MP28224DQ-LF [MPS]
Switching Regulator, Current-mode, 2.4A, 1800kHz Switching Freq-Max, 3 X3 MM, ROHS COMPLIANT, MO-229VEED-5, QFN-10;
| 型号： | MP28224DQ-LF |
| 厂家： | 
MONOLITHIC POWER SYSTEMS |
| 描述： | Switching Regulator, Current-mode, 2.4A, 1800kHz Switching Freq-Max, 3 X3 MM, ROHS COMPLIANT, MO-229VEED-5, QFN-10 开关 输出元件 |
| 文件： | 总7页 (文件大小：204K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
MP28224
1.5A Step-Down Switcher
with Auxiliary 0.5A LDO
The Future of Analog IC Technology
FEATURES
DESCRIPTION
•
•
•
1.5A and 0.5A Outputs
The MP28224 is an internally compensated
1.5MHz fixed frequency PWM 1.5A step-down
switcher with an auxiliary 0.5A low dropout
(LDO) linear regulator. It is ideal for powering
portable equipment that runs from a single cell
Lithium-Ion (Li+) Battery. The MP28224 can
provide 1.5A and 0.5A of load current from a
2.5V to 6V input voltage. Both output voltages
can be regulated as low as 0.6V.
Internal Power MOSFET Switches
Stable with Low ESR Output Ceramic
Capacitors
•
•
•
•
•
•
•
•
•
•
•
Up to 95% Efficiency
1μA Shutdown Current
1.5MHz Switching Frequency
Thermal Shutdown
Cycle-by-Cycle Over Current Protection
Short Circuit Protection
Internal Soft-start for Switcher
Power On Reset Output
2.5V to 6V Input Range VIN1 for Switcher
1.1V to VIN1 Input Range VIN2 for LDO
Available in 10-Pin QFN Packages
The 1.5A switcher features an integrated
high-side switch and synchronous rectifier for
high efficiency. With peak current mode control
and internal compensation, the MP28224 can
be stabilized with ceramic capacitors and small
inductors. Fault condition protection includes
cycle-by-cycle current limiting and thermal
shutdown.
APPLICATIONS
•
•
•
•
•
DVD+/-RW Drives
Smart Phones
PDAs
Digital Cameras
Portable Instruments
The auxiliary 0.5A LDO output is used to power
noise sensitive circuitry. It has a separate input
supply to reduce power dissipation and noise
from the main switcher.
MP28224 is available in the small 10-pin QFN
packages.
“MPS” and “The Future of Analog IC Technology” are Registered Trademarks of
Monolithic Power Systems, Inc.
TYPICAL APPLICATION
POWER OK
9
2
OFF ON
EN1
IN1
EN2
PWROK
3
4
6
1
8
V
IN
L1
2.5V - 6V
7
OUT2
SW1
IN2
OUT2
FB2
MP28224
1.2V @ 0.5A
OUT1
1.8V @ 1.5A
10
5
FB1
GND
MP28224 Rev. 0.1
12/13/2007
1
MPS Confidential Information. Unauthorized Photocopy and Duplication Prohibited.
MP28224 – 1.5A STEP-DOWN SWITCHER WITH AUXILIARY 0.5A LDO
PACKAGE REFERENCE
ABSOLUTE MAXIMUM RATINGS (1)
IN1, OUT1/2 to GND .................–0.3V to + 6.5V
IN2 to GND.........................–0.3V to VIN1 + 0.3V
SW1 to GND.......................–0.3V to VIN1 + 0.3V
PWROK to GND.........................–0.3V to +6.5V
FB1/2, EN1/2 to GND.................–0.3V to +6.5V
Operating Temperature .............–40°C to +85°C
Junction Temperature...............................150°C
Lead Temperature....................................260°C
Storage Temperature .............–65°C to +150°C
TOP VIEW
FB1
EN1
IN1
1
2
3
4
5
10 FB2
9
8
7
6
EN2
PWROK
OUT2
IN2
SW1
GND
Recommended Operating Conditions (2)
Supply Voltage VIN1 ........................... 2.5V to 6V
Supply Voltage VIN2 ..........................1.2V to VIN1
Output Voltage VOUT__........................ 0.6V to 6V
Operating Temperature .............–40°C to +85°C
EXPOSED PAD
ON BACKSIDE
Part Number**
Package
Temperature
QFN10
(3mm x 3mm)
MP28224DQ
–40°C to +85°C
Thermal Resistance (3)
θJA
θJC
** For Tape & Reel, add suffix –Z (eg. MP28224DQ–Z)
For RoHS packaging compliant, add suffix –LF (eg.
QFN10 (3mm x 3mm).............50...... 12... °C/W
MP28224DQ–LF–Z)
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.
ELECTRICAL CHARACTERISTICS (4)
VIN1/2 = VEN1/2 = 3.6V, TA = +25°C, unless otherwise noted.
Parameters
Condition
Min
Typ
Max
Units
VIN1/2 = 3.6V, VEN1=3.6V, VEN2=0V
500
600
VFB1 = 0.58V
No Load Supply Current
VIN1/2 = 3.6V, VEN1=0V, VEN2=3.6V
100
VFB2 = 0.62V
Shutdown Current
VEN1/2 = 0V, VIN1/2 = 6V
Hysteresis = 20°C
0.01
150
1
μA
Thermal Shutdown Trip Threshold
°C
FB1/2 with respect to the Nominal
Value
PWROK Upper Trip Threshold
PWROK Lower Trip Threshold
10
%
FB1/2 with respect to the Nominal
Value
–10
%
V
PWROK Output Lower Voltage
PWROK Deglitch Timer (FB1)
PWROK Deglitch Timer (FB2)
EN1/2 Trip Threshold
ISINK = 5mA
0.3
1.5
Switching Regulator
LDO
50
150
0.96
1
μs
–40°C ≤ TA ≤ +85°C
0.3
V
EN1/2 Pull Down Resistor
MΩ
MP28224 Rev. 0.1
12/13/2007
2
MPS Confidential Information. Unauthorized Photocopy and Duplication Prohibited.
MP28224 – 1.5A STEP-DOWN SWITCHER WITH AUXILIARY 0.5A LDO
ELECTRICAL CHARACTERISTICS (4) (continued)
VIN1/2 = VEN1/2 = 3.6V, TA = +25°C, unless otherwise noted.
Parameters
Condition
Min
Typ
Max
Units
Switching Regulator
IN1 Under Voltage Lockout Threshold Rising Edge, Hysteresis=0.2V
1.7
2.0
2.2
V
V
TA = +25°C
0.588 0.600 0.612
0.582 0.600 0.618
Regulated FB1Voltage
–40°C ≤ TA ≤ +85°C
FB1 Input Bias Current
VFB1 = 0.62V
ISW1 = 100mA
ISW1 = –100mA
–50
–2
0.1
0.1
+50
nA
Ω
SW1 PFET On Resistance
SW1 NFET On Resistance
Ω
V
EN = 0V, VIN = 6V
SW1 Leakage Current
–1
+1
μA
VSW = 0V or 6V
Duty Cycle = 100%,
Current Pulse Width < 1ms
SW1 PFET Peak Current Limit
1.6
1.2
2.0
1.5
2.4
1.8
A
Oscillator Frequency
Linear Regulator LDO
IN2 Input Range
MHz
ILOAD2 = 10mA, VOUT2=VFB2
TA = +25°C
1.1
VIN1
V
V
0.588 0.600 0.612
0.582 0.600 0.618
Regulated FB2 Voltage
–40°C ≤ TA ≤ +85°C
VFB2 = 0.6V
FB2 Input Bias Current
OUT2 Output Current
OUT2 Short Protection
Dropout Voltage
–50
500
–2
+50
nA
mA
mA
mV
VOUT2 = 1.2V
VOUT2 = 0V
700
250
ILOAD = 0.3A, VOUT2 = 1.2V
Notes:
4) Production test at +25°C. Specifications over the temperature range are guaranteed by design and characterization.
PIN FUNCTIONS
Pin #
Name Description
1
2
FB1
EN1
Feedback Input for the switcher output VOUT1.
Enable Inputs for the switcher.
Main Input Supply Pin. Input supply for both the switcher and the auxiliary low dropout (LDO)
linear regulator.
3
IN1
4
5
6
SW1
GND
IN2
Switcher switch node.
Ground.
Input Supply for the auxiliary linear regulator LDO output power device.
Output of the 500mA LDO. The LDO is designed to be stable with an external minimum 1µF
ceramic capacitor at 500mA load current.
7
OUT2
Power On Reset Open Drain Output. HIGH output indicates that both outputs are within ±10%
of the regulation value. LOW output indicates that the output is out of ±10% window. PWROK
is pulled down in shutdown. The PWROK window comparators have 50µs deglitch timer for
the switcher and 150µs deglitch timer for the linear regulator LDO to avoid false trigger during
load transient.
8
PWROK
9
EN2
FB2
Enable Input for the linear regulator LDO.
10
Feedback Input for the linear regulator output VOUT2.
MP28224 Rev. 0.1
12/13/2007
3
MPS Confidential Information. Unauthorized Photocopy and Duplication Prohibited.
MP28224 – 1.5A STEP-DOWN SWITCHER WITH AUXILIARY 0.5A LDO
OPERATION
The MP28224 is a constant frequency current
mode PWM 1.5A step-down switcher with an
auxiliary 0.5A low dropout (LDO) linear
regulator. The MP28224 is optimized for low
voltage, Li-Ion battery powered applications
where high efficiency and small size are critical.
is dropping close to the output voltage. When
the duty cycle reaches 100%, the main switch is
held on continuously to deliver current to the
output up to the PFET current limit. The output
voltage then becomes the input voltage minus
the voltage drop across the main switch and the
inductor.
The MP28224 uses an external resistor divider
to set both the switcher and LDO output voltage
from 0.6V to 6V.
Short Circuit Protection
When the output is shorted to ground, the
oscillator frequency is reduced to prevent the
inductor current from increasing beyond the
PFET current limit. The PFET current limit is
also reduced to lower the short circuit current.
The frequency and current limit will return to the
normal values once the short circuit condition is
removed and the feedback voltage reaches
0.6V.
1.5A Step-Down Switcher
The switcher integrates both a main switch and
a synchronous rectifier, which provides high
efficiency and eliminates an external Schottky
diode.
The switcher can achieve 100% duty cycle. The
duty cycle D of a step-down switcher is defined
as:
Maximum Load Current
The MP28224 can operate down to 2.5V input
voltage; however the maximum load current
decreases at lower input due to a large IR drop
on the main switch and synchronous rectifier.
The slope compensation signal reduces the
peak inductor current as a function of the duty
cycle to prevent sub-harmonic oscillations at
duty cycles greater than 50%. Conversely, the
current limit increases as the duty cycle
decreases.
VOUT
D = TON × fOSC ×100% ≈
×100%
VIN
Where TON is the main switch on time and fOSC
is the oscillator frequency (1.5MHz).
Current Mode PWM Control
Slope compensated current mode PWM control
provides stable switching and cycle-by-cycle
current limiting for superior load and line
response in addition to protection of the internal
main switch and synchronous rectifier. The
MP28224 switches at a constant frequency
(1.5MHz) and regulates the output voltage.
During each cycle the PWM comparator
modulates the power transferred to the load by
changing the inductor peak current based on
the feedback error voltage. During normal
operation, the main switch is turned on for a
certain time to ramp the inductor current at
each rising edge of the internal oscillator, and
switched off when the peak inductor current is
above the error voltage. When the main switch
is off, the synchronous rectifier will be turned on
immediately and stay on until the next cycle
starts.
Power OK
The MP28224 provides an open-drain PWROK
output that goes high after both channels reach
regulation during startup. PWROK goes low
after one of the output channels goes out of
regulation by ±10% or when device enters
shutdown. There is deglitch timer built in to
avoid PWROK false triggered during load
transient: 50µS for the switcher and 150µS for
the LDO.
0.5A Linear Regulator
The auxiliary 500mA low dropout (LDO) linear
regulator has separate input IN2 and output
OUT2 pins for the internal power device. The
control circuitry of the LDO takes power from
the main input supply IN1. Both IN1 and IN2
input supplies must be presented for the LDO
working properly. The LDO power device input
IN2 can be connected to the switcher output
(Figure1) or directly to the main supply IN1
Dropout Operation
The MP28224 allows the main switch to remain
on for more than one switching cycle and
increases the duty cycle while the input voltage
MP28224 Rev. 0.1
12/13/2007
4
MPS Confidential Information. Unauthorized Photocopy and Duplication Prohibited.
MP28224 – 1.5A STEP-DOWN SWITCHER WITH AUXILIARY 0.5A LDO
(Figure2). If the IN2 tied to the IN1, it is optional
to insert a RC filter between IN1 and IN2. The
RC filter will reduce switching noise coupling
from IN1 to IN2 and power dissipation inside
the MP28224.
APPLICATION INFORMATION
Output Voltage Setting
Where ΔIL is inductor ripple current. Choose
inductor ripple current approximately 30% of the
maximum load current, 1.5A.
The external resistor divider sets the output
voltage. The feedback resistor R1 of the switcher
also sets the feedback loop bandwidth with the
internal compensation capacitor (see Figure 1).
The maximum inductor peak current is:
ΔIL
IL(MAX) = ILOAD
+
Choose R1 of the switcher around 300kꢀ for
2
optimal transient response. R2 is then given by:
Switcher Input Capacitor CIN1 Selection
The input capacitor reduces the surge current
drawn from the input and switching noise from
the device. The input capacitor impedance at
the switching frequency shall be less than input
source impedance to prevent high frequency
switching current passing to the input. Ceramic
capacitors with X5R or X7R dielectrics are
highly recommended because of their low ESR
and small temperature coefficients. For most
applications, a 10μF capacitor is sufficient.
R1
R2 =
VOUT1
−1
0.6V
Choose R4 of the LDO around 60kꢀ for good
loop response. R3 is then given by:
VOUT 2
R3 = R4× (
−1)
0.6V
Table 1—Resistor Selection vs. Output
Voltage Setting
Switcher Output Capacitor CO1 Selection
The output capacitor keeps output voltage
ripple small and ensures regulation loop stable.
The output capacitor impedance shall be low at
the switching frequency. Ceramic capacitors
with X5R or X7R dielectrics are recommended.
The output ripple ΔVOUT is approximately:
VOUT R1
R2
300kꢀ (1%)
R3
R4
60kꢀ
(1%)
60kꢀ
(1%)
300kꢀ
1.2V
1.5V
1.8V
2.5V
(1%)
90kꢀ
(1%)
60kꢀ
(1%)
300kꢀ
200kꢀ (1%)
150kꢀ (1%)
95.3kꢀ (1%)
(1%)
120kꢀ
(1%)
60kꢀ
(1%)
300kꢀ
(1%)
⎛
⎞
VOUT × (VIN −VOUT
VIN × fOSC × L
)
1
⎜
⎟
⎟
ΔVOUT ≤ VOUT
×
× ESR
⎜
⎝
8× fOSC ×C01
190kꢀ
(1%)
60kꢀ
(1%)
300kꢀ
(1%)
⎠
Inductor Selection
A 1μH to 10μH inductor with DC current rating
at least 25% higher than the maximum load
current is recommended for most applications.
For best efficiency, the inductor DC resistance
shall be <200mꢀ. For most designs, the
inductance value can be derived from the
following equation:
VOUT
×
(
V
− VOUT
)
IN
L =
V × ΔIL × fOSC
IN
MP28224 – 1.5A STEP-DOWN SWITCHER WITH AUXILIARY 0.5A LDO
PC Board Layout
Thermal Dissipation
Power dissipation shall be considered when
both channels of the MP28224 provide
maximum 1.5A switcher output current and
0.5A LDO output current to the loads at high
The high current paths (GND, IN1/IN2 and SW1)
should be placed very close to the device with
short, direct and wide traces. Input capacitors
should be placed as close as possible to the
respective IN and GND pins. The external
feedback resistors shall be placed next to the
FB pins. Keep the switching nodes SW1 short
and away from the feedback network.
ambient
temperature.
If
the
junction
temperature rises above 150°C, the MP28224
two channels will be shut down.
The junction-to-ambient thermal resistance of
the 10-pin QFN (3mm x 3mm) RΘJA is 50°C/W.
The maximum power dissipation is about 1.6W
when the MP28224 is operating in a 70°C
ambient temperature environment.
150o C − 70o C
PDMAX
=
=1.6W
50o C /W
MP28224 Rev. 0.1
12/13/2007
6
MPS Confidential Information. Unauthorized Photocopy and Duplication Prohibited.
MP28224 – 1.5A STEP-DOWN SWITCHER WITH AUXILIARY 0.5A LDO
PACKAGE INFORMATION
QFN10
2.90
3.10
0.30
0.50
1.45
1.75
PIN 1 ID
SEE DETAIL A
PIN 1 ID
MARKING
0.18
0.30
10
1
5
2.25
2.55
2.90
3.10
PIN 1 ID
INDEX AREA
0.50
BSC
6
TOP VIEW
BOTTOM VIEW
PIN 1 ID OPTION A
R0.20 TYP.
PIN 1 ID OPTION B
R0.20 TYP.
0.80
1.00
0.20 REF
0.00
0.05
SIDE VIEW
DETAIL A
NOTE:
2.90
1.70
1) ALL DIMENSIONS ARE IN MILLIMETERS.
0.70
0.25
2) EXPOSED PADDLE SIZE DOES NOT INCLUDE MOLD FLASH.
3) LEAD COPLANARITY SHALL BE 0.10 MILLIMETER MAX.
4) DRAWING CONFORMS TO JEDEC MO-229, VARIATION VEED-5.
5) DRAWING IS NOT TO SCALE.
2.50
0.50
RECOMMENDED LAND PATTERN
NOTICE: The information in this document is subject to change without notice. Please contact MPS for current specifications.
Users should warrant and guarantee that third party Intellectual Property rights are not infringed upon when integrating MPS
products into any application. MPS will not assume any legal responsibility for any said applications.
MP28224 Rev. 0.1
12/13/2007
www.MonolithicPower.com
MPS Proprietary Information. Unauthorized Photocopy and Duplication Prohibited.
© 2007 MPS. All Rights Reserved.
7
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