MP28490DN [MPS]
Switching Regulator, Current-mode, 9A, 600kHz Switching Freq-Max, PDSO8, SOIC-8;
| 型号： | MP28490DN |
| 厂家： | 
MONOLITHIC POWER SYSTEMS |
| 描述： | Switching Regulator, Current-mode, 9A, 600kHz Switching Freq-Max, PDSO8, SOIC-8 开关 光电二极管 输出元件 |
| 文件： | 总10页 (文件大小：338K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
MP28490
5A, 30V, 420kHz
Step-Down Converter
The Future of Analog IC Technology
DESCRIPTION
FEATURES
The MP28490 is a monolithic step-down switch
mode converter with a built in internal power
MOSFET. It achieves 5A continuous output
current over a wide input supply range with
excellent load and line regulation.
•
•
•
•
•
•
•
Wide 4.5V to 30V Operating Input Range
5A Output Current
50mΩ Internal Power MOSFET Switch
Power Good Indicator
Fixed 420kHz Frequency
Synchronizable up to 1.5MHz
Cycle-by-Cycle Over Current Protection with
hiccup
Current mode operation provides fast transient
response and eases loop stabilization.
Fault condition protection includes cycle-by-cycle
current limiting and thermal shutdown.
•
•
•
Thermal Shutdown
Output Adjustable from 0.8V to 15V
Stable with Low ESR Output Ceramic
Capacitors
Available in a Thermally Enhanced 8-Pin
SOIC Package
The MP28490 requires a minimum number of
readily available standard external components
and is available in an 8-pin SOIC package with
exposed pad.
•
APPLICATIONS
•
•
•
•
Digital Set Top Boxes
Personal Video Recorders
Broadband Communications
Flat Panel Television and Monitors
“MPS” and “The Future of Analog IC Technology” are Registered Trademarks of
Monolithic Power Systems, Inc.
TYPICAL APPLICATION
8
2
1
IN
BST
3
6
7
VCC
SW
PG
5
EN/SYNC
FB
OFF ON
GND
4
MP28490 Rev.1.0
9/17/2009
www.MonolithicPower.com
MPS Proprietary Information. Unauthorized Photocopy and Duplication Prohibited.
© 2009 MPS. All Rights Reserved.
1
MP28490 – 5A, 30V, 420KHZ STEP-DOWN CONVERTER
PACKAGE REFERENCE
ABSOLUTE MAXIMUM RATINGS (1)
Supply Voltage VIN....................................... 32V
VSW.......................–0.3V (-5V for < 10ns) to 33V
VBS ....................................................... VSW + 6V
All Other Pins.................................–0.3V to +6V
Junction Temperature...............................150°C
Lead Temperature....................................260°C
Storage Temperature ..............–65°C to +150°C
TOP VIEW
SW
BST
VCC
GND
1
2
3
4
8
7
6
5
IN
EN/SYNC
PG
Recommended Operating Conditions (2)
Supply Voltage VIN........................... 4.5V to 30V
Output Voltage VOUT ........................ 0.8V to 15V
Operating Temperature .............–40°C to +85°C
FB
EXPOSED PAD
ON BACKSIDE
Thermal Resistance (3)
θJA
θJC
Part Number*
MP28490DN
Package
Temperature
SOIC8E ..................................50...... 10... °C/W
SOIC8E
–40°C to +85°C
Notes:
1) Exceeding these ratings may damage the device.
2) The device is not guaranteed to function outside of its
operating conditions.
For Tape & Reel, add suffix –Z (eg. MP28490DN–Z)
For RoHS Compliant Packaging, add suffix –LF
(eg. MP28490DN–LF–Z)
*
3) Measured on approximately 1” square of 1 oz copper.
ELECTRICAL CHARACTERISTICS
VIN = 12V, TA = +25°C, unless otherwise noted.
Parameters
Symbol Condition
Min
Typ
Max
Units
V
Feedback Voltage
VFB
IFB
0.788 0.808 0.828
4.5V ≤ VIN ≤ 30V
VFB = 0.8V
Feedback Current
10
45
0
7.5
420
115
90
100
4.1
880
nA
mΩ
μA
A
kHz
kHz
%
ns
V
mV
V
V
Switch On Resistance (4)
Switch Leakage
RDS(ON)
VEN = 0V, VSW = 0V
10
9
600
205
Current Limit (4)
Oscillator Frequency
Fold-back Frequency
Maximum Duty Cycle
Minimum On Time
Under Voltage Lockout Threshold Rising
Under Voltage Lockout Threshold Hysteresis
EN Input Low Voltage
EN Input High Voltage
fSW
VFB = 0.6V
VFB = 0V
240
25
85
VFB = 0.6V
tON
3.9
1.2
4.3
0.4
VEN = 2V
2
0
EN Input Current
μA
VEN = 0V
Sync Frequency Range (Low)
Sync Frequency Range (High)
Enable Turnoff Delay
Supply Current (Shutdown)
Supply Current (Quiescent)
Thermal Shutdown
FSYNCL
FSYNCH
TOFF
300
1.5
5.0
0
0.9
150
kHz
MHz
μs
μA
mA
°C
VEN = 0V
VEN = 2V, VFB = 1V
1.1
Power Good Control
Power Good Threshold Rising
Power Good Threshold Hysteresis
PG Pin Level
0.69
0.74
40
0.79
0.4
V
mV
V
VPG
PG Sink 4mA
Note:
4) Guaranteed by design.
MP28490 Rev.1.0
9/17/2009
www.MonolithicPower.com
MPS Proprietary Information. Unauthorized Photocopy and Duplication Prohibited.
© 2009 MPS. All Rights Reserved.
2
MP28490 – 5A, 30V, 420KHZ STEP-DOWN CONVERTER
PIN FUNCTIONS
Pin #
Name
Description
1
SW
Switch Output.
Bootstrap. This capacitor is needed to drive the power switch’s gate above the supply
voltage. It is connected between SW and BS pins to form a floating supply across the power
switch driver.
2
3
4
BST
VCC
GND
Bias Supply. Decouple this pin with a 1µF ceramic capacitor.
Ground. This pin is the voltage reference for the regulated output voltage. For this reason
care must be taken in its layout. This node should be placed outside of the D1 to C1 ground
path to prevent switching current spikes from inducing voltage noise into the part.
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 foldback comparator lowers the oscillator frequency when the FB voltage is
below 250mV.
5
FB
Power Good Indicator. The output of this pin is LOW if the output voltage is 10% less than
the nominal voltage; otherwise it is an open drain.
6
7
8
PG
EN/SYNC On/Off Control Input and Synchronization Pin.
Supply Voltage. The MP28490 operates from a +4.5V to +30V unregulated input. C1 is
needed to prevent large voltage spikes from appearing at the input.
IN
MP28490 Rev.1.0
9/17/2009
www.MonolithicPower.com
MPS Proprietary Information. Unauthorized Photocopy and Duplication Prohibited.
© 2009 MPS. All Rights Reserved.
3
MP28490 – 5A, 30V, 420KHZ STEP-DOWN CONVERTER
TYPICAL PERFORMANCE CHARACTERISTICS
VIN = 12V, VOUT = 3.3V, IOUT = 5A, TA = +25ºC, unless otherwise noted.
Efficiency vs
Output Current
Enabled Supply Current
vs Input Voltage
Disabled Supply Current
vs Input Voltage
0.35
100
95
1100
1050
1000
V
=5V
IN
0.30
0.25
0.20
0.15
0.10
0.05
0
V
=12V
IN
90
85
80
950
900
V
=30V
IN
75
70
850
800
V
=1V
FB
V
=0V
EN
0
10
20
30
40
0
10
20
30
40
1
2
3
4
5
30
5
OUTPUT CURRENT (A)
INPUT VOLTAGE (V)
V
CC Regulator Line
Regulation
Case Temperature vs
Output Current
Operating Range
70
60
50
40
30
20
10
0
100
10
4.9
4.7
4.5
V
SPEC
D
Limit
O_MAX
MAX
4.3
4.1
3.9
3.7
3.5
1
420KHz
V
FB_MIN
I
=10mA
CC
0.1
0
5
10
15
20 25
0
5
10 15 20 25 30 35
INPUT VOLTAGE(V)
0
1
2
3
4
5
6
OUTPUT CURRENT (A)
INPUT VOLTAGE (V)
Load Regulation
Line Regulation
Peak Current vs
Duty Cycle
9.5
9.0
8.5
8.0
7.5
7.0
6.5
6.0
1.005
1.000
0.995
0.990
0.985
0.980
1.00035
1.00030
1.00025
1.00020
1.00015
1.00010
1.00005
1.00000
0.99995
V
=30V
IN
V
=12V
IN
I=5A
5
9
13 17 21 25 29 33
INPUT VOLTAGE (V)
0
1
2
3
4
20
40
60
80
100
OUTPUT CURRENT (A)
DUTY CYCLE (%)
MP28490 Rev.1.0
9/17/2009
www.MonolithicPower.com
MPS Proprietary Information. Unauthorized Photocopy and Duplication Prohibited.
© 2009 MPS. All Rights Reserved.
4
MP28490 – 5A, 30V, 420KHZ STEP-DOWN CONVERTER
TYPICAL PERFORMANCE CHARACTERISTICS (continued)
VIN = 12V, VOUT = 3.3V, IOUT = 5A, TA = +25ºC, unless otherwise noted.
Power Up Without Load
HICCUP Output Short
Power Up With 5A Load
V
V
IN
IN
10V/div.
10V/div.
V
OUT
2V/div.
V
V
OUT
OUT
2V/div.
2V/div.
V
SW
5V/div.
V
V
SW
SW
I
5V/div.
5V/div.
INDUCTOR
5A/div.
I
I
INDUCTOR
5A/div.
INDUCTOR
5A/div.
2ms/div.
2ms/div.
Enable Startup
at Full Load
Input Ripple Voltage
Enable Startup
at No Load
V
EN
V
EN
5V/div.
V
IN
5V/div.
200mV/div.
V
V
OUT
OUT
2V/div.
2V/div.
V
V
SW
SW
V
SW
5V/div.
5V/div.
10V/div.
I
I
INDUCTOR
5A/div.
INDUCTOR
5A/div.
Output Ripple Voltage
Load Transient Response
V
V
OUT
OUT
100mV/div.
10mV/div.
V
SW
5V/div.
I
INDUCTOR
5A/div.
I
INDUCTOR
2A/div.
MP28490 Rev.1.0
9/17/2009
www.MonolithicPower.com
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© 2009 MPS. All Rights Reserved.
5
MP28490 – 5A, 30V, 420KHZ STEP-DOWN CONVERTER
OPERATION
IN
CURRENT SENSE
D
AMPLIFIER
- -
+
x40
Σ
REGULATOR
BST
SW
PG
OSCILLATOR
420KHz
REGULATOR
REFERENCE
EN/SYNC
BYPASS
Q
DRIVER
S
+
--
R
R
CURRENT
LIMIT
COMPARATOR
1pF
0.74V
54pF
0.81 V
REF
+
--
+
POWER
GOOD
--
FB
PWM
ERROR
AMPLIFIER
COMPARATOR
GND
Figure 1—Functional Block Diagram
fixed frequency,
Error Amplifier
The MP28490 is
a
synchronous, step-down switching regulator
with an integrated high-side power MOSFET. It
achieves 5A continuous output current over a
wide input supply range with excellent load and
line regulation. It provides a single highly
efficient solution with current mode control for
fast loop response and easy compensation.
The error amplifier compares the FB pin voltage
with the internal 0.81V reference (REF) and
outputs a current proportional to the difference
between the two. This output current is then
used to charge or discharge the internal
compensation network to form the COMP
voltage, which is used to control the power
MOSFET current. The optimized internal
compensation network minimizes the external
component counts and simplifies the control
loop design.
The MP28490 operates in a fixed frequency,
peak current control mode to regulate the
output voltage. A PWM cycle is initiated by the
internal clock. The integrated high-side power
MOSFET is turned on and remains on until its
current reaches the value set by the COMP
voltage. When the power switch is off, it
remains off until the next clock cycle starts. If, in
90% of one PWM period, the current in the
power MOSFET does not reach the COMP set
current value, the power MOSFET will be
forced to turn off.
Internal Regulator
Most of the internal circuitries are powered from
the 5V internal regulator. This regulator takes
the VIN input and operates in the full VIN range.
When VIN is greater than 5.0V, the output of
the regulator is in full regulation. When VIN is
lower than 5.0V, the output decreases. Since
this internal regulator provides the bias current
for the bottom gate driver that requires
significant amount of current depending upon
the external MOSFET selection, a 1uF ceramic
capacitor for decoupling purpose is required.
Power Good Indicator
When the FB is below 0.74V, the PG pin will be
internally pulled low. When the FB is above
0.74V, the PG becomes an open-drain output.
MP28490 Rev.1.0
9/17/2009
www.MonolithicPower.com
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© 2009 MPS. All Rights Reserved.
6
MP28490 – 5A, 30V, 420KHZ STEP-DOWN CONVERTER
Thermal Shutdown
Enable/Synch Control
The MP28490 has a dedicated Enable/Synch
control pin (EN/SYNC). By pulling it high or low,
the IC can be enabled and disabled by EN. Tie
EN to VIN for automatic start up. To disable the
part, EN must be pulled low for at least 5µs.
Thermal shutdown is implemented to prevent
the chip from operating at exceedingly high
temperatures. When the silicon die temperature
is higher than 150°C, it shuts down the whole
chip. When the temperature is lower than its
lower threshold, typically 140°C, the chip is
enabled again.
The MP28490 can be synchronized to external
clock range from 300KHz up to 1.5MHz through
the EN/SYNC pin. The internal clock rising
edge is synchronized to the external clock rising
edge.
Floating Driver and Bootstrap Charging
The floating power MOSFET driver is powered
by an external bootstrap capacitor. This floating
driver has its own UVLO protection. This
UVLO’s rising threshold is 2.2V with a
hysteresis of 150mV. The bootstrap capacitor
voltage is regulated internally (Figure 2). Even
at no load condition, as long as VIN is 3V higher
than VOUT, C4 will have enough voltage
provided by VIN through D1, M1, C4, L1 and C2.
If (VIN-VSW) is more than 5V, U2 will regulate M1
to maintain a 5V BST voltage across C4.
Under-Voltage Lockout (UVLO)
Under-voltage lockout (UVLO) is implemented
to protect the chip from operating at insufficient
supply
voltage.
The
MP28490
UVLO
comparator monitors the output voltage of the
internal regulator, BYPASS. The UVLO rising
threshold is about 4.0V while its falling
threshold is about 3.6V.
Internal Soft-Start
D1
The soft-start is implemented to prevent the
converter output voltage from overshooting
during startup. When the chip starts, the
internal circuitry generates a soft-start voltage
(SS) ramping up from 0V to 1.2V. When it is
lower than the internal reference (REF), SS
overrides REF so the error amplifier uses SS as
the reference. When SS is higher than REF,
REF regains control.
V
IN
M1
+
--
BST
SW
+
--
U2
5V
C4
V
OUT
L1
C2
Over-Current-Protection and Hiccup
The MP28490 has cycle-by-cycle over current
limit when the inductor current peak value
exceeds the set current limit threshold.
Meanwhile, output voltage starts to drop until
FB is below the Under-Voltage(UV) threshold,
typically 30% below the reference. Once a UV
is triggered, the MP28490 enters hiccup mode
to periodically restart the part. This protection
mode is especially useful when the output is
dead-short to ground. The average short circuit
current is greatly reduced to alleviate the
thermal issue and to protect the regulator. The
MP28490 exits the hiccup mode once the over
current condition is removed.
Figure 2—Internal Bootstrap Charging Circuit
Startup and Shutdown
If both VIN and EN are higher than their
appropriate thresholds, the chip starts. The
reference block starts first, generating stable
reference voltage and currents, and then the
internal regulator is enabled. The regulator
provides stable supply for the remaining
circuitries.
Three events can shut down the chip: EN low,
VIN low and thermal shutdown. In the shutdown
procedure, the signaling path is first blocked to
avoid any fault triggering. The COMP voltage
and the internal supply rail are then pulled down.
The floating driver is not subject to this shutdown
command.
MP28490 Rev.1.0
9/17/2009
www.MonolithicPower.com
MPS Proprietary Information. Unauthorized Photocopy and Duplication Prohibited.
© 2009 MPS. All Rights Reserved.
7
MP28490 – 5A, 30V, 420KHZ STEP-DOWN CONVERTER
Output Rectifier Diode
The output rectifier diode supplies the current to
APPLICATION INFORMATION
The schematic on the front page shows a typical
MP28490 application. The IC can provide up to
5A output current at a nominal output voltage of
3.3V. For proper thermal performance, the
exposed pad of the device must be soldered
down to the printed circuit board.
the inductor when the high-side switch is off. To
reduce losses due to the diode forward voltage
and recovery times, use a Schottky diode.
Choose a diode whose maximum reverse
voltage rating is greater than the maximum
input voltage, and whose current rating is
greater than the maximum load current. Table 2
Setting the Output Voltage
The external resistor divider is used to set the
output voltage (see the schematic on front
page). The feedback resistor R1 also sets the
feedback loop bandwidth with the internal
compensation capacitor (see Figure 1). Choose
R1 to be around 40.2kꢀ for optimal transient
response. R2 is then given by:
lists
manufacturers.
example
Schottky
diodes
and
Table 2—Diode Selection Guide
Voltage/Current
Diode
Rating
30V, 5A
30V, 6A
Manufacture
Diodes Inc.
On Semi
B530C
MBRD630CT
R1
R2 =
VOUT
Selecting the Input Capacitor
− 1
0.8V
The input capacitor (C1) reduces the surge
current drawn from the input and the switching
noise from the device. The input capacitor
impedance at the switching frequency should
be less than the input source impedance to
prevent high frequency switching current from
passing to the input. Ceramic capacitors with
Table 1—Resistor Selection for Common
Output Voltages
VOUT (V)
1.8
R1 (kΩ)
40.2 (1%)
40.2 (1%)
40.2 (1%)
40.2 (1%)
R2 (kΩ)
32.4 (1%)
19.1 (1%)
13 (1%)
2.5
3.3
5
X5R
or
X7R
dielectrics
are
highly
recommended because of their low ESR and
small temperature coefficients. For 6A output
applications, a 22µF capacitor is sufficient.
7.68 (1%)
Selecting the Inductor
A 1µH to 10µH inductor with a DC current rating
of at least 25% percent higher than the
maximum load current is recommended for
most applications. For highest efficiency, the
inductor DC resistance should be less than
15mꢀ. For most designs, the inductance value
can be derived from the following equation.
Selecting the Output Capacitor
The output capacitor (C2) keeps output voltage
small and ensures regulation loop stability. The
output capacitor impedance should be low at
the switching frequency. Ceramic capacitors
with X5R or X7R dielectrics are recommended.
PC Board Layout
VOUT × (VIN − VOUT
VIN × ΔIL × fOSC
)
The high current paths (GND, IN and SW)
should be placed very close to the device with
short, direct and wide traces. The input
capacitor needs to be as close as possible to
the IN and GND pins. The external feedback
resistors should be placed next to the FB pin.
Keep the switching node SW short and away
from the feedback network. Keep the EN trace
away from the feedback network, and also an
isolation with ground trace between the EN and
FB pins (highly recommended).
L =
Where ΔIL is the inductor ripple current.
Choose inductor current to be approximately
30% of the maximum load current, 5A. The
maximum inductor peak current is:
ΔIL
IL(MAX) = ILOAD
+
2
Under light load conditions below 100mA, larger
inductance is recommended for improved efficiency.
MP28490 Rev.1.0
9/17/2009
www.MonolithicPower.com
MPS Proprietary Information. Unauthorized Photocopy and Duplication Prohibited.
© 2009 MPS. All Rights Reserved.
8
MP28490 – 5A, 30V, 420KHZ STEP-DOWN CONVERTER
External Bootstrap Diode
An external bootstrap diode may enhance the
efficiency of the regulator, the applicable
conditions of external BST diode are:
z
VOUT=5V or 3.3V; and
VOUT
VIN
z
Duty cycle is high: D=
>65%
In these cases, an external BST diode is
recommended from the output of the voltage
regulator to BST pin, as shown in Fig.3
External BST Diode
IN4148
BST
CBST
5V or 3.3V
SW
+
COUT
L
Figure 3—Add Optional External Bootstrap
Diode to Enhance Efficiency
The recommended external BST diode is
IN4148, and the BST cap is 0.1~1µF.
MP28490 Rev.1.0
9/17/2009
www.MonolithicPower.com
MPS Proprietary Information. Unauthorized Photocopy and Duplication Prohibited.
© 2009 MPS. All Rights Reserved.
9
MP28490 – 5A, 30V, 420KHZ STEP-DOWN CONVERTER
PACKAGE INFORMATION
SOIC8E (EXPOSED PAD)
0.189(4.80)
0.197(5.00)
0.124(3.15)
0.136(3.45)
8
5
0.150(3.80)
0.157(4.00)
0.228(5.80)
0.244(6.20)
0.089(2.26)
0.101(2.56)
PIN 1 ID
1
4
TOP VIEW
BOTTOM VIEW
SEE DETAIL "A"
0.051(1.30)
0.067(1.70)
SEATING PLANE
0.000(0.00)
0.006(0.15)
0.0075(0.19)
0.0098(0.25)
0.013(0.33)
0.020(0.51)
SIDE VIEW
0.050(1.27)
BSC
FRONT VIEW
0.010(0.25)
0.020(0.50)
x 45o
GAUGE PLANE
0.010(0.25) BSC
0.050(1.27)
0.024(0.61)
0.063(1.60)
0.016(0.41)
0.050(1.27)
0o-8o
DETAIL "A"
0.103(2.62)
0.213(5.40)
NOTE:
1) CONTROL DIMENSION IS IN INCHES. DIMENSION IN
BRACKET IS IN MILLIMETERS.
2) PACKAGE LENGTH DOES NOT INCLUDE MOLD FLASH,
PROTRUSIONS OR GATE BURRS.
3) PACKAGE WIDTH DOES NOT INCLUDE INTERLEAD FLASH
OR PROTRUSIONS.
0.138(3.51)
4) LEAD COPLANARITY (BOTTOM OF LEADS AFTER FORMING)
SHALL BE 0.004" INCHES MAX.
5) DRAWING CONFORMS TO JEDEC MS-012, VARIATION BA.
6) DRAWING IS NOT TO SCALE.
RECOMMENDED LAND PATTERN
NOTICE: The information in this document is subject to change without notice. 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.
MP28490 Rev. 1.0
9/17/2009
www.MonolithicPower.com
MPS Proprietary Information. Unauthorized Photocopy and Duplication Prohibited.
© 2009 MPS. All Rights Reserved.
10
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