The Future of Analog IC Technology
High Efficiency, Fast Transient, 2A,
4.2V-20V Input Synchronous
Step-down Converter in QFN12 (2x3mm)
FEATURES
•
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•
•
•
•
•
•
•
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Wide 4.2V to 20V Operating Input Range
2A Output Current
Low R
DS
(ON) Internal Power MOSFETs
Proprietary Switching Loss Reduction
Technique
Power-Good Indicator in QFN Package
Soft Shutdown
Programmable Switching Frequency
OCP, SCP, OVP, UVP Protection and
Thermal Shutdown
Optional OCP Protection: Latch-Off Mode
and Hiccup Mode
Output Adjustable from 0.815V to 13V
Available in a QFN12 (2mmx3mm) Package
Networking Systems
Distributed Power Systems
MP28259
DESCRIPTION
The MP28259 is a fully-integrated synchronous,
rectified, step-down switch mode converter with
programmable frequency. It offers a very
compact solution that can achieve a 2A
continuous output current over a wide input
supply range with excellent load and line
regulation, and can operate at high efficiency
over a wide output current load range.
Constant-On-Time
(COT)
control
mode
provides fast transient response and eases loop
stabilization.
Full protection features include SCP, OCP, OVP,
UVP, and thermal shut down.
The MP28259 requires a minimal number of
readily-available standard external components.
The device is available in a space saving
2mmx3mm 12-pin QFN package.
APPLICATIONS
All MPS parts are lead-free and adhere to the RoHS directive. For MPS green
status, please visit MPS website under Quality Assurance. “MPS” and “The
Future of Analog IC Technology” are Registered Trademarks of Monolithic
Power Systems, Inc.
TYPICAL APPLICATION
9
IN
VIN
4.2V - 20V
BST
3
R7
C1
C3
MP28259
8
FREQ
SW
2, 10
L1
VOUT
1.2V
R1
C2
C5
4
VCC
R4
7
C4
220pF
OFF ON EN
5
6
FB
EN
PG
R2
GND
1, 11, 12
MP28259 Rev. 1.34
www.MonolithicPower.com
4/27/2012
MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited.
© 2012 MPS. All Rights Reserved.
1
MP28259 – 2A, 4.2V-20V INPUT, FAST TRANSIENT SYNCHRONOUS STEP-DOWN CONVERTER
ORDERING INFORMATION
Part Number*
MP28259DD
MP28259DD-A
OCP Protection
Latch-off mode
Hiccup mode
Package
QFN12 (2x3mm)
QFN12 (2x3mm)
Top Marking
AAT
ACX
* For Tape & Reel, add suffix –Z (e.g. MP28259DD–Z).
For RoHS Compliant Packaging, add suffix –LF (e.g. MP28259DD–LF–Z)
PACKAGE REFERENCE
TOP VIEW
GND
GND
SW
BST
VCC
EN
12
11
10
9
8
7
6
GND
SW
IN
FREQ
FB
1
2
3
4
5
SW
PG
QFN12 (2x3mm)
ABSOLUTE MAXIMUM RATINGS
(1)
Supply Voltage V
IN
.......................................22V
V
SW
...-0.3V(-4V<10ns) to V
IN
+ 0.3V(24V<10ns)
V
BST
.................................................... V
SW
+ 6V
All Other Pins................................. -0.3V to +6V
(2)
Continuous Power Dissipation (T
A
= 25°C)
QFN12 (2x3mm) ........................................1.8W
Junction Temperature ............................. 150°C
Lead Temperature ................................... 260°C
Storage Temperature............... -65°C to +150°C
Thermal Resistance
(4)
QFN12 (2x3mm) .................... 70 ...... 15...
°C/W
Notes:
1) Exceeding these ratings may damage the device.
2) The maximum allowable power dissipation is a function of the
maximum junction temperature T
J
(MAX), the junction-to-
ambient thermal resistance
θ
JA
, and the ambient temperature
T
A
. The maximum allowable continuous power dissipation at
any ambient temperature is calculated by P
D
(MAX) = (T
J
(MAX)-T
A
)/θ
JA
. Exceeding the maximum allowable power
dissipation will cause excessive die temperature, and the
regulator will go into thermal shutdown. Internal thermal
shutdown circuitry protects the device from permanent
damage.
3) The device is not guaranteed to function outside of its
operating conditions.
4) Measured on JESD51-7, 4-layer PCB.
θ
JA
θ
JC
Recommended Operating Conditions
(3)
Supply Voltage V
IN
.......................... 4.2V to 20V
Output Voltage V
OUT
.................... 0.815V to 13V
Operating Junction Temp. (T
J
). -40°C to +125°C
MP28259 Rev. 1.34
www.MonolithicPower.com
4/27/2012
MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited.
© 2012 MPS. All Rights Reserved.
2
MP28259 – 2A, 4.2V-20V INPUT, FAST TRANSIENT SYNCHRONOUS STEP-DOWN CONVERTER
ELECTRICAL CHARACTERISTICS
V
IN
= 12V, T
A
= 25°C, unless otherwise noted.
Parameters
Supply current (shutdown)
Supply current (quiescent)
HS switch-on resistance
LS switch On-resistance
Switch leakage
Current limit
One-shot on time
Minimum off time
Fold-back off time
OCP hold-off time
Feedback toltage
Feedback current
Soft-start time
EN rising threshold
EN threshold hysteresis
EN input current
Power-good rising threshold
Power-good falling threshold
Power-good delay
Power-good sink current
capability
Power-good leakage current
VIN under-voltage lockout
Threshold Rising
VIN under-voltage lockout
threshold hysteresis
Thermal shutdown
Thermal shutdown hysteresis
Note:
5) Guaranteed by design.
(5)
Symbol
I
IN
I
IN
HS
RDS-ON
LS
RDS-ON
SW
LKG
I
LIMIT
T
ON
T
OFF
T
FB
T
OC
V
FB
I
FB
T
SS
EN
Vth-Hi
EN
Vth-Hys
IEN
PG
Vth-Hi
PG
Vth-Lo
PGTd
V
PG
I
PG_LEAK
INUV
Vth
INUV
HYS
T
SD
T
SD-HYS
Condition
V
EN
= 0V
V
EN
= 2V, V
FB
= 0.9V
Min
Typ
0
360
130
80
0
Max
Units
μA
μA
mΩ
mΩ
V
EN
= 0V, V
SW
= 0V or
12V
After soft-start time-out
R
7
= 300kΩ, V
OUT
= 1.2V
I
LIM
= 1
I
LIM
= 1
T
A
= 25°C
T
A
= -40°C to 85°C
V
FB
= 800mV
10
μA
A
ns
ns
μs
μs
mV
mV
nA
ms
V
mV
μA
V
FB
V
FB
ms
3
4
250
220
4.5
50
815
10
1
1.35
500
2
0
0.9
0.85
0.5
0.4
10
3.1
300
150
25
807
803
823
827
50
1.6
1.05
V
EN
= 2V
V
EN
= 0V
Sink 4mA
V
PG
= 3.3V
V
nA
V
mV
°C
°C
MP28259 Rev. 1.34
www.MonolithicPower.com
4/27/2012
MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited.
© 2012 MPS. All Rights Reserved.
3
MP28259 – 2A, 4.2V-20V INPUT, FAST TRANSIENT SYNCHRONOUS STEP-DOWN CONVERTER
PIN FUNCTIONS
QFN12
(2x3mm)
Pin #
9
1, 11, 12
2, 10,
Exposed Pad
3
4
5
7
8
6
Name
Description
Supply Voltage. The MP28259 operates from a +4.2V to +20V input rail. C1 is
needed to decouple the input rail. Use wide PCB traces and multiple vias to make the
connection.
System Ground. These pins are the reference ground for the regulated output
voltage, and require special consideration during PCB layout.
Switch Output. Connect with wide PCB traces.
Bootstrap. Requires a capacitor connected between SW and BST pins is required to
form a floating supply across the high-side switch driver.
Bias Supply. Decouple with a 4.7µF ceramic capacitor as close to this pin as
possible.
EN = 1 to enable the MP28259. For automatic start-up, connect EN pin to VIN with a
pull-up resistor.
Feedback. Sets the output voltage when connected to the tap of an external resistor
divider, connected between output and GND.
Frequency. Set during CCM operation. Connect a resistor R
7
to IN to set the
switching frequency. Decouple with a 1nF capacitor.
Power-Good Output, The output of this pin is an open drain that goes high if the
output voltage is higher than 90% of the nominal voltage. There is a delay of (0.5ms
+ 0.5xSS time) delay from FB
≥
90% to PG goes high.
IN
GND
SW
BST
VCC
EN
FB
FREQ
PG
MP28259 Rev. 1.34
www.MonolithicPower.com
4/27/2012
MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited.
© 2012 MPS. All Rights Reserved.
4
MP28259 – 2A, 4.2V-20V INPUT, FAST TRANSIENT SYNCHRONOUS STEP-DOWN CONVERTER
TYPICAL PERFORMANCE CHARACTERISTICS
V
IN
= 12V, V
OUT
= 1.2V, L = 2μH, T
A
= 25°C, unless otherwise noted.
Efficiency vs.
Load Current
95
85
80
75
70
65
60
55
50
0.01
0.1
I
OUT
(A)
1
10
V
IN
=16V
F
SW
=500kHz
V
IN
=12V
100
95
90
85
80
75
70
0.01
0.1
I
OUT
(A)
1
10
V
IN
=12V
0
V
IN
=8V
-0.2
-0.4
-0.6
-0.8
-1
-1.2
5
7
9
11 13 15 17 19 21
V
IN
(V)
90 V
IN
=5V
Line Regulation
I
OUT
=2A
Load Regulation
0.5
V
IN
=16V
0
-0.5
-1
-1.5
-2
0
0.5
1
I
OUT
(A)
1.5
2
V
IN
=12V
14
12
10
8
6
4
2
0
0
0.5
1
I
OUT
(A)
1.5
2
0
0
0.5
1
I
OUT
(A)
1.5
2
V
IN
=12V
5
15
20
10
V
IN
=12V
V
OUT
VS
. I
OUT
V
OUT
=1.2V, Freq=500kHz
500
480
460
F
SW
(kHz)
F
SW
(kHz)
500
480
460
440
420
400
1.24
1.22
1.2
VOUT(V)
V
IN
=12V
V
IN
=16V
V
IN
=8V
V
IN
=5V
440
420
400
380
360
-40 -20 0 20 40 60 80 100 120 140
1.18
1.16
1.14
1.12
5
9
13
V
IN
(V)
17
21
1.1
0.01
0.1
I
OUT
(A)
1
10
MP28259 Rev. 1.34
www.MonolithicPower.com
4/27/2012
MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited.
© 2012 MPS. All Rights Reserved.
5
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