duty Cycle
Minimum Low-Side On-Time

OUTPUT DRIVERS/DRIVERS SUPPLY (V

Undervoltage Lockout V

DRV Undervoltage Lockout
Hysteresis

DH On-Resistance

DL On-Resistance

DH Peak Current C

Minimum Voltage 200 mV

GND

= V

= 0V, CIN = 1FF, C

PGND

COMP

EN_H

EN_L

EN

SW

SW

SW

RT

V

RAMP

VALLEY

DRV

DRV_UVLOVDRV

= 4.7FF, RRT = 49.9kI, TA = TJ = -40NC to +125NC, unless otherwise

VCC

V

= 1.4V 50 80 110

COMP

VEN rising 1.14 1.20 1.26 V
VEN falling 1.05 V
VEN = 5.5V -1 +1

RRT = 150kI
RRT = 49.9kI
RRT = 14.3kI

(Note 3) 100 1000 kHz

RRT = 49.9kI

fSW = 300kHz (RRT = 49.9kI)
fSW = 1MHz (RRT = 49.9kI)

)

rising 4.0 4.2 4.4 V

Low, sinking 100mA,
V

- VLX = 5V

BST

High, sourcing 100mA,
V

- VLX = 5V

BST

Low, sinking 100mA,
V

= VCC = 5.25V

DRV

High, sourcing 100mA,
V

= VCC = 5.25V

DRV

Sinking,
V

- VLX = 5V

LOAD

= 10nF

BST

Sourcing,
V

- VLX = 5V

BST

80 100 120 kHz

270 300 330 kHz

0.9 1 1.1 MHz

1.15 1.2 1.25 V

1.5 V

1.5 V

85 87.5 %

110 ns

400 mV

1 3

1.5 4

1 3

1.5 4

3

2

MAX15046

FA

FA

I

A

_______________________________________________________________________________________ 3

40V, High-Performance Synchronous
Buck Controller

ELECTRICAL CHARACTERISTICS (continued)

(VIN = 24V, VEN = 5V, V
noted. Typical values are at TA = +25NC.) (Note 2)

PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS

DL Peak Current C

MAX15046

DH, DL Break-Before-Make Time
(Dead Time)

SOFT-START

Soft-Start Duration 2048

Reference Voltage Steps 64 Steps

CURRENT LIMIT/HICCUP

Cycle-by-Cycle Valley Current­Limit Threshold Adjustment
Range

GND

= V

= 0V, CIN = 1FF, C

PGND

= 4.7FF, RRT = 49.9kI, TA = TJ = -40NC to +125NC, unless otherwise

VCC

= 10nF

LOAD

V

- V

CSP

PGND

valley limit =
V

/10

LIM

Sinking, V
= 5.25V

Sourcing, V
VCC = 5.25V

V

LIM

,

V

LIM

= VCC

DRV

=

DRV

= 0.3V 30

= 3V 300

3

2

10 ns

Switching

A

Cycles

mV

LIM Reference Current I

LIM Reference Current
Temperature Coefficient

CSP Input Bias Current V

Number of Consecutive Current­Limit Events to Hiccup

Hiccup Timeout 4096

Peak Low-Side Sink Current-Limit
Threshold

POWER-GOOD (PGOOD)

PGOOD Threshold VFB rising 90 94 97.5 %V
PGOOD Threshold Hysteresis VFB falling 2.65 %V
PGOOD Output Low Voltage V
PGOOD Output Leakage Current I

THERMAL SHUTDOWN

Thermal Shutdown Threshold Temperature rising +150
Thermal Shutdown Hysteresis 20

Note 2: All devices are 100% tested at room temperature and guaranteed by design over the specified temperature range.

Note 3: Select RRT as:

R

=

RT

f (1 x 10 )(f )

+

SW SW

LIM

PGOOD_LIPGOOD

LEAK_PGOODVPGOOD

×

-7 2

9

17.3 10

V

= 0.3V to 3V, TA = +25NC

LIM

= 40V -1 +1

CSP

7 Events

V

- V

CSP

R

= 30kI, V

ILIM

TA = +25NC

, where fSW is in Hertz.

, sink limit = V

PGND

= 1.5V,

LIM

= 2mA, VEN = 0V 0.4 V

= 40V, VEN = 5V, VFB = 1V -1 +1

LIM

/20,

45 50 55

2300

75 mV

ppm/NC

Switching

Cycles

FA

FA

FB

FB

FA

NC
NC

4 ______________________________________________________________________________________

40V, High-Performance Synchronous

EFFICIENCY vs. LOAD CURRENT

EFFICIENCY (%)

EFFICIENCY vs. LOAD CURRENT

EFFICIENCY (%)

V

(V)

FREQUENCY (kHz)

FREQUENCY (kHz)

Buck Controller

Typical Operating Characteristics

(VIN = 24V, TA = +25NC, unless otherwise noted.)

MAX15046

(VIN = 24V)

100

90

80

70

60

50

40

30

20

10

0

V

= 3.3V

OUT

V

= 1.8V

OUT

V

= 5V

OUT

0 15

LOAD CURRENT (A)

VCC vs. LOAD CURRENT

5.256

5.254

5.252

5.250

(V)

CC

V

5.248

5.246

5.244

5.242

LOAD CURRENT (mA)

(VIN = 12V)

100

90

MAX15046 toc01

80

70

V

= 1.2V

OUT

12963

60

50

40

30

20

10

0

0 15

V

= 1.2V

OUT

V

= 1.8V

OUT

V

OUT

LOAD CURRENT (A)

= 3.3V

V

= 5V

OUT

12963

0.50

0.45

MAX15046 toc02

0.40

0.35

0.30

0.25

0.20

0.15

% OUTPUT FROM NORMAL

0.10

0.05

0

VCC LINE REGULATION

MAX15046 toc05

(V)
V

CC

5.266

5.265

5.264

5.263

5.262

5.261

5.260

4035302520151050 45

MAX15046 toc04

5.2

I

= 5mA, 10mA, 20mA, 30mA

5.0

4.8

CC

4.6

4.4

4.2

4.0
0 40

VCC

I

VCC

= 40mA

VIN (V)

3530252015105

V

vs. LOAD CURRENT

OUT

0 12

LOAD CURRENT (A)

108642

VCC vs. TEMPERATURE

I

= 5mA

LOAD

-40 125
TEMPERATURE (NC)

1109580655035205-10-25

MAX15046 toc03

MAX15046 toc06

SWITCHING FREQUENCY

vs. R

1000

900

800

700

600

500

400

300

200

100

0

0 160

RT

RRT (kI)

_______________________________________________________________________________________ 5

SWITCHING FREQUENCY

vs. TEMPERATURE

1200

1000

MAX15046 toc07

800

600

400

200

0

1208040

-40 125

RT = 25.5kI

TEMPERATURE (NC)

RT = 14.3kI

RT = 49.9kI

RT = 150kI

MAX15046 toc08

1109580655035205-10-25

2.8
CDH = CDL = 0

2.7

2.6

(mA)

2.5

IN

I

2.4

2.3

2.2

100 1000

IIN vs.

SWITCHING FREQUENCY

MAX15046 toc09

FREQUENCY (kHz)

40V, High-Performance, Synchronous
Buck Controller

Typical Operating Characteristics (continued)

(VIN = 24V, TA = +25NC, unless otherwise noted.)

LIM REFERENCE CURRENT

vs. TEMPERATURE

80

75

70

MAX15046

65

60

CURRENT (FA)

55

50

45

40

-40 125
TEMPERATURE (NC)

LOAD TRANSIENT ON OUT (1A TO 15A)

200Fs/div

11095-25 -10 5 35 50 6520 80

MAX15046 toc12b

SINK AND SOURCE CURRENT LIMIT

THRESHOLDS vs. RESISTANCE (R

0.20

0.15

0.10

MAX15046 toc10

0.05

0

-0.05

-0.10

-0.15

-0.20

CURRENT-LIMIT THRESHOLD (V)

-0.25

-0.30

-0.35
0 70

LOAD TRANSIENT ON OUT (1A TO 6A)

V

OUT

200mV/div

I

OUT

5A/div

SINK CURRENT LIMIT

SOURCE CURRENT LIMIT

RESISTANCE (kI)

200Fs/div

ILIM

605030 402010

MAX15046 toc12c

)

MAX15046 toc11

V

OUT

100mV/div

I

OUT

5A/div

LOAD TRANSIENT ON OUT (1A TO 10A)

200Fs/div

MAX15046 toc12a

STARTUP DISABLE FROM EN

= 3.3I)

(R

LOAD

4ms/div

MAX15046 toc13

V

OUT

200mV/div

I

OUT

5A/div

IN
20V/div

EN
5V/div

V

OUT

2V/div

PGOOD
5V/div

STARTUP AND DISABLE FROM IN

= 3.3kI)

(R

LOAD

20ms/div

MAX15046 toc14

IN
10V/div

V

OUT

2V/div

PGOOD
5V/div

STARTUP WITH PREBIASED

OUTPUT (4.0V)

4ms/div

MAX15046 toc15a

24V

IN
10V/div

4V

V

OUT

2V/div

PGOOD
5V/div

STARTUP WITH PREBIASED

OUTPUT (1.0V)

4ms/div

6 ______________________________________________________________________________________

MAX15046 toc15b

24V

IN
10V/div

1V

V

OUT

2V/div

PGOOD
5V/div

40V, High-Performance, Synchronous

STARTUP WITH PREBIASED

Buck Controller

Typical Operating Characteristics (continued)

(VIN = 24V, TA = +25NC, unless otherwise noted.)

MAX15046

OUTPUT (2V)

4ms/div

MAX15046 toc15c

V

OUT

= 3.3V

DH_ AND DL_ DISOVERLAP

40ns/div

24V

IN
10V/div

2V

V

OUT

2V/div

PGOOD
5V/div

MAX15046 toc17a

STARTUP WITH PREBIASED

OUTPUT (0.5V)

V

DH

20V/div

V

DL

5V/div

V

LX

20V/div

4ms/div

MAX15046 toc15d

V

OUT

= 3.3V

SINK CURRENT-LIMIT WAVEFORMS

24V

V

IN

10V/div

0.5V

V

OUT

2V/div

PGOOD
5V/div

DH_ AND DL_ DISOVERLAP

40ns/div

(5V PREBIASED)

200Fs/div

MAX15046 toc17b

MAX15046 toc16

V

DH

20V/div

V

DL

5V/div

V

LX

20V/div

V

OUT

500mV/div

V

LX

50V/div

I

LX

5A/div

OUTPUT SHORT-CIRCUIT BEHAVIOUR

OUTPUT VOLTAGE AND CURRENT

10ms/div

MAX15046 toc18

V

OUT

200mV/div

I

OUT

10A/div

LINE-TRANSIENT RESPONSE

10ms/div

MAX15046 toc19

24V

V

IN

200mV/div

5V

V

OUT

(AC-COUPLED)
200mV/div

_______________________________________________________________________________________ 7

MONITOR