MPS CDRH4D28C/LD 1.2a, 24v, 1.4mhz step-down converter in a tsot23-6 Datasheet

TM
MP2359
1.2A, 24V, 1.4MHz
Step-Down Converter in a TSOT23-6
The Future of Analog IC Technology
TM
DESCRIPTION
FEATURES
The MP2359 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.
•
•
•
The MP2359 requires a minimum number of
readily available standard external components.
The MP2359 is available in TSOT23-6 and
SOT23-6 packages.
EVALUATION BOARD REFERENCE
Board Number
Dimensions
EV2359DJ-00B
2.1”X x 1.9”Y x 0.4”Z
•
•
•
•
•
•
•
•
1.2A Peak Output Current
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 and SOT23-6
Packages
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
5
IN
BST
12V
90
CB
10nF
MP2359
OFF ON
100
1
4
EN
GND
2
SW
6
D1
B230A
FB
3
VIN = 12V
80
VOUT
3.3V @ 1.2A
EFFICIENCY (%)
VIN
70
VIN = 24V
60
50
40
30
20
10
0
0.01
MP2359 Rev. 1.1
6/23/2006
VOUT = 5V
0.1
1
LOAD CURRENT (A)
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1
TM
MP2359 – 1.2A, 24V, 1.4MHz STEP-DOWN CONVERTER IN A TSOT23-6
ABSOLUTE MAXIMUM RATINGS (1)
PACKAGE REFERENCE
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
TOP VIEW
BST
1
6
SW
GND
2
5
IN
Recommended Operating Conditions
FB
3
4
Supply Voltage VIN ........................... 4.5V to 24V
Output Voltage VOUT ...................... 0.81V to 15V
Ambient Temperature ................–40°C to +85°C
EN
Thermal Resistance
Part Number*
Package
Temperature
MP2359DJ
TSOT23-6
–40°C to +85°C
MP2359DT
SOT23-6
–40°C to +85°C
*
(2)
For Tape & Reel, add suffix –Z (eg. MP2359DJ–Z)
For RoHS compliant packaging, add suffix –LF (eg.
MP2359DJ–LF–Z)
(3)
θJA
θJC
TSOT23-6.............................. 220 .... 110.. °C/W
SOT23-6 ................................ 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.
3) Measured on approximately 1” square of 1 oz copper.
ELECTRICAL CHARACTERISTICS
VIN = 12V, TA = +25°C, unless otherwise noted.
Parameters
Symbol Condition
Feedback Voltage
VFB
Feedback Current
Switch-On Resistance (4)
Switch Leakage
Current Limit (4)
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
IFB
Typ
Max
Units
0.790
0.810
0.830
V
0.1
0.35
RDS(ON)
VEN = 0V, VSW = 0V
fSW
VFB = 0.6V
VFB = 0V
VFB = 0.6V
10
1.2
tON
2.5
1.8
1.4
460
87
100
2.8
150
1.7
3.1
0.4
1.2
EN Input Current
Supply Current (Shutdown)
Supply Current (Quiescent)
Thermal Shutdown (4)
4.5V ≤ VIN ≤ 24V
VFB = 0.8V
Min
IS
IQ
VEN = 2V
VEN = 0V
VEN = 0V
VEN = 2V, VFB = 1V
2.1
0.1
0.1
0.8
150
µA
Ω
µA
A
MHz
KHz
%
ns
V
mV
V
V
µA
1.0
1.0
µA
mA
°C
Note:
4) Guaranteed by design.
MP2359 Rev. 1.1
6/23/2006
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TM
MP2359 – 1.2A, 24V, 1.4MHz STEP-DOWN CONVERTER IN A TSOT23-6
PIN FUNCTIONS
Pin #
Name Description
1
BST
2
GND
3
FB
4
EN
5
IN
6
SW
Bootstrap. A capacitor is connected between SW and BS pins to form a floating supply across
the power switch driver. This capacitor is needed to drive the power switch’s gate above the
supply voltage.
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.
On/Off Control Input. Pull EN above 1.2V to turn the device on.
Supply Voltage. The MP2359 operates from a +4.5V to +24V unregulated input. C1 is needed
to prevent large voltage spikes from appearing at the input.
Switch Output.
TYPICAL PERFORMANCE CHARACTERISTICS
VIN = 12V, VOUT = 3.3V, L = 4.7µH, C1 = 10µF, C2 = 22µF, TA = +25ºC, unless otherwise noted.
100
Efficiency vs
Load Current
100
VIN = 18V
90
80
80
70
70
60
EFFICIENCY (%)
EFFICIENCY (%)
90
VIN = 24V
50
40
30
10
VIN = 24V
60
50
40
30
10
VOUT = 2.5V
0
0.01
0.1
1
LOAD CURRENT ( A)
0
0.01
10
0.818
0.816
0.814
0.812
0.810
0.808
0.806
0.804
0.802
0.800
-50 -25 0 25 50 75 100 125 150
DIE TEMPERATURE (OC)
SWITCHING FREQUENCY (MHz)
0.820
VOUT = 5V
0.1
1
LOAD CURRENT (A)
10
Switching Frequency vs
Die Temperature
Feedback Voltage vs
Die Temperature
FEEDBACK VOLTAGE (V)
VIN = 12V
20
20
MP2359 Rev. 1.1
6/23/2006
Efficiency vs
Load Current
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 75 100 125 150
DIE TEMPERATURE (OC)
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TM
MP2359 – 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
IOUT = 0.5A
3.0
CURRENT LIMIT (A)
2.5
VOUT
20mV/div.
VOUT
AC Coupled
50mV/div.
2.0
1.5
1.0
IL
500mA/div.
ILOAD
1A/div.
0.5
0
VSW
10V/div.
IL
1A/div.
0
20
40
60
80
DUTY CYCLE (%)
400ns/div.
100
Short Circuit Entry
Short Circuit Recovery
Start-up through Enable
No Load
VEN
5V/div.
VOUT
1V/div.
VOUT
1V/div.
IL
1A/div.
VOUT
1V/div.
VSW
10V/div.
IL
500mA/div.
IL
1A/div.
Shut-down through Enable
Start-up through Enable
VEN
5V/div.
VEN
5V/div.
VOUT
2V/div.
IL
1A/div.
MP2359 Rev. 1.1
6/23/2006
IOUT = 1A Resistive Load
VEN
5V/div.
VOUT
2V/div.
VOUT
1V/div.
VSW
10V/div.
Shut-down through Enable
No Load
IOUT = 1A Resistive Load
VSW
10V/div.
IL
1A/div.
VSW
10V/div.
IL
1A/div.
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© 2006 MPS. All Rights Reserved.
4
TM
MP2359 – 1.2A, 24V, 1.4MHz STEP-DOWN CONVERTER IN A TSOT23-6
OPERATION
The MP2359 is a current mode buck regulator.
That is, the EA output voltage is proportional to
the peak inductor current.
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 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 FlipFlop is reset and M1 is turned off. The external
Schottky rectifier diode (D1) conducts the
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.
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.
IN 5
RAMP
GENERATOR
EN 4
REGULATOR
D
REGULATOR
OSCILLATOR
1.4MHz/460KHz
S
+
-1pF
REFERENCE
FB 3
CURRENT SENSE
AMPLIFIER
+
--
x20
Q
DRIVER
1
BST
6
SW
M1
R
CURRENT
LIMIT
COMPARATOR
R
27pF
+EA
--
ERROR
AMPLIFIER
+
--
PWM
COMPARATOR
GND 2
Figure 1—Functional Block Diagram
MP2359 Rev. 1.1
6/23/2006
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TM
MP2359 – 1.2A, 24V, 1.4MHz STEP-DOWN CONVERTER IN A TSOT23-6
APPLICATION INFORMATION
Setting Output Voltage
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:
R2 =
R1
VOUT
−1
0.81V
Table 1—Resistor Selection for Common
Output Voltages
VOUT (V)
R1 (kΩ)
R2 (kΩ)
1.8
2.5
3.3
5
80.6 (1%)
49.9 (1%)
49.9 (1%)
49.9 (1%)
64.9 (1%)
23.7 (1%)
16.2 (1%)
9.53 (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’s DC resistance should be less than
200mΩ. Refer to Table 2 for suggested surface
mount inductors. For most designs, the required
inductance value can be derived from the
following equation.
L=
VOUT × ( VIN − VOUT )
VIN × ∆IL × f SW
Where ∆IL 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:
IL(MAX ) = ILOAD +
∆I L
2
Under light load conditions below 100mA, a
larger inductance is recommended for improved
efficiency. See Table 2 for suggested inductors.
Also note that the maximum recommended load
current is 1A if the duty cycle exceeds 35%.
MP2359 Rev. 1.1
6/23/2006
Selecting the Input Capacitor
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.
Selecting the Output Capacitor
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.
PC Board Layout
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.
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.
5V (External) or
VIN (4.5V to 5V)
BS
MP2359
10nF
SW
Figure 2—External Bootstrap Diode
This diode is also recommended for high duty cycle
operation (when
VOUT
>65%) applications.
VIN
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TM
MP2359 – 1.2A, 24V, 1.4MHz STEP-DOWN CONVERTER IN A TSOT23-6
Table 2—Suggested Surface Mount Inductors
Manufacturer
Part Number
Inductance(µH)
Max DCR(Ω)
Toko
Sumida
Wurth Electronics
A921CY-4R7M
CDRH4D28C/LD
7440530047
4.7
4.7
4.7
0.027
0.036
0.038
Current
Rating (A)
1.66
1.5
2.0
Dimensions
L x W x H (mm3)
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
VIN
IN
BS
1
D2
1N4148
(Optional)
C3
22nF
4
OFF ON
MP2359
EN
Notes:
1) D3 can be installed if VIN < 5V
2) D2 can be installed if VOUT < 5V
3) No need for both D2 and D3
SW
VOUT
3.3V
D1
B230A-13-F
FB
GND
6
3
U1
Figure 3—1.4MHz, 3.3V Output at 1A Step-Down Converter
VIN
6V-12V
5
IN
BST
1
C3
10nF
MP2359
SW
6
D1
1N5819HW-7
-VOUT
OFF ON
4
EN
GND
FB
-VOUT
3
LED1
LED2
2
LED3
-VOUT
-VOUT
Figure 4—White LED Driver Application
MP2359 Rev. 1.1
6/23/2006
www.MonolithicPower.com
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TM
MP2359 – 1.2A, 24V, 1.4MHz STEP-DOWN CONVERTER IN A TSOT23-6
PACKAGE INFORMATION
TSOT23-6
6
See Note 7
EXAMPLE
TOP MARK
4
AAAA
PIN 1
0.95
BSC
0.60
TYP
2.80
3.00
1
1.20
TYP
1.50
1.70
2.60
TYP
2.60
3.00
3
TOP VIEW
RECOMMENDED LAND PATTERN
0.84
0.90
1.00 MAX
0.09
0.20
SEATING PLANE
0.30
0.50
0.95 BSC
0.00
0.10
SEE DETAIL "A"
FRONT VIEW
SIDE VIEW
NOTE:
GAUGE PLANE
0.25 BSC
0.30
0.50
0o-8o
DETAIL “A”
MP2359 Rev. 1.1
6/23/2006
1) ALL DIMENSIONS ARE IN MILLIMETERS.
2) PACKAGE LENGTH DOES NOT INCLUDE MOLD FLASH,
PROTRUSION OR GATE BURR.
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.
7) PIN 1 IS LOWER LEFT PIN WHEN READING TOP MARK FROM
LEFT TO RIGHT, (SEE EXAMPLE TOP MARK)
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TM
MP2359 – 1.2A, 24V, 1.4MHz STEP-DOWN CONVERTER IN A TSOT23-6
SOT23-6
6
See Note 7
EXAMPLE
TOP MARK
4
AAAA
PIN 1
0.95
BSC
0.60
TYP
2.80
3.00
1
1.20
TYP
1.50
1.70
2.60
TYP
2.60
3.00
3
TOP VIEW
RECOMMENDED LAND PATTERN
0.90
1.30
1.45 MAX
0.09
0.20
SEATING PLANE
0.30
0.50
0.95 BSC
0.00
0.15
SEE DETAIL "A"
FRONT VIEW
SIDE VIEW
NOTE:
GAUGE PLANE
0.25 BSC
0o-8o
0.30
0.55
DETAIL “A”
1) ALL DIMENSIONS ARE IN MILLIMETERS.
2) PACKAGE LENGTH DOES NOT INCLUDE MOLD FLASH,
PROTRUSION OR GATE BURR.
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.
7) PIN 1 IS LOWER LEFT PIN WHEN READING TOP MARK FROM
LEFT TO RIGHT, (SEE EXAMPLE TOP MARK)
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.
MP2359 Rev. 1.1
6/23/2006
www.MonolithicPower.com
MPS Proprietary Information. Unauthorized Photocopy and Duplication Prohibited.
© 2006 MPS. All Rights Reserved.
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