19-4123; Rev 2; 10/08
KIT
ATION
EVALU
BLE
AVAILA
15A Step-Down Regulator with Internal Switches
General Description
The MAX15035 pulse-width modulation (PWM) controller
provides high efficiency, excellent transient response,
and high DC-output accuracy. Combined with the inter-
nal low on-resistance MOSFETs, the MAX15035 pro-
vides a highly efficient and compact solution for small
form factor applications that need a high-power density.
Maxim’s proprietary Quick-PWM™ quick-response,
constant on-time PWM control scheme handles wide
input/output voltage ratios (low-duty-cycle applications)
with ease and provides 100ns instant-on response to
load transients while maintaining a relatively constant
switching frequency. The output voltage can be dynam-
ically controlled using the dynamic REFIN, which sup-
ports input voltages between 0V to 2V. The REFIN
adjustability combined with a resistive voltage-divider
on the feedback input allows the MAX15035 to be con-
figured for any output voltage between 0V to 0.9V
IN
.
The controller senses the current across the synchro-
nous rectifier to achieve a low-cost and highly efficient
valley current-limit protection. External current-limit con-
trol is provided to allow higher current-limit settings for
applications with heatsinks and air flow, or for lower
current applications that need lower current-limit set-
tings to avoid overdesigning the application circuit. The
adjustable current limit provides a high degree of flexi-
bility, allowing thermally compensated protection or
foldback current-limit protection using a voltage-divider
partially derived from the output.
The MAX15035 includes a voltage-controlled soft-start
and soft-shutdown to limit the input surge current, pro-
vide a monotonic power-up into a precharged output,
and provide a predictable soft-start time. The controller
also includes output fault protection—undervoltage and
overvoltage protection—as well as thermal-fault protec-
tion.
The MAX15035 is available in a small 40-pin, 6mm x 6mm,
TQFN package.
o
4.5V to 26V Input Voltage Range
o
Fast Transient Response
o
Monotonic Power-Up with Precharged Output
o
Supports Any Output Capacitor
No Compensation Required with Polymers/
Tantalum
Stable with Ceramic Output Capacitors Using
External Compensation
o
Dynamically Adjustable Output Voltage
0.5% V
OUT
Accuracy Over Line and Load
o
Adjustable Valley Current-Limit Protection
Thermal Compensation with NTC
Supports Foldback Current Limit
o
Programmable Switching Frequency
o
Overvoltage Protection
o
Undervoltage Protection
o
Voltage Soft-Start and Soft-Shutdown
o
Power-Good Window Comparator
Features
MAX15035
Ordering Information
PART
MAX15035ETL+
TEMP RANGE
-40°C to +85°C
PIN-PACKAGE
40 TQFN-EP*
+Denotes
a lead-free/RoHS-compliant package.
*EP
= Exposed pad.
Pin Configuration
AGND
TON
IN
IN
IN
IN
30 29 28 27 26 25 24 23 22 21
N.C. 31
FB 32
ILIM 33
REFIN 34
REF 35
SKIP 36
V
CC
37
PGOOD 38
N.C. 39
N.C. 40
LX
AGND
EP1
EP3
20 IN
IN
19 IN
18 IN
IN
IN
17 N.C.
16 LX
15 PGND
14 PGND
13 PGND
12 PGND
11 PGND
1
N.C.
2
EN
3
AGND
4
V
DD
5
LX
6
PGND
7
PGND
8
PGND
9
PGND
10
PGND
TOP VIEW
Applications
Server Computers
GPU Core Supplies
DDR Memory—VDDQ or VTT
Point-of-Load Applications
Step-Down Power Supplies
Storage Power Supplies
EP2
+
Quick-PWM is a trademark of Maxim Integrated Products, Inc.
THIN QFN
(6mm x 6mm)
________________________________________________________________
Maxim Integrated Products
N.C.
BST
MAX15035
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.
15A Step-Down Regulator with Internal Switches
MAX15035
ABSOLUTE MAXIMUM RATINGS
IN to PGND.............................................................-0.3V to +28V
TON to GND ...........................................................-0.3V to +28V
V
DD
to GND ..............................................................-0.3V to +6V
V
CC
to GND ................................................-0.3V to (V
DD
+ 0.3V)
EN,
SKIP,
PGOOD to GND.......................................-0.3V to +6V
REF, REFIN to GND....................................-0.3V to (V
CC
+ 0.3V)
ILIM, FB to GND .........................................-0.3V to (V
CC
+ 0.3V)
GND to PGND .......................................................-0.3V to +0.3V
LX to PGND ...............................................................-1V to +28V
BST to PGND...............................................(V
DD
- 0.3V) to +34V
BST to LX..................................................................-0.3V to +6V
BST to V
DD
.............................................................-0.3V to +28V
REF Short Circuit to GND ...........................................Continuous
IN RMS Current Rating (continuous)......................................15A
PGND RMS Current Rating (continuous) ...............................20A
Continuous Power Dissipation (T
A
= +70°C)
40-Pin, 6mm x 6mm Thin QFN (T4066-MCM)
(derate 27mW/°C above +70°C) ................................2162mW
Operating Temperature Range ...........................-40°C to +85°C
Junction Temperature Range ..........................................+150°C
Storage Temperature Range .............................-65°C to +150°C
Lead Temperature (soldering, 10s) .................................+300°C
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
(Circuit of Figure 1, V
IN
= 12V, V
DD
= V
CC
= V
EN
= 5V, REFIN = ILIM = REF,
SKIP
= GND.
T
A
= 0°C to +85°C,
unless otherwise spec-
ified. Typical values are at T
A
= +25°C.) (Note 1)
PARAMETER
PWM CONTROLLER
Input Voltage Range
Quiescent Supply Current (V
DD
)
Shutdown Supply Current (V
DD
)
V
CC
Undervoltage Lockout
Threshold
V
DD
-to-V
CC
Resistance
On-Time
Minimum Off-Time
TON Shutdown Supply Current
REFIN Voltage Range
REFIN Input Current
FB Voltage Range
V
REFIN
I
REFIN
V
FB
V
IN
I
DD
+ I
CC
I
SHDN
V
UVLO(VCC)
R
CC
t
ON
t
OFF(MIN)
V
IN
= 12V,
V
FB
= 1.0V
(Note 3)
(Note 3)
EN = GND, V
TON
= 26V,
V
CC
= 0V or 5V, T
A
= +25°C
(Note 2)
T
A
= +25°C, REFIN = 0.5V to 2V
(Note 2)
V
REFIN
= 0.5V,
measured at FB,
V
IN
= 4.5V to 26V,
SKIP
= V
DD
V
REFIN
= 1.0V
V
REFIN
= 2.0V
FB Input Bias Current
FB Output Low Voltage
Load-Regulation Error
Line-Regulation Error
I
FB
I
SINK
= 3mA
SKIP
= V
DD
V
CC
= 4.5V to 5.5V, V
IN
= 4.5V to 26V
0.1
0.2
T
A
= +25°C
T
A
= 0°C to +85°C
T
A
= +25°C
T
A
= 0°C to +85°C
T
A
= 0°C to +85°C
0
-50
0
0.495
0.493
0.995
0.993
1.990
-0.1
2.0
1.0
0.5
R
TON
= 97.5kΩ (600kHz)
R
TON
= 200kΩ (300kHz)
R
TON
= 302.5kΩ (200kHz)
123
275
379
FB forced above REFIN
EN = GND, T
A
= +25°C
Rising edge, PWM disabled below this
level; hysteresis = 100mV
3.95
4.5
0.7
0.1
4.2
20
164
303
442
225
0.01
205
331
505
350
1
V
REF
+50
V
REF
0.505
0.507
V
1.005
1.007
2.010
+0.1
0.4
μA
V
%
%
ns
μA
V
nA
V
ns
26.0
1.2
2
4.45
V
mA
μA
V
Ω
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
FB Voltage Accuracy
V
FB
V
FB
= 0.5V to 2.0V, T
A
= +25°C
2
_______________________________________________________________________________________
15A Step-Down Regulator with Internal Switches
ELECTRICAL CHARACTERISTICS (continued)
(Circuit of Figure 1, V
IN
= 12V, V
DD
= V
CC
= V
EN
= 5V, REFIN = ILIM = REF,
SKIP
= GND.
T
A
= 0°C to +85°C,
unless otherwise spec-
ified. Typical values are at T
A
= +25°C.) (Note 1)
PARAMETER
Soft-Start/Soft-Stop Slew Rate
Dynamic REFIN Slew Rate
REFERENCE
Reference Voltage
FAULT DETECTION
With respect to the internal target voltage
(error comparator threshold); rising edge;
hysteresis = 50mV
OVP
Dynamic transition
Minimum OVP threshold
Output Overvoltage
Fault-Propagation Delay
Output Undervoltage-Protection
Trip Threshold
Output Undervoltage
Fault-Propagation Delay
PGOOD Propagation Delay
PGOOD Output-Low Voltage
PGOOD Leakage Current
Dynamic REFIN Transition Fault
Blanking Threshold
Thermal-Shutdown Threshold
CURRENT LIMIT
ILIM Input Range
ILIM Input Bias Current
Current-Limit Threshold
Current-Limit Threshold
(Negative)
Current-Limit Threshold
(Zero Crossing)
Ultrasonic Frequency
V
ILIMIT
V
INEG
V
ZX
T
A
= +25°C, ILIM = 0.4V to 2V
V
ILIM
= 0.4V, V
GND
- V
LX
ILIM = REF (2.0V), V
GND
- V
LX
V
ILIM
= 0.4V, V
GND
- V
LX
V
ILIM
= 0.4V,
V
GND
- V
LX
,
SKIP
= GND or open
SKIP
= open (3.3V); V
FB
= V
REFIN
+ 50mV
18
0.4
-0.1
18
92
20
100
-24
1
30
V
REF
+0.1
22
108
V
μA
mV
mV
mV
kHz
T
SHDN
I
PGOOD
t
OVP
FB forced 25mV above trip threshold
With respect to the internal target voltage
(error comparator threshold) falling edge;
hysteresis = 50mV
FB forced 25mV below trip threshold
UVP falling edge, 25mV overdrive
t
PGOOD
OVP rising edge, 25mV overdrive
Startup delay
I
SINK
= 3mA
FB = REFIN (PGOOD high impedance),
PGOOD forced to 5V, T
A
= +25°C
Fault blanking initiated; REFIN deviation
from the internal target voltage (error
comparator threshold); hysteresis = 10mV
Temperature rising, hysteresis = 15°C
±50
160
100
250
300
V
REF
+
0.30
0.7
5
μs
350
mV
V
REF
V
CC
= 4.5V
to 5.5V
No load
I
REF
= -10μA to +50μA
1.990
1.98
2.00
2.010
2.02
V
SYMBOL
SS
SR
DYN
SR
CONDITIONS
Rising/falling edge on EN
Rising edge on REFIN
MIN
0.4
3
TYP
1.2
9.45
MAX
2.2
18
UNITS
mV/μs
mV/μs
MAX15035
Output Overvoltage-Protection
Trip Threshold
V
UVP
-240
-200
-160
mV
t
UVP
100
200
5
5
200
350
μs
μs
350
0.4
1
V
μA
mV
°C
_______________________________________________________________________________________
3
15A Step-Down Regulator with Internal Switches
MAX15035
ELECTRICAL CHARACTERISTICS (continued)
(Circuit of Figure 1, V
IN
= 12V, V
DD
= V
CC
= V
EN
= 5V, REFIN = ILIM = REF,
SKIP
= GND.
T
A
= 0°C to +85°C,
unless otherwise spec-
ified. Typical values are at T
A
= +25°C.) (Note 1)
PARAMETER
Ultrasonic Current-Limit
Threshold
Internal BST Switch
On-Resistance
INPUTS AND OUTPUTS
EN Logic-Input Threshold
EN Logic-Input Current
V
EN
I
EN
EN rising edge, hysteresis = 450mV (typ)
EN forced to GND or V
DD
, T
A
= +25°C
High (5V V
DD
)
SKIP
Quad-Level Input Logic
Levels
V
SKIP
Open (3.3V)
Ref (2.0V)
Low (GND)
SKIP
Logic-Input Current
I
SKIP
SKIP
forced to GND or V
DD
, T
A
= +25°C
-2
1.20
-0.5
V
CC
-
0.4
3.0
1.7
3.6
2.3
0.4
+2
μA
V
1.7
2.20
+0.5
V
μA
R
BST
SYMBOL
CONDITIONS
SKIP
= open (3.3V); V
FB
= V
REFIN
+ 50mV,
V
GND
- V
LX
I
BST
= 10mA, V
DD
= 5V
MIN
TYP
-35
4
7
MAX
UNITS
mV
Ω
ELECTRICAL CHARACTERISTICS
(Circuit of Figure 1, V
IN
= 12V, V
DD
= V
CC
= V
EN
= 5V, REFIN = ILIM = REF,
SKIP
= GND.
T
A
= -40°C to +85°C,
unless otherwise
specified.) (Note 1)
PARAMETER
PWM CONTROLLER
Input Voltage Range
Quiescent Supply Current (V
DD
)
On-Time
Minimum Off-Time
REFIN Voltage Range
FB Voltage Range
V
IN
I
DD
+ I
CC
t
ON
t
OFF(MIN)
V
REFIN
V
FB
FB forced above REFIN
V
IN
= 12V,
V
FB
= 1.0V
(Note 3)
(Note 3)
(Note 2)
(Note 2)
Measured at FB,
V
IN
= 4.5V to
26V,
SKIP
=
V
DD
V
REFIN
= 0.5V
V
REFIN
= 1.0V
V
REFIN
= 2.0V
0
0
0.49
0.99
1.985
R
TON
= 97.5kΩ (600kHz)
R
TON
= 200kΩ (300kHz)
R
TON
= 302.5kΩ (200kHz)
115
270
368
4.5
26
1.2
213
336
516
400
V
REF
V
REF
0.51
1.01
2.015
V
ns
V
V
ns
V
mA
SYMBOL
CONDITIONS
MIN
MAX
UNITS
FB Voltage Accuracy
V
FB
4
_______________________________________________________________________________________
15A Step-Down Regulator with Internal Switches
ELECTRICAL CHARACTERISTICS (continued)
(Circuit of Figure 1, V
IN
= 12V, V
DD
= V
CC
= V
EN
= 5V, REFIN = ILIM = REF,
SKIP
= GND. T
A
=
-40°C to +85°C,
unless otherwise
specified.) (Note 1)
PARAMETER
REFERENCE
Reference Voltage
FAULT DETECTION
Output Overvoltage-Protection
Trip Threshold
Output Undervoltage-Protection
Trip Threshold
Output Undervoltage
Fault-Propagation Delay
PGOOD Output-Low Voltage
V
CC
Undervoltage Lockout
Threshold
CURRENT LIMIT
ILIM Input Range
Current-Limit Threshold
Ultrasonic Frequency
INPUTS AND OUTPUTS
EN Logic-Input Threshold
V
EN
EN rising edge hysteresis = 450mV (typ)
High (5V V
DD
)
SKIP
Quad-Level Input
Logic Levels
V
SKIP
Mid (3.3V)
Ref (2.0V)
Low (GND)
1.20
V
CC
-
0.4
3.0
1.7
3.6
2.3
0.4
V
2.20
V
V
ILIMIT
V
ILIM
= 0.4V, V
GND
= V
LX
ILIM = REF (2.0V), V
GND
- V
LX
SKIP
= open (3.3V), V
FB
= V
REFIN
+ 50mV
0.4
17
90
17
V
REF
23
110
V
mV
kHz
V
UVLO(VCC)
OVP
With respect to the internal target voltage
(error comparator threshold) rising edge;
hysteresis = 50mV
With respect to the internal target voltage
(error comparator threshold);
falling edge; hysteresis = 50mV
FB forced 25mV below trip threshold
I
SINK
= 3mA
Rising edge, PWM disabled below this level,
hysteresis = 100mV
3.95
250
350
mV
V
REF
V
DD
= 4.5V to 5.5V
1.985
2.015
V
SYMBOL
CONDITIONS
MIN
MAX
UNITS
MAX15035
UVP
-240
-160
mV
t
UVP
80
400
0.4
4.45
μs
V
V
Note 1:
Limits are 100% production tested at T
A
= +25°C. Maximum and minimum limits over temperature are guaranteed by
design and characterization.
Note 2:
The 0 to 0.5V range is guaranteed by design, not production tested.
Note 3:
On-time and off-time specifications are measured from 50% point to 50% point at the unloaded LX node. The typical 25ns
dead time that occurs between the high-side driver falling edge (high-side MOSFET turn-off) and the low-side MOSFET turn-
on) is included in the on-time measurement. Similarly, the typical 25ns dead time that occurs between the low-side driver
falling edge (low-side MOSFET turn-off) and the high-side driver rising edge (high-side MOSFET turn-on) is included in the
off-time measurement.
_______________________________________________________________________________________
5
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