MP2494
2A, 55V, 100kHz Step-Down Converter
DESCRIPTION
FEATURES
The MP2494 is a monolithic step-down switch
mode converter. It achieves 2A continuous
output current over a wide input supply range
with excellent load and line regulation.
MP2494 achieves low EMI signature with well
controlled switching edges.
Fault condition protection includes cycle-by-cycle
current limiting and thermal shutdown.
The MP2494 requires a minimum number of
readily available standard external components.
The MP2494 is available in SOIC8 and SOIC8E
package.
Wide 4.5V to 55V Operating Input Range
Output Adjustable from 0.8V to 45V
0.25Ω Internal Power MOSFET Switch
Stable with Low ESR Output Ceramic
Capacitors
Fixed 100kHz Frequency
Low EMI signature
Thermal Shutdown
Cycle-by-Cycle Over Current Protection
Available in SOIC8 and SOIC8E packages
APPLICATIONS
USB Power Supplies
Automotive Cigarette Lighter Adapters
All MPS parts are lead-free, halogen free, and adhere to the RoHS directive. For
MPS green status, please visit MPS website under Quality Assurance. “MPS”
and “The Future of Analog IC Technology” are Registered Trademarks of
Monolithic Power Systems, Inc.
TYPICAL APPLICATION
MP2494 Rev. 1.1
4/13/2018
www.MonolithicPower.com
MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited.
© 2018 MPS. All Rights Reserved.
1
MP2494 –2A, 55V, 100kHz STEP-DOWN CONVERTER
ORDERING INFORMATION
Part Number
MP2494DS*
MP2494DN**
Package
SOIC8
SOIC8E
Top Marking
MP2494DS
MP2494DN
* For Tape & Reel, add suffix –Z (e.g. MP2494DS–Z);
For RoHS, compliant packaging, add suffix –LF (e.g. MP2494DS–LF–Z).
** For Tape & Reel, add suffix –Z (e.g. MP2494DN–Z);
For RoHS, compliant packaging, add suffix –LF (e.g. MP2494DN–LF–Z).
PACKAGE REFERENCE
SOIC8
SOIC8E
ABSOLUTE MAXIMUM RATINGS (1)
Thermal Resistance
Input Voltage VIN ..........................................60V
VSW ...................................... –0.3V to VIN + 0.3V
VBST ..................................................VSW + 6.5V
All Other Pins ............................. –0.3V to +6.5V
Junction Temperature .............................. 150C
Lead Temperature ................................... 260C
Storage Temperature .............. –65C to +150C
(2)
Continuous Power Dissipation (TA = +25°C)
SOIC8...................................................... 1.38W
SOIC8E .....................................................2.5W
SOIC8 .................................... 90 ...... 45 ... C/W
SOIC8E .................................. 50 ...... 10 ... C/W
Recommended Operating Conditions
(3)
Input Voltage VIN ............................. 4.5V to 55V
Output Voltage VOUT........................ 0.8V to 45V
Operating Junction Temp. (TJ). -40°C to +125°C
MP2494 Rev. 1.1
4/13/2018
(4)
θJA
θJC
Notes:
1) Exceeding these ratings may damage the device.
2) The maximum allowable power dissipation is a function of the
maximum junction temperature TJ (MAX), the junction-toambient thermal resistance θJA, and the ambient temperature
TA. The maximum allowable continuous power dissipation at
any ambient temperature is calculated by PD (MAX) = (TJ
(MAX)-TA)/θJA. 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.
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© 2018 MPS. All Rights Reserved.
2
MP2494 –2A, 55V, 100kHz STEP-DOWN CONVERTER
ELECTRICAL CHARACTERISTICS (5)
VIN = 12V, TA = +25C, unless otherwise noted.
Parameters
Symbol
Feedback Voltage
VFB
Feedback Bias Current
IBIAS(FB)
Switch On Resistance
RDS(ON)
Switch Leakage
Current Limit
Condition
Min
Typ
Max
Units
4.5V VIN 55V
0.78
0.8
0.82
V
VFB = 0.8V
VEN = 0V, VSW = 0V
10
nA
0.25
Ω
0.1
(5)
10
3.5
Oscillator Frequency
Boot-Strap Voltage
Minimum On Time
fSW
VFB = 0.6V
80
VBST - VSW
(5)
tON
100
μA
A
120
kHz
4.3
V
VFB = 1V
100
ns
SW rising edge
trise
VIN =12V, VOUT =5V, IOUT =2A
50
ns
SW falling edge
tfall
VIN =12V, VOUT =5V, IOUT =2A
50
ns
EN Input Low Voltage
EN Input High Voltage
EN Input Bias Current
Under Voltage Lockout
Threshold Rising
Under Voltage Lockout
Threshold Hysteresis
Supply Current (Shutdown)
Supply Current (Quiescent)
Thermal Shutdown
(5)
0.4
VEN=0-6V
1.8
-10
-2
10
V
V
μA
3.0
3.3
3.6
V
200
VEN=0V
VEN = 2V, VFB = 1V
mV
4
10
μA
500
800
μA
150
°C
Notes:
5) Guaranteed by design
MP2494 Rev. 1.1
4/13/2018
www.MonolithicPower.com
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© 2018 MPS. All Rights Reserved.
3
MP2494 –2A, 55V, 100kHz STEP-DOWN CONVERTER
PIN FUNCTIONS
Package
Pin #
Name
1
VIN
2
GND
3
EN
4
FB
5
6
SS
GS
7
BST
8
SW
MP2494 Rev. 1.1
4/13/2018
Description
Supply Voltage. The MP2494 operates from a +4.5V to +55V unregulated input. CIN is
needed to prevent large voltage spikes from appearing at the input. Put CIN as close to
the IC as possible. It is the drain of the internal power device and power supply for the
whole chip.
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 CIN
ground path to prevent switching current spikes from inducing voltage noise into the part.
On/Off Control Input.
An external resistor divider from the output to GND tapped to the FB pin sets the output
voltage. It is pulled up to 4V power supply internally by a 2Meg resistor.
Connect to an external capacitor used for Soft-Start.
Ground Sense Input. Connect to ground.
Bootstrap. This capacitor is needed to drive the power switch’s gate above the supply
voltage. It is connected between SW and BST pins to form a floating supply across the
power switch driver. An on-chip regulator is used to charge up the external boot-strap
capacitor. If the on-chip regulator is not strong enough, one optional diode can be
connected from IN or OUT to charge the external boot-strap capacitor.
Switch Output. It is the source of power device.
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© 2018 MPS. All Rights Reserved.
4
MP2494 –2A, 55V, 100kHz STEP-DOWN CONVERTER
TYPICAL PERFORMANCE CHARACTERISTICS
C1 =220μF, C2 =2.2μF, C3 =39μF, C4 =22μF, L =39μH, TA =25°C, unless otherwise noted.
MP2494 Rev. 1.1
4/13/2018
www.MonolithicPower.com
MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited.
© 2018 MPS. All Rights Reserved.
5
MP2494 –2A, 55V, 100kHz STEP-DOWN CONVERTER
TYPICAL PERFORMANCE CHARACTERISTICS (continued)
C1 =220μF, C2 =2.2μF, C3 =39μF, C4 =22μF, L =39μH, TA =25°C, unless otherwise noted.
MP2494 Rev. 1.1
4/13/2018
www.MonolithicPower.com
MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited.
© 2018 MPS. All Rights Reserved.
6
MP2494 –2A, 55V, 100kHz STEP-DOWN CONVERTER
OPERATION
Main Control Loop
The MP2494 is a current mode buck regulator.
That is, the EA output voltage is proportional to
the peak inductor current.
If the Current Sense Amplifier plus Slope
Compensation signal does not exceed the
COMP voltage, then the falling edge of the CLK
resets the Flip-Flop.
At the beginning of a cycle SW 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 100kHz
CLK signal sets the RS Flip-Flop. Its output
turns on SW 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 0.8V bandgap reference. The polarity is
such that an FB pin voltage lower than 0.8V
increases the EA output voltage. Since the EA
output voltage is proportional to the peak
inductor current, an increase in its voltage
increases current delivered to the output. An
external Schottky Diode (D1) carries the
inductor current when SW is off.
The increasing inductor current is sensed and
amplified by the Current Sense Amplifier. Ramp
compensation is summed to Current Sense
Amplifier output and compared to the Error
Amplifier output by the Current Comparator.
When the Current Sense Amplifier plus Slope
Compensation signal exceeds the EA output
voltage, the RS Flip-Flop is reset and the
MP2494 reverts to its initial SW off state.
MP2494 Rev. 1.1
4/13/2018
Enable Control
The MP2494 has an Enable control pin (EN).
Drive EN above 1.8V to turn on the MP2494.
Drive EN below 0.4V to turn it off. Tie EN to VIN
for automatic start up.
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© 2018 MPS. All Rights Reserved.
7
MP2494 –2A, 55V, 100kHz STEP-DOWN CONVERTER
Figure 1—Function Block Diagram
MP2494 Rev. 1.1
4/13/2018
www.MonolithicPower.com
MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited.
© 2018 MPS. All Rights Reserved.
8
MP2494 –2A, 55V, 100kHz STEP-DOWN CONVERTER
APPLICATION INFORMATION
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 300kΩ for optimal transient
response. R2 is then given by:
R2
R1
VOUT
1
0.8 V
Table 1—Resistor Selection for Common
Output Voltages
VOUT (V)
R1 (kΩ)
R2 (kΩ)
1.8
2.5
3.3
5
300 (1%)
300 (1%)
300 (1%)
300 (1%)
240 (1%)
141.1 (1%)
96 (1%)
57.1 (1%)
Selecting the Inductor
A 33µH to 47µH 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
200mΩ. For most designs, the inductance value
can be derived from the following equation.
L
VOUT ( VIN VOUT )
VIN IL f OSC
Where ΔIL is the inductor ripple current.
Choose inductor current ripple to be
approximately 30% of the maximum load
current, 2A. The maximum inductor peak
current is:
IL(MAX ) ILOAD
IL
2
Selecting the Input Capacitor
The input capacitor reduces the surge current
drawn from the input and also 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
pass 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 4.7µF capacitor is sufficient.
Selecting the Output Capacitor
The output capacitor 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
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.
External Bootstrap Diode
It is recommended that an external bootstrap
diode be added when the system has a 5V
fixed input or the power supply generates a 5V
output. This helps improve the efficiency of the
regulator. The bootstrap diode can be a low
cost one such as IN4148 or BAT54.
This diode is also recommended for high duty
cycle operation (when
VOUT
>65%) and high
VIN
output voltage (VOUT>12V) applications.
5V
Under light load conditions below 100mA, larger
inductance is recommended for improved
efficiency.
BS
MP2494
10nF
SW
Figure 2—External Bootstrap Diode
MP2494 Rev. 1.1
4/13/2018
www.MonolithicPower.com
MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited.
© 2018 MPS. All Rights Reserved.
9
MP2494 –2A, 55V, 100kHz STEP-DOWN CONVERTER
PACKAGE INFORMATION
SOIC8E
0.189(4.80)
0.197(5.00)
8
0.124(3.15)
0.136(3.45)
5
0.150(3.80)
0.157(4.00)
PIN 1 ID
1
0.228(5.80)
0.244(6.20)
0.089(2.26)
0.101(2.56)
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)
0.013(0.33)
0.020(0.51)
0.0075(0.19)
0.0098(0.25)
SIDE VIEW
0.050(1.27)
BSC
FRONT VIEW
0.010(0.25)
x 45o
0.020(0.50)
GAUGE PLANE
0.010(0.25) BSC
0.050(1.27)
0.024(0.61)
0o-8o
0.016(0.41)
0.050(1.27)
0.063(1.60)
DETAIL "A"
0.103(2.62)
0.213(5.40)
NOTE:
0.138(3.51)
RECOMMENDED LAND PATTERN
MP2494 Rev. 1.1
4/13/2018
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.
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.
www.MonolithicPower.com
MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited.
© 2018 MPS. All Rights Reserved.
10
MP2494 –2A, 55V, 100kHz STEP-DOWN CONVERTER
PACKAGE INFORMATION
SOIC8
0.189(4.80)
0.197(5.00)
8
0.050(1.27)
0.024(0.61)
5
0.063(1.60)
0.150(3.80)
0.157(4.00)
PIN 1 ID
1
0.228(5.80)
0.244(6.20)
0.213(5.40)
4
TOP VIEW
RECOMMENDED LAND PATTERN
0.053(1.35)
0.069(1.75)
SEATING PLANE
0.004(0.10)
0.010(0.25)
0.013(0.33)
0.020(0.51)
0.0075(0.19)
0.0098(0.25)
SEE DETAIL "A"
0.050(1.27)
BSC
SIDE VIEW
FRONT VIEW
0.010(0.25)
x 45o
0.020(0.50)
GAUGE PLANE
0.010(0.25) BSC
0o-8o
0.016(0.41)
0.050(1.27)
DETAIL "A"
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.
4) LEAD COPLANARITY (BOTTOM OF LEADS AFTER FORMING)
SHALL BE 0.004" INCHES MAX.
5) DRAWING CONFORMS TO JEDEC MS-012, VARIATION AA.
6) DRAWING IS NOT TO SCALE.
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.
MP2494 Rev. 1.1
4/13/2018
www.MonolithicPower.com
MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited.
© 2018 MPS. All Rights Reserved.
11
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