LM26420

Manufacturer Part NumberLM26420
ManufacturerTexas Instruments
LM26420 datasheet
 


Specifications of LM26420

Vin(min)(v)3Vin(max)(v)5.5
Vout(min)(v)0.8Vout(max)(v)4.5
TopologyBuckPin/package16SON, 16WQFN, 16WSON, 20HTSSOP
Vout2(min)(v)0.8Vout2(max)(v)4.5
Regulated Outputs(#)2Frequency(min)(khz)1850, 400
Pwm ModeCurrent Mode Control  
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LM26420
LM26420 Dual 2.0A, High Frequency Synchronous Step-Down DC-DC Regulator
Literature Number: SNVS579C

LM26420 Summary of contents

  • Page 1

    ... LM26420 LM26420 Dual 2.0A, High Frequency Synchronous Step-Down DC-DC Regulator Literature Number: SNVS579C ...

  • Page 2

    ... DC/DC conversion with fast transient response and accurate regulation in the smallest possible PCB area. With a minimum of external components, the LM26420 is easy to use. The ability to drive two 2.0A loads with an internal 75 mΩ PMOS top switch and an internal 50 mΩ NMOS bottom switch using state-of-the-art 0.5 µ ...

  • Page 3

    ... Connection Diagrams 16-Pin LLP (TOP VIEW) Ordering Information Frequency Order Number Option LM26420XMH LM26420XMHX 2.2MHz LM26420XSQ LM26420XSQX LM26420YMH LM26420YMHX 0.55MHz LM26420YSQ LM26420YSQX NOPB versions available as well www.national.com 30069601 NSC Package Package Type Drawing eTSSOP-20 MXA20A LLP-16 SQB16A eTSSOP-20 MXA20A LLP-16 SQB16A ...

  • Page 4

    Pin Descriptions 20-Pin eTSSOP Pin Name Function 3, 4 VIND Power Input supply for Buck 1. 1 17, 18 VIND Power Input supply for Buck VINC Input supply for control circuitry. 6,7 PGND Power ground pin for ...

  • Page 5

    ... LM26420-X LM26420-Y LLP-16 Package eTSSOP-20 Package LLP-16 Package eTSSOP-20 Package 3.3V IN and Sink/Source FB Pin Voltage Rising FB Pin Voltage Rising LM26420X 0.9 FB LM26420X 0.7 FB All Options LM26420X 0.9 FB LM26420X V = 0.7 FB LM26420Y V = 0.7 FB All Options (Note 2) 150°C − ...

  • Page 6

    Symbol Parameter Junction to Ambient θ LFPM Air Flow (Note θ Junction to Case (Note JC T Thermal Shutdown Temperature SD Note 1: Absolute maximum ratings indicate limits beyond which damage to the device may occur. Operating Range ...

  • Page 7

    Typical Performance Characteristics All curves taken 5.0V with configuration in typical application circuit shown in Application Information section of this IN datasheet 25°C, unless otherwise specified. J η vs Load "X" 5V, V ...

  • Page 8

    Load "X" & 3V 1.2V IN OUT 30069688 η vs Load "X" & 3V 0.8V IN OUT 30069641 Load Regulation 1.8V (All Options) ...

  • Page 9

    Line Regulation - "X" 1.8V, I OUT OUT Oscillator Frequency vs Temperature - "X" R TOP vs Temperature (LLP-16 Package) DSON www.national.com = 1,000mA 30069627 Oscillator Frequency vs Temperature - "Y" 30069647 R DSON 30069649 8 Line Regulation ...

  • Page 10

    R TOP vs Temperature (eTSSOP-20 Package) DSON I (Quiescent Current Switching) - "X" Q Load Transient Response - X Version (V = 1.2V, 25-100% Load Transient) OUT R BOTTOM vs Temperature (eTSSOP-20 Package) DSON 30069691 I (Quiescent Current Switching) - ...

  • Page 11

    Start-Up (Soft-Start 1.8V @ 1A, V OUT V vs Temperature FB Reverse Current Limit vs Temperature www.national.com = 5V) IN 30069657 30069659 30069680 10 Enable - Disable (V = 1. 5V) OUT IN 30069658 ...

  • Page 12

    Simplified Block Diagram Per Buck FIGURE 1. 11 30069604 www.national.com ...

  • Page 13

    ... Simplified Block Diagram (Figure 1), which depicts the functional blocks for one of the two channels, and to the waveforms in Figure 2. The LM26420 supplies a regu- lated output voltage by switching the internal PMOS and NMOS switches at constant frequency and variable duty cy- cle ...

  • Page 14

    ... PRECISION ENABLE The LM26420 features independent precision enables that allow the converter to be controlled by an external signal. This feature allows the device to be sequenced either by a external control signal or the output of another converter in conjunction with a resistor divider network. It can also be set to turn specific input voltage when used in conjunction with a re- sistor divider network connected to the input voltage ...

  • Page 15

    ... FET switch from dipping when the FET is turned on, therefore providing a healthy line rail for the LM26420 to work with. Since typically most of the AC current is provided by the local input capaci- tors, the power loss in those capacitors can be a concern. In the case of the LM26420 regulator, since the two channels operate 180° ...

  • Page 16

    ... Given the availability and quality of MLCCs and the expected output voltage of designs using the LM26420, there is really no need to review any other capacitor technologies. Another benefit of ceramic capacitors is their ability to bypass high frequency noise. A certain amount the winding resistance of the inductor ...

  • Page 17

    ... IC with a direct connection from VINC and AGND. USING PRECISION ENABLE AND POWER GOOD The LM26420's precision enable and power good pins ad- dress many of the sequencing requirements required today's challenging applications. Each output can be controlled inde- pendently and have independent power goods. This allows for a multitude of ways to control each output ...

  • Page 18

    ... FIGURE 9. V controlling V IN The LM26420's power good feature is design with hysterysis in order to insure no false power good flags are asserted dur- ing large transient. Once power good is asserted high, it will not be pulled low until the output voltage exceeds +/-14% of the setpoint for a during of ~7.5µS (typ.), see figure below. ...

  • Page 19

    ... IND OUT The LM26420 conduction loss is mainly associated with the two internal FETs: If the inductor ripple current is fairly small, the conduction losses can be simplified to: www.national.com Switching losses are also associated with the internal FETs. They occur during the switch on and off transition periods, where voltages and currents overlap resulting in power loss ...

  • Page 20

    ... R = Thermal resistance from chip junction to ambient air θJA Heat in the LM26420 due to internal power dissipation is re- moved through conduction and/or convection. Conduction: Heat transfer occurs through cross sectional ar- eas of material. Depending on the material, the transfer of heat can be considered to have poor to good thermal con- ductivity properties (insulator vs ...

  • Page 21

    LLP Package For certain high power applications, the PCB land may be modified to a "dog bone" shape (see Figure 6). By increasing the size of ground plane, and adding thermal vias, the R www.national.com FIGURE 11. Internal LLP Connection ...

  • Page 22

    ... LM26420X Design Example 1 FIGURE 13. LM26420X (2.2MHz): V Part Buck Regulator C3, C4 15µF, 6.3V, 1206, X5R C1 33µF, 6.3V, 1206, X5R C2 22µF, 6.3V, 1206, X5R C5 0.47µF, 10V, 0805, X7R L1 L2 10.0kΩ, 0603, 1% R3, R4 4.99kΩ, 0603 49.9kΩ, 0603, 1% R5, R6 21.5kΩ, 0603 4.99Ω, 0603, 1% ...

  • Page 23

    ... LM26420X Design Example 2 FIGURE 14. LM26420X (2.2MHz): V Part R3 R7, R2 www.national.com = 5V 1.8V @ 2.0A and V IN OUT1 Bill of Materials Part Value Manufacturer 2A Buck Regulator 15µF, 6.3V, 1206, X5R 33µF, 6.3V, 1206, X5R 22µF, 6.3V, 1206, X5R 0.47µF, 10V, 0805, X7R 1.0µH, 7.9A 0.7µ ...

  • Page 24

    ... LM26420X Design Example 3 FIGURE 15. LM26420X (2.2MHz): V Part Buck Regulator C3, C4 15µF, 6.3V, 1206, X5R C1 22µF, 6.3V, 1206, X5R C2 33µF, 6.3V, 1206, X5R C5 0.47µF, 10V, 0805, X7R L1, L2 10.0kΩ, 0603, 1% R3, R4 12.7kΩ, 0603 49.9kΩ, 0603, 1% R5, R6 31.6kΩ, 0603 4.99Ω, 0603, 1% ...

  • Page 25

    ... LM26420Y Design Example 4 FIGURE 16. LM26420Y (550kHz): V Part ID U1 C3, C4 C1 www.national.com = 5V 1.2V @ 2.0A and V IN OUT1 Bill of Materials Part Value Manufacturer 2A Buck Regulator 22µF, 6.3V, 1206, X5R 33µF, 6.3V, 1206, X5R 47µF, 6.3V, 1206, X5R 0.47µF, 10V, 0805, X7R 3.3µ ...

  • Page 26

    ... LM26420Y Design Example 5 FIGURE 17. LM26420Y (550kHz): V Part Buck Regulator C3, C4 22µF, 6.3V, 1206, X5R C1, C2, C6, C7, C8 47µF, 6.3V, 1206, X5R C5 0.47µF, 10V, 0805, X7R L1 L2 10.0kΩ, 0603, 1% R3, R4 49.9kΩ, 0603, 1% R5, R6 12.7kΩ, 0603 4.99Ω, 0603 1.8V @ 2.0A and V IN OUT1 ...

  • Page 27

    ... LM26420Y Design Example 6 FIGURE 18. LM26420Y (550kHz): V Part ID U1 C3, C4 C1, C2 L1 www.national.com = 5V 3.3V @ 2.0A and V IN OUT1 Bill of Materials Part Value Manufacturer 2A Buck Regulator 22µF, 6.3V, 1206, X5R 47µF, 6.3V, 1206, X5R 0.47µF, 10V, 0805, X7R 5.0µH, 2.82A 10.0kΩ, 0603, 1% 12.7kΩ ...

  • Page 28

    Physical Dimensions inches (millimeters) unless otherwise noted 20-Lead eTSSOP Package NS Package Number MXA20A 16-Lead LLP Package NS Package Number SQB16A 27 www.national.com ...

  • Page 29

    For more National Semiconductor product information and proven design tools, visit the following Web sites at: www.national.com Products Amplifiers www.national.com/amplifiers Audio www.national.com/audio Clock and Timing www.national.com/timing Data Converters www.national.com/adc Interface www.national.com/interface LVDS www.national.com/lvds Power Management www.national.com/power Switching Regulators www.national.com/switchers LDOs ...

  • Page 30

    ... Texas Instruments Incorporated and its subsidiaries (TI) reserve the right to make corrections, modifications, enhancements, improvements, and other changes to its products and services at any time and to discontinue any product or service without notice. Customers should obtain the latest relevant information before placing orders and should verify that such information is current and complete. All products are sold subject to TI’ ...