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MP1522
25V Step-Up Converter in a SOT23-5 Package
The Future of Analog IC Technology
DESCRIPTION
The MP1522 is a step up converter that generates up to a 25V output voltage from a 2.7V to 25V input. It uses a current limited Variable Frequency control algorithm to optimize efficiency and minimize external component size and cost. The internal 0.5 N-Channel MOSFET switch can withstand up to 28V allowing the MP1522 to produce high output voltage with high efficiency. The MP1522 includes input under voltage and over temperature protection. The MP1522 is available in tiny 5-pin SOT23 and 3x3 QFN6 packages.
FEATURES
* * * * * * * * Internal 0.5 Power Switch Output Voltage up to 25V Up to 90% Efficiency Low 1A Shutdown Current Input Under Voltage Protection Thermal Shutdown Internal Current Limit Available in Tiny 5-Pin SOT23 and 6-Pin 3x3 QFN Packages Handheld Computers, PDAs Cell Phones Digital Still and Video Cameras Small LCD Displays
APPLICATIONS
* * * *
EVALUATION BOARD REFERENCE
Board Number EV0022 Dimensions 2.2"X x 1.5"Y x 0.5"Z
"MPS" and "The Future of Analog IC Technology" are Registered Trademarks of Monolithic Power Systems, Inc.
TYPICAL APPLICATION
VIN 3.3V
100 90
Efficiency vs Load Current with BIAS Tied to VOUT
10V 5.0V 3.3V
OFF ON
4
EN
SW
1 5 3
VOUT 20V C2 1nF
EFFICIENCY (%)
D1 RB751
80 70 60
MP1522
2 GND
BIAS FB
VOUT = 12V
50 1
MP1522_TAC_S01
10
100
1000
MP1522_TAC_EC01
LOAD CURRENT (mA)
MP1522 Rev. 1.9 12/9/2005
www.MonolithicPower.com MPS Proprietary Information. Unauthorized Photocopy and Duplication Prohibited. (c) 2005 MPS. All Rights Reserved.
1
MP1522 - 25V STEP-UP CONVERTER IN A SOT23-5 PACKAGE
PACKAGE REFERENCE
TOP VIEW
SW GND FB 1 5 BIAS
ABSOLUTE MAXIMUM RATINGS (1)
BIAS .............................................. -0.3V to 28V SW ................................................. -0.5V to 28V All Other Pins................................... -0.3V to 6V Junction Temperature...............................150C Solder Temperature..................................260C Storage Temperature ................-65C to 150C
MARKING
4 EN
MP1522_PD01-TSOT23-5
2 3
Recommended Operating Conditions
(2)
BIAS Supply Voltage ....................... 2.7V to 25V Output Voltage....................................VIN to 25V Operating Temperature .............-20C to +85C
Thermal Resistance
(3)
Part Number* MP1522ET MP1522EQ *
Package SOT23-5 3x3 QFN6
Temperature -20C to +85C -20C to +85C
SOT23-5 ................................ 220 .... 110.. C/W 3x3 QFN6 ............................... 50 ...... 14... C/W
Notes: 1) Exceeding these ratings may damage the device. 2) The device is not guaranteed to function outside of its operating conditions. 3) Measured on approximately 1" square of 1 oz copper.
JA
JC
For Tape & Reel, add suffix -Z (eg. MP1522ET-Z) For Lead Free, add suffix -LF (eg. MP1522ET-LF-Z)
ELECTRICAL CHARACTERISTICS
VBIAS = VEN = 5.0V, TA = +25C, unless otherwise noted.
Parameter Symbol Condition Supply Current (Shutdown) IBIAS (OFF) VEN = 0V Supply Current (Quiescent) IBIAS(ON) VFB = 1.3V Min Off Time, Normal TOFF VFB = 1.23V Operation Min Off Time, Start-Up (4) TOFF VFB = 0V Undervoltage Lockout BIAS Under Voltage Lockout UVLO VBIAS Rising, 100mV Hysteresis (Typical) Enable EN Threshold VEN Rising EN Hysteresis EN Input Bias Current VEN = 0V, 5V Feedback Comparator FB Regulation Threshold VFB Falling (5) FB Hysteresis FB Input Bias Current VFB = 1.23V Output Switch SW On-Resistance (5) RON VBIAS = 5.0V SW Current Limit SW Leakage Current VSW=25V (5) Thermal Shutdown
Notes: 4) First 64 pulses after EN switches High 5) Guaranteed by design.
Min
300
Typ 1 650 550 1.6
Max 3 750 700
Units A A ns s
2.1
2.3
2.65
V
0.8
1.1 60
2.0 1
V mV A V mV nA mA A C
1.19 -150
1.23 10 -80 0.5 450 160
1.27
0.6 10
300
MP1522 Rev. 1.9 12/9/2005
www.MonolithicPower.com MPS Proprietary Information. Unauthorized Photocopy and Duplication Prohibited. (c) 2005 MPS. All Rights Reserved.
2
MP1522 - 25V STEP-UP CONVERTER IN A SOT23-5 PACKAGE
PIN FUNCTIONS
Pin # 1 2 3 4 Name SW GND FB EN Description 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 25V. Ground. Feedback Input. Connect a resistive voltage divider from the output voltage to FB to set the output voltage. The feedback regulation threshold is 1.23V. Regulator On/Off Control Input. A high voltage at EN turns on the converter, and a low voltage turns it off. When not used, connect EN to the input source for automatic startup. If EN is driven over 6V, place a 100k resistor in series with EN. Internal Power Input. BIAS powers the internal circuitry. Connect BIAS to the output for more enhancement on the internal MOSFET gate at low VIN. If the input source remains above 3.0V, BIAS can be connected to the input source to reduce power consumption.
5
BIAS
OPERATION
The MP1522 is a step-up converter that operates from an input voltage as low as 2.7V and generates an output voltage up to 25V. The 0.5 internal N-Channel MOSFET power switch is driven with a variable frequency, constantpeak-current architecture for improved regulation and low operating current. The 550ns minimum off-time is extended to 1.6s during start-up to yield a smooth glitch free turn-on. Start-up mode is activated at initial power-up or when exiting the 1A shutdown state. The MP1522 features an internal regulator allowing it to be powered from the output for improved low-input voltage operation, or powered from the input source for reduced power consumption due to quiescent current.
L1 VIN
BIAS (5)
D1 VOUT
SW (1)
C4 C1
R3
EN (4)
R2
C2
C3
REGULATOR INTERNAL POWER
GND
OFF ON
CONTROL LOGIC CURRENT
-+ 450mA
FB (3)
ERROR AMP -+ 1.23V
GND (2)
R1
MP1522_BD01
Figure 1--Functional Block Diagram
MP1522 Rev. 1.9 12/9/2005 www.MonolithicPower.com MPS Proprietary Information. Unauthorized Photocopy and Duplication Prohibited. (c) 2005 MPS. All Rights Reserved.
3
MP1522 - 25V STEP-UP CONVERTER IN A SOT23-5 PACKAGE
Variable Frequency Constant-Peak-Current Operation When the power MOSFET is turned on the inductor current increases until the 0.45A current limit is reached. The Power MOSFET is then turned off for a minimum of 550ns. At the end of this 550ns transition if the feedback pin is still lower than the 1.23V internal reference the power MOSFET will again be turned on, otherwise the MP1522 waits until the voltage drops below the threshold before turning on the MOSFET again. This process allows for optimal use of the inductor, while minimizing the output ripple and size of the output capacitor and maintaining low operating current. Setting the Output Voltage The output voltage is set by a resistive voltage divider connecting the output voltage to FB. The voltage divider reduces the output voltage down by the ratio:
VOUT R1 + R2 = VFB R1
On/Off Control The EN input is used to turn the converter on and off. A high input at EN turns the converter on and a low level turns the converter off. When EN is not being used, connect to the input source for automatic startup. For inputs greater than 6V, pull EN to VIN through a 100k resistor. Input Capacitor To reduce noise, use a low ESR/ESL type input capacitor. A 1F surface mount ceramic capacitor close to the input supply side of the inductor minimizes EMI and ripple current at the input source. See the section on printed circuit board layout for reducing noise and emissions. A bypass capacitor is typically required to prevent noise at the MP1522. This capacitor should also be a low ESR/ESL type capacitor. Place a 0.1F surface mount ceramic capacitor between BIAS and GND as close to the MP1522 as possible. Output Capacitor To minimize output voltage ripple and noise use a low ESR/ESL type output capacitor. Typically a 1F surface mount ceramic capacitor is sufficient. When using aluminum electrolytics, tantalum or aluminum polymer capacitors the ESR/ESL dominate the output ripple. See the section on printed circuit board layout. Inductor The inductor stores energy during the power MOSFET switch on-time. This energy is transferred to the output during the switch offtime. Select an inductor whose peak-current rating is greater than the 450mA peak current limit of the MP1522. Lower value inductors yield higher switching frequencies and thus lower output ripple voltage. However, using too low a value inductor will cause an increase in peak current limit due to the delay of the current-limit comparator. Choose an inductor such that the peak current limit is reached in 550ns or longer. The minimum value inductor for this criterion is:
L 1.31 x 10 -6 x VIN (H)
Solving for VOUT
R1 + R2 VOUT = VFB R1
Where VOUT is the output voltage, and VFB is the 1.23V feedback threshold. Substituting the feedback threshold voltage:
R1 + R2 VOUT = 1.23 V R1
R1 can range from 10k to 200k. R2 is determined the equation:
V R2 = R1 OUT VFB - 1
For example for an output voltage of 20V and R1 = 130k the formula yields:
20 R2 = 130k - 1 1.23 V
R2 = 2M the closest standard 1% resistor value. The feedback divider requires a feed-forward capacitor connected in parallel with R2. This capacitor is typically in the range of 1nF-10nF.
MP1522 Rev. 1.9 12/9/2005
For maximum VIN = 3.3V, use an inductor value greater than 4.7H, and for maximum VIN = 5V use an inductor value greater than 6.8H.
www.MonolithicPower.com MPS Proprietary Information. Unauthorized Photocopy and Duplication Prohibited. (c) 2005 MPS. All Rights Reserved.
4
MP1522 - 25V STEP-UP CONVERTER IN A SOT23-5 PACKAGE
Diode The high switching frequencies of the MP1522 require the use of fast recovery or Schottky barrier diodes. In low voltage applications Schottky barrier diodes are recommended for maximum efficiency. The reverse breakdown voltage should be approximately 1.5X the output voltage. Printed Circuit Board Layout The printed circuit board layout is important in order to minimize noise and prevent erratic operation. Keep the ground leads short and robust with minimum lead lengths between the input and output capacitors and ground. Place the feedback resistive voltage divider as close to FB as possible to prevent switching noise injection into FB. The use of surface mount capacitors with their low ESL is required to minimize noise at the MP1522. Use separate power and quiet ground planes connected together at a single point whenever possible to minimize.ground.bounce.
Table 1--Output Current vs. Input Voltage
VIN (V) 3.3 3.3 3.3 3.3 5 5 5 10 10 10 VOUT (V) 5 12 18 25 12 18 25 12 18 25 IOUT (mA) 67 28 15 10 44 32 19 122 75 51
VIN 3.3V
OFF ON
4
EN
SW
1 5 3
D1 RB751 C2 1nF
VOUT 20V
MP1522
2 GND
BIAS FB
MP1522_TAC_F02
Figure 2--Typical Boost Application
MP1522 Rev. 1.9 12/9/2005
www.MonolithicPower.com MPS Proprietary Information. Unauthorized Photocopy and Duplication Prohibited. (c) 2005 MPS. All Rights Reserved.
5
MP1522 - 25V STEP-UP CONVERTER IN A SOT23-5 PACKAGE
PACKAGE INFORMATION
SOT23-5
2.900.100
5
0.950 TYP.
0.950 TYP.
10 TYP. (2 plcs)
0
C L
0~3
0.20 BSC.
Gauge Plane
0.45 0.10
0.350(MIN) 0.500(MAX) (5 PLCS)
C L
10 TYP. (2 plcs) 10 TYP. (2 plcs)
0
0
0.127 TYP
10 TYP. (2 plcs)
0
0.05(MIN) 0.15(MAX)
Dimensions are in millimeters
NOTE: 1. Dimensions and tolerances are as per ANSI Y14.5M, 1982. 2. Package surface to be matte finish VDI 11~13. 3. Die is facing up for mold. Die is facing down for trim/form, ie. reverse trim/form. 4. The footlength measuring is based on the gauge plane method.
5. Dimensions are exclusive of mold flash and gate burr.
MP1522 Rev. 1.9 12/9/2005
www.MonolithicPower.com MPS Proprietary Information. Unauthorized Photocopy and Duplication Prohibited. (c) 2005 MPS. All Rights Reserved.
6
MP1522 - 25V STEP-UP CONVERTER IN A SOT23-5 PACKAGE
3x3 QFN6
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.
MP1522 Rev. 1.9 12/9/2005 www.MonolithicPower.com MPS Proprietary Information. Unauthorized Photocopy and Duplication Prohibited. (c) 2005 MPS. All Rights Reserved.
7

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