19-4108; Rev 1; 5/09
IT
TION K
VALUA
E
BLE
AVAILA
Low-Cost, Small, 4.5V to 28V Wide Operating
Range, DC-DC Synchronous Buck Controller
General Description
The MAX15026 synchronous step-down controller oper-
ates from a 4.5V to 28V input voltage range and gener-
ates an adjustable output voltage from 85% of the input
voltage down to 0.6V while supporting loads up to 25A.
The device allows monotonic startup into a prebiased
bus without discharging the output and features adap-
tive internal digital soft-start.
The MAX15026 offers the ability to adjust the switching
frequency from 200kHz to 2MHz with an external resis-
tor. The MAX15026’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 resis-
tor. This protects the DC-DC 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 MAX15026 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 cur-
rent limit and thermal shutdown.
Sink-mode current limit prevents reverse inductor cur-
rent from reaching dangerous levels when the device is
sinking current from the output.
The MAX15026 is available in a space-saving and ther-
mally enhanced 3mm x 3mm, 14-pin TDFN-EP pack-
age. The MAX15026 operates over the extended -40°C
to +85°C and automotive -40°C to +125°C temperature
ranges.
PART
MAX15026BETD+
MAX15026BATD+
Features
o
o
o
o
4.5V to 28V or 5V ±10% Input Supply Range
0.6V to (0.85 x V
IN
) Adjustable Output
Adjustable 200kHz to 2MHz Switching Frequency
Ability to Start into a Prebiased Load
MAX15026
o
Lossless, Cycle-by-Cycle Valley Mode Current
Limit with Adjustable, Temperature-Compensated
Threshold
o
o
o
o
Sink-Mode Current-Limit Protection
Adaptive Internal Digital Soft-Start
±1% Accurate Voltage Reference
Internal Boost Diode
o
Adaptive Synchronous Rectification Eliminates
External Freewheeling Schottky Diode
o
Hiccup-Mode Short-Circuit Protection
o
Thermal Shutdown
o
Power-Good Output and Enable Input for Power
Sequencing
o
±5% Accurate Enable Input Threshold
Ordering Information
TEMP RANGE
-40°C to +85°C
-40°C to +125°C
PIN-PACKAGE
14 TDFN-EP*
14 TDFN-EP*
+Denotes
a lead(Pb)-free/RoHS-compliant package.
*EP
= Exposed pad.
Pin Configuration
TOP VIEW
Applications
Set-Top Boxes
LCD TV Secondary Supplies
Switches/Routers
Power Modules
DSP Power Supplies
Points-of-Load Regulators
IN
V
CC
PGOOD
EN
LIM
COMP
FB
1
2
3
4
5
6
7
*EP
+
14
13
12
DH
LX
BST
DL
DRV
GND
RT
MAX15026
11
10
9
8
TDFN
(3mm x 3mm)
*EP = EXPOSED PAD.
________________________________________________________________
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.
Low-Cost, Small, 4.5V to 28V Wide Operating
Range, DC-DC Synchronous Buck Controller
MAX15026
ABSOLUTE MAXIMUM RATINGS
IN to GND ...............................................................-0.3V to +30V
BST to GND ............................................................-0.3V to +36V
LX to GND .................................................................-1V to +30V
EN to GND................................................................-0.3V to +6V
PGOOD to GND .....................................................-0.3V to +30V
BST to LX..................................................................-0.3V to +6V
DH to LX ...............................................….-0.3V to (V
BST
+ 0.3V)
DRV to GND .............................................................-0.3V to +6V
DL to GND ................................................-0.3V to (V
DRV
+ 0.3V)
V
CC
to GND...............-0.3V to the lower of +6V and (V
IN
+ 0.3V)
All Other Pins to GND.................................-0.3V to (V
CC
+ 0.3V)
V
CC
Short Circuit to GND ...........................................Continuous
DRV Input Current.............................................................600mA
PGOOD Sink Current ............................................................5mA
Continuous Power Dissipation (T
A
= +70°C) (Note 1)
14-Pin TDFN-EP, Multilayer Board
(derate 24.4mW/°C above +70°C) ..............................1951mW
Operating Temperature Range
MAX15026BETD+.............................................-40°C to +85°C
MAX15026BATD+...........................................-40°C to +125°C
Junction Temperature ......................................................+150°C
Storage Temperature Range .............................-60°C to +150°C
Lead Temperature (soldering, 10s) .................................+300°C
Note 1:
Dissipation wattage values are based on still air with no heatsink. Actual maximum power dissipation is a function of heat
extraction technique and may be substantially higher. 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 consid-
erations, refer to
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.
ELECTRICAL CHARACTERISTICS
(V
IN
= 12V, R
RT
= 27kΩ, R
LIM
= 30kΩ, C
VCC
= 4.7µF, C
IN
= 1µF, T
A
= -40°C to +85°C (MAX15026BETD+), T
A
= T
J
= -40°C to
+125°C (MAX15026BATD+), unless otherwise noted. Typical values are at T
A
= +25°C.) (Note 2)
PARAMETER
GENERAL
Input Voltage Range
Quiescent Supply Current
Shutdown Supply Current
Enable to Output Delay
V
CC
High to Output Delay
V
CC
REGULATOR
Output Voltage
V
CC
Regulator Dropout
V
CC
Short-Circuit Output Current
V
CC
Undervoltage Lockout
V
CC
Undervoltage Lockout
Hysteresis
ERROR AMPLIFIER (FB, COMP)
FB Input Voltage Set-Point
FB Input Bias Current
FB to COMP Transconductance
Amplifier Open-Loop Gain
Amplifier Unity-Gain Bandwidth
V
COMP-RAMP
Minimum Voltage
COMP Source/Sink Current
I
COMP
V
COMP
= 1.4V
50
Capacitor from COMP to GND = 50pF
V
FB
I
FB
g
M
V
FB
= 0.6V
I
COMP
= ±20µA
585
-250
600
1200
80
4
160
80
110
591
597
+250
1800
mV
nA
µS
dB
MHz
mV
µA
V
CC_UVLO
V
CC
6V < V
IN
< 28V, I
LOAD
= 25mA
V
IN
= 12V, 1mA < I
LOAD
< 70mA
V
IN
= 4.5V, I
LOAD
= 70mA
V
IN
= 5V
V
CC
rising
100
3.8
200
4.0
400
5.0
5.25
5.5
0.28
300
4.2
V
V
mA
V
mV
EN = V
CC
I
IN_SBY
V
IN
4.5
V
IN
= V
CC
= V
DRV
V
FB
= 0.9V, no switching
EN = GND
4.5
1.75
290
480
375
28
5.5
2.75
500
V
mA
µA
µs
µs
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
2
_______________________________________________________________________________________
Low-Cost, Small, 4.5V to 28V Wide Operating
Range, DC-DC Synchronous Buck Controller
ELECTRICAL CHARACTERISTICS (continued)
(V
IN
= 12V, R
RT
= 27kΩ, R
LIM
= 30kΩ, C
VCC
= 4.7µF, C
IN
= 1µF, T
A
= -40°C to +85°C (MAX15026BETD+), T
A
= T
J
= -40°C to
+125°C (MAX15026BATD+), unless otherwise noted. Typical values are at T
A
= +25°C.) (Note 2)
PARAMETER
ENABLE (EN)
EN Input High
EN Input Low
EN Input Leakage Current
OSCILLATOR
Switching Frequency
1MHz Switching Frequency
2MHz Switching Frequency
Switching Frequency Adjustment
Range (Note 3)
RT Voltage
PWM Ramp Peak-to-Peak
Amplitude
PWM Ramp Valley
Minimum Controllable On-Time
Maximum Duty Cycle
Minimum Low-Side On-Time
OUTPUT DRIVERS/DRIVER SUPPLY (DRV)
DRV Undervoltage Lockout
DRV Undervoltage Lockout
Hysteresis
DH On-Resistance
DL On-Resistance
DH Peak Current
DL Peak Current
DH/DL Break-Before-Make Time
SOFT-START
Soft-Start Duration
Reference Voltage Steps
CURRENT LIMIT/HICCUP
Current-Limit Threshold
Adjustment Range
Cycle-by-cycle valley current-limit
threshold adjustment range
valley limit = V
LIM
/10
30
300
mV
2048
64
Switching
Cycles
Steps
Low, sinking 100mA, V
BST
= 5V
High, sourcing 100mA, V
BST
= 5V
Low, sinking 100mA, V
BST
= 5.2V
High, sourcing 100mA, V
BST
= 5.2V
C
LOAD
= 10nF
C
LOAD
= 10nF
Sinking
Sourcing
Sinking
Sourcing
V
DRV_UVLO
V
DRV
rising
4.0
4.2
400
1
1.5
1
1.5
4
3
4
3
10
3
4.5
3
4.5
4.4
V
mV
Ω
Ω
A
A
ns
f
SW
= 600kHz
R
RT
= 15.7kΩ
85
75
V
RT
V
RAMP
V
VALLEY
f
SW
R
RT
= 27kΩ
R
RT
= 15.7kΩ
R
RT
= 7.2kΩ
540
0.9
1.8
200
1.19
1.205
1.8
0.8
65
88
110
150
100
600
1
2.0
660
1.1
2.4
2000
1.22
kHz
MHz
MHz
kHz
V
V
V
ns
%
ns
V
EN_H
V
EN_L
I
LEAK_EN
V
EN
rising
V
EN
falling
V
EN
= 5.5V
1.14
0.997
-1
1.20
1.05
1.26
1.103
+1
V
V
µA
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
MAX15026
Time from high side at 1V to low side at
1V
_______________________________________________________________________________________
3
Low-Cost, Small, 4.5V to 28V Wide Operating
Range, DC-DC Synchronous Buck Controller
MAX15026
ELECTRICAL CHARACTERISTICS (continued)
(V
IN
= 12V, R
RT
= 27kΩ, R
LIM
= 30kΩ, C
VCC
= 4.7µF, C
IN
= 1µF, T
A
= -40°C to +85°C (MAX15026BETD+), T
A
= T
J
= -40°C to
+125°C (MAX15026BATD+), unless otherwise noted. Typical values are at T
A
= +25°C.) (Note 2)
PARAMETER
LIM Reference Current
LIM Reference Current Tempco
Number of Consecutive Current-
Limit Events to Hiccup
Soft-Start Timeout
Soft-Start Restart Timeout
Hiccup Timeout
Peak Low-Side Sink Current
Limit
BOOST
Boost Switch Resistance
POWER-GOOD OUTPUT
PGOOD Threshold Rising
PGOOD Threshold Falling
PGOOD Output Leakage
PGOOD Output Low Voltage
THERMAL SHUTDOWN
Thermal-Shutdown Threshold
Thermal-Shutdown Hysteresis
Temperature rising
Temperature falling
+150
20
°C
°C
I
LEAK_PGD
V
PGOOD_L
V
IN
= V
PGOOD
= 28V, V
EN
= 5V, V
FB
= 1V
I
PGOOD
= 2mA, EN = GND
90
88
-1
94.5
92
97.5
94.5
+1
0.4
%V
FB
%V
FB
µA
V
V
IN
= V
CC
= 5V, I
BST
= 10mA
3
8
Ω
Out of soft-start
Sink limit = 1.5V, R
LIM
= 30kΩ (Note 4)
SYMBOL
I
LIM
CONDITIONS
V
LIM
= 0.3V to 3V (Note 4)
V
LIM
= 0.3V to 3V
MIN
45
TYP
50
2300
7
4096
8192
4096
75
MAX
55
UNITS
µA
ppm/°C
Events
Switching
Cycles
Switching
Cycles
Switching
Cycles
mV
Note 2:
All devices are 100% tested at room temperature and guaranteed by design over the specified temperature range.
17.3
×
10
9
Note 3:
Select R
RT
as:
R
RT
=
where f
SW
is in Hertz.
f
SW
+
(1x10
−
7
)x(f
SW 2
)
Note 4:
T
A
= +25°C.
4
_______________________________________________________________________________________
Low-Cost, Small, 4.5V to 28V Wide Operating
Range, DC-DC Synchronous Buck Controller
Typical Operating Characteristics
(V
IN
= 12V, T
A
= +25°C, unless otherwise noted.) (See the circuit of Figure 5.)
EFFICIENCY vs. LOAD CURRENT
(V
IN
= 12V, V
CC
= V
DRV
= 5V)
MAX15026 toc01
MAX15026 toc02
MAX15026
EFFICIENCY vs. LOAD CURRENT
100
90
80
EFFICIENCY (%)
70
60
50
40
30
20
10
0
0
2
4
6
8
10
12
LOAD CURRENT (A)
V
OUT
= 3.3V
V
OUT
= 1.2V
V
OUT
= 5V
V
OUT
= 1.8V
100
90
80
EFFICIENCY (%)
70
60
50
40
30
20
10
0
0
V
OUT
vs. LOAD CURRENT
-0.1
% OUTPUT FROM NOMINAL
-0.2
-0.3
-0.4
-0.5
-0.6
-0.7
-0.8
-0.9
-1.0
MAX15026 toc03
0
V
OUT
= 5V
V
OUT
= 3.3V
V
OUT
= 1.8V
V
OUT
= 1.2V
2
4
6
8
10
12
0
2
4
6
8
10
12
LOAD CURRENT (A)
LOAD CURRENT (A)
V
CC
vs. LOAD CURRENT
MAX15026 toc04
V
CC
LINE REGULATION
5mA
5.2
5.1
5.0
V
CC
(V)
4.9
4.8
4.7
4.6
5.240
5.238
5.236
0
5
10
15
V
IN
(V)
20
25
30
-40
50mA
5.244
V
CC
(V)
5.242
MAX15026 toc05
V
CC
vs. TEMPERATURE
MAX15026 toc06
5.265
5.260
5.255
5.250
V
CC
(V)
5.245
5.240
5.235
5.230
5.225
0
20
60
40
LOAD CURRENT (mA)
80
5.3
5.248
5.246
4.5
4.4
4.3
100
-15
10
35
60
85
TEMPERATURE (°C)
SWITCHING FREQUENCY
vs. RESISTANCE
MAX15026 toc07
SWITCHING FREQUENCY
vs. TEMPERATURE
MAX15026 toc08
SUPPLY CURRENT
vs. SWITCHING FREQUENCY
80
SUPPLY CURRENT (mA)
70
60
50
40
30
20
10
MAX15026 toc09
2500
SWITCHING FREQUENCY (kHz)
2500
SWITCHING FREQUENCY (kHz)
90
2000
2000
R
RT
= 7.2kΩ
1500
R
RT
= 15.7kΩ
R
RT
= 27kΩ
R
RT
= 85kΩ
1500
1000
1000
500
500
0
0
20
40
60
80
100
RESISTANCE (kΩ)
0
-40
-15
10
35
60
85
TEMPERATURE (°C)
0
100
1000
SWITCHING FREQUENCY (kHz)
10,000
_______________________________________________________________________________________
5
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