MP29368DJ [MPS]
Switching Regulator, Current-mode, 1.8A, 1700kHz Switching Freq-Max, PDSO6, MO-193AB, TSOT-23, 6 PIN;
| 型号： | MP29368DJ |
| 厂家： | 
MONOLITHIC POWER SYSTEMS |
| 描述： | Switching Regulator, Current-mode, 1.8A, 1700kHz Switching Freq-Max, PDSO6, MO-193AB, TSOT-23, 6 PIN 开关 光电二极管 |
| 文件： | 总8页 (文件大小：357K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
TM
MP29368
1.2A, 24V, 1.4MHz
Step-Down Converter in a TSOT23-6
TM
The Future of Analog IC Technology
FEATURES
DESCRIPTION
•
•
•
1.2A Peak Output Current
The MP29368 is a monolithic step-down switch
mode converter with a built-in power MOSFET.
It achieves 1.2A peak output current over a
wide input supply range with excellent load and
line regulation. Current mode operation
provides fast transient response and eases loop
stabilization. Fault condition protection includes
cycle-by-cycle current limiting and thermal
shutdown.
0.35Ω Internal Power MOSFET Switch
Stable with Low ESR Output Ceramic
Capacitors
•
•
•
•
•
•
•
•
Up to 92% Efficiency
0.1μA Shutdown Mode
Fixed 1.4MHz Frequency
Thermal Shutdown
Cycle-by-Cycle Over Current Protection
Wide 4.5V to 24V Operating Input Range
Output Adjustable from 0.81V to 15V
Available in TSOT23-6 Package
The MP29368 requires a minimum number of
readily available standard external components.
The MP29368 is available in TSOT23-6 package.
APPLICATIONS
•
•
•
•
Distributed Power Systems
Battery Charger
Pre-Regulator for Linear Regulators
WLED Drivers
“MPS” and “The Future of Analog IC Technology” are Trademarks of Monolithic
Power Systems, Inc.
TYPICAL APPLICATION
Efficiency vs
Load Currents
100
5
1
6
V
IN = 12V
V
12V
IN
BST
IN
90
80
70
60
50
40
30
20
10
0
CB
10nF
V
OUT
3.3V @ 1.2A
MP29368 SW
V
IN = 24V
D1
B230A
4
3
EN
FB
OFF ON
GND
2
V
OUT = 5V
0.01
0.1
LOAD CURRENT (A)
10
1
MP29368 Rev. 1.2
12/13/2007
www.MonolithicPower.com
MPS Proprietary Information. Unauthorized Photocopy and Duplication Prohibited.
© 2007 MPS. All Rights Reserved.
1
TM
MP29368 – 1.2A, 24V, 1.4MHz STEP-DOWN CONVERTER IN A TSOT23-6
PACKAGE REFERENCE
ABSOLUTE MAXIMUM RATINGS (1)
Supply Voltage VIN....................................... 26V
VSW....................................... –0.3V to VIN + 0.3V
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
Recommended Operating Conditions (2)
Supply Voltage VIN........................... 4.5V to 24V
Output Voltage VOUT ...................... 0.81V to 15V
Ambient Temperature................–40°C to +85°C
TOP VIEW
BST
GND
FB
1
2
3
6
5
4
SW
IN
EN
Thermal Resistance (3)
θJA
θJC
TSOT23-6..............................220.... 110.. °C/W
Notes:
1) Exceeding these ratings may damage the device.
2) The device function is not guaranteed outside of the
recommended operating conditions.
Part Number*
MP29368DJ
Package
TSOT23-6
Temperature
–40°C to +85°C
For Tape & Reel, add suffix –Z (eg. MP29368DJ–Z)
For RoHS compliant packaging, add suffix –LF (eg.
MP29368DJ–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
0.790 0.810 0.830
4.5V ≤ VIN ≤ 24V
Feedback Current
Switch-On Resistance (4)
VFB = 0.8V
0.1
0.35
10
μA
Ω
RDS(ON)
Switch Leakage
Current Limit (4)
VEN = 0V, VSW = 0V
μA
A
1.8
Oscillator Frequency
Fold-back Frequency
Maximum Duty Cycle
Minimum On-Time (4)
Under Voltage Lockout Threshold Rising
Under Voltage Lockout Threshold Hysteresis
EN Input Low Voltage
EN Input High Voltage
fSW
VFB = 0.6V
VFB = 0V
1.2
1.4
460
87
1.7
MHz
KHz
%
VFB = 0.6V
tON
100
2.8
150
ns
2.5
1.2
3.1
0.4
V
mV
V
V
VEN = 2V
2.1
0.1
0.1
0.8
150
EN Input Current
μA
VEN = 0V
Supply Current (Shutdown)
Supply Current (Quiescent)
Thermal Shutdown (4)
IS
VEN = 0V
1.0
1.0
μA
mA
°C
IQ
VEN = 2V, VFB = 1V
Note:
4) Guaranteed by design.
MP29368 Rev. 1.2
12/13/2007
www.MonolithicPower.com
MPS Proprietary Information. Unauthorized Photocopy and Duplication Prohibited.
© 2007 MPS. All Rights Reserved.
2
TM
MP29368 – 1.2A, 24V, 1.4MHz STEP-DOWN CONVERTER IN A TSOT23-6
PIN FUNCTIONS
Pin # Name Description
Bootstrap. A capacitor is connected between SW and BS pins to form a floating supply across
BST the power switch driver. This capacitor is needed to drive the power switch’s gate above the
supply voltage.
1
2
Ground. This pin is the voltage reference for the regulated output voltage. For this reason care
GND 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
3
FB
250mV.
4
5
6
EN
IN
On/Off Control Input. Pull EN above 1.2V to turn the device on.
Supply Voltage. The MP29368 operates from a +4.5V to +24V unregulated input. C1 is needed
to prevent large voltage spikes from appearing at the input.
SW Switch Output.
TYPICAL PERFORMANCE CHARACTERISTICS
VIN = 12V, VOUT = 3.3V, L = 4.7µH, C1 = 10µF, C2 = 22µF, TA = +25ºC, unless otherwise noted.
Efficiency vs
Load Current
Efficiency vs
Load Current
100
90
80
70
60
50
40
30
20
10
0
100
90
80
70
60
50
40
30
20
10
0
V
IN = 12V
V
IN = 18V
V
IN = 24V
V
IN = 24V
V
OUT = 2.5V
V
OUT = 5V
0.01
0.1
LOAD CURRENT (A)
10
1
0.01
0.1
LOAD CURRENT ( A)
10
1
Switching Frequency vs
Die Temperature
Feedback Voltage vs
Die Temperature
0.820
0.818
0.816
0.814
0.812
0.810
0.808
0.806
0.804
0.802
0.800
1.50
1.48
1.46
1.44
1.42
1.40
1.38
1.36
1.34
1.32
1.30
-50 -25
0
25 50 75
125 150
-50 -25
0
25 50 75
125 150
100
100
DIE TEMPERATURE (OC)
DIE TEMPERATURE (OC)
MP29368 Rev. 1.2
12/13/2007
www.MonolithicPower.com
MPS Proprietary Information. Unauthorized Photocopy and Duplication Prohibited.
© 2007 MPS. All Rights Reserved.
3
TM
MP29368 – 1.2A, 24V, 1.4MHz STEP-DOWN CONVERTER IN A TSOT23-6
TYPICAL PERFORMANCE CHARACTERISTICS (continued)
VIN = 12V, VOUT = 3.3V, L = 4.7µH, C1 = 10µF, C2 = 22µF, TA = +25ºC, unless otherwise noted.
Current Limit vs
Duty Cycle
Steady State Test
I
= 0.5A
OUT
3.0
2.5
2.0
1.5
1.0
0.5
0
V
OUT
V
20mV/div.
OUT
AC Coupled
50mV/div.
V
SW
I
10V/div.
L
1A/div.
I
L
500mA/div.
I
LOAD
1A/div.
400ns/div.
0
20
40
60
80
100
DUTY CYCLE (%)
Short Circuit Entry
Short Circuit Recovery
Start-up through Enable
No Load
V
EN
5V/div.
V
OUT
V
OUT
1V/div.
1V/div.
V
OUT
1V/div.
V
SW
10V/div.
I
L
I
I
L
1A/div.
L
1A/div.
500mA/div.
Shut-down through Enable
Start-up through Enable
Shut-down through Enable
No Load
I
= 1A Resistive Load
I
= 1A Resistive Load
OUT
OUT
V
V
EN
EN
V
EN
5V/div.
5V/div.
5V/div.
V
OUT
2V/div.
V
V
OUT
OUT
1V/div.
2V/div.
V
SW
V
SW
V
10V/div.
SW
10V/div.
10V/div.
I
I
L
L
I
L
1A/div.
1A/div.
1A/div.
MP29368 Rev. 1.2
12/13/2007
www.MonolithicPower.com
MPS Proprietary Information. Unauthorized Photocopy and Duplication Prohibited.
© 2007 MPS. All Rights Reserved.
4
TM
MP29368 – 1.2A, 24V, 1.4MHz STEP-DOWN CONVERTER IN A TSOT23-6
OPERATION
The MP29368 is a current mode buck regulator.
That is, the EA output voltage is proportional to
the peak inductor current.
If the sum of the Current Sense Amplifier output
and the Slope Compensation signal does not
exceed the EA output for a whole cycle, then
the falling edge of the CLK resets the Flip-Flop.
At the beginning of a cycle, M1 is off. The EA
output voltage is higher than the current sense
amplifier output, and the current comparator’s
output is low. The rising edge of the 1.4MHz
CLK signal sets the RS Flip-Flop. Its output
turns on M1 thus connecting the SW pin and
inductor to the input supply.
The output of the Error Amplifier integrates the
voltage difference between the feedback and
the 0.81V bandgap reference. The polarity is
such that a FB pin voltage lower than 0.81V
increases the EA output voltage. Since the EA
output voltage is proportional to the peak
inductor current, an increase in its voltage also
increases current delivered to the output.
The increasing inductor current is sensed and
amplified by the Current Sense Amplifier. Ramp
compensation is summed to the Current Sense
Amplifier output and compared to the Error
Amplifier output by the PWM Comparator.
When the sum of the Current Sense Amplifier
output and the Slope Compensation signal
exceeds the EA output voltage, the RS Flip-
Flop is reset and M1 is turned off. The external
Schottky rectifier diode (D1) conducts the
inductor current.
IN
5
CURRENT SENSE
AMPLIFIER
- -
+
x20
RAMP
GENERATOR
D
REGULATOR
BST
SW
1
6
OSCILLATOR
1.4MHz/460KHz
EN
4
REGULATOR
REFERENCE
M1
Q
DRIVER
S
+
--
R
R
CURRENT
LIMIT
COMPARATOR
1pF
27pF
+
+
EA
--
--
FB
3
2
PWM
ERROR
AMPLIFIER
COMPARATOR
GND
Figure 1—Functional Block Diagram
MP29368 Rev. 1.2
12/13/2007
www.MonolithicPower.com
MPS Proprietary Information. Unauthorized Photocopy and Duplication Prohibited.
© 2007 MPS. All Rights Reserved.
5
TM
MP29368 – 1.2A, 24V, 1.4MHz STEP-DOWN CONVERTER IN A TSOT23-6
APPLICATION INFORMATION
Selecting the Input Capacitor
Setting Output Voltage
The input capacitor reduces the surge current
drawn from the input supply 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
through 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 4.7µF
capacitor is sufficient.
The external resistor divider is used to set the
output voltage (see the schematic on front
page). Table 1 shows a list of resistor selection
for common output voltages. The feedback
resistor R1 also sets the feedback loop
bandwidth with the internal compensation
capacitor (see Figure 1). R2 can be determined
by:
R1
VOUT
R2 =
− 1
0.81V
Selecting the Output Capacitor
Table 1—Resistor Selection for Common
Output Voltages
The output capacitor keeps the output voltage
ripple small and ensures feedback loop stability.
The output capacitor impedance should be low
at the switching frequency. Ceramic capacitors
with X5R or X7R dielectrics are recommended
for their low ESR characteristics. For most
applications, a 22µF ceramic capacitor will be
sufficient.
VOUT (V)
1.8
R1 (kΩ)
80.6 (1%)
49.9 (1%)
49.9 (1%)
49.9 (1%)
R2 (kΩ)
64.9 (1%)
23.7 (1%)
16.2 (1%)
9.53 (1%)
2.5
3.3
5
PC Board Layout
Selecting the Inductor
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 switch node traces
short and away from the feedback network.
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’s DC resistance should be less than
200mꢀ. Refer to Table 2 for suggested surface
mount inductors. For most designs, the required
inductance value can be derived from the
following equation.
External Bootstrap Diode
It is recommended that an external bootstrap
diode be added when the input voltage is no
greater than 5V or the 5V rail is available in the
system. This helps improve the efficiency of the
regulator. The bootstrap diode can be a low
cost one such as IN4148 or BAT54.
VOUT × (VIN − VOUT
VIN × ΔIL × fSW
)
L =
Where ΔIL is the inductor ripple current.
Choose the inductor ripple current to be 30% of
the maximum load current. The maximum
inductor peak current is calculated from:
5V (External) or
V
(4.5V to 5V)
IN
BS
ΔIL
IL(MAX) = ILOAD
+
10nF
MP29368
2
SW
Under light load conditions below 100mA, a
larger inductance is recommended for improved
efficiency. See Table 2 for suggested inductors.
Figure 2—External Bootstrap Diode
This diode is also recommended for high duty cycle
VOUT
Also note that the maximum recommended load
current is 1A if the duty cycle exceeds 35%.
operation (when
>65%) applications.
VIN
MP29368 Rev. 1.2
12/13/2007
www.MonolithicPower.com
MPS Proprietary Information. Unauthorized Photocopy and Duplication Prohibited.
© 2007 MPS. All Rights Reserved.
6
TM
MP29368 – 1.2A, 24V, 1.4MHz STEP-DOWN CONVERTER IN A TSOT23-6
Table 2—Suggested Surface Mount Inductors
Dimensions
Current
Rating (A)
Manufacturer
Part Number
Inductance(µH)
Max DCR(ꢀ)
L x W x H (mm3)
Toko
Sumida
Wurth Electronics
A921CY-4R7M
CDRH4D28C/LD
7440530047
4.7
4.7
4.7
0.027
0.036
0.038
1.66
1.5
2.0
6 x 6.3 x 3
5.1 x 5.1 x 3
5.8 x 5.8 x 2.8
TYPICAL APPLICATION CIRCUITS
D3
1N4148
(Optional)
5
1
6
3
V
IN
BS
IN
D2
1N4148
(Optional)
C3
22nF
4
V
OUT
3.3V
EN
SW
MP29368
OFF ON
D1
B230A-13-F
Notes:
1) D3 can be installed if V < 5V
IN
OUT
2) D2 can be installed if V
< 5V
FB
GND
3) No need for both D2 and D3
U1
Figure 3—1.4MHz, 3.3V Output at 1A Step-Down Converter
5
1
6
V
IN
BST
IN
6V-12V
C3
10nF
MP29368 SW
D1
1N5819HW-7
LED1
LED2
LED3
-V
-V
OUT
OUT
4
3
EN
FB
OFF ON
GND
2
-V
OUT
-V
OUT
Figure 4—White LED Driver Application
MP29368 Rev. 1.2
12/13/2007
www.MonolithicPower.com
MPS Proprietary Information. Unauthorized Photocopy and Duplication Prohibited.
© 2007 MPS. All Rights Reserved.
7
TM
MP29368 – 1.2A, 24V, 1.4MHz STEP-DOWN CONVERTER IN A TSOT23-6
PACKAGE INFORMATION
TSOT23-6
0.95
BSC
0.60
TYP
2.80
3.00
6
4
1.20
TYP
See Note 7
EXAMPLE
TOP MARK
1.50
1.70
2.60
TYP
2.60
3.00
AAAA
PIN 1
1
3
TOP VIEW
RECOMMENDED LAND PATTERN
0.84
0.90
1.00 MAX
SEATING PLANE
0.09
0.20
0.30
0.50
0.00
0.10
0.95 BSC
SEE DETAIL "A"
FRONT VIEW
SIDE VIEW
NOTE:
1) ALL DIMENSIONS ARE IN MILLIMETERS.
2) PACKAGE LENGTH DOES NOT INCLUDE MOLD FLASH,
PROTRUSION OR GATE BURR.
GAUGE PLANE
0.25 BSC
3) PACKAGE WIDTH DOES NOT INCLUDE INTERLEAD FLASH
OR PROTRUSION.
4) LEAD COPLANARITY (BOTTOM OF LEADS AFTER FORMING)
SHALL BE 0.10 MILLIMETERS MAX.
5) DRAWING CONFORMS TO JEDEC MO-193, VARIATION AB.
6) DRAWING IS NOT TO SCALE.
0.30
0.50
0o-8o
7) PIN 1 IS LOWER LEFT PIN WHEN READING TOP MARK FROM
LEFT TO RIGHT, (SEE EXAMPLE TOP MARK)
DETAIL “A”
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.
MP29368 Rev. 1.2
12/13/2007
www.MonolithicPower.com
MPS Proprietary Information. Unauthorized Photocopy and Duplication Prohibited.
© 2007 MPS. All Rights Reserved.
8
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