MP8725
The Future of Analog IC Technology
21V, 5A, 500kHz
Synchronous Step-down Converter
DESCRIPTION
The MP8725 is a high frequency synchronous
rectified step-down switch mode converter with
built in internal power MOSFETs. It offers a
very compact solution to achieve 5A continuous
output current over a wide input supply range
with excellent load and line regulation. The
MP8725 operates at high efficiency over a wide
output current load range.
Current mode operation provides fast transient
response and eases loop stabilization.
Full protection features include OCP and thermal
shut down.
The MP8725 requires a minimum number of
readily available standard external components
and is available in a space saving 3mm x 4mm
14-pin QFN package.
FEATURES
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
Wide 4.5V to 21V Operating Input Range
5A Output Current
Low R
DS
(ON) Internal Power MOSFETs
Proprietary Switching Loss Reduction
Technique
Fixed 500kHz Switching Frequency
Sync from 300kHz to 2MHz External Clock
Internal Compensation
OCP Protection and Thermal Shutdown
Output Adjustable from 0.8V
Available in 14-pin QFN3x4 Package
Notebook Systems and I/O Power
Networking Systems
Digital Set Top Boxes
Personal Video Recorders
Flat Panel Television and Monitors
Distributed Power Systems
APPLICATIONS
“MPS” and “The Future of Analog IC Technology” are Registered Trademarks of
Monolithic Power Systems, Inc.
The information in this datasheet about the product and its associated
technologies are proprietary and intellectual property of Monolithic Power
Systems and are protected by copyright and pending patent applications.
TYPICAL APPLICATION
（FOR
NOTEBOOK）
Efficiency
4.5V-21V
VIN
C1
22uF
PG
9 PG
R3
100K
11
C3
0.1uF
7
SW
2,3,4,5
1
IN
BST
6
100
90
L1
2uH
V
OUT
=1.2V
Vin=5V
Vin=12V
EFFICIENCY (%)
C4
0.1uF
80
70
60
50
40
30
20
10
0
0
1
2
3
4
5
OUTPUT CURRENT (A)
Vin=21V
MP8725
VCC
FB
EN/SYNC
8
Rt
24.9K
R1
4.99K
C2
47uF
R2
10K
ON/OFF
NC
10
GND
12,13
AGND
14
MP8725 Rev. 1.0
9/21/2011
www.MonolithicPower.com
MPS Proprietary Information. Unauthorized Photocopy and Duplication Prohibited.
© 2011 MPS. All Rights Reserved.
1
MP8725 – 5A, 21V, SYNCHRONOUS STEP-DOWN CONVERTER WITH INTERNAL MOSFETS
ORDERING INFORMATION
Part Number*
MP8725EL
Package
3x4 QFN14
Top Marking
8725
Free Air Temperature (T
A
)
-20°C to +85°C
For Tape & Reel, add suffix –Z (e.g. MP8725EL–Z).
For RoHS compliant packaging, add suffix –LF (e.g. MP8725EL–LF–Z)
PACKAGE REFERENCE
AGND
NC
ABSOLUTE MAXIMUM RATINGS
(1)
Supply Voltage V
IN
....................................... 22V
V
SW
.........................–0.3V (-5V for<10ns) to 23V
V
BS
....................................................... V
SW
+ 6V
All Other Pins ..................................-0.3V to +6V
(2)
Continuous Power Dissipation (T
A
= +25°C)
……………………………………………....2.6W
Junction Temperature ...............................150°C
Lead Temperature ....................................260°C
Storage Temperature............... -65°C to +150°C
Thermal Resistance
(4)
3x4 QFN14 ............................. 48 ...... 11...
°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
...........................4.5V to 21V
Operating Junct. Temp (T
J
)...... -20°C to +125°C
MP8725 Rev. 1.0
9/21/2011
www.MonolithicPower.com
MPS Proprietary Information. Unauthorized Photocopy and Duplication Prohibited.
© 2011 MPS. All Rights Reserved.
2
MP8725 – 5A, 21V, SYNCHRONOUS STEP-DOWN CONVERTER WITH INTERNAL MOSFETS
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
(4)
Oscillator Frequency
Fold-back Frequency
Maximum Duty Cycle
Sync Frequency Range
Feedback Voltage
Feedback Current
EN Rising Threshold
EN Threshold Hysteresis
EN Input Current
EN Turn Off Delay
Power Good Rising Threshold
Power Good Falling Threshold
Power Good Delay
Power Good Sink Current
Capability
Power Good Leakage Current
V
IN
Under Voltage Lockout
Threshold Rising
V
IN
Under Voltage Lockout
Threshold Hysteresis
VCC Regulator
VCC Load Regulation
Soft-Start Period
Thermal Shutdown
Note:
5) Guaranteed by design.
Symbol
I
IN
I
q
HS
RDS-ON
LS
RDS-ON
SW
LKG
I
LIMIT
F
SW
F
FB
D
MAX
F
SYNC
V
FB
I
FB
V
EN_RISING
V
EN_HYS
I
EN
EN
Td-Off
PG
Vth-Hi
PG
Vth-Lo
PG
Td
V
PG
I
PG_LEAK
INUV
Vth
INUV
HYS
V
CC
Condition
V
EN
= 0V
V
EN
= 2V, V
FB
= 1V
Min
Typ
0
0.7
120
20
0
Max
Units
μA
mA
mΩ
mΩ
μA
A
kHz
f
SW
%
MHz
mV
nA
V
V
μA
μs
V
FB
V
FB
μs
V
EN
= 0V, V
SW
= 0V or
12V
V
FB
= 0.75V
V
FB
= 300mV
V
FB
= 700mV
5.5
425
85
0.3
789
1.0
V
EN
= 2V
V
EN
= 0V
10
8
575
6
500
0.25
90
805
10
1.3
0.4
2
0
5
0.9
0.7
20
V
FB
= 800mV
2
821
50
1.6
Sink 4mA
V
PG
= 3.3V
3.8
4.0
880
Icc=5mA
2.5
5
5
4
150
0.4
10
4.2
V
nA
V
mV
V
%
ms
°C
5.5
T
SD
MP8725 Rev. 1.0
9/21/2011
www.MonolithicPower.com
MPS Proprietary Information. Unauthorized Photocopy and Duplication Prohibited.
© 2011 MPS. All Rights Reserved.
3
MP8725 – 5A, 21V, SYNCHRONOUS STEP-DOWN CONVERTER WITH INTERNAL MOSFETS
PIN FUNCTIONS
Pin #
1
2,3,4,5
6
7
Name
IN
SW
BST
EN/SYNC
Description
Supply Voltage. The MP8725 operates from a +4.5V to +21V input rail. C1 is
needed to decouple the input rail. Use wide PCB traces and multiple vias to make
the connection.
Switch Output. Use wide PCB traces and multiple vias to make the connection.
Bootstrap. A capacitor connected between SW and BS pins is required to form a
floating supply across the high-side switch driver.
EN=1 to enable the chip. External clock can be applied to EN pin for changing
switching frequency. For automatic start-up, connect EN pin to VIN by proper EN
resistor divider as Figure 2 shows.
Feedback. An external resistor divider from the output to GND, tapped to the FB
pin, sets the output voltage. To prevent current limit run away during a short circuit
fault condition the frequency fold-back comparator lowers the oscillator frequency
when the FB voltage is below 500mV.
Power Good Output, the output of this pin is open drain. Power good threshold is
90% low to high and 70% high to low of regulation value.
No Internal Connection.
Bias Supply. Decouple with 0.1μF~0.22μF cap. And the capacitance should be no
more than 0.22μF.
System Ground. This pin is the reference ground of the regulated output voltage.
For this reason care must be taken in PCB layout.
Signal Ground. AGND is not internally connected to System Ground, make sure
AGND connected to system Ground in PCB layout.
8
FB
9
10,
Exposed Pad
11
12,13
14
PG
NC
VCC
GND
AGND
MP8725 Rev. 1.0
9/21/2011
www.MonolithicPower.com
MPS Proprietary Information. Unauthorized Photocopy and Duplication Prohibited.
© 2011 MPS. All Rights Reserved.
4
MP8725 – 5A, 21V, SYNCHRONOUS STEP-DOWN CONVERTER WITH INTERNAL MOSFETS
TYPICAL PERFORMANCE CHARACTERISTICS
VIN = 12V, VOUT = 1.2V, L = 1.8µH, TA = +25ºC, unless otherwise noted.
Enable Supply Current
vs Input Voltage
ENABLE SUPPLY CURRENT (mA)
1000
900
800
700
600
500
400
300
0
V
FB
=1V
5
10
15
20
INPUT VOLTAGE (V)
25
-1
0
0
0.5
5
1
Disable Supply Current
vs Input Voltage
VCC Regulator Line Regulation
6
5.5
Vcc(V)
V
EN
=0V
5
10
15
20
INPUT VOLTAGE (V)
25
4.5
4
3.5
3
-0.5
0
5
10
15
20
INPUT VOLTAGE (V)
25
Peak Current vs Duty Cycle
8
7.5
100
Operating Range
1
0.8
0.6
10
0.4
0.2
0
-0.2
1
-0.4
-0.6
-0.8
0.1
-1
Load Regulation
7
6.5
6
5.5
5
OUTPUT VOLTAGE (V)
PEAK CURRENT (A)
V
IN
=12.0V
V
IN
=21.0V
V
IN
=4.5V
0 10 20 30 40 50 60 70 80 90 100
0
5
10
15
20
INPUT VOLTAGE (V)
25
0
1
2
3
4
OUTPUT CURRENT (A)
5
Line Regulation
0.6
50
45
40
35
30
25
20
15
10
5
0
Case Temperature Rise
vs Output Current
)
0.2
0
-0.2
-0.4
-0.6
0
I
O
=0.0A
I
O
=2.5A
I
O
=5.0A
5
10
15
20
25
CASE TEMPERATURE RISE (
0.4
0
1
2
3
4
5
6
INPUT VOLTAGE (V)
OUTPUT CURRENT (A)
MP8725 Rev. 1.0
9/21/2011
www.MonolithicPower.com
MPS Proprietary Information. Unauthorized Photocopy and Duplication Prohibited.
© 2011 MPS. All Rights Reserved.
5
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