LM3352 Regulated 200 mA Buck-Boost Switched Capacitor DC/DC Converter General Description The LM3352 is a CMOS switched capacitor DC/DC converter that produces a regulated output voltage by automatically stepping up (boost) or stepping down (buck) the input voltage. It accepts an input voltage between 2.5V and 5.5V. The LM3352 is available in three standard output voltage versions: 2.5V, 3.0V and 3.3V. If other output voltage options between 1.8V and 4.0V are desired, please contact your National Semiconductor representative. The LM3352’s proprietary buck-boost architecture enables up to 200 mA of load current at an average efficiency greater than 80%. Typical operating current is only 400 µA and the typical shutdown current is only 2.5 µA. The LM3352 is available in a 16-pin TSSOP package. This package has a maximum height of only 1.1 mm. The high efficiency of the LM3352, low operating and shutdown currents, small package size, and the small size of the overall solution make this device ideal for battery powered, portable, and hand-held applications. Features n Regulated VOUT with ± 3% accuracy n Standard output voltage options: 2.5V, 3.0V and 3.3V n Custom output voltages available from 1.8V to 4.0V in 100 mV increments n 2.5V to 5.5V input voltage n Up to 200 mA output current n > 80% average efficiency n Uses few, low-cost external components n Very small solution size n 400 µA typical operating current n 2.5 µA typical shutdown current n 1 MHz switching frequency (typical) n Architecture and control methods provide high load current and good efficiency n TSSOP-16 package n Over-temperature protection Applications n 1-cell Lilon battery-operated equipment including PDAs, hand-held PCs, cellular phones n Flat panel displays n Hand-held instruments n NiCd, NiMH, or alkaline battery powered systems n 3.3V to 2.5V and 5.0V to 3.3V conversion Typical Operating Circuit DS101037-1 © 1999 National Semiconductor Corporation DS101037 www.national.com LM3352 Regulated 200 mA Buck-Boost Switched Capacitor DC/DC Converter September 1999 Connection Diagram DS101037-2 Top View TSSOP-16 Pin Package See NS Package Number MTC16 Ordering Information NSC Package Drawing Supplied As LM3352MTCX-2.5 Order Number TSSOP-16 Package Type MTC16 2.5k Units, Tape and Reel LM3352MTC-2.5 TSSOP-16 MTC16 94 Units, Rail LM3352MTCX-3.0 TSSOP-16 MTC16 2.5k Units, Tape and Reel LM3352MTC-3.0 TSSOP-16 MTC16 94 Units, Rail LM3352MTCX-3.3 TSSOP-16 MTC16 2.5k Units, Tape and Reel LM3352MTC-3.3 TSSOP-16 MTC16 94 Units, Rail Pin Description Pin Number Name 1 GND Ground* 2 C3− Negative Terminal for C3 3 C3+ Positive Terminal for C3 4 C2− Negative Terminal for C2 5 C2+ Positive Terminal for C2 6 C1− Negative Terminal for C1 7 C1+ Positive Terminal for C1 8 VOUT Regulated Output Voltage Ground* 9 GND 10 VIN 11 NC 12 GND 13 SD 14 GND Function Input Supply Voltage This pin must be left unconnected. Ground* Active Low CMOS Logic-Level Shutdown Input Ground* 15 CFIL Filter Capacitor; A 1 µF ceramic capacitor is suggested. 16 GND Ground* *All GND pins of the LM3352 must be connected to the same ground. www.national.com 2 Absolute Maximum Ratings (Note 1) Lead Temperature (Soldering, 5 sec.) ESD Rating (Note 3) human body model machine model If Military/Aerospace specified devices are required, please contact the National Semiconductor Sales Office/ Distributors for availability and specifications. VOUT Pin All Other Pins Power Dissipation (TA = 25˚C) (Note 2) TJMAX (Note 2) θJA (Note 2) Storage Temperature 260˚C 2 kV 100V Operating Ratings −0.5V to 4.5V −0.5V to 5.6V Input Voltage (VIN ) Output Voltage (VOUT ) Ambient Temperature (TA ) (Note 2) Junction Temperature (T J) (Note 2) 700 mW 150˚C 150˚C/W −65˚C to +150˚C 2.5V to 5.5V 1.8V to 4.0V −40˚C to +85˚C −40˚C to +125˚C Electrical Characteristics Limits in standard typeface are for TJ = 25˚C, and limits in boldface type apply over the full operating temperature range. Unless otherwise specified: C1 = C2 = C3 = 0.33 µF; CIN = 15 µF; COUT = 33 µF; VIN = 3.5V. Parameter Conditions Min Typ Max 2.463 2.5 2.537 2.425/2.400 2.5 2.575/2.600 2.425/2.400 2.5 2.575/2.600 2.425/2.400 2.5 2.575/2.600 Units LM3352-2.5 Output Voltage (V OUT) VIN = 3.5V; I LOAD = 100 mA 2.8V < VIN < 5.5V; 1 mA < ILOAD < 100 mA 3.6V < VIN < 4.9V; 1 mA < ILOAD < 200 mA 4.9V < VIN < 5.5V; 1 mA < ILOAD < 175 mA Efficiency Output Voltage Ripple (Peak-to-Peak) ILOAD = 15 mA 85 ILOAD = 150 mA, VIN = 4.0V 75 ILOAD = 50 mA C OUT = 33 µF tantalum 75 V % mVP-P LM3352-3.0 Output Voltage (V OUT) Efficiency Output Voltage Ripple (Peak-to-Peak) 2.955 3.0 3.045 2.5V < VIN < 5.5V; 1 mA < ILOAD < 100 mA VIN = 3.5V; I 2.910/2.880 3.0 3.090/3.120 3.8V < VIN < 5.5V; 1 mA < ILOAD < 200 mA 2.910/2.880 3.0 3.090/3.120 LOAD = 100 mA ILOAD = 15 mA 80 ILOAD = 150 mA, VIN = 4.0V 75 ILOAD = 50 mA C OUT = 33 µF tantalum 75 V % mVP-P LM3352-3.3 Output Voltage (V OUT) Efficiency Output Voltage Ripple (Peak-to-Peak) 3.251 3.3 3.349 2.5V < VIN < 5.5V; 1 mA < ILOAD < 100 mA VIN = 3.5V; I 3.201/3.168 3.3 3.399/3.432 4.0V < VIN < 5.5V; 1 mA < ILOAD < 200 mA 3.201/3.168 3.3 3.399/3.432 LOAD = 100 mA ILOAD = 15 mA 90 ILOAD = 150 mA, VIN = 4.0V 80 ILOAD = 50 mA C OUT = 33 µF tantalum 75 V % mVP-P LM3352-ALL OUTPUT VOLTAGE VERSIONS Operating Quiescent Current Measured at Pin VIN; I LOAD = 0A (Note 4) 400 500 Shutdown Quiescent Current SD Pin at 0V (Note 5) 2.5 5 µA 1 1.35 MHz 0.2 VIN V Switching Frequency 0.65 SD Input Threshold Low 2.5V < VIN < 5.5V SD Input Threshold High 2.5V < VIN < 5.5V 0.8 VIN 3 µA V www.national.com Electrical Characteristics (Continued) Limits in standard typeface are for TJ = 25˚C, and limits in boldface type apply over the full operating temperature range. Unless otherwise specified: C1 = C2 = C3 = 0.33 µF; CIN = 15 µF; COUT = 33 µF; VIN = 3.5V. Parameter Conditions Min Typ Max Units 0.1 1.0 µA LM3352-ALL OUTPUT VOLTAGE VERSIONS SD Input Current Measured at SD Pin; SD Pin = VIN = 5.5V Note 1: “Absolute Maximum Ratings” indicate limits beyond which damage to the device may occur. Electrical specifications do not apply when operating the device beyond its rated operating conditions. Note 2: As long as TA ≤ +85˚C, all electrical characteristics hold true for the 3.0V and 3.3V options at all current loads and the 2.5V option at all loads when VIN ≤ 5V. For VIN > 5V with the 2.5V option, the junction temperature rise above ambient is: ∆T = 540IL−23 where IL is in amps. The output current must be derated at higher ambient temperatures to make sure TJ does not exceed 150˚C when operating the 2.5V option at VIN > 5V. Note 3: The human body model is a 100 pF capacitor discharged through a 1.5 kΩ resistor into each pin. The machine model is a 200 pF capacitor discharged directly into each pin. Note 4: The VOUT pin is forced to 200 mV above the typical VOUT. This is to insure that the internal switches are off. Note 5: The output capacitor COUT is fully discharged before measurement. Typical Performance Characteristics Unless otherwise specified TA = 25˚C. VOUT vs. VIN VOUT vs. VIN DS101037-4 VOUT vs. VIN DS101037-5 VOUT vs. VIN DS101037-6 www.national.com DS101037-7 4 Typical Performance Characteristics Unless otherwise specified TA = 25˚C. (Continued) VOUT vs. VIN VOUT vs. VIN DS101037-8 VOUT vs. VIN DS101037-9 VOUT vs. VIN DS101037-10 VOUT vs. VIN DS101037-11 Load Transient Response DS101037-12 DS101037-14 5 www.national.com Typical Performance Characteristics Unless otherwise specified TA = 25˚C. (Continued) Efficiency vs. VIN Efficiency vs. VIN DS101037-20 Efficiency vs. VIN DS101037-21 Switching Frequency vs. VIN DS101037-23 DS101037-22 Operating Quiescent Current vs. VIN VOUT Ripple vs. COUT DS101037-30 DS101037-24 www.national.com 6 Typical Performance Characteristics Unless otherwise specified TA = 25˚C. (Continued) VOUT Ripple vs. COUT VOUT Ripple vs. COUT DS101037-31 DS101037-32 Applications Information DS101037-3 FIGURE 1. Block Diagram gains based on inputs from the A/D and the comparator. The gain signal is sent to the phase generator which then sends the appropriate timing and configuration signals to the switch array. This dual loop provides regulation over a wide range of loads efficiently. Since efficiency is automatically optimized, the curves for VOUT vs. VIN and Efficiency vs. VIN in the Typical Performance Characteristics section exhibit small variations. The reason is that as input voltage or output load changes, the digital control loops are making decisions on how to optimize efficiency. As the switch array is reconfigured, small variations in output voltage and efficiency result. In all cases where these small variations are observed, the part is operating correctly; minimizing output voltage changes and optimizing efficiency. Operating Principle The LM3352 is designed to provide a step-up/step-down voltage regulation in battery powered systems. It combines switched capacitor circuitry, reference, comparator, and shutdown logic in a single 16-pin TSSOP package. The LM3352 can provide a regulated voltage between 1.8V and 4V from an input voltage between 2.5V and 5.5V. It can supply a load current up to 200 mA. As shown in Figure 1, the LM3352 employs two feedback loops to provide regulation in the most efficient manner possible. The first loop is from VOUT through the comparator COMP, the AND gate G1, the phase generator, and the switch array. The comparator’s output is high when VOUT is less than the reference VREF. Regulation is provided by gating the clock to the switch array. In this manner, charge is transferred to the output only when needed. The second loop controls the gain configuration of the switch array. This loop consists of the comparator, the digital control block, the phase generator, and the switch array. The digital control block computes the most efficient gain from a set of seven Charge Pump Capacitor Selection A 0.33 µF ceramic capacitor is suggested for C1, C2 and C3. To ensure proper operation over temperature variations, an X7R dielectric material is recommended. 7 www.national.com choice for low ripple, high frequency applications. However, the temperature stability of the ceramics is bad, except for the X7R and X5R dielectric types. High capacitance values ( > 1 µF) are achievable from companies such as Taiyo-yuden which are suitable for use with regulators. Ceramics are taller and larger than the tantalums of the same capacitance value. Filter Capacitor Selection a) CAPACITOR TECHNOLOGIES The three major technologies of capacitors that can be used as filter capacitors for LM3352 are: i) tantalum, ii) ceramic and iii) polymer electrolytic technologies. i) Tantalum iii) Polymer Electrolytic Polymer electrolytic is a third suitable technology. Polymer capacitors provide some of the best features of both the ceramic and the tantalum technologies. They provide very low ESR values while still achieving high capacitance values. However, their ESR is still higher than the ceramics, and their capacitance value is lower than the tantalums of the same size. Polymers offer good frequency stability (comparable to ceramics) and good temperature stability (comparable to tantalums). The Aluminum Polymer Electrolytics offered by Cornell-Dubilier and Panasonic, and the POSCAPs offered by Sanyo fall under this category. Tantalum capacitors are widely used in switching regulators. Tantalum capacitors have the highest CV rating of any technology; as a result, high values of capacitance can be obtained in relatively small package sizes. It is also possible to obtain high value tantalum capacitors in very low profile ( < 1.2 mm) packages. This makes the tantalums attractive for low-profile, small size applications. Tantalums also possess very good temperature stability; i.e., the change in the capacitance value, and impedance over temperature is relatively small. However, the tantalum capacitors have relatively high ESR values which can lead to higher voltage ripple and their frequency stability (variation over frequency) is not very good, especially at high frequencies ( > 1 MHz). Table 1 compares the features of the three capacitor technologies. ii) Ceramic Ceramic capacitors have the lowest ESR of the three technologies and their frequency stability is exceptionally good. These characteristics make the ceramics an attractive TABLE 1. Comparison of Capacitor Technologies Ceramic Tantalum Polymer Electrolytic ESR Lowest High Low Relative Height Low for Small Values ( < 10 µF); Taller for Higher Values Lowest Low Relative Footprint Large Small Largest Temperature Stability X7R/X5R-Acceptable Good Good Frequency Stability Good Acceptable Good VOUT Ripple Magnitude @ < 50 mA Low High Low VOUT Ripple Magnitude @ > 100 mA Low Slightly Higher Low dv/dt of VOUT Ripple @ All Loads Lowest High Low ii) Input Capacitor (CIN) The input capacitor CIN directly affects the magnitude of the input ripple voltage, and to a lesser degree the VOUT ripple. A higher value CIN will give a lower VIN ripple. To optimize low input and output ripple as well as size a 15 µF polymer electrolytic, 22 µF ceramic, or 33 µF tantalum capacitor is recommended. This will ensure low input ripple at 200 mA load current. If lower currents will be used or higher input ripple can be tolerated then a smaller capacitor may be used to reduce the overall size of the circuit. The lower ESR ceramics and polymer electrolytics achieve a lower VIN ripple than the higher ESR tantalums of the same value. Tantalums make a good choice for small size, very low profile applications. The ceramics and polymer electrolytics are a good choice for low ripple, low noise applications where size is less of a concern. The 15 µF polymer electrolytics are physically much larger than the 33 µF tantalums and 22 µF ceramics. b) CAPACITOR SELECTION i) Output Capacitor (COUT) The output capacitor COUT directly affects the magnitude of the output ripple voltage so COUT should be carefully selected. The graphs titled VOUT Ripple vs. COUT in the Typical Performance Characteristics section show how the ripple voltage magnitude is affected by the COUT value and the capacitor technology. These graphs are taken at the gain at which worst case ripple is observed. In general, the higher the value of COUT, the lower the output ripple magnitude. At lighter loads, the low ESR ceramics offer a much lower VOUT ripple than the higher ESR tantalums of the same value. At higher loads, the ceramics offer a slightly lower VOUT ripple magnitude than the tantalums of the same value. However, the dv/dt of the VOUT ripple with the ceramics and polymer electrolytics is much lower than the tantalums under all load conditions. The tantalums are suggested for very low profile, small size applications. The ceramics and polymer electrolytics are a good choice for low ripple, low noise applications where size is less of a concern. www.national.com 8 Filter Capacitor Selection Of the different capacitor technologies, a sample of vendors that have been verified as suitable for use with the LM3352 are shown in Table 2. (Continued) iii) CFIL A 1 µF, XR7 ceramic capacitor should be connected to pin CFIL. This capacitor provides the filtering needed for the internal supply rail of the LM3352. TABLE 2. Capacitor Vendor Information Manufacturer Ceramic Tantalum Polymer Electrolytic Taiyo-yuden Tel Fax (408) 573-4150 (408) 573-4159 Website www.t-yuden.com AVX (803) 448-9411 (803) 448-1943 www.avxcorp.com Sprague/Vishay (207) 324-4140 (207) 324-7223 www.vishay.com Nichicon (847) 843-7500 (847) 843-2798 www.nichicon.com Cornell-Dubilier (ESRD) (508) 996-8561 (508) 996-3830 www.cornell-dubilier.com Sanyo (POSCAP) (619) 661-6322 (619) 661-1055 www.sanyovideo.com circuit, such as the LP3470, is recommended if greater start up loads are expected. Under certain conditions the LM3352 can start up with greater load currents without the use of a Power On Reset Circuit (See application note AN-1144: Maximizing Startup Loads with the LM3352 Regulated Buck/Boost Switched Capacitor Converter). Maximum Available Output Current The LM3352 cannot provide 200 mA under all VIN and VOUT conditions. The VOUT vs VIN graphs in the Typical Performance Characteristics section show the minimum VIN at which the LM3352 is capable of providing different load currents while maintaining VOUT regulation. Refer to the Electrical Characteristics for guaranteed conditions. Thermal Protection During output short circuit conditions, the LM3352 will draw high currents causing a rise in the junction temperature. On-chip thermal protection circuitry disables the charge pump action once the junction temperature exceeds the thermal trip point, and re-enables the charge pump when the junction temperature falls back to a safe operating point. Maximum Load Under Start-Up Due to the LM3352’s unique start-up sequence, it is not able to start up under all load conditions. Starting with 45 mA or less will allow the part to start correctly under any temperature or input voltage conditions. After the output is in regulation, any load up to the maximum as specified in the Electrical Characteristics may be applied. Using a Power On Reset Typical Application Circuits DS101037-33 FIGURE 2. Basic Buck/Boost Regulator 9 www.national.com Typical Application Circuits (Continued) DS101037-15 FIGURE 3. Low Output Noise and Ripple Buck/Boost Regulator between the capacitors and the IC short and direct. Use of a ground plane is recommended. Figure 4 shows a typical layout as used in the LM3352 evaluation board. Layout Considerations Due to the 1 MHz typical switching frequency of the LM3352, careful board layout is a must. It is important to place the capacitors as close to the IC as possible and to keep the traces DS101037-16 FIGURE 4. Typical Layout, Top View (magnification 2.8X) www.national.com 10 inches (millimeters) unless otherwise noted TSSOP-16 Pin Package For Ordering, Refer to Ordering Information Table NS Package Number MTC16 LIFE SUPPORT POLICY NATIONAL’S PRODUCTS ARE NOT AUTHORIZED FOR USE AS CRITICAL COMPONENTS IN LIFE SUPPORT DEVICES OR SYSTEMS WITHOUT THE EXPRESS WRITTEN APPROVAL OF THE PRESIDENT AND GENERAL COUNSEL OF NATIONAL SEMICONDUCTOR CORPORATION. As used herein: 1. Life support devices or systems are devices or systems which, (a) are intended for surgical implant into the body, or (b) support or sustain life, and whose failure to perform when properly used in accordance with instructions for use provided in the labeling, can be reasonably expected to result in a significant injury to the user. National Semiconductor Corporation Americas Tel: 1-800-272-9959 Fax: 1-800-737-7018 Email: [email protected] www.national.com National Semiconductor Europe Fax: +49 (0) 1 80-530 85 86 Email: [email protected] Deutsch Tel: +49 (0) 1 80-530 85 85 English Tel: +49 (0) 1 80-532 78 32 Français Tel: +49 (0) 1 80-532 93 58 Italiano Tel: +49 (0) 1 80-534 16 80 2. A critical component is any component of a life support device or system whose failure to perform can be reasonably expected to cause the failure of the life support device or system, or to affect its safety or effectiveness. National Semiconductor Asia Pacific Customer Response Group Tel: 65-2544466 Fax: 65-2504466 Email: [email protected] National Semiconductor Japan Ltd. Tel: 81-3-5639-7560 Fax: 81-3-5639-7507 National does not assume any responsibility for use of any circuitry described, no circuit patent licenses are implied and National reserves the right at any time without notice to change said circuitry and specifications. LM3352 Regulated 200 mA Buck-Boost Switched Capacitor DC/DC Converter Physical Dimensions