Rainbow Electronics MAX15023 User Manual

General Description

The MAX15023 dual, synchronous step-down controller
operates from a 5.5V to 28V or 5V ±10% input voltage
range and generates two independent output voltages.
Each output is adjustable from 85% of the input voltage
down to 0.6V and supports loads of 12A or higher. Input
voltage ripple and total RMS input ripple current are
reduced by interleaved 180° out-of-phase operation.

The MAX15023 offers the ability to adjust the switching
frequency from 200kHz to 1MHz with an external resistor.
The MAX15023’s adaptive synchronous rectification elimi­nates the need for external freewheeling Schottky diodes.
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 DC­DC components from damage during output overloaded
conditions or output short-circuit faults without requiring a
current-sense resistor. Hiccup-mode current limit reduces
power dissipation during short-circuit conditions. The
MAX15023 includes two independent power-good out­puts and two independent enable inputs with precise
turn-on/turn-off thresholds, which can be used for supply
monitoring and for power sequencing.

Additional protection features include cycle-by-cycle,
low-side, sink peak current limit, and thermal shutdown.
Cycle-by-cycle, low-side, sink peak current limit prevents
reverse inductor current from reaching dangerous levels
when the device is sinking current from the output. The
MAX15023 also allows prebiased startup without dis­charging the output and features adaptive internal digital
soft-start. This new proprietary feature enables monoton­ic charging of externally large output capacitors at start­up, and achieves good control of the peak inductor
current during hiccup-mode short-circuit protection.

The MAX15023 is available in a space-saving and ther­mally enhanced 4mm x 4mm, 24-pin TQFN-EP pack­age. The device operates over the -40°C to +85°C
extended temperature range.

Applications

Point-of-Load Regulators

Set-Top Boxes

LCD TV Secondary Supplies

Switches/Routers

Power Modules

DSP Power Supplies

Features

o 5.5V to 28V or 5V ±10% Input Supply Range
o 0.6V to (0.85 x VIN) Adjustable Outputs
o Adjustable 200kHz to 1MHz Switching Frequency
o Guaranteed Monotonic Startup into a Prebiased

Load

o Lossless, Cycle-by-Cycle, Low-Side, Source Peak

Current Limit with Adjustable, Temperature­Compensated Threshold

o Cycle-by-Cycle, Low-Side, Sink Peak Current-

Limit Protection

o Proprietary Adaptive Internal Digital Soft-Start
o ±1% Accurate Voltage Reference
o Internal Boost Diodes
o Adaptive Synchronous Rectification Eliminates

External Freewheeling Schottky Diodes

o Hiccup-Mode Short-Circuit Protection and

Thermal Shutdown

o Power-Good Outputs and Analog Enable Inputs

for Power Sequencing

MAX15023

Wide 4.5V to 28V Input, Dual-Output

Synchronous Buck Controller

________________________________________________________________

Maxim Integrated Products

1

Pin Configuration

Ordering Information

19-4219; Rev 0; 7/08

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.

EVALUATION KIT

AVAILABLE

PART TEMP RANGE

PIN-PACKAGE

MAX15023ETG+

24 TQFN-EP*

+

Denotes a lead-free/RoHS-compliant package.

*

EP = Exposed pad.

-40°C to +85°C

TOP VIEW

CC

SGND

LIM2

LIM1

COMP1

FB2

COMP2

1718 16 14 13

RT

19

20

IN

21

22

23

+

24

12

FB1

EN1

V

15

MAX15023

456

3

EN2

TQFN

PGOOD2

*EP

PGOOD1

DL2

DL1

PGND2

12

11

10

9

8

7

PGND1

LX2

BST2

DH2

DH1

BST1

LX1

*EXPOSED PAD (CONNECT TO GROUND).

MAX15023

Wide 4.5V to 28V Input, Dual-Output
Synchronous Buck Controller

2 _______________________________________________________________________________________

ABSOLUTE MAXIMUM RATINGS

ELECTRICAL CHARACTERISTICS

(VIN= 12V, RT = 33kΩ, C

VCC

= 4.7µF, C

IN

= 1µF, TA= -40°C to +85°C, unless otherwise noted. Typical values are at TA= +25°C.)

(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.

Note 1: These power limits are due to the thermal characteristics of the package, absolute maximum junction temperature (150°C),

and the JEDEC 51-7 defined setup. Maximum power dissipation could be lower, limited by the thermal shutdown protection
included in this IC.

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 http://www.maxim-ic.com/thermal-tutorial

.

IN to SGND.............................................................-0.3V to +30V

BST_ to V

CC

............................................................-0.3V to +30V

LX_ to SGND .............................................................-1V to +30V

EN_ to SGND............................................................-0.3V to +6V

PGOOD_ to SGND .................................................-0.3V to +30V

BST_ to LX_ ..............................................................-0.3V to +6V

DH_ to LX_ ..........................................….-0.3V to (V

BST_

+ 0.3V)

DL_ to PGND_ ............................................-0.3V to (V

CC

+ 0.3V)

SGND to PGND_ .................................................. -0.3V to +0.3V

V

CC

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

IN

+ 0.3V)

All Other Pins to SGND...............................-0.3V to (V

CC

+ 0.3V)
V

CC

Short Circuit to SGND.........................................Continuous

V

CC

Input Current (IN = VCC, internal LDO not used) ......600mA

PGOOD_ Sink Current ........................................................20mA

Continuous Power Dissipation (T

A

= +70°C)(Note 1)

24-Pin TQFN-EP (derate 27.8mW/°C above +70°C) ..2222.2mW

Junction-to-Case Thermal Resistance (θ

JC

)

24-Pin TQFN-EP ..............................................................3°C/W

Junction-to-Ambient Thermal Resistance (θ

JA

)(Note 2)

24-Pin TQFN-EP ............................................................36°C/W

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

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

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

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

PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS

GENERAL

Input Voltage Range V

Quiescent Supply Current I

Standby Supply Current I

VCC REGULATOR

Output Voltage V

VCC Regulator Dropout I

VCC Short-Circuit Output Current VIN = 5V 150 250 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

Amplifier Open-Loop Gain No load 80 dB

Amplifier Unity-Gain Bandwidth 10 MHz

CC_UVLOVCC

IN

VIN = V

V

IN

IN_SBYVEN1

CC

FB_

FB_

g

m

FB1

6V < VIN < 28V, I

VIN = 6V, 1mA < I

LOAD

V

FB_

I

COMP

CC

= V

= V

falling 3.6 3.8 4 V

= 0.9V, no switching 4.5 6 mA

FB2

= SGND 0.21 0.35 mA

EN2

= 5mA

LOAD

< 100mA

LOAD

= 100mA 0.07 V

= 0.6V -250 +250 nA

= ±40µA 650 1200 1900 µS

5.5 28

4.5 5.5

5.00 5.2 5.50 V

430 mV

594 600 606 mV

V

MAX15023

Wide 4.5V to 28V Input, Dual-Output

Synchronous Buck Controller

_______________________________________________________________________________________ 3

ELECTRICAL CHARACTERISTICS (continued)

(VIN= 12V, RT = 33kΩ, C

VCC

= 4.7µF, C

IN

= 1µF, TA= -40°C to +85°C, unless otherwise noted. Typical values are at TA= +25°C.)

(Note 3)

PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS

COMP_ Swing (High) 2.4 V

COMP_ Swing (Low) No load at COMP_ 0.6 V

COMP_ Source/Sink Current I

ENABLE (EN_)

EN_ Input High V

EN_ Input Hysteresis V

EN_ Input Leakage Current I

OSCILLATOR

Switching Frequency f

Switching Frequency
Adjustment Range

PWM Ramp Peak-to-Peak
Amplitude

PWM Ramp Valley V

Phase Shift Between
Channels

Minimum Controllable On-Time 60 100 ns

Maximum Duty Cycle 86 87.5 %

OUTPUT DRIVERS

DH_ On-Resistance

DL_ On-Resistance

DH_ Peak Current C

DL_ Peak Current C

DH_, DL_ Break-Before-Make
Time (Dead Time)

SOFT-START

Soft-Start Duration 2048

Reference Voltage Steps 64 Steps

LEAK_EN_

COMP_

EN_H

EN_HYS

SW

V

RAMP

VALLEY

| I

EN_ rising 1.15 1.20 1.25 V

Each converter 460 500 540 kHz

(Note 4) 200 1000 kHz

From DH1 to DH2 rising edges 180 Degrees

Low, sinking 100mA, V

H i g h, sour ci ng 100m A, V

Low, sinking 100mA, VCC = 5.2V 0.75

High, sourcing 100mA, V

COMP_

LOAD

LOAD

|, V

COMP_

= 10nF

= 10nF

= 1.5V 45 80 120 µA

150 mV

-250 +250 nA

1.42 V

0.72 V

- V

BST_

B S T _

CC

Sinking 3

Sourcing 2

Sinking 3

Sourcing 2

= 5V 1

LX_

- V

= 5V 1.2

L X _

= 5.2V 1.4

15 ns

Switching

Ω

Ω

A

A

cycles

MAX15023

Wide 4.5V to 28V Input, Dual-Output
Synchronous Buck Controller

4 _______________________________________________________________________________________

ELECTRICAL CHARACTERISTICS (continued)

(VIN= 12V, RT = 33kΩ, C

VCC

= 4.7µF, C

IN

= 1µF, TA= -40°C to +85°C, unless otherwise noted. Typical values are at TA= +25°C.)

(Note 3)

Note 3: All

Electrical Characteristics

limits over temperature are 100% tested at room temperature and guaranteed by design over

the specified temperature range.

Note 4: Select R

T

as

CURRENT LIMIT/HICCUP

Cycle-by-Cycle, Low-Side,
Source Peak Current-Limit
Threshold Adjustment Range

LIM_ Reference Current I

LIM_ Reference Current TC V

Number of Consecutive Current­Limit Events to Hiccup

Hiccup Timeout Out of soft-start 7936

Cycle-by-Cycle, Low-Side,
Sink Peak Current-Limit Sense
Voltage

BOOST

Boost Switch Resistance VIN = VCC = 5.2V, I

POWER-GOOD OUTPUTS

PGOOD_ Threshold

PGOOD_ Output Leakage I

PGOOD_ Output Low Voltage V

THERMAL SHUTDOWN

Thermal Shutdown Threshold Temperature rising +150 °C

Thermal Shutdown Hysteresis Temperature falling 20 °C

PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS

LIM_

LEAK_PGDVPGOOD_

PGOOD_LIPGOOD_

Source peak limit = V

V

= 0.3V to 3V, TA = +25°C 45 50 55 µA

LIM_

= 0.3V 2400 ppm/°C

LIM_

V

rising 88.5 92.5 96.5

FB_

falling 85.5 89.5 93.5

V

FB_

= 28V, V

= 2mA, EN_ = SGND 0.4 V

/10 30 300 mV

LIM_

7 Events

/

V

L IM _

24

= 10mA 4.5 8 Ω

BST_

EN_

= 5V, V

= 0.8V 1 µA

FB_

Switching

cycles

V

%

V

FB( N OM IN A L)

Rk

()

Ω= ×

T

fkHz

(())

SW

24806

.

1 0663

(

24806

has a

1

farad

unit

).

MAX15023

Wide 4.5V to 28V Input, Dual-Output

Synchronous Buck Controller

_______________________________________________________________________________________ 5

Typical Operating Characteristics

(Supply = IN = 12V, unless otherwise noted. See

Typical Application Circuit

of Figure 6.)

EFFICIENCY

vs. LOAD CURRENT

95

V

90
85
80
75
70
65
60
55

EFFICIENCY (%)

50
45
40
35
30

0.1 100

= 3.3V

OUT1

LOAD CURRENT (A)

MAX15023 toc01

V

= 1.2V

OUT1

VIN = 12V

101

VCC VOLTAGE

vs. LOAD CURRENT

5.40

5.35

5.30

5.25

5.20

5.15

SUPPLY VOLTAGE (V)

5.10

5.05

5.00
0 150

LOAD CURRENT (mA)

MAX15023 toc04

13512015 30 45 75 9060 105

EFFICIENCY

vs. LOAD CURRENT

100

95
90
85
80
75
70
65
60

EFFICIENCY (%)

55
50
45
40
35
30

V

= 3.3V

OUT1

0.1 100
LOAD CURRENT (A)

VCC VOLTAGE

vs. IN VOLTAGE

5.50

5.35

5.20

5.05

4.90

4.75

VOLTAGE (V)

4.60

CC

V

4.45

4.30

4.15

4.00
428

I

= 5mA

LOAD

I

= 50mA

LOAD

IN VOLTAGE (V)

V

OUT1

= 1.2V

VIN = VCC = 5V

101

OUTPUT VOLTAGE CHANGE

101.0

100.8

MAX15023 toc02

100.6

100.4

100.2

100.0

99.8

99.6

OUTPUT VOLTAGE CHANGE (%)

99.4

99.2

99.0
012

5.50

I

= 5mA

LOAD

5.45

5.40

MAX15023 toc05

5.35

5.30

5.25

5.20

SUPPLY VOLTAGE (V)

5.15

5.10

5.05

5.00

242016128

-40 85

vs. LOAD CURRENT

MAX15023 toc03

OUT1

108642

LOAD CURRENT (A)

VCC VOLTAGE

vs. TEMPERATURE

MAX15023 toc06

303510-15

TEMPERATURE (°C)

SWITCHING FREQUENCY

vs. R

1300
1200
1100
1000

900
800
700
600
500
400

SWITCHING FREQUENCY (kHz)

300
200
100

10 90

T

RT (kΩ)

SWITCHING FREQUENCY

vs. TEMPERATURE

800
750
700

MAX15023 toc07

650
600
550
500
450
400
350

SWITCHING FREQUENCY (kHz)

300

RT = 66.5kΩ

250
200

807050 6030 4020

-40 85

RT = 22.1kΩ

RT = 33.2kΩ

603510-15

TEMPERATURE (°C)

MAX15023 toc08

210

VIN = 12V

180

150

120

90

CURRENT (mA)

IN

I

60

30

0

200 1000

IIN CURRENT

vs. SWITCHING FREQUENCY

CDL = C

= 10nF

DH

CDL = C

DH

CDL = C

CDL = C

= 0nF

DH

SWITCHING FREQUENCY (kHz)

= 4.7nF

= 1nF

DH

MAX15023 toc09

900800700600500400300

MAX15023

Wide 4.5V to 28V Input, Dual-Output
Synchronous Buck Controller

6 _______________________________________________________________________________________

Typical Operating Characteristics (continued)

(Supply = IN = 12V, unless otherwise noted. See

Typical Application Circuit

of Figure 6.)

I

IN

+ I

VCC

CURRENT

vs. SWITCHING FREQUENCY

MAX15023 toc10

SWITCHING FREQUENCY (kHz)

I

IN

+ I

VCC

CURRENT (mA)

900800700600500400300

30

60

90

120

150

180

210

0

200 1000

VIN = V

CC

= 5V

C

DL_

= C

DH_

= 10nF

C

DL_

= C

DH_

= 4.7nF

C

DL_

= C

DH_

= 1nF

CDL = C

DH

= 0nF

EN_ TURN-ON AND TURN-OFF THRESHOLD

vs. TEMPERATURE

MAX15023 toc11

TEMPERATURE (°C)

EN_ TURN-ON AND TURN-OFF THRESHOLDS

603510-15

1.025

1.050

1.075

1.100

1.125

1.150

1.175

1.200

1.225

1.250

1.000

-40 85

EN_ RISING

EN_ FALLING

LIM_ CURRENT

vs. TEMPERATURE

MAX15023 toc12

TEMPERATURE (°C)

LIM_ CURRENT (µA)

603510-15

40

42

44

46

48

50

52

54

56

58

60

38

-40 85

I

LIM2

I

LIM1

SHUTDOWN CURRENT

vs. TEMPERATURE

MAX15023 toc13

TEMPERATURE (°C)

SHUTDOWN CURRENT (µA)

603510-15

205

210

215

220

225

230

200

-40 85

CURRENT-LIMIT THRESHOLD

vs. R

LIM

MAX15023 toc14

R

LIM

(kΩ)

CURRENT-LIMIT THRESHOLD (mV)

555040 4515 20 25 30 3510

30

60

90

120

150

180

210

240

270

300

0

560

SOURCE CURRENT LIMIT

SINK CURRENT LIMIT

LOAD TRANSIENT ON OUT1

MAX15023 toc15

10µs/div

V

OUT1

(AC-COUPLED)

100mV/div

V

OUT2

(AC-COUPLED)

50mV/div

I

OUT1

5A/div

LOAD TRANSIENT ON OUT2

MAX15023 toc16

10µs/div

V

OUT2

(AC-COUPLED)

200mV/div

V

OUT1

(AC-COUPLED)

100mV/div

I

OUT2

2A/div

MAX15023

Wide 4.5V to 28V Input, Dual-Output

Synchronous Buck Controller

_______________________________________________________________________________________ 7

Typical Operating Characteristics (continued)

(Supply = IN = 12V, unless otherwise noted. See

Typical Application Circuit

of Figure 6.)

STARTUP AND DISABLE FROM EN

MAX15023 toc19

2ms/div

V

EN2

5V/div

V

IN

10V/div

V

OUT2

2V/div

V

PGOOD2

5V/div

I

OUT2

= 500mA

STARTUP AND TURN-OFF FROM IN

MAX15023 toc20

4ms/div

V

IN

10V/div

V

OUT1

1V/div

V

PGOOD1

5V/div

EN1 = EN2 = V

CC

I

OUT1

= 1.2A

STARTUP AND TURN-OFF FROM IN

MAX15023 toc21

4ms/div

V

IN

10V/div

V

OUT2

2V/div

V

PGOOD2

5V/div

I

OUT2

= 500mA

STARTUP INTO PREBIASED OUTPUT

(0.5V PREBIASED)

MAX15023 toc22

2ms/div

V

OUT1

500mV/div

0V

LINE-TRANSIENT RESPONSE

MAX15023 toc17

2ms/div

V

IN

5V/div

V

OUT1

(AC-COUPLED)

50mV/div

V

OUT2

(AC-COUPLED)

100mV/div

STARTUP AND DISABLE FROM EN

MAX15023 toc18

2ms/div

V

EN1

5V/div

V

IN

10V/div

V

OUT1

500mV/div

V

PGOOD1

5V/div

I

OUT1

= 1.2A

MAX15023

Wide 4.5V to 28V Input, Dual-Output
Synchronous Buck Controller

8 _______________________________________________________________________________________

Typical Operating Characteristics (continued)

(Supply = IN = 12V, unless otherwise noted. See

Typical Application Circuit

of Figure 6.)

STARTUP INTO PREBIASED OUTPUT

(1V PREBIASED)

MAX15023 toc23

2ms/div

V

OUT1

500mV/div

0V

STARTUP INTO PREBIASED OUTPUT

(1.5V PREBIASED)

MAX15023 toc24

2ms/div

V

OUT1

500mV/div

0V

DH_ AND DL_ DISOVERLAP

MAX15023 toc25

20ns/div

V

DH1

10V/div

V

DL1

5V/div

V

LX1

10V/div

I

OUT1

= 5A

DH_ AND DL_ DISOVERLAP

MAX15023 toc26

20ns/div

V

DH1

10V/div
V

DL1

5V/div

V

LX1

10V/div

I

OUT1

= 5A

OUT-OF-PHASE SWITCHING FORMS

MAX15023 toc27

1µs/div

V

LX1

10V/div

V

LX2

10V/div

I

LX1

5A/div

I

LX2

2A/div

I

OUT1

= 5A

I

OUT2

= 2.5A

SINK CURRENT-LIMIT WAVEFORMS

MAX15023 toc28

100µs/div

V

OUT1

200mV/div

V

LX1

20V/div

I

LX1

2A/div

1.5V PREBIASED

MAX15023

Wide 4.5V to 28V Input, Dual-Output

Synchronous Buck Controller

_______________________________________________________________________________________ 9

Pin Description

PIN NAME FUNCTION

1 FB1

2 EN1

3 EN2

4 PGOOD1

5 DL1

6 PGND1

7 LX1

8 BST1

9 DH1

10 DH2

11 BST2

12 LX2

Feedback Input for Regulator 1. Connect FB1 to a resistive divider between Output 1 and SGND to adjust
the output voltage between 0.6V and (0.85 x input voltage (V)). See the Setting the Output Voltage section.

Active-High Enable Input for Regulator 1. When the voltage at EN1 exceeds 1.2V (typ), the controller begins
regulating OUT1. When the voltage falls below 1.05V (typ), the regulator is turned off. The EN1 input can be
used for power sequencing and as a secondary UVLO. Connect EN1 to V

Active-High Enable Input for Regulator 2. When the voltage at EN2 exceeds 1.2V (typ), the controller begins
regulating OUT2. When the voltage falls below 1.05V (typ), the regulator is turned off. The EN2 input can be
used for power sequencing and as a secondary UVLO. Connect EN2 to V

Power-Good Output (Open Drain) for Channel 1. To obtain a logic signal, pull up PGOOD1 with an external
resistor connected to a positive voltage below 28V.

Low-Side Gate-Driver Output for Regulator 1. DL1 swings from V
reaches the UVLO rising threshold voltage.

Low-Side Gate-Driver Supply Return (Regulator 1). Connect to the source of the low-side MOSFET of
Regulator 1.

External Inductor Connection for Regulator 1. Connect LX1 to the switched side of the inductor. LX1 serves
as the lower supply rail for the DH1 high-side gate driver and as sensing input of the synchronous
MOSFET’s V

Boost Flying-Capacitor Connection for Regulator 1. Connect a ceramic capacitor with a minimum value of
100nF between BST1 and LX1.

High-Side Gate-Driver Output for Regulator 1. DH1 swings from LX1 to BST1. DH1 is low before V
reaches the UVLO rising threshold voltage.

High-Side Gate-Driver Output for Regulator 2. DH2 swings from LX2 to BST2. DH2 is low before V
reaches the UVLO rising threshold voltage.

Boost Flying-Capacitor Connection for Regulator 2. Connect a ceramic capacitor with a minimum value of
100nF between BST2 and LX2.

External Inductor Connection for Regulator 2. Connect LX2 to the switched side of the inductor. LX2 serves
as the lower supply rail for the DH2 high-side gate driver and as sensing input of the synchronous
MOSFET’s V

drop (drain terminal).

DS

drop (drain terminal).

DS

for always-on applications.

CC

for always-on applications.

CC

to PGND1. DL1 is low before V

CC

CC

CC

CC