TM

MP1540
1.3MHz, 18V
Step-Up Converter
TM
The Future of Analog IC Technology

DESCRIPTION FEATURES
The MP1540 is a 5-pin thin TSOT23 current • On Board Power MOSFET
mode step-up converter intended for small, low • Uses Tiny Capacitors and Inductors
power applications. The MP1540 switches at • 1.3MHz Fixed Switching Frequency
1.3MHz and allows the use of tiny, low cost • Internal Soft-Start
capacitors and inductors 2mm or less in height. • Operates with Input Voltage as Low as
Internal soft-start results in small inrush current 2.5V and Output Voltage as High as 18V
and extends battery life. The MP1540 operates • 12V at 200mA from 5V Input
from an input voltage as low as 2.5V and can • UVLO, Thermal Shutdown
generate 12V at up to 200mA from a 5V
• Internal Current Limit
supply.
• Available in a TSOT23-5 Package
The MP1540 includes under voltage lockout,
current limiting, and thermal overload APPLICATIONS
protection to prevent damage in the event of an • Camera Phone Flash
output overload. The MP1540 is available in a • Handheld Computers and PDAs
small 5-pin TSOT23 package.
• Digital Still and Video Cameras
• External Modems
• Small LCD Displays
• White LED Driver
“MPS” and “The Future of Analog IC Technology” are Trademarks of Monolithic
Power Systems, Inc.

TYPICAL APPLICATION
D1 Efficiency vs Load Current
VIN VOUT
5V 12V 100
200mA 95
VIN = 5V
90
EFFICIENCY (%)

85
80 VIN = 3.3V
5 1
75 VIN = 4.2V
IN SW
4 70
OFF ON EN
MP1540 65
2 3
GND FB 60
55
50
0 75 150 225 300 375 450
LOAD CURRENT (mA)
MP1540_TAC01
MP1540_TAC_EC01

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MP1540 – 1.3MHz, 18V STEP-UP CONVERTER

PACKAGE REFERENCE ABSOLUTE MAXIMUM RATINGS (1)

SW Pin ........................................ –0.3V to +20V
TOP VIEW All Other Pins ............................. –0.3V to +6.5V
Junction Temperature .............................. 150°C
SW 1 5 IN
Lead Temperature.................................... 260°C
Storage Temperature .............. –65°C to +150°C
GND 2 D9YW Recommended Operating Conditions
(2)

Supply Voltage VIN ............................ 2.5V to 6V

FB 3 4 EN Output Voltage VOUT ........................... 3V to 18V
Operating Temperature ............. –40°C to +85°C
MP1540_PD01_TSOT23-5
(3)
Thermal Resistance θJA θJC
TSOT23-5.............................. 220.....110 ..°C/W
Part Number* Package Temperature
Notes:
MP1540DJ TSOT23-5 –40°C to +85°C 1) Exceeding these ratings may damage the device.
2) The device is not guaranteed to function outside of its
* For Tape & Reel, add suffix –Z (eg. MP1540DJ–Z) operating conditions.
For Lead Free, add suffix –LF (eg. MP1540DJ–LF–Z) 3) Measured on approximately 1” square of 1 oz copper.

ELECTRICAL CHARACTERISTICS
VIN = VEN = 5V, TA = +25°C unless specified otherwise.
Parameters Symbol Condition Min Typ Max Units
Operating Input Voltage VIN 2.5 6 V
Under Voltage Lockout 2.25 2.45 V
Under Voltage Lockout
92 mV
Hysteresis
Supply Current (Shutdown) VEN = 0V 0.1 1 µA
Supply Current (Quiescent) VFB = 1.3V 635 850 µA
Switching Frequency fSW 1.0 1.3 1.6 MHz
Maximum Duty Cycle VFB = 0V 80 85 %
EN Threshold VEN Rising 1.0 1.3 1.6 V
EN Threshold VEN Rising, VIN = 2.5V 1.1 V
EN Hysteresis 100 mV
EN Input Bias Current VEN = 0V, 6V 1 µA
FB Voltage VFB 1.21 1.25 1.29 V
FB Input Bias Current VFB = 1.25V –100 –30 nA
SW On-Resistance (4) RDS (ON) 0.65 Ω
SW Current Limit (4) 1.9 A
SW Leakage VSW = 15V 1 µA
(4)
Thermal Shutdown 160 °C
Note:
4) Guaranteed by design.

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MP1540 – 1.3MHz, 18V STEP-UP CONVERTER

TYPICAL PERFORMANCE CHARACTERISTICS

VIN = VEN = 5V, TA = +25°C unless specified otherwise.
Feedback Voltage vs Frequency vs
Temperature Temperature
1.270 1.6
FEEDBACK VOLTAGE (V)

1.5

FREQUENCY (MHz)
1.260
1.4

1.250 1.3

1.2
1.240
1.1

1.230 1.0
-50 0 50 100 150 -50 0 50 100 150
TEMPERATURE (°C) TEMPERATURE (°C)
MP1540_TPC01 MP1540_TPC02

Maximum Duty Cycle vs Supply Current vs

Temperature Temperature
85.0 750
MAXIMUM DUTY CYCLE (%)

84.6 700

84.2
650
83.8
600
83.4
550
83.0

82.6 500
-50 0 50 100 150 -50 0 50 100 150
TEMPERATURE (°C) TEMPERATURE (°C)
MP1540_TPC03 MP1540_TPC04

RDS (ON) vs Current Limit vs

Input Voltage Duty Cycle
0.80 1.6

0.75 1.5
CURRENT LIMIT (A)

0.70 1.4

0.65 1.3

0.60 1.2

0.55 1.1

0.50 1.0
2 3 4 5 6 30 40 50 60 70 80
INPUT VOLTAGE (V) DUTY CYCLE (%)
MP1540_TPC05 MP1540_TPC06

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MP1540 – 1.3MHz, 18V STEP-UP CONVERTER

PIN FUNCTIONS
Pin # Name Pin Function
Power Switch Output. SW is the drain of the internal MOSFET switch. Connect the power
1 SW
inductor and output rectifier to SW. SW can swing between GND and 20V.
2 GND Ground.
3 FB Feedback Input. FB voltage is 1.25V. Connect a resistor divider to FB.
Regulator On/Off Control Input. A high input at EN turns on the converter, and a low input
4 EN turns it off. When not used, connect EN to the input source for automatic startup. The EN
pin cannot be left floating.
5 IN Input Supply Pin. Must be locally bypassed.

OPERATION
The MP1540 uses a fixed frequency, peak The voltage at the output of the error amplifier is
current mode boost regulator architecture to an amplified version of the difference between
regulate voltage at the feedback pin. The the 1.25V bandgap reference voltage and the
operation of the MP1540 can be understood by feedback voltage. In this way the peak current
referring to the block diagram of Figure 1. level keeps the output in regulation. If the
feedback voltage starts to drop, the output of the
At the start of each oscillator cycle the MOSFET
error amplifier increases. This results in more
is turned on through the control circuitry. To
current to flow through the power MOSFET, thus
prevent sub-harmonic oscillations at duty cycles
increasing the power delivered to the output.
greater than 50 percent, a stabilizing ramp is
added to the output of the current sense The MP1540 has internal soft start to limit the
amplifier and the result is fed into the negative amount of input current at startup and to also
input of the PWM comparator. When this voltage limit the amount of overshoot on the output.
equals the output voltage of the error amplifier The current limit is increased by a fourth every
the power MOSFET is turned off. 40µs giving a total soft start time of 120µs.

RC CC
SW
1

FB 3 -
+
CONTROL
+ LOGIC M1
-
ERROR
AMPLIFIER PWM
1.25V COMPARATOR
+
+
-

CURRENT 2
SENSE
1.3MHz AMPLIFIER GND
OSC
MP1540_F01_BD01

Figure 1—Functional Block Diagram

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MP1540 – 1.3MHz, 18V STEP-UP CONVERTER

APPLICATIONS INFORMATION
COMPONENT SELECTION Selecting the Inductor
The inductor is required to force the output
Setting the Output Voltage
voltage higher while being driven by the lower
Set the output voltage by selecting the resistive input voltage. Choose an inductor that does not
voltage divider ratio. Use 11.8kΩ for the low- saturate at the SW current limit. A good rule for
side resistor R2 of the voltage divider.
determining the inductance is to allow the peak-
Determine the high-side resistor R1 by the
to-peak ripple current to be approximately 30%-
equation:
50% of the maximum input current. Make sure
R2(VOUT - VFB ) that the peak inductor current is below 75% of
R1 =
VFB the typical current limit at the duty cycle used to
prevent loss of regulation due to the current
Where VOUT is the output voltage and VFB is the limit variation.
feedback voltage.
Calculate the required inductance value L using
For R2 = 11.8kΩ and VFB = 1.25V, then the equations:
R1 (kΩ) = 9.44kΩ (VOUT – 1.25V). VIN (VOUT - VIN )
L=
Selecting the Input Capacitor VOUT × fSW × ∆I
An input capacitor is required to supply the AC
VOUT × ILOAD (MAX )
ripple current to the inductor, while limiting noise IIN(MAX ) =
at the input source. This capacitor must have low VIN × η
ESR, so ceramic is the best choice.
∆I = (30% − 50%)IIN(MAX )
Use an input capacitor value of 4.7µF or
greater. This capacitor must be placed Where ILOAD(MAX) is the maximum load current, ∆I
physically close to the IN pin. Since it reduces is the peak-to-peak inductor ripple current and η
the voltage ripple seen at IN, it also reduces the is efficiency. For the MP1540, 4.7µH is
amount of EMI passed back along that line to recommended for input voltages less than 3.3V
the other circuitry. and 10µH for inputs greater than 3.3V.
Selecting the Output Capacitor Selecting the Diode
A single 4.7µF to 10µF ceramic capacitor The output rectifier diode supplies current to the
usually provides sufficient output capacitance inductor when the internal MOSFET is off. To
for most applications. If larger amounts of reduce losses due to diode forward voltage and
capacitance are desired for improved line recovery time, use a Schottky diode. Choose a
support and transient response, tantalum diode whose maximum reverse voltage rating is
capacitors can be used in parallel with the greater than the maximum output voltage. It is
ceramic. The impedance of the ceramic capacitor recommended to choose the MBR0520 for most
at the switching frequency is dominated by the applications. This diode is used for load currents
capacitance, and so the output voltage ripple is less than 500mA. If the average current is more
mostly independent of the ESR. The output than 500mA the Microsemi UPS5817 is a good
voltage ripple VRIPPLE is calculated as: choice.
ILOAD (VO UT − VIN )
VRIPPLE =
VO UT × C2 × f SW

Where VIN is the input voltage, ILOAD is the load

current, C2 is the capacitance of the output
capacitor, and fSW is the 1.3MHz switching
frequency.

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MP1540 – 1.3MHz, 18V STEP-UP CONVERTER

Compensation To stabilize the regulation control loop, the

The MP1540 uses an amplifier to compensate crossover frequency (the frequency where the
the feedback loop rather than a traditional loop gain drops to 0dB or a gain of 1, indicated
transconductance amplifier like most current as fC) should be at least one decade below the
mode regulators. Frequency compensation is right-half-plane zero and should be at most
provided by an internal resistor and capacitor 75KHz. fRHPZ is at its lowest frequency at
along with an external resistor. The system maximum output load current (RLOAD is at a
uses two poles and one zero to stabilize the minimum) and minimum input voltage.
control loop. The poles are fP1 set by the output
For the MP1540 it is recommended that a 47kΩ
capacitor and load resistance, and fP2 set by the
to 100kΩ resistor be placed in series with the FB
internal compensation capacitor, the gain of the
pin and the resistor divider as seen in Figure 2.
error amplifier and the resistance seen looking
For most applications this is all that is needed for
out at the feedback node REQ. The zero fZ1 is set
stable operation. If greater phase margin is
internally around 20KHz. These are determined
needed a series resistor and capacitor can be
by the equations:
placed in parallel with the high-side resistor R1 as
1 seen in Figure 2. The pole and zero set by the
fP1 =
π × C2 × R LOAD lead-lag compensation network are:

1 1
fP 2 = fP 3 =
(
2 × π × 7.9 × 10 −9 × R EQ) ⎛
⎜
1
⎞
⎟
2 × π × C3 × ⎜ R4 + ⎟
f Z1 = 20KHz ⎜ 1 1 1 ⎟
⎜ + + ⎟
⎝ R1 R2 R3 ⎠
Where RLOAD is the load resistance and REQ is:
1
(R1× R2) f Z2 =
R EQ = R3 + 2 × π × C3 × (R1 + R 4 )
(R1 + R2)
Layout Considerations
Where R1, R2, and R3 are seen in Figure 2. High frequency switching regulators require
The DC loop gain is: very careful layout for stable operation and low
noise. All components must be placed as close
VIN × R LOAD × VFB
A VDC = 500 × to the IC as possible. Keep the path between
2
VOUT L1, D1, and C2 extremely short for minimal
noise and ringing. C1 must be placed close to
There is also a right-half-plane zero (fRHPZ) that the IN pin for best decoupling. All feedback
exists in all continuous mode (inductor current components must be kept close to the FB pin to
does not drop to zero on each cycle) step up prevent noise injection on the FB pin trace. The
converters. The frequency of the right half plane ground return of C1 and C2 should be tied
zero is: close to the GND pin.
2
VIN × R LOAD
fRHPZ = 2
2 × π × L × VOUT

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MP1540 – 1.3MHz, 18V STEP-UP CONVERTER

TYPICAL APPLICATIONS
D1
MBR0520L VOUT
VIN 12V
5V 200mA

5 1
IN SW C3
4
OFF ON EN 100pF
MP1540
2 3
GND FB

MP1540_F02

Figure 2—VIN = 5V, VOUT = 12V, IOUT = 200mA Boost Circuit

D1
MBR0520
VIN
3V to 5.5V

LED1

LED2
5 1
IN SW
4 LED3
OFF ON EN
MP1540
2 3
GND FB

Q1
ZXMN2A03E6TA
FLASH

MP1540_F03

Figure 3—Typical Application Circuit for Driving Flashlight LEDs

(20mA Torch Current, 100mA Flash Current)

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MP1540 – 1.3MHz, 18V STEP-UP CONVERTER

PACKAGE INFORMATION

TSOT23-5
2.90 BSC 3

0.950 0.950
TYP. TYP.
10°TYP.
(2 plcs)

2.80 BSC
1.60 BSC
CL

+ 4°
- 0°
0°
±0.10
0.400
0.25 BSC.
Gauge Plane
0.300(Min)
0.500(Max) CL
(5 PLCS)
0.87±0.03
1.00 Max.

SEATING PLANE

0.127 TYP.
0.00-0.10
10° TYP.
(2 plcs)

NOTE:
1. Dimensions and tolerances are as per ANSI
Y14.5M, 1994.
2. Die is facing up for mold. Die is facing
down for trim/form, ie. reverse trim/form.
3. Dimensions are exclusive of mold flash and gate burr.
4. The footlength measuring is based on the
gauge plane method.
5. All specification comply to Jedec Spec MO193 Issue C.

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.

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