MP28128
2.5A, 1.5MHz Synchronous
Step-Down Converter
The Future of Analog IC Technology
DESCRIPTION
The MP28128 is a 1.5MHz fixed frequency
PWM synchronous step-down regulator with
internal compensation. MP28128 operates from
a 2.7V to 6V input and generates an adjustable
output voltage from 0.8V to 0.9xV
IN
at up to
2.5A load current.
The MP28128 integrates an 80mΩ high-side
switch and a 60mΩ synchronous rectifier for
high efficiency without an external Schottky
diode. With peak current mode control and
internal compensation, the MP28128 based
solution delivers a very compact footprint with a
minimum component count. Fault condition
protection
includes
hiccup
short-circuit
protection, cycle-by-cycle current limiting and
thermal shutdown. Other features include
frequency synchronization input, internal soft-
start and power good output.
The MP28128 is available in a small 3mm x
3mm 10-lead QFN package.
FEATURES
•
•
•
•
•
•
•
•
•
•
•
•
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•
•
•
2.5A Output Current
Input Operation Range: 2.7V to 6V
1.5% Output Accuracy
Internal Power MOSFET Switches
All Ceramic Capacitor Design
1.5MHz Fixed Switching Frequency
Internal Soft-Start
Frequency Synchronization Input
Power Good Output
Cycle-by-Cycle Current Limiting
Thermal Shutdown
3mm x 3mm 10-lead QFN Package
µP/ASIC/DSP/FPGA Core and I/O Supplies
Printers and LCD TVs
Network and Telecom Equipment
Point of Load Regulators
APPLICATIONS
“MPS” and “The Future of Analog IC Technology” are Trademarks of Monolithic
Power Systems, Inc.
TYPICAL APPLICATION
Efficiency vs.
Output Current
V
IN
IN
BS
SW
95
90
85
80
75
70
0
0.5
1
1.5
2
2.5
OUTPUT CURRENT (A)
5V to 1.8V 5V to 3.3V
5V to 2.5V
POK
POK
OFF ON
EN/SYNC
GND
FB
EFFICIENCY (%)
MP28128 Rev. 0.92
2/13/2009
www.MonolithicPower.com
MPS Proprietary Information. Unauthorized Photocopy and Duplication Prohibited.
© 2009 MPS. All Rights Reserved.
1
MP28128 – 2.5A, 1.5MHz SYNCHRONOUS STEP-DOWN CONVERTER
PACKAGE REFERENCE
TOP VIEW
FB
GND
SW
IN
BS
1
2
3
4
5
10
9
8
7
6
EN/SYNC
GND
SW
IN
POK
ABSOLUTE MAXIMUM RATINGS
(1)
IN to GND ...................................
–
0.3V to +6.5V
SW to GND ..........................
–
0.3V to V
IN
+ 0.3V
SW to GND ............ -2.5V to V
IN
+2.5V for <50nS
FB, EN/SYNC, POK to GND..........
–
0.3V to +6.5V
BS to SW ....................................
–
0.3V to +6.5V
Junction Temperature...............................150°C
Lead Temperature ....................................260°C
Storage Temperature ..............
–
65°C to +150°C
Recommended Operating Conditions
(2)
EXPOSED PAD
ON BACKSIDE
Connect to GND
Supply Voltage V
IN
............................. 2.7V to 6V
Output Voltage V
OUT
................. 0.8V to 0.9 x V
IN
Operating Temperature .............
–
40°C to +85°C
Thermal Resistance
Part Number*
MP28128DQ
*
Package
QFN10
(3mm x 3mm)
Temperature
–40°C to +85°C
(3)
QFN10 (3mm x 3mm) ............. 50 ...... 12...
°C/W
Notes:
1) Exceeding these ratings may damage the device.
2) The device is not guaranteed to function outside of its
operating conditions.
3) Measured on approximately 1” square of 1 oz copper.
θ
JA
θ
JC
For Tape & Reel, add suffix –Z (eg. MP28128DQ–Z)
For RoHS Compliant Packaging, add suffix –LF
(eg. MP28128DQ–LF–Z)
ELECTRICAL CHARACTERISTICS
(4)
V
IN
= V
EN
= 3.6V, T
A
= +25°C, unless otherwise noted.
Parameters
Supply Current
Shutdown Current
IN Undervoltage Lockout
Threshold
IN Undervoltage Lockout
Hysteresis
Regulated FB Voltage
Condition
V
EN
= V
IN
V
FB
= 0.85V
V
EN
= 0V, V
IN
= 6V
Rising Edge
Min
Typ
750
1
2.59
210
T
A
= +25°C
–40°C
≤
T
A
≤
+85°C
V
FB
= 0.85V
–40°C
≤
T
A
≤
+85°C
–40°C
≤
T
A
≤
+85°C
0.788
0.780
1.6
0.4
120
80
60
–10
1.8
10
0.800
0.800
±50
0.812
0.820
2.69
Max
Units
µA
µA
V
mV
V
V
nA
V
V
µs
mΩ
mΩ
µA
V
FB Input Current
EN High Threshold
EN Low Threshold
Internal Soft-Start Time
High-Side Switch On-Resistance I
SW
= 300mA
Low-Side Switch On-Resistance I
SW
= –300mA
V
EN
= 0V; V
IN
= 6V
SW Leakage Current
V
SW
= 0V or 6V
BS Under Voltage Lockout
Threshold
MP28128 Rev. 0.92
2/13/2009
www.MonolithicPower.com
MPS Proprietary Information. Unauthorized Photocopy and Duplication Prohibited.
© 2009 MPS. All Rights Reserved.
2
MP28128 – 2.5A, 1.5MHz SYNCHRONOUS STEP-DOWN CONVERTER
ELECTRICAL CHARACTERISTICS
(4)
(continued)
V
IN
= V
EN
= 3.6V, T
A
= +25°C, unless otherwise noted.
Parameters
High-Side Switch Current Limit
Low-Side Switch Current Limit
Oscillator Frequency
Maximum Synch Frequency
Minimum Synch Frequency
Minimum On Time
Maximum Duty Cycle
POK Upper Trip Threshold
POK Lower Trip Threshold
POK Output Voltage Low
POK Deglitch Timer
Thermal Shutdown Threshold
Condition
Sourcing
Sinking
Min
4.0
1.2
Typ
4.5
3.5
1.5
2
1
50
90
10
-10
30
150
Max
Units
A
A
MHz
MHz
MHz
ns
%
%
%
V
µs
°C
1.8
FB respect to the nominal value
FB respect to the nominal value
I
SINK
= 5mA
Hysteresis = 20°C
0.4
Note:
4) Production test at +25°C. Specifications over the temperature range are guaranteed by design and characterization.
PIN FUNCTIONS
Pin #
6
4, 7
3, 8
2, 9
5
1
Name
POK
IN
SW
GND,
Exposed
Pad
BS
Description
Open Drain Power Good Output. “HIGH” output indicates V
OUT
is within ±10% window.
“LOW” output indicates V
OUT
is out of ±10% window. POK is pulled down in shutdown.
Input Supply. A decoupling capacitor to ground is required close to these pins to reduce
switching spikes.
Switch Node Connection to the Inductor. These pins connect to the internal high and low-
side power MOSFET switches. All SW pins must be connected together externally.
Ground. Connect these pins with larger copper areas to the negative terminals of the input
and output capacitors. Exposed pad and GND must be connected together.
10
Bootstrap. A capacitor between this pin and SW provides a floating supply for the high-side
gate driver.
Feedback. This is the input to the error amplifier. An external resistive divider connects this
FB
pin between the output and GND. The voltage on the FB pin compares to the internal 0.8V
reference to set the regulation voltage.
Enable and Frequency Synchronization Input Pin. Forcing this pin below 0.4V shuts down
EN/SYNC the part. Forcing this pin above 1.6V turns on the part. Applying a 1MHz to 2MHz clock
signal to this pin synchronizes the internal oscillator frequency to the external source.
MP28128 Rev. 0.92
2/13/2009
www.MonolithicPower.com
MPS Proprietary Information. Unauthorized Photocopy and Duplication Prohibited.
© 2009 MPS. All Rights Reserved.
3
MP28128 – 2.5A, 1.5MHz SYNCHRONOUS STEP-DOWN CONVERTER
TYPICAL PERFORMANCE CHARACTERISTICS
V
IN
= 5V, V
OUT
= 1.8V, T
A
= +25ºC, unless otherwise noted.
Steady State Operation
No Load
V
OUT
10mV/div.
Steady State Operation
Half Load
V
OUT
10mV/div.
Steady State Operation
Full Load
V
OUT
10mV/div.
Inductor
1A/div.
Inductor
1A/div.
V
SW
5V/div.
Inductor
1A/div.
V
SW
5V/div.
V
SW
5V/div.
400ns/div
400ns/div
400ns/div
Load Transient
1.25A-2.5A Step Resistive Load
Start-up through enable
No Load
V
OUT
100mV/div.
V
OUT
1V/div.
V
POK
2V/div.
Inductor
1A/div.
V
EN
2V/div.
MP28128 Rev. 0.92
2/13/2009
www.MonolithicPower.com
MPS Proprietary Information. Unauthorized Photocopy and Duplication Prohibited.
© 2009 MPS. All Rights Reserved.
4
MP28128 – 2.5A, 1.5MHz SYNCHRONOUS STEP-DOWN CONVERTER
TYPICAL PERFORMANCE CHARACTERISTICS
V
IN
= 5V, V
OUT
= 1.8V, T
A
= +25ºC, unless otherwise noted.
Start Up through Enable
Full Load
Shut Down through Enable
No Load
Shut Down through Enable
Full Load
V
OUT
1V/div.
V
POK
2V/div.
V
OUT
1V/div.
V
EN
2V/div.
V
POK
5V/div.
v
400ms/div
V
OUT
2V/div.
V
EN
5V/div.
V
EN
2V/div.
V
POK
2V/div.
1ms/div
Short Circut Protection
V
IN
=5V,V
OUT
=1.8V
Short Circuit Recovery
V
IN
=5V,V
OUT
=1.8V
V
OUT
1V/div.
V
SW
5V/div.
V
OUT
1V/div.
V
SW
5V/div.
Inductor
2A/div.
400 s/div
Inductor
1A/div.
1ms/div
MP28128 Rev. 0.92
2/13/2009
www.MonolithicPower.com
MPS Proprietary Information. Unauthorized Photocopy and Duplication Prohibited.
© 2009 MPS. All Rights Reserved.
5
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