Product Folder Sample & Buy Support & Community Tools & Software Technical Documents LM2621 SNVS033D – MAY 2004 – REVISED NOVEMBER 2015 LM2621 Low Input Voltage, Step-Up DC-DC Converter 1 Features 3 Description • The LM2621 is a high efficiency, step-up DC-DC switching regulator for battery-powered and low input voltage systems. It accepts an input voltage between 1.2 V and 14 V and converts it into a regulated output voltage. The output voltage can be adjusted between 1.24 V and 14 V. It has an internal 0.17-Ω N-Channel MOSFET power switch. Efficiencies up to 90% are achievable using the LM2621. 1 • • • • • • • • • Small VSSOP8 Package (Half the Footprint of Standard 8-Pin SOIC Package) 1.09-mm Package Height Up to 2-MHz Switching Frequency 1.2-V to 14-V Input Voltage 1.24-V to 14-V Adjustable Output Voltage Up to 1A Load Current 0.17-Ω Internal MOSFET Up to 90% Regulator Efficiency 80-µA Typical Operating Current < 2.5-µA Specified Supply Current In Shutdown 2 Applications • • • • • • • • • • PDAs, Cellular Phones 2-Cell and 3-Cell Battery-Operated Equipment PCMCIA Cards, Memory Cards Flash Memory Programming TFT/LCD Applications 3.3-V to 5.0-V Conversion GPS Devices Two-Way Pagers Palmtop Computers Hand-Held Instruments The high switching frequency (adjustable up to 2 MHz) of the LM2621 allows for tiny surface mount inductors and capacitors. Because of the unique constant-duty-cycle gated oscillator topology very high efficiencies are realized over a wide load range. The supply current is reduced to 80 µA because of the BiCMOS process technology. In the shutdown mode, the supply current is less than 2.5 µA. The LM2621 is available in a VSSOP-8 package. This package uses half the board area of a standard 8-pin SOIC and has a height of just 1.09 mm. Device Information(1) PART NUMBER LM2621 PACKAGE BODY SIZE (NOM) VSSOP (8) 3.00 mm x 3.00 mm (1) For all available packages, see the orderable addendum at the end of the datasheet. Typical Application Circuit 1 An IMPORTANT NOTICE at the end of this data sheet addresses availability, warranty, changes, use in safety-critical applications, intellectual property matters and other important disclaimers. PRODUCTION DATA. LM2621 SNVS033D – MAY 2004 – REVISED NOVEMBER 2015 www.ti.com Table of Contents 1 2 3 4 5 6 7 Features .................................................................. Applications ........................................................... Description ............................................................. Revision History..................................................... Pin Configuration and Functions ......................... Specifications......................................................... 1 1 1 2 3 3 6.1 6.2 6.3 6.4 6.5 3 4 4 4 5 Absolute Maximum Ratings ...................................... Recommended Operating Conditions....................... Thermal Information .................................................. Electrical Characteristics........................................... Typical Characteristics .............................................. Detailed Description .............................................. 8 7.1 7.2 7.3 7.4 Overview ................................................................... Functional Block Diagram ......................................... Feature Description................................................... Device Functional Modes.......................................... 8 8 8 9 8 Application and Implementation ........................ 10 8.1 Application Information............................................ 10 8.2 Typical Applications ................................................ 10 9 Power Supply Recommendations...................... 15 10 Layout................................................................... 15 10.1 Layout Guidelines ................................................. 15 10.2 Layout Example .................................................... 15 11 Device and Documentation Support ................. 16 11.1 11.2 11.3 11.4 11.5 11.6 Device Support...................................................... Documentation Support ........................................ Community Resources.......................................... Trademarks ........................................................... Electrostatic Discharge Caution ............................ Glossary ................................................................ 16 16 16 16 16 16 12 Mechanical, Packaging, and Orderable Information ........................................................... 16 4 Revision History Changes from Revision C (November 2012) to Revision D • 2 Page Added Pin Configuration and Functions section, Handling Rating table, Feature Description section, Device Functional Modes, Application and Implementation section, Power Supply Recommendations section, Layout section, Device and Documentation Support section, and Mechanical, Packaging, and Orderable Information section ................................................................................................................................................................................... 1 Submit Documentation Feedback Copyright © 2004–2015, Texas Instruments Incorporated Product Folder Links: LM2621 LM2621 www.ti.com SNVS033D – MAY 2004 – REVISED NOVEMBER 2015 5 Pin Configuration and Functions DGK Package 8-Pin VSSOP Top View PGND 1 8 SW EN 2 7 BOOT FREQ 3 6 VDD FB 4 5 SGND Pin Functions PIN NAME NO. TYPE (1) PGND 1 EN 2 I Active-Low Shutdown Input FREQ 3 A Frequency Adjust. An external resistor connected between this pin and Pin 6 (VDD) sets the switching frequency of the LM2621. FB 4 A Output Voltage Feedback SGND 5 GND Signal Ground VDD 6 PWR Power Supply for Internal Circuitry BOOT 7 PWR Bootstrap Supply for the Gate Drive of Internal MOSFET Power Switch SW 8 PWR Drain of the Internal MOSFET Power Switch (1) GND DESCRIPTION Power Ground I = Input, O = Output, PWR = Power, GND = Ground, A = Analog 6 Specifications 6.1 Absolute Maximum Ratings See (1) (2) MIN MAX UNIT SW Pin Voltage –0.5 14.5 V BOOT, VDD, EN and FB Pins –0.5 10 V 100 µA 500 mW 150 °C 260 °C 150 °C FREQ Pin Power Dissipation (TA=25°C) TJmax (3) (3) Lead Temp. (Soldering, 5 sec) Storage temperature, Tstg (1) (2) (3) –65 Stresses beyond those listed under Absolute Maximum Ratings may cause permanent damage to the device. These are stress ratings only, which do not imply functional operation of the device at these or any other conditions beyond those indicated under Recommended Operating Conditions. Exposure to absolute-maximum-rated conditions for extended periods may affect device reliability. If Military/Aerospace specified devices are required, please contact the Texas Instruments Sales Office/ Distributors for availability and specifications. The maximum power dissipation must be derated at elevated temperatures and is dictated by Tjmax (maximum junction temperature), θJA (junction to ambient thermal resistance), and TA (ambient temperature). The maximum allowable power dissipation at any temperature is Pdmax = (Tjmax - TA)/ θJA or the number given in the Absolute Maximum Ratings, whichever is lower. Submit Documentation Feedback Copyright © 2004–2015, Texas Instruments Incorporated Product Folder Links: LM2621 3 LM2621 SNVS033D – MAY 2004 – REVISED NOVEMBER 2015 www.ti.com 6.2 Recommended Operating Conditions over operating free-air temperature range (unless otherwise noted) MIN VDD NOM MAX UNIT 2.5 5 V FB 0 VDD V EN 0 VDD V BOOT 0 10 V –40 85 °C Ambient Temperature, TA 6.3 Thermal Information LM2621 THERMAL METRIC (1) DGK (VSSOP) UNIT 8 PINS (2) RθJA Junction-to-ambient thermal resistance 160 °C/W RθJC(top) Junction-to-case (top) thermal resistance 52.7 °C/W RθJB Junction-to-board thermal resistance 80.1 °C/W ψJT Junction-to-top characterization parameter 5.5 °C/W ψJB Junction-to-board characterization parameter 78.8 °C/W RθJC(bot) Junction-to-case (bottom) thermal resistance N/A °C/W (1) (2) For more information about traditional and new thermal metrics, see the Semiconductor and IC Package Thermal Metrics application report, SPRA953. The maximum power dissipation must be derated at elevated temperatures and is dictated by Tjmax (maximum junction temperature), θJA (junction to ambient thermal resistance), and TA (ambient temperature). The maximum allowable power dissipation at any temperature is Pdmax = (Tjmax - TA)/ θJA or the number given in the Absolute Maximum Ratings, whichever is lower. 6.4 Electrical Characteristics Unless otherwise specified: VDD= VOUT= 3.3 V, TJ = 25°C. PARAMETER VIN_ST TEST CONDITIONS Minimum Start-Up Supply Voltage (1) ILOAD = 0 mA VIN_OP Minimum Operating Supply Voltage (once started) ILOAD = 0 mA VFB FB Pin Voltage MIN TYP ILOAD = 0 mA, –40°C to 85°C 1.2 0.65 1.2028 1.2772 VOUT_MAX Maximum Output Voltage 14 VHYST Hysteresis Voltage (2) 30 –40°C to 85°C Efficiency 87% VIN = 2.5 V; VOUT = 3.3 V; ILOAD = 200 mA 87% D Switch Duty Cycle IDD Operating Quiescent Current (3) FB Pin > 1.3 V; EN Pin at VDD Shutdown Quiescent Current (4) VDD, BOOT and SW Pins at 5.0 V; EN Pin < 200 mV 60% (1) (2) (3) (4) 4 mV 80% 80 FB Pin > 1.3 V; EN Pin at VDD, –40°C to 85°C 110 Switch Peak Current Limit µA 0.01 µA VDD, BOOT and SW Pins at 5.0 V; EN Pin < 200 mV, –40°C to 85°C ICL V 70% −40°C to 85°C ISD V V 45 VIN = 3.6 V; VOUT = 5 V; ILOAD = 500 mA UNIT V 1.24 –40°C to 85°C η MAX 1.1 2.5 2.85 A Output in regulation, VOUT = VOUT (NOMINAL) ± 5% This is the hysteresis value of the internal comparator used for the gated-oscillator control scheme. This is the current into the VDD pin. This is the total current into pins VDD, BOOT, SW and FREQ. Submit Documentation Feedback Copyright © 2004–2015, Texas Instruments Incorporated Product Folder Links: LM2621 LM2621 www.ti.com SNVS033D – MAY 2004 – REVISED NOVEMBER 2015 Electrical Characteristics (continued) Unless otherwise specified: VDD= VOUT= 3.3 V, TJ = 25°C. PARAMETER RDS_ON TEST CONDITIONS MIN MOSFET Switch On Resistance TYP MAX UNIT Ω 0.17 ENABLE SECTION VEN_LO VEN_HI (5) EN Pin Voltage Low (5) –40°C to 85°C (5) –40°C to 85°C EN Pin Voltage High 0.15VDD 0.7VDD V V When the EN pin is below VEN_LO, the regulator is shut down; when it is above VEN_HI, the regulator is operating. 6.5 Typical Characteristics VOUT = 5.0 V VOUT = 3.3 V Figure 1. Efficiency vs Load Current Figure 2. Efficiency vs Load Current Figure 3. VFB vs Temperature Figure 4. IOP vs Temperature Submit Documentation Feedback Copyright © 2004–2015, Texas Instruments Incorporated Product Folder Links: LM2621 5 LM2621 SNVS033D – MAY 2004 – REVISED NOVEMBER 2015 www.ti.com Typical Characteristics (continued) Figure 5. ISD vs Temperature Figure 6. ISD vs VDD VOUT = 3.3 V 6 Figure 7. IOP vs VDD Figure 8. VIN_ST vs Load Current Figure 9. Switching Frequency vs RFQ Figure 10. Peak Inductor Current vs Load Current Submit Documentation Feedback Copyright © 2004–2015, Texas Instruments Incorporated Product Folder Links: LM2621 LM2621 www.ti.com SNVS033D – MAY 2004 – REVISED NOVEMBER 2015 Typical Characteristics (continued) Figure 11. Maximum Load Current vs Input Voltage Submit Documentation Feedback Copyright © 2004–2015, Texas Instruments Incorporated Product Folder Links: LM2621 7 LM2621 SNVS033D – MAY 2004 – REVISED NOVEMBER 2015 www.ti.com 7 Detailed Description 7.1 Overview The LM2621 is designed to provide step-up DC-DC voltage regulation in battery-powered and low-input voltage systems. It combines a step-up switching regulator, N-channel power MOSFET, built-in current limit, thermal limit, and voltage reference in a single 8-pin VSSOP package Pin Configuration and Functions. The switching DC-DC regulator boosts an input voltage between 1.2 V and 14 V to a regulated output voltage between 1.24 V and 14 V. The LM2621 starts from a low 1.1-V input and remains operational down to 0.65 V. This device is optimized for use in cellular phones and other applications requiring a small size, low profile, as well as low quiescent current for maximum battery life during stand-by and shutdown. A high-efficiency gatedoscillator topology offers an output of up to 1 A. Additional features include a built-in peak switch current limit, and thermal protection circuitry. 7.2 Functional Block Diagram 7.3 Feature Description 7.3.1 Gated Oscillator Control Scheme A unique gated oscillator control scheme enables the LM2621 to have an ultra-low quiescent current and provides a high efficiency over a wide load range. The switching frequency of the internal oscillator is programmable using an external resistor and can be set between 300 kHz and 2 MHz. This control scheme uses a hysteresis window to regulate the output voltage. When the output voltage is below the upper threshold of the window, the LM2621 switches continuously with a fixed duty cycle of 70% at the switching frequency selected by the user. During the first part of each switching cycle, the internal N-channel MOSFET switch is turned on. This causes the current to ramp up in the inductor and store energy. During the second part of each switching cycle, the MOSFET is turned off. The voltage across the inductor reverses and forces current through the diode to the output filter capacitor and the load. Thus when the LM2621 switches continuously, the output voltage starts to ramp up. When the output voltage hits the upper threshold of the window, the LM2621 stops switching completely. This causes the output voltage to droop because the energy stored in the output capacitor is depleted by the load. When the output voltage hits the lower threshold of the hysteresis window, the LM2621 starts switching continuously again causing the output voltage to ramp up towards the upper threshold. Figure 12 shows the switch voltage and output voltage waveforms. Because of this type of control scheme, the quiescent current is inherently very low. At light loads the gated oscillator control scheme offers a much higher efficiency compared to the conventional PWM control scheme. 8 Submit Documentation Feedback Copyright © 2004–2015, Texas Instruments Incorporated Product Folder Links: LM2621 LM2621 www.ti.com SNVS033D – MAY 2004 – REVISED NOVEMBER 2015 Feature Description (continued) Figure 12. Typical Step-Up Regulator Waveforms 7.3.2 Low Voltage Start-Up The LM2621 can start-up from input voltages as low as 1.1 V. On start-up, the control circuitry switches the Nchannel MOSFET continuously at 70% duty cycle until the output voltage reaches 2.5 V. After this output voltage is reached, the normal step-up regulator feedback and gated oscillator control scheme take over. Once the device is in regulation it can operate down to a 0.65-V input, since the internal power for the IC can be bootstrapped from the output using the VDD pin. 7.3.3 Output Voltage Ripple Frequency A major component of the output voltage ripple is due to the hysteresis used in the gated oscillator control scheme. The frequency of this voltage ripple is proportional to the load current. The frequency of this ripple does not necessitate the use of larger inductors and capacitors however, since the size of these components is determined by the switching frequency of the oscillator which can be set up to 2 MHz using an external resistor. 7.3.4 Internal Current Limit and Thermal Protection An internal cycle-by-cycle current limit serves as a protection feature. This is set high enough (2.85 A typical, approximately 4 A maximum) so as not to come into effect during normal operating conditions. An internal thermal protection circuitry disables the MOSFET power switch when the junction temperature (TJ) exceeds about 160°C. The switch is re-enabled when TJ drops below approximately 135°C. 7.4 Device Functional Modes 7.4.1 Shutdown The LM2621 features a shutdown mode that reduces the quiescent current to less than a specified 2.5-µA overtemperature. This extends the life of the battery in battery powered applications. During shutdown, all feedback and control circuitry is turned off. The regulator's output voltage drops to one diode drop below the input voltage. Entry into the shutdown mode is controlled by the active-low logic input pin EN (Pin 2). When the logic input to this pin pulled below 0.15 VDD, the device goes into shutdown mode. The logic input to this pin should be above 0.7 VDD for the device to work in normal step-up mode. Submit Documentation Feedback Copyright © 2004–2015, Texas Instruments Incorporated Product Folder Links: LM2621 9 LM2621 SNVS033D – MAY 2004 – REVISED NOVEMBER 2015 www.ti.com 8 Application and Implementation NOTE Information in the following applications sections is not part of the TI component specification, and TI does not warrant its accuracy or completeness. TI’s customers are responsible for determining suitability of components for their purposes. Customers should validate and test their design implementation to confirm system functionality. 8.1 Application Information The LM2621 is primarily used as a Boost type step-up converter. The following section provides information regarding connection and component choices to build a successful boost converter. Examples of typical applications are also provided including a SEPIC step-up/step-down topology. More details on designing a SEPIC converter can be found here: SLYT309. 8.2 Typical Applications 8.2.1 Step-Up DC-DC Converter Typical Application Using LM2621 Figure 13. Typical Circuit 8.2.1.1 Design Requirements In order to successfully build an application, the designer should have the following parameters: • Output voltage to set the feedback voltage divider and to assess the source for biasing the VDD pin. • Input voltage range (min and max) to ensure safe operation within absolute max. rating of the IC. • Output current to ensure that the system will not hit the internal peak current limit of the IC (2.85 A typical) during normal operation. 8.2.1.2 Detailed Design Procedure 8.2.1.2.1 Setting the Output Voltage The output voltage of the step-up regulator can be set between 1.24 V and 14 V by connecting a feedback resistive divider made of RF1 and RF2. The resistor values are selected as follows: RF2 = RF1 /[(VOUT/ 1.24) −1] (1) A value of 150 kΩ is suggested for RF1. Then, RF2 can be selected using the above equation. A 39-pF capacitor (CF1) connected across RF1 helps in feeding back most of the AC ripple at VOUT to the FB pin. This helps reduce the peak-to-peak output voltage ripple as well as improve the efficiency of the step-up regulator, because a set hysteresis of 30 mV at the FB pin is used for the gated oscillator control scheme. 10 Submit Documentation Feedback Copyright © 2004–2015, Texas Instruments Incorporated Product Folder Links: LM2621 LM2621 www.ti.com SNVS033D – MAY 2004 – REVISED NOVEMBER 2015 Typical Applications (continued) 8.2.1.2.2 Bootstrapping When the output voltage (VOUT) is between 2.5 V and 5.0 V a bootstrapped operation is suggested. This is achieved by connecting the VDD pin (Pin 6) to VOUT. However if the VOUT is outside this range, the VDD pin should be connected to a voltage source whose range is between 2.5 V and 5 V. This can be the input voltage (VIN), VOUT stepped down using a linear regulator, or a different voltage source available in the system. This is referred to as non-bootstrapped operation. The maximum acceptable voltage at the BOOT pin (Pin 7) is 10 V. 8.2.1.2.3 Setting the Switching Frequency The switching frequency of the oscillator is selected by choosing an external resistor (RFQ) connected between FREQ and VDD pins. See Figure 9 for choosing the RFQ value to achieve the desired switching frequency. A high switching frequency allows the use of very small surface mount inductors and capacitors and results in a very small solution size. A switching frequency between 300 kHz and 2 MHz is recommended. 8.2.1.2.4 Inductor Selection The LM2621's high switching frequency enables the use of a small surface mount inductor. A 6.8-µH shielded inductor is suggested. The inductor should have a saturation current rating higher than the peak current it will experience during circuit operation (see Figure 10). Less than 100-mΩ ESR is suggested for high efficiency. Open-core inductors cause flux linkage with circuit components and interfere with the normal operation of the circuit. They should be avoided. For high efficiency, choose an inductor with a high frequency core material, such as ferrite, to reduce the core losses. To minimize radiated noise, use a toroid, pot core or shielded core inductor. The inductor should be connected to the SW pin as close to the IC as possible. See Table 1 for a list of the inductor manufacturers. 8.2.1.2.5 Output Diode Selection A Schottky diode should be used for the output diode. The forward current rating of the diode should be higher than the load current, and the reverse voltage rating must be higher than the output voltage. Do not use ordinary rectifier diodes, since slow switching speeds and long recovery times cause the efficiency and the load regulation to suffer. Table 1 shows a list of the diode manufacturers. 8.2.1.2.6 Input and Output Filter Capacitors Selection Tantalum chip capacitors are recommended for the input and output filter capacitors. A 22-µF capacitor is suggested for the input filter capacitor. It should have a DC working voltage rating higher than the maximum input voltage. A 68-µF tantalum capacitor is suggested for the output capacitor. The DC working voltage rating should be greater than the output voltage. Very high ESR values (> 3Ω) should be avoided. 8.2.1.3 Application Curves Figure 14. Startup Vin=1.2V,Vout-5V, 10ms/div 1V/div (Ch3:Vin,Ch1:Vout) Figure 15. Startup Vin=3.3V,Vout-5V, 10ms/div 1V/div (Ch3:Vin,Ch1:Vout) Submit Documentation Feedback Copyright © 2004–2015, Texas Instruments Incorporated Product Folder Links: LM2621 11 LM2621 SNVS033D – MAY 2004 – REVISED NOVEMBER 2015 www.ti.com Typical Applications (continued) 8.2.2 5-V / 0.5-A Step-Up Regulator Figure 16. 5-V/0.5A Step-Up Regulator 8.2.2.1 Design Requirements Design requirement is the same to the typical application shown earlier. Components have been chosen that comply with the required maximum height. See Design Requirements for the design requirement and following sections for the detailed design procedure. 8.2.2.2 Detailed Design Procedure Follow the detailed design procedure in Detailed Design Procedure. 12 Submit Documentation Feedback Copyright © 2004–2015, Texas Instruments Incorporated Product Folder Links: LM2621 LM2621 www.ti.com SNVS033D – MAY 2004 – REVISED NOVEMBER 2015 Typical Applications (continued) Table 1. Bill of Materials Manufacturer Part Number U1 TI LM2621MM C1 Vishay/Sprague 595D226X06R3B2T, Tantalum C2 Vishay/Sprague 595D686X0010C2T, Tantalum D1 Motorola MBRS140T3 L Coilcraft DT1608C-682 8.2.3 2-mm Tall 5-V / 0.2-A Step-Up Regulator for Low Profile Applications Figure 17. 2-mm Tall 5-V/0.2A Step-Up Regulator for Low Profile Applications 8.2.3.1 Design Requirements Design requirement is the same to the typical application shown earlier. Components have been chosen that comply with the required maximum height. See Design Requirements for the design requirement and following sections for the detailed design procedure. 8.2.3.2 Detailed Design Procedure Follow the detailed design procedure in Detailed Design Procedure. Table 2. Bill of Materials Manufacturer Part Number U1 TI LM2621MM C1 Vishay/Sprague 592D156X06R3B2T, Tantalum C2 Vishay/Sprague 592D336X06R3C2T, Tantalum D1 Motorola MBRS140T3 L Vishay/Dale ILS-3825-03 Submit Documentation Feedback Copyright © 2004–2015, Texas Instruments Incorporated Product Folder Links: LM2621 13 LM2621 SNVS033D – MAY 2004 – REVISED NOVEMBER 2015 www.ti.com 8.2.4 3.3-V / 0.5-A SEPIC Regulator Figure 18. 3.3-V/0.5-A SEPIC Regulator 8.2.4.1 Design Requirements Design requirement for the SEPIC is similar to that of a boost but the current flowing through the switch is the addition of the current flowing through L1 and L2. As a result, the peak current through the main switch is IIN+IOUT+0.5xDeltaIL1+0.5xDeltaIL2. See SLYT309 for detail on the specific design requirement of a SEPIC converter. 8.2.4.2 Detailed Design Procedure Follow the detailed design procedure in Detailed Design Procedure. Table 3. Bill of Materials Manufacturer Part Number Description U1 TI LM2621MM Low Input Voltage Regulator C1 Sanyo 10CV220AX, SMT AL-Electrolytic 220 µF C2 TDK C2012X7R1C225M, MLCC 2.2 µF C3 Vishay VJ0603A331KXXAT 33 pF C4 TDK C3225X7R0J107MT 100 µF C5, C6 Vishay VJ0603Y104KXXAT 0.1 µF D1 Philips BAT54C VR = 1V D2 Vishay MBRS120 1A / VR = 20V L1, L2 Coilcraft DO1813P-682HC 6.8 µH R1 Vishay CRCW08054990FRT6 499 Ω R2 Vishay CRCW08051503FRT6 150 kΩ R3 Vishay CRCW08053923FRT6 392 kΩ R4 Vishay CRCW08059092FRT6 90.9 kΩ 14 Submit Documentation Feedback Copyright © 2004–2015, Texas Instruments Incorporated Product Folder Links: LM2621 LM2621 www.ti.com SNVS033D – MAY 2004 – REVISED NOVEMBER 2015 9 Power Supply Recommendations The power line feeding the LM2621 should have low impedance. The input capacitor of the system should be placed as close to VIN as possible. If the power supply is very noisy, an additional bulk capacitor might be necessary in the system to ensure that clean power is delivered to the IC. 10 Layout 10.1 Layout Guidelines High switching frequencies and high peak currents make a proper layout of the PC board an important part of design. Poor design can cause excessive EMI and ground-bounce, both of which can cause malfunction and loss of regulation by corrupting voltage feedback signal and injecting noise into the control section. Power components - such as the inductor, input and output filter capacitors, and output diode - should be placed as close to the regulator IC as possible, and their traces should be kept short, direct and wide. The ground pins of the input and output filter capacitors and the PGND and SGND pins of LM2621 should be connected using short, direct and wide traces. The voltage feedback network (RF1, RF2, and CF1) should be kept very close to the FB pin. Noisy traces, such as from the SW pin, should be kept away from the FB and VDD pins. The traces that run between Vout and the FB pin of the IC should be kept away from the inductor flux. Always provide sufficient copper area to dissipate the heat due to power loss in the circuitry and prevent the thermal protection circuitry in the IC from shutting the IC down. 10.2 Layout Example Figure 19. LM2621 PCB Layout Submit Documentation Feedback Copyright © 2004–2015, Texas Instruments Incorporated Product Folder Links: LM2621 15 LM2621 SNVS033D – MAY 2004 – REVISED NOVEMBER 2015 www.ti.com 11 Device and Documentation Support 11.1 Device Support 11.1.1 Third-Party Products Disclaimer TI'S PUBLICATION OF INFORMATION REGARDING THIRD-PARTY PRODUCTS OR SERVICES DOES NOT CONSTITUTE AN ENDORSEMENT REGARDING THE SUITABILITY OF SUCH PRODUCTS OR SERVICES OR A WARRANTY, REPRESENTATION OR ENDORSEMENT OF SUCH PRODUCTS OR SERVICES, EITHER ALONE OR IN COMBINATION WITH ANY TI PRODUCT OR SERVICE. 11.2 Documentation Support 11.2.1 Related Documentation For related documentation, see the following: • Designing DC/DC converters based on SEPIC topology, SLYT309 11.3 Community Resources The following links connect to TI community resources. Linked contents are provided "AS IS" by the respective contributors. They do not constitute TI specifications and do not necessarily reflect TI's views; see TI's Terms of Use. TI E2E™ Online Community TI's Engineer-to-Engineer (E2E) Community. Created to foster collaboration among engineers. At e2e.ti.com, you can ask questions, share knowledge, explore ideas and help solve problems with fellow engineers. Design Support TI's Design Support Quickly find helpful E2E forums along with design support tools and contact information for technical support. 11.4 Trademarks E2E is a trademark of Texas Instruments. All other trademarks are the property of their respective owners. 11.5 Electrostatic Discharge Caution These devices have limited built-in ESD protection. The leads should be shorted together or the device placed in conductive foam during storage or handling to prevent electrostatic damage to the MOS gates. 11.6 Glossary SLYZ022 — TI Glossary. This glossary lists and explains terms, acronyms, and definitions. 12 Mechanical, Packaging, and Orderable Information The following pages include mechanical, packaging, and orderable information. This information is the most current data available for the designated devices. This data is subject to change without notice and revision of this document. For browser-based versions of this data sheet, refer to the left-hand navigation. 16 Submit Documentation Feedback Copyright © 2004–2015, Texas Instruments Incorporated Product Folder Links: LM2621 IMPORTANT NOTICE Texas Instruments Incorporated and its subsidiaries (TI) reserve the right to make corrections, enhancements, improvements and other changes to its semiconductor products and services per JESD46, latest issue, and to discontinue any product or service per JESD48, latest issue. Buyers should obtain the latest relevant information before placing orders and should verify that such information is current and complete. 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