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MP1541
1.3MHz Boost Converter
The Future of Analog IC Technology
DESCRIPTION
The MP1541 is a 5-pin thin SOT23 current mode step up converter intended for small, low power applications. The MP1541 switches at 1.3MHz and allows the use of tiny, low cost capacitors and inductors 2mm or less in height. Internal soft start results in small inrush current and extends battery life. The MP1541 operates from an input voltage as low as 2.5V and can generate 12V at up to 200mA from a 5V supply. The MP1541 includes under-voltage lockout, current limiting, and thermal overload protection to prevent damage in the event of an output overload. The MP1541 is available in a small 5-pin TSOT23 package.
FEATURES
On Board Power MOSFET Uses Tiny Capacitors and Inductors 1.3MHz Fixed Switching Frequency Internally Compensated Internal Soft-Start Operates with Input Voltage as Low as 2.5V and Output Voltage as High as 22V 12V at 200mA from 5V Input UVLO, Thermal Shutdown Internal Current Limit Available in a TSOT23-5 Package
APPLICATIONS
Camera Phone Flash Handheld Computers and PDAs Digital Still and Video Cameras External Modems Small LCD Displays White LED Driver
"MPS" and "The Future of Analog IC Technology" are Registered Trademarks of Monolithic Power Systems, Inc.
TYPICAL APPLICATION
VIN 5V D1 VOUT 12V 200mA
EFFICIENCY (%)
Efficiency vs Load Current
100 95 90 85 80 75 70 65 60 55 50 0 VOUT = 12V 75 150 225 300 375 450 LOAD CURRENT (mA)
MP1541-TAC-EC01
VIN = 5V
5
OFF ON IN 4 EN
1
SW
VIN = 3.3V
VIN = 4.2V
2
MP1541
GND FB
3
MP1541-TAC01
MP1541 Rev.1.3 3/20/2006
www.MonolithicPower.com MPS Proprietary Information. Unauthorized Photocopy and Duplication Prohibited. (c) 2006 MPS. All Rights Reserved.
1
MP1541 - 1.3MHz BOOST CONVERTER
PACKAGE REFERENCE
TOP VIEW
SW GND FB 1 5 IN
ABSOLUTE MAXIMUM RATINGS (1)
SW Pin........................................... -0.3V to 25V All Other Pins................................ -0.3V to 6.5V Junction Temperature...............................150C Lead Temperature ....................................260C Storage Temperature ..............-65C to +150C
B3YW
4 EN
MP1541-PD01-TSOT23
2 3
Recommended Operating Conditions
(2)
Supply Voltage VIN ............................. 2.5V to 6V Output Voltage VOUT ........................... 3V to 22V Operating Temperature .............-40C to +85C
Thermal Resistance
Part Number* MP1541DJ * Package TSOT23-5 Marking: B3YW
(3)
Temperature -40C to +85C
TSOT25 ................................. 220 .... 110.. C/W
Notes: 1) Exceeding these ratings may damage the device. 2) The device is not guaranteed to function outside of its operating range. 3) Measured on approximately 1" square of 1oz. copper.
JA
JC
For Tape & Reel, add suffix -Z (eg. MP1541DJ-Z) For Lead Free, add suffix -LF (eg. MP1541DJ-LF-Z)
ELECTRICAL CHARACTERISTICS
VIN = VEN = 5V, TA = +25C unless otherwise specified.
Parameters Operating Input Voltage Undervoltage Lockout Undervoltage Lockout Hysteresis Supply Current (Shutdown) Supply Current (Quiescent) Switching Frequency Maximum Duty Cycle EN Threshold EN Threshold EN Hysteresis EN Input Bias Current FB Voltage FB Input Bias Current SW On-Resistance SW Current Limit SW Leakage Thermal Shutdown
(4) (4) (4)
Symbol VIN
Condition
Min 2.5
Typ 2.25 92
Max 6 2.45
Units V V mV
VEN = 0V VFB = 1.3V fSW VFB = 0V VEN Rising VEN Rising, VIN = 2.5V VEN = 0V, 6V VFB VFB = 1.25V RDS (ON) VSW = 15V 1.21 -100 1.0 80 1.0
0.1 635 1.3 85 1.3 1.1 100
1 850 1.6 1.6
A A MHz % V V mV
1 1.25 -30 0.65 1.9 1 160 1.29
A V nA A A C
Note: 4) Guaranteed by design.
MP1541 Rev.1.3 3/20/2006
www.MonolithicPower.com MPS Proprietary Information. Unauthorized Photocopy and Duplication Prohibited. (c) 2006 MPS. All Rights Reserved.
2
MP1541 - 1.3MHz BOOST CONVERTER
TYPICAL PERFORMANCE CHARACTERISTICS
Feedback Voltage vs Temperature
1.252 1.40 1.35 1.30 1.25 1.20 1.15 -50
Frequency vs Temperature
FEEDBACK VOLTAGE (V)
1.248 1.246 1.244 1.242 -50
0 50 100 TEMPERATURE (C)
150
FREQUENCY (MHz)
1.250
0 50 100 TEMPERATURE (C)
150
MP1541-TPC01
MP1541-TPC02
Maximum Duty Cycle vs Temperature
84.1 640 635 630 625 620 615 0 50 100 TEMPERATURE (C) 150
Supply Current vs Temperature
MAXIMUM DUTY CYCLE (%)
84.0 83.9 83.8 83.7 83.6 83.5 -50
610 -50
0 50 100 TEMPERATURE (C)
150
MP1541-TPC03
MP1541-TPC04
RDS (ON) vs Input Voltage
0.80 0.75 0.70 0.65 0.60 0.55 0.50 1.6 1.5 1.4 1.3 1.2 1.1 2 3 4 5 INPUT VOLTAGE (V) 6 1.0
Current Limit vs Duty Cycle
CURRENT LIMIT (A)
30
40
50 60 70 DUTY CYCLE (%)
80
MP1541-TPC05
MP1541-TPC06
MP1541 Rev.1.3 3/20/2006
www.MonolithicPower.com MPS Proprietary Information. Unauthorized Photocopy and Duplication Prohibited. (c) 2006 MPS. All Rights Reserved.
3
MP1541 - 1.3MHZ BOOST CONVERTER
PIN FUNCTIONS
Pin # 1 2 3 4 5 Name Function SW GND FB EN IN Power Switch Output. SW is the drain of the internal MOSFET switch. Connect the power inductor and output rectifier to SW. SW can swing between GND and 22V. Ground. 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 turns it off. When not used, connect EN to the input source for automatic startup. The EN pin cannot be left floating. Input Supply Pin. Must be locally bypassed.
OPERATION
The MP1541 uses a fixed frequency, peak current mode boost regulator architecture to regulate voltage at the feedback pin. The operation of the MP1541 can be understood by referring to the block diagram of Figure 1. At the start of each oscillator cycle the MOSFET is turned on through the control circuitry. To prevent sub-harmonic oscillations at duty cycles greater than 50 percent, a stabilizing ramp is added to the output of the current sense amplifier and the result is fed into the negative input of the PWM comparator. When this voltage equals the output voltage of the error amplifier the power MOSFET is turned off. The voltage at the output of the error amplifier is an
RC CC
amplified version of the difference between the 1.25V bandgap reference voltage and the feedback voltage. In this way the peak current level keeps the output in regulation. If the feedback voltage starts to drop, the output of the error amplifier increases. This results in more current to flow through the power MOSFET, thus increasing the power delivered to the output. The MP1541 has internal soft start to limit the amount of input current at startup and to also limit the amount of overshoot on the output. The current limit is increased by a fourth every 40s giving a total soft start time of 120s.
SW 1
FB
3
+ + ERROR AMPLIFIER CONTROL LOGIC M1
1.25V
PWM COMPARATOR + + CURRENT SENSE AMPLIFIER 2 GND
1.3MHz OSC
MP1541-F01-BD01
Figure 1--Functional Block Diagram
MP1541 Rev.1.3 3/20/2006
www.MonolithicPower.com MPS Proprietary Information. Unauthorized Photocopy and Duplication Prohibited. (c) 2006 MPS. All Rights Reserved.
4
MP1541 - 1.3MHZ BOOST CONVERTER
APPLICATIONS INFORMATION
COMPONENT SELECTION
Setting the Output Voltage Set the output voltage by selecting the resistive voltage divider ratio. Use 11.8k for the lowside resistor R2 of the voltage divider. Determine the high-side resistor R1 by the equation:
R1 = R2(VOUT - VFB ) VFB
where VOUT is the output voltage. For R2 = 11.8k and VFB = 1.25V, then R1 (k) = 9.44k (VOUT - 1.25V). Selecting the Input Capacitor An input capacitor is required to supply the AC ripple current to the inductor, while limiting noise at the input source. This capacitor must have low ESR, so ceramic is the best choice. Use an input capacitor value of 4.7F or greater. This capacitor must be placed physically close to the IN pin. Since it reduces the voltage ripple seen at IN, it also reduces the amount of EMI passed back along that line to the other circuitry. Selecting the Output Capacitor A single 4.7F to 10F ceramic capacitor usually provides sufficient output capacitance for most applications. If larger amounts of capacitance is desired for improved line support and transient response, tantalum capacitors can be used in parallel with the ceramic. The impedance of the ceramic capacitor at the switching frequency is dominated by the capacitance, and so the output voltage ripple is mostly independent of the ESR. The output voltage ripple VRIPPLE is calculated as:
VRIPPLE = ILOAD (VO UT - VIN ) VO UT x C2 x f SW
Selecting the Inductor The inductor is required to force the output voltage higher while being driven by the lower input voltage. Choose an inductor that does not saturate at the SW current limit. A good rule for determining the inductance is to allow the peakto-peak ripple current to be approximately 30%50% of the maximum input current. Make sure that the peak inductor current is below 75% of the typical current limit at the duty cycle used to prevent loss of regulation due to the current limit variation. Calculate the required inductance value L using the equations:
L= VIN (VOUT - VIN ) VOUT x fSW x I
IIN(MAX ) =
VOUT x ILOAD (MAX ) VIN x
I = (30% - 50%)IIN(MAX )
Where ILOAD(MAX) is the maximum load current, I is the peak-to-peak inductor ripple current, and is efficiency. For the MP1541, 4.7H is recommended for input voltages less than 3.3V and 10H for inputs greater than 3.3V. Selecting the Diode The output rectifier diode supplies current to the inductor when the internal MOSFET is off. To reduce losses due to diode forward voltage and recovery time, use a Schottky diode. Choose a diode whose maximum reverse voltage rating is greater than the maximum output voltage. For output voltage less than 20V, it is recommended to choose the MBR0520 for most applications. This diode is used for load currents less than 500mA. If the average current is more than 500mA the Microsemi UPS5817 is a good choice.
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.
MP1541 Rev.1.3 3/20/2006
www.MonolithicPower.com MPS Proprietary Information. Unauthorized Photocopy and Duplication Prohibited. (c) 2006 MPS. All Rights Reserved.
5
MP1541 - 1.3MHz BOOST CONVERTER Compensation The MP1541 uses an amplifier to compensate the feedback loop rather than a traditional transconductance amplifier like most current mode regulators. Frequency compensation is provided by an internal resistor and capacitor along with an external resistor. The system uses two poles and one zero to stabilize the control loop. The poles are fP1 set by the output capacitor and load resistance, and fP2 set by the internal compensation capacitor Cc, the gain of the error amplifier and the resistance seen looking out at the feedback node REQ. The zero fZ1 is set internally around 20kHz. These are determined by the equations:
fP1 = fP 2 = 1 x C2 x R LOAD
To stabilize the regulation control loop, the crossover frequency (the frequency where the loop gain drops to 0dB or a gain of 1, indicated as fC) should be at least one decade below the right-half-plane zero and should be at most 75kHz. fRHPZ is at its lowest frequency at maximum output load current (RLOAD is at a minimum) and minimum input voltage. For the MP1541 it is recommended that a 47k to 100k resistor be placed in series with the FB pin and the resistor divider as seen in Figure 2. For most applications this is all that is needed for stable operation. If greater phase margin is needed a series resistor and capacitor can be placed in parallel with the high-side resistor R1 as seen in Figure 2. The pole and zero set by the lead-lag compensation network are:
fP 3 = 1 1 2 x x C3 x R4 + 1 1 1 + + R1 R2 R3
f Z2 = 1 2 x x C3 x (R1 + R 4 )
2 x x 7.9 x 10 -9 x R EQ f Z1 = 20kHz
(
1
)
Where RLOAD is the load resistance and REQ is:
R EQ = R3 + (R1x R2) (R1 + R2)
Where R1, R2, and R3 are seen in Figure 2. The DC loop gain is:
A VDC = 500 VIN R LOAD VFB VOUT
2
LAYOUT CONSIDERATIONS
High frequency switching regulators require very careful layout for stable operation and low noise. All components must be placed as close to the IC as possible. Keep the path between L1, D1, and C2 extremely short for minimal noise and ringing. C1 must be placed close to the IN pin for best decoupling. All feedback components must be kept close to the FB pin to prevent noise injection on the FB pin trace. The ground return of C1 and C2 should be tied close to the GND pin. See the MP1541 demo board layout for reference.
There is also a right-half-plane zero (fRHPZ) that exists in all continuous mode (inductor current does not drop to zero on each cycle) step up converters. The frequency of the right half plane zero is:
fRHPZ = VIN x R LOAD 2 x x L x VOUT
2 2
MP1541 Rev.1.3 3/20/2006
www.MonolithicPower.com MPS Proprietary Information. Unauthorized Photocopy and Duplication Prohibited. (c) 2006 MPS. All Rights Reserved.
6
MP1541 - 1.3MHz BOOST CONVERTER
TYPICAL APPLICATION CIRCUITS
VIN 5V D1 MBR0520L VOUT 12V 200mA
5 OFF ON 4 2 IN EN GND
1 SW
C3 100pF
3
MP1541
FB
MP1541-F02-TBC01
Figure 2--VIN = 5V, VOUT = 12V, IOUT = 200mA Boost Circuit
VIN 3V to 5.5V
D1 MBR0520
LED1 LED2
5 OFF ON 4 2 IN EN GND 1 SW
LED3
3
MP1541
FB
FLASH
Q1 ZXMN2A03E6TA
MP1541-F03-TAC01
Figure 3--Typical Application Circuit for Driving Flashlight LEDs (20mA Torch Current, 100mA Flash Current)
MP1541 Rev.1.3 3/20/2006
www.MonolithicPower.com MPS Proprietary Information. Unauthorized Photocopy and Duplication Prohibited. (c) 2006 MPS. All Rights Reserved.
7
MP1541 - 1.3MHz BOOST CONVERTER
PACKAGE INFORMATION
TSOT23-5
2.90 BSC
3
0.950 TYP.
0.950 TYP.
10TYP. (2 plcs)
3
C L
1.60 BSC
2.80 BSC
0
0.25 BSC.
+ 4 - 0
0.400
0.10
0.300(Min) 0.500(Max) (5 PLCS)
Gauge Plane
C L
1.00 Max.
0.870.03
SEATING PLANE
0.00-0.10
10 TYP. (2 plcs)
0.127 TYP.
Dimensions are in millimeters
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. 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.
MP1541Rev. 1.3 3/20/2006 www.MonolithicPower.com MPS Proprietary Information. Unauthorized Photocopy and Duplication Prohibited. (c) 2006 MPS. All Rights Reserved.
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