LM2757 Switched Capacitor Boost Regulator with High Impedance Output in Shutdown General Description Features The LM2757 is a constant frequency pre-regulated switchedcapacitor charge pump that operates at 1.25 MHz to produce a low-noise regulated output voltage. The device can be configured to provide up to 100 mA at 4.1V, 110 mA at 4.5V, or 180 mA at 5V. Excellent efficiency is achieved without the use of an inductor by operating the charge pump in a gain of either 3/2 or 2 according to the input voltage and output voltage option selection. The LM2757 presents a high impedance at the VOUT pin when shut down. This allows for use in applications that require the regulated output bus to be driven by another supply while the LM2757 is shut down. A perfect fit for space-constrained, battery-operated applications, the LM2757 requires only 4 small, inexpensive ceramic capacitors. LM2757 is a tiny 1.2 mm X 1.6 mm 12–bump micro SMD device. Built in soft-start, over-current protection, and thermal shutdown features are also included in this device. ■ Inductorless solution uses only 4 small ceramic ■ ■ ■ ■ ■ ■ ■ ■ ■ capacitors. True input-output and output-input disconnect. Up to 180 mA output current capability (5V). Selectable 4.1V, 4.5V or 5.0V output. Pre-regulation minimizes input current ripple. 1.24 MHz switching frequency for a low-noise, low-ripple output voltage. Efficient dual gain converter (2X, 3/2X). Integrated Over Current Protection. Integrated Thermal Shutdown Protection. Tiny 1.2 mm X 1.6 mm X 0.4 mm pitch, 12–bump micro SMD package. Applications ■ ■ ■ ■ ■ ■ ■ Keypad LED Drive USB/USB-OTG Power Cellular Phone SIM cards Audio amplifier power supplies Low-current Camera Flash General Purpose Li-Ion-to-5V Conversion Supercapacitor Charger Typical Application Circuit 30033723 30033701 © 2007 National Semiconductor Corporation 300337 www.national.com LM2757 Switched Capacitor Boost Regulator with High Impedance Output in Shutdown October 2007 LM2757 Connection Diagram and Package Mark Information 12–Bump Micro SMD Package, 0.4mm Pitch National Semiconductor Package Number TMD12 30033702 Note 1: The actual physical placement of the package marking will vary from part to part. The package marking "X" designates the single digit date code. "V" is a NSC internal code for die traceability. Both will vary considerably. "DL" identifies the device (part number, option, etc.). Pin Descriptions Pin # Name Description A1 C2+ Flying Capacitor C2 Connection A2 VOUT Regulated Output Voltage A3 C1+ Flying Capacitor C1 Connection B1 C1− Flying Capacitor C1 Connection B2 VIN Input Voltage Connection Input Voltage Connection B3 VIN C1 GND Ground Connection C2 GND Ground Connection C3 C2− Flying Capacitor C2 Connection D1 NC No Connect — Do not connect this pin to any node, voltage or GND. Must be left floating. D2 M1 Mode select pin 1 D3 M0 Mode select pin 0 Mode Selection Definition M0 M1 OUTPUT VOLTAGE MODE 0 0 Device Shutdown, Output High Impedance 0 1 5.0V 1 0 4.5V 1 1 4.1V Order Information Order Number LM2757TM LM2757TMX www.national.com Package Mark ID Package XV (A1 Bump Marking) DL 12–Bump µSMD 0.4mm pitch 2 Supplied as: 1000 Units, Tape & Reel 4000 Units, Tape & Reel Operating Ratings If Military/Aerospace specified devices are required, please contact the National Semiconductor Sales Office/ Distributors for availability and specifications. (Notes 2, 3) VIN Pin: Voltage to GND M0, M1 pins: Voltage to GND Continuous Power Dissipation (Note 4) Junction Temperature (TJ-MAX) Storage Temperature Range Maximum Lead Temperature (Soldering, 10 sec.) ESD Rating (Note 5) Human Body Model: Input Voltage Range Junction Temperature (TJ) Range Ambient Temperature (TA) Range (Note 6) -0.3V to 6.0V -0.3V to 6.0V Internally Limited 2.7V to 5.5V -30°C to +110°C -30°C to +85°C Thermal Properties 150ºC -65ºC to +150º C 265ºC Electrical Characteristics LM2757 Absolute Maximum Ratings (Notes 2, 3) Junction-to-Ambient Thermal Resistance (θJA), micro SMD Package (Note 7) 75°C/W 2.5 kV (Notes 3, 8) Limits in standard typeface are for TA = 25ºC. Limits in boldface type apply over the full operating ambient temperature range (-30°C ≤ TA ≤ +85°C) . Unless otherwise noted, specifications apply to the Typical Application Circuit (pg. 1) with: VIN = 3.6V, V (M0) = 0V, V(M1) = VIN,CIN = C2 = 0.47 µF, CIN= COUT = 1.0 µF (Note 9). Symbol Parameter Condition Min Typ Max 4.870 (−2.6%) 5.0 5.130 (+2.6%) 4.865 (−2.7%) 5.0 5.130 (+2.6%) 3.0V ≤ VIN ≤ 5.5V IOUT = 0 to 110 mA V(M0) = VIN, V(M1) = 0V 4.406 (–2.1%) 4.5 4.613 (+2.5%) 3.0V ≤ VIN ≤ 5.5V IOUT = 0 to 100 mA V(M0) = VIN, V(M1) = VIN 3.985 (–2.8%) 4.1 4.223 (+3.0%) V(M0) = 0V, V(M1) = VIN (5.0V) IOUT = 0 mA VIN = 3.6V 2.4 2.79 V(M0) = VIN, V(M1) = 0V (4.5V) IOUT = 0 mA VIN = 3.6V 1.5 1.80 V(M0) = VIN, V(M1) = VIN (4.1V) IOUT = 0 mA VIN = 3.6V 1.3 1.65 V(M0) = 0V, V(M1) = 0V VIN = 3.6V 1.1 2.0 Units 3.2V ≤ VIN ≤ 5.5V –30°C ≤ TA ≤ +60°C IOUT = 0 to 180 mA V(M0) = 0V, V(M1) = VIN 3.0V ≤ VIN ≤ 5.5V VOUT IQ Output Voltage Quiescent Supply Current ISD Shutdown Supply Current VR Output Voltage Ripple fSW Switching Frequency VIN Logic Input High –30°C ≤ TA ≤ +85°C IOUT = 0 to 150 mA V(M0) = 0V, V(M1) = VIN IOUT = 150 mA V(M0) = 0V, V(M1) = VIN (5.0V) 20 V mA µA mVp–p 3.0V ≤ VIN ≤ 5.5V 3.0V ≤ VIN ≤ 5.5V Input pins: M1, M0 3.0V ≤ VIN ≤ 5.5V 3 0.932 (-25%) 1.0 1.242 1.552 (+25%) MHz VIN V www.national.com LM2757 Symbol Parameter VIL Logic Input Low RPULLDOWN Condition Input pins: M1, M0 Min 3.0V ≤ VIN ≤ 5.5V 0 Logic Input Pulldown Resistance (M0, M1) V(M1, M0) = 5.5V 324 IIH Logic Input High Current IIL Logic Input Low Current VG Gain Transition Voltage ISC Short Circuit Output Current ION VOUT Turn-On Time from Shutdown (Note 10) Typ Max Units 0.40 V 457 kΩ Input Pins: M1, M0 V(M1, M0) = 1.8V(Note 11) 5 µA Input Pins: M1, M0 V(M1, M0) = 0V 10 µA 1.5X to 2X, V(M0) = VIN, V(M1)=0V 3.333 V 2X to 1.5X, V(M0) = VIN, V(M1)=0V 3.413 V Hysteresis, V(M0) = VIN, V(M1)=0V 80 mV 1.5X to 2X, V(M0) = 0V, V(M1)=VIN 3.87 V 2X to 1.5X, V(M0) = 0V, V(M1)=VIN 3.93 V Hysteresis, V(M0) = 0V, V(M1)=VIN 60 mV VOUT = 0V 250 mA 300 µs Note 2: Absolute Maximum Ratings indicate limits beyond which damage to the component may occur. Operating Ratings are conditions under which operation of the device is guaranteed. Operating Ratings do not imply guaranteed performance limits. For guaranteed performance limits and associated test conditions, see the Electrical Characteristics tables. Note 3: All voltages are with respect to the potential at the GND pins. Note 4: Internal thermal shutdown circuitry protects the device from permanent damage. Thermal shutdown engages at TJ=145°C (typ.) and disengages at TJ=135°C (typ.). Note 5: The Human body model is a 100 pF capacitor discharged through a 1.5 kΩ resistor into each pin. Note 6: In applications where high power dissipation and/or poor package thermal resistance is present, the maximum ambient temperature may have to be derated. Maximum ambient temperature (TA-MAX) is dependent on the maximum operating junction temperature (TJMAX-OP=125°C), the maximum power dissipation of the device in the application (PD-MAX), and the junction-to-ambient thermal resistance of the part/package in the application (θJA), as given by the following equation: TA-MAX = TJ-MAX-OP – (θJA × PD-MAX). Note 7: Junction-to-ambient thermal resistance (θJA) is taken from a thermal modeling result, performed under the conditions and guidelines set forth in the JEDEC standard JESD51-7. The test board is a 4–layer FR-4 board measuring 102 mm x 76 mm x 1.6 mm with a 2x1 array of thermal vias. The ground plane on the board is 50 mm x 50 mm. Thickness of copper layers are 36 µm/18 µm/18 µm/36 µm (1.5 oz./1 oz./1 oz./1.5 oz.). Ambient temperature in simulation is 22° C, still air. Power dissipation is 1W. The value of θJA in LM2757 in micro SMD-12 could fall in a range as wide as 50°C/W to 150°C/W (if not wider), depending on PWB material, layout and environmental conditions. In applications where high maximum power dissipation exists (high VIN, high IOUT), special care must be paid to thermal dissipation issues. For more information on these topics, please refer to Application Note 1112: Micro SMD Wafer Level Chip Scale Package (µSMD). Note 8: Min and Max limits are guaranteed by design, test, or statistical analysis. Typical numbers are not guaranteed, but do represent the most likely norm. Note 9: CIN, COUT, C1, C2: Low-ESR Surface-Mount Ceramic Capacitors (MLCCs) used in setting electrical characteristics. Note 10: Turn-on time is measured from when the M0 or M1 signal is pulled high until the output voltage crosses 90% of its final value. Note 11: There is a 450 kΩ (typ.) pull-down resistor connected internally to each logic input. www.national.com 4 LM2757 Block Diagram 30033703 5 www.national.com LM2757 Typical Performance Characteristics Unless otherwise specified: VIN = 3.6V, V(M0) = 0V, V(M1) = VIN, C1 = C2 = 0.47µF, CIN = COUT = 1.0µF, TA = 25ºC. Capacitors are low-ESR multi-layer ceramic capacitors (MLCC's). Efficiency vs. Input Voltage, 5V Mode Efficiency vs. Input Voltage, 4.5V Mode 30033704 30033705 Efficiency vs. Input Voltage, 4.1V Mode Output Voltage vs. Output Current, 5V Mode 30033706 30033707 Output Voltage vs. Output Current, 4.5V Mode Output Voltage vs. Output Current, 4.1V Mode 30033708 www.national.com 30033709 6 Output Voltage vs. Input Voltage, 5V Mode 30033710 30033711 Output Voltage vs. Input Voltage, 4.5V Mode Output Voltage vs. Input Voltage, 4.1V Mode 30033712 30033713 Output Leakage Current, Device Shutdown Current Limit vs. Input Voltage 30033714 30033715 7 www.national.com LM2757 Output Voltage Ripple vs. Output Current, 5V Mode LM2757 Oscillator Frequency vs. Input Voltage Operating Current vs. Input Voltage 30033716 30033717 Shutdown Supply Current vs. Input Voltage Startup Behavior, 5V Mode 30033719 VIN = 3.6V, Load = 200mA CH2: VOUT; Scale: 1V/Div, DC Coupled CH4: IIN; Scale: 200mA/Div, DC Coupled Time scale: 100µs/Div 30033718 Line Step (3.5V to 4V) Load Step with a Li-Ion Battery, 10mA to 200mA 30033721 30033720 VBATT = 4V, VOUT = 5V Mode CH1: VOUT; Scale: 50mV/Div, AC Coupled CH4: IOUT; Scale: 100mA/Div, DC Coupled Time scale: 10µs/Div Load = 200mA, VOUT = 5V Mode CH1: VIN; Scale: 1V/Div, DC Coupled CH2: VOUT; Scale: 100mV/Div, AC Coupled Time scale: 100µs/Div www.national.com 8 LM2757 Load Step with a Li-Ion Battery 200mA to 10mA 30033722 VBATT = 4V, VOUT = 5V Mode CH1: VOUT; Scale: 50mV/Div, AC Coupled CH4: IOUT; Scale: 100mA/Div, DC Coupled Time scale: 10µs/Div 9 www.national.com LM2757 mode select pins. The voltage mode is selected according to the following table. Operation Description OVERVIEW The LM2757 is a switched capacitor converter that produces a regulated output voltage of either 5V, 4.5V or 4.1V depending on the mode selected. The core of the part is a highly efficient charge pump that utilizes fixed frequency pre-regulation to minimize ripple and power losses over wide input voltage and output current ranges. A description of the principal operational characteristics of the LM2757 is detailed in the Circuit Description, and Efficiency Performance sections. These sections refer to details in the Block Diagram. M1 Output Voltage Mode 0 0 Device Shutdown, Output High Impedance 0 1 5V 1 0 4.5V 1 1 4.1V SHUTDOWN WITH OUTPUT HIGH IMPEDANCE The LM2757 is in shutdown mode when there is a logic Low voltage on both mode select pins (M0, M1). When in shutdown, the output of the LM2757 is high impedance, allowing an external supply to drive the output line such as in USB OTG applications. Refer to the output leakage current graph in the Typical Performance Characteristics section for typical leakage currents into the VOUT pin, when driven by a separate supply during shutdown. Output leakage increases with temperature, with the lowest leakage occurring at -30°C and the highest leakage at 85°C (on which the graph is based). CIRCUIT DESCRIPTION The core of the LM2757 is a two-phase charge pump controlled by an internally generated non-overlapping clock. The charge pump operates by using external flying capacitors C1, C2 to transfer charge from the input to the output. At input voltages below 3.9V (typ.) for the 5V mode, the LM2757 operates in a 2x gain, with the input current being equal to 2x the load current. At input voltages above 3.9V (typ.) for the 5V mode, the part utilizes a gain of 3/2x, resulting in an input current equal to 3/2 times the load current. For the 4.5V mode, the LM2757 operates in a 2x gain when the input voltage is below 3.35V (typ.) and transitions to a 3/2x gain when the input voltage is above 3.35V (typ.). For the 4.1V mode, the device utilizes the 3/2x gain for the entire input voltage range. The two phases of the switched capacitor switching cycle will be referred to as the "phase one" and the "phase two". During phase one, one flying capacitor is charged by the input supply while the other flying capacitor is connected to the output and delivers charge to the load . After half of the switching cycle [ t = 1/(2×FSW) ], the LM2757 switches to phase two. In this configuration, the capacitor that supplied charge to the load in phase one is connected to the input to be recharged while the capacitor that had been charged in the previous phase is connected to the output to deliver charge. With this topology, output ripple is reduced by delivering charge to the output in every phase. The LM2757 uses fixed frequency pre-regulation to regulate the output voltage. The input and output connections of the flying capacitors are made with internal MOS switches. Preregulation limits the gate drive of the MOS switch connected between the voltage input and the flying capacitors. Controlling the on resistance of this switch limits the amount of charge transferred into and out of each flying capacitor during the charge and discharge phases, and in turn helps to keep the output ripple very low. SOFT START The LM2757 employs soft start circuitry to prevent excessive input inrush currents during startup. At startup, the output voltage gradually rises from 0V to the nominal output voltage. This occurs in 300µs (typ.). Soft-start is engaged when the part is enabled. THERMAL SHUTDOWN Protection from damage related to overheating is achieved with a thermal shutdown feature. When the junction temperature rises to 145ºC (typ.), the part switches into shutdown mode. The LM2757 disengages thermal shutdown when the junction temperature of the part is reduced to 135ºC (typ.). Due to the high efficiency of the LM2757, thermal shutdown and/or thermal cycling should not be encountered when the part is operated within specified input voltage, output current, and ambient temperature operating ratings. If thermal cycling is seen under these conditions, the most likely cause is an inadequate PCB layout that does not allow heat to be sufficiently dissipated out of the device. CURRENT LIMIT PROTECTION The LM2757 charge pump contains current limit protection circuitry that protects the device during VOUT fault conditions where excessive current is drawn. Output current is limited to 250mA (typ). Application Information EFFICIENCY PERFORMANCE Charge-pump efficiency is derived in the following two ideal equations (supply current and other losses are neglected for simplicity): RECOMMENDED CAPACITOR TYPES The LM2757 requires 4 external capacitors for proper operation. Surface-mount multi-layer ceramic capacitors are recommended. These capacitors are small, inexpensive and have very low equivalent series resistance (ESR, ≤ 15mΩ typ.). Tantalum capacitors, OS-CON capacitors, and aluminum electrolytic capacitors generally are not recommended for use with the LM2757 due to their high ESR, as compared to ceramic capacitors. For most applications, ceramic capacitors with an X7R or X5R temperature characteristic are preferred for use with the LM2757. These capacitors have tight capacitance tolerance (as good as ±10%) and hold their value over temperature (X7R: ±15% over -55ºC to 125ºC; X5R: ±15% over -55ºC to 85ºC). IIN = G × IOUT E = (VOUT × IOUT) ÷ (VIN × IIN) = VOUT ÷ (G × VIN) In the equations, G represents the charge pump gain. Efficiency is at its highest as G×VIN approaches VOUT. Refer to the efficiency graph in the Typical Performance Characteristics section for detailed efficiency data. The transition between gains of 3/2, and 2 are clearly distinguished by the sharp discontinuity in the efficiency curve. ENABLE AND VOLTAGE MODE SELECTION The LM2757 is enabled when either one of the mode select pins (M0, M1) has a logic High voltage applied to it. There are 450kΩ pulldown resistors connected internally to each of the www.national.com M0 10 Manufacturer INPUT CAPACITOR AND INPUT VOLTAGE RIPPLE The input capacitor (CIN) is a reservoir of charge that aids a quick transfer of charge from the supply to the flying capacitors during the charge phase of operation. The input capacitor helps to keep the input voltage from drooping at the start of the charge phase when the flying capacitors are connected to the input. It also filters noise on the input pin, keeping this noise out of sensitive internal analog circuitry that is biased off the input line. Much like the relationship between the output capacitance and output voltage ripple, input capacitance has a dominant and first-order effect on input ripple magnitude. Increasing (decreasing) the input capacitance will result in a proportional decrease (increase) in input voltage ripple. Input voltage, output current, and flying capacitance also will affect input ripple levels to some degree. In typical high-current applications, a 1.0µF low-ESR ceramic capacitor is recommended on the input. Different input capacitance values can be used to reduce ripple, shrink the solution size, and/or cut the cost of the solution. But changing the input capacitor may also require changing the flying capacitor and/or output capacitor to maintain good overall circuit performance. Performance of the LM2757 with different capacitor setups is discussed below in Recommended Capacitor Configurations. Contact Information AVX www.avx.com Murata www.murata.com Taiyo-Yuden www.t-yuden.com TDK www.component.tdk.com Vishay-Vitramon www.vishay.com FLYING CAPACITORS The flying capacitors (C1, C2) transfer charge from the input to the output. Flying capacitance can impact both output current capability and ripple magnitudes. If flying capacitance is too small, the LM2757 may not be able to regulate the output voltage when load currents are high. On the other hand, if the flying capacitance is too large, the flying capacitor might overwhelm the input and output capacitors, resulting in increased input and output ripple. In typical high-current applications, 0.47µF low-ESR ceramic capacitors are recommended for the flying capacitors. Polarized capacitors (tantalum, aluminum electrolytic, etc.) must not be used for the flying capacitor, as they could become reverse-biased during LM2757 operation. OUTPUT CAPACITOR AND OUTPUT VOLTAGE RIPPLE The output capacitor in the LM2757 circuit (COUT) directly impacts the magnitude of output voltage ripple. Other prominent factors also affecting output voltage ripple include input voltage, output current and flying capacitance. Due to the complexity of the regulation topology, providing equations or models to approximate the magnitude of the ripple can not be easily accomplished. But one important generalization can be made: increasing (decreasing) the output capacitance will result in a proportional decrease (increase) in output voltage ripple. In typical high-current applications, a 1.0µF low-ESR ceramic output capacitor is recommended. Different output capacitance values can be used to reduce ripple, shrink the solution size, and/or cut the cost of the solution. But changing the output capacitor may also require changing the flying capacitor and/or input capacitor to maintain good overall circuit performance. Performance of the LM2757 with different capacitor setups in discussed in the section Recommended Capacitor Configurations. RECOMMENDED CAPACITANCE The data in Table 1 can be used to assist in the selection of capacitance for each node that best balances solution size and cost with the electrical requirements of the application. As previously discussed, input and output ripple voltages will vary with output current and input voltage. The numbers provided show expected ripple voltage with VIN = 3.6V and a load current of 200mA at 5V output, 100mA at 4.5V output, and 100mA at 4.1V output. The table offers a first look at approximate ripple levels and provides a comparison of different capacitance configurations, but is not intended to be a guarantee of performance. With any capacitance configuration 11 www.national.com LM2757 High ESR in the output capacitor increases output voltage ripple. If a ceramic capacitor is used at the output, this is usually not a concern because the ESR of a ceramic capacitor is typically very low and has only a minimal impact on ripple magnitudes. If a different capacitor type with higher ESR is used (tantalum, for example), the ESR could result in high ripple. To eliminate this effect, the net output ESR can be significantly reduced by placing a low-ESR ceramic capacitor in parallel with the primary output capacitor. The low ESR of the ceramic capacitor will be in parallel with the higher ESR, resulting in a low net ESR based on the principles of parallel resistance reduction. Capacitors with a Y5V or Z5U temperature characteristic are generally not recommended for use with the LM2757. These types of capacitors typically have wide capacitance tolerance (+80%, -20%) and vary significantly over temperature (Y5V: +22%, -82% over -30ºC to +85ºC range; Z5U: +22%, -56% over +10ºC to +85ºC range). Under some conditions, a 1µFrated Y5V or Z5U capacitor could have a capacitance as low as 0.1µF. Such detrimental deviation is likely to cause Y5V and Z5U capacitors to fail to meet the minimum capacitance requirements of the LM2757. Net capacitance of a ceramic capacitor decreases with increased DC bias. This degradation can result in lower capacitance than expected on the input and/or output, resulting in higher ripple voltages and currents. Using capacitors at DC bias voltages significantly below the capacitor voltage rating will usually minimize DC bias effects. Consult capacitor manufacturers for information on capacitor DC bias characteristics. Capacitance characteristics can vary quite dramatically with different application conditions, capacitor types, and capacitor manufacturers. It is strongly recommended that the LM2757 circuit be thoroughly evaluated early in the design-in process with the mass-production capacitors of choice. This will help ensure that any such variability in capacitance does not negatively impact circuit performance. The voltage rating of the output capacitor should be 10V or more. For example, a 10V 0603 1.0µF is acceptable for use with the LM2757, as long as the capacitance does not fall below a minimum of 0.5µF in the intended application. All other capacitors should have a voltage rating at or above the maximum input voltage of the application. The capacitors should be selected such that the capacitance on the input does not fall below 0.7µF, and the capacitance of the flying capacitors does not fall below 0.2µF. The table below lists some leading ceramic capacitor manufacturers. LM2757 Note 12: Refer to the text in the Recommended Capacitor Configurations section for detailed information on the data in this table chosen, always verify that the performance of the ripple waveforms are suitable for the intended application. The same capacitance value must be used for all the flying capacitors. Layout Guidelines TABLE 1. LM2757 Performance with Different Capacitor Configurations (Note 12) Capacitor Configuration (VIN = 3.6V) Typical 5.0V, 200mA Output Ripple Typical 4.5V, 100mA Output Ripple Typical 4.1V, 100mA Output Ripple CIN = 1µF, COUT = 1µF, C1, C2 = 0.47µF 32mV 12mV 11mV CIN = 0.68µF, COUT = 1µF, C1, C2 = 0.47µF 32mV 11mV 11mV CIN = 0.68µF, COUT = 0.47µF, C1, C2 = 0.47µF 51mV 15mV 15mV CIN = 0.68µF, COUT = 0.47µF, C1, C2 = 0.22µF 53mV 18mV 18mV www.national.com Proper board layout will help to ensure optimal performance of the LM2757 circuit. The following guidelines are recommended: • Place capacitors as close to the LM2757 as possible, and preferably on the same side of the board as the IC. • Use short, wide traces to connect the external capacitors to the LM2757 to minimize trace resistance and inductance. • Use a low resistance connection between ground and the GND pin of the LM2757. Using wide traces and/or multiple vias to connect GND to a ground plane on the board is most advantageous. 12 LM2757 Physical Dimensions inches (millimeters) unless otherwise noted NSC Package TMD12AAA Micro SMD Wafer Level Package X1: 1215 µm +/- 30 µm X2: 1615 µm +/- 30 µm X3: 600 µm +/- 75 µm Bump pitch: 0.4 mm 13 www.national.com LM2757 Switched Capacitor Boost Regulator with High Impedance Output in Shutdown Notes THE CONTENTS OF THIS DOCUMENT ARE PROVIDED IN CONNECTION WITH NATIONAL SEMICONDUCTOR CORPORATION (“NATIONAL”) PRODUCTS. NATIONAL MAKES NO REPRESENTATIONS OR WARRANTIES WITH RESPECT TO THE ACCURACY OR COMPLETENESS OF THE CONTENTS OF THIS PUBLICATION AND RESERVES THE RIGHT TO MAKE CHANGES TO SPECIFICATIONS AND PRODUCT DESCRIPTIONS AT ANY TIME WITHOUT NOTICE. NO LICENSE, WHETHER EXPRESS, IMPLIED, ARISING BY ESTOPPEL OR OTHERWISE, TO ANY INTELLECTUAL PROPERTY RIGHTS IS GRANTED BY THIS DOCUMENT. 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All other brand or product names may be trademarks or registered trademarks of their respective holders. Copyright© 2007 National Semiconductor Corporation For the most current product information visit us at www.national.com National Semiconductor Americas Customer Support Center Email: [email protected] Tel: 1-800-272-9959 www.national.com National Semiconductor Europe Customer Support Center Fax: +49 (0) 180-530-85-86 Email: [email protected] Deutsch Tel: +49 (0) 69 9508 6208 English Tel: +49 (0) 870 24 0 2171 Français Tel: +33 (0) 1 41 91 8790 National Semiconductor Asia Pacific Customer Support Center Email: [email protected] National Semiconductor Japan Customer Support Center Fax: 81-3-5639-7507 Email: [email protected] Tel: 81-3-5639-7560