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LM2678

www.ti.com

SNVS029I –MARCH 2000–REVISED APRIL 2013

LM2678 SIMPLE SWITCHER

High Efficiency 5A Step-Down Voltage Regulator

Check for Samples: LM2678

FEATURES

DESCRIPTION

The LM2678 series of regulators are monolithic

• Efficiency Up to 92%

integrated circuits which provide all of the active

• Simple and Easy to Design with (Using Off-

functions for a step-down (buck) switching regulator

The-Shelf External Components)

capable of driving up to 5A loads with excellent line

• 120 mΩ DMOS Output Switch

and load regulation characteristics. High efficiency

(>90%) is obtained through the use of a low ON-

• 3.3V, 5V and 12V Fixed Output and Adjustable

resistance DMOS power switch. The series consists

(1.2V to 37V ) Versions

of fixed output voltages of 3.3V, 5V and 12V and an

• 50μA Standby Current When Switched OFF

adjustable output version.

• ±2% Maximum Output Tolerance Over Full

The SIMPLE SWITCHER

concept provides for a

Line and Load Conditions

complete design using a minimum number of external

• Wide Input Voltage Range: 8V to 40V

components. A high fixed frequency oscillator

(260KHz) allows the use of physically smaller sized

• 260 KHz Fixed Frequency Internal Oscillator

components. A family of standard inductors for use

• −40 to +125°C Operating Junction Temperature

with the LM2678 are available from several

Range

manufacturers to greatly simplify the design process.

The LM2678 series also has built in thermal

APPLICATIONS

shutdown, current limiting and an ON/OFF control

• Simple to Design, High Efficiency (>90%) Step-

input that can power down the regulator to a low

Down Switching Regulators

50μA quiescent current standby condition. The output

voltage is ensured to a ±2% tolerance. The clock

• Efficient System Pre-Regulator for Linear

frequency is controlled to within a ±11% tolerance.

Voltage Regulators

• Battery Chargers

Typical Application

Please be aware that an important notice concerning availability, standard warranty, and use in critical applications of

Texas Instruments semiconductor products and disclaimers thereto appears at the end of this data sheet.

2SIMPLE SWITCHER, Switchers Made Simple are registered trademarks of Texas Instruments.

3All other trademarks are the property of their respective owners.

PRODUCTION DATA information is current as of publication date.

Products conform to specifications per the terms of the Texas

Instruments standard warranty. Production processing does not

necessarily include testing of all parameters.

Summary of content (35 pages)

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LM2678 www.ti.com SNVS029I – MARCH 2000 – REVISED APRIL 2013 LM2678 SIMPLE SWITCHER® High Efficiency 5A Step-Down Voltage Regulator Check for Samples: LM2678 FEATURES DESCRIPTION • • The LM2678 series of regulators are monolithic integrated circuits which provide all of the active functions for a step-down (buck) switching regulator capable of driving up to 5A loads with excellent line and load regulation characteristics.
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LM2678 SNVS029I – MARCH 2000 – REVISED APRIL 2013 www.ti.com Connection Diagrams Top View Top View Figure 1. DDPAK Package See Package Number KTW0007B Figure 2. TO-220 Package See Package Number NDZ0007B Top View * 1 14 VSW VIN 2 13 VSW VIN 3 12 VSW CB 4 11 * * 5 10 * * 6 9 GND FB 7 8 ON/OFF DAP** * No Connections ** Connect to Pin 9 on PCB Figure 3. VSON-14 Package See Package Number NHM0014A These devices have limited built-in ESD protection.
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LM2678 www.ti.com SNVS029I – MARCH 2000 – REVISED APRIL 2013 Operating Ratings Supply Voltage 8V to 40V −40°C to 125°C Junction Temperature Range (TJ) Electrical Characteristics LM2678-3.3 Limits appearing in bold type face apply over the entire junction temperature range of operation, −40°C to 125°C. Specifications appearing in normal type apply for TA = TJ = 25°C. Parameter Test Conditions Typ (1) Min (2) Max (2) Units 3.234/3.201 3.366/3.
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LM2678 SNVS029I – MARCH 2000 – REVISED APRIL 2013 www.ti.com All Output Voltage Versions Electrical Characteristics Limits appearing in bold type face apply over the entire junction temperature range of operation, −40°C to 125°C. Specifications appearing in normal type apply for TA = TJ = 25°C. Unless otherwise specified VIN=12V for the 3.3V, 5V and Adjustable versions and VIN=24V for the 12V version. Parameter Test Conditions Typ Min Max Units 4.2 6 mA 50 100/150 μA 8.3/8.
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LM2678 www.ti.com SNVS029I – MARCH 2000 – REVISED APRIL 2013 Typical Performance Characteristics Normalized Output Voltage Line Regulation Figure 4. Figure 5. Efficiency vs Input Voltage Efficiency vs ILOAD Figure 6. Figure 7. Switch Current Limit Operating Quiescent Current Figure 8. Figure 9.
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LM2678 SNVS029I – MARCH 2000 – REVISED APRIL 2013 www.ti.com Typical Performance Characteristics (continued) Standby Quiescent Current ON/OFF Threshold Voltage Figure 10. Figure 11. ON/OFF Pin Current (Sourcing) Switching Frequency Figure 12. Figure 13. Feedback Pin Bias Current Continuous Mode Switching Waveforms VIN = 20V, VOUT = 5V, ILOAD = 5A L = 10 μH, COUT = 400 μF, COUTESR = 13 mΩ Figure 14. 6 A. VSW Pin Voltage, 10 V/div. B. Inductor Current, 2 A/div C.
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LM2678 www.ti.com SNVS029I – MARCH 2000 – REVISED APRIL 2013 Typical Performance Characteristics (continued) Discontinuous Mode Switching Waveforms VIN = 20V, VOUT = 5V, ILOAD = 500 mA L = 10 μH, COUT = 400 μF, COUTESR = 13 mΩ A. VSW Pin Voltage, 10 V/div. B. Inductor Current, 1 A/div C. Output Ripple Voltage, 20 mV/div AC-Coupled Figure 16. Horizontal Time Base: 1 μs//iv Load Transient Response for Continuous Mode VIN = 20V, VOUT = 5V L = 10 μH, COUT = 400 μF, COUTESR = 13 mΩ A.
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LM2678 SNVS029I – MARCH 2000 – REVISED APRIL 2013 www.ti.
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LM2678 www.ti.com SNVS029I – MARCH 2000 – REVISED APRIL 2013 APPLICATION HINTS The LM2678 provides all of the active functions required for a step-down (buck) switching regulator. The internal power switch is a DMOS power MOSFET to provide power supply designs with high current capability, up to 5A, and highly efficient operation. The LM2678 is part of the SIMPLE SWITCHER® family of power converters.
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LM2678 SNVS029I – MARCH 2000 – REVISED APRIL 2013 www.ti.com DESIGN CONSIDERATIONS Figure 19. Basic Circuit for Fixed Output Voltage Applications. Figure 20. Basic Circuit for Adjustable Output Voltage Applications Power supply design using the LM2678 is greatly simplified by using recommended external components.
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LM2678 www.ti.com SNVS029I – MARCH 2000 – REVISED APRIL 2013 INDUCTOR The inductor is the key component in a switching regulator. For efficiency the inductor stores energy during the switch ON time and then transfers energy to the load while the switch is OFF. Nomographs are used to select the inductance value required for a given set of operating conditions. The nomographs assume that the circuit is operating in continuous mode (the current flowing through the inductor never falls to zero).
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LM2678 SNVS029I – MARCH 2000 – REVISED APRIL 2013 www.ti.com INPUT CAPACITOR Fast changing currents in high current switching regulators place a significant dynamic load on the unregulated power source. An input capacitor helps to provide additional current to the power supply as well as smooth out input voltage variations. Like the output capacitor, the key specifications for the input capacitor are RMS current rating and working voltage.
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LM2678 www.ti.com SNVS029I – MARCH 2000 – REVISED APRIL 2013 A simple test to determine if this condition might exist for a suspect application is to apply a short circuit across the output of the converter, and then remove the shorted output condition. In an application with properly selected external components, the output will recover smoothly. Practical values of external components that have been experimentally found to work well under these specific operating conditions are COUT = 47µF, L = 22µH.
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LM2678 SNVS029I – MARCH 2000 – REVISED APRIL 2013 www.ti.com Step 4: Use Table 6 to determine an output capacitor. With a 3.3V output and a 15μH inductor there are four through-hole output capacitor solutions with the number of same type capacitors to be paralleled and an identifying capacitor code given. Table 3 provides the actual capacitor characteristics.
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LM2678 www.ti.com SNVS029I – MARCH 2000 – REVISED APRIL 2013 Step 3: To use the nomograph for the adjustable device, Figure 24, requires a calculation of the inductor Volt•microsecond constant (E•T expressed in V•μS) from the following formula: where • VSAT is the voltage drop across the internal power switch which is Rds(ON) times Iload (3) In this example this would be typically 0.12Ω x 3.5A or 0.42V and VD is the voltage drop across the forward bisased Schottky diode, typically 0.5V.
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LM2678 SNVS029I – MARCH 2000 – REVISED APRIL 2013 www.ti.com Inductor Selection Guides For Continuous Mode Operation 16 Figure 21. LM2678-3.3 Figure 22. LM2678-5.0 Figure 23. LM2678-12 Figure 24.
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LM2678 www.ti.com SNVS029I – MARCH 2000 – REVISED APRIL 2013 Table 1. Inductor Manufacturer Part Numbers Inductor Reference Number Inductance (µH) Current (A) L23 33 L24 22 L25 Renco Pulse Engineering Through Hole Surface Mount Coilcraft Through Hole Surface Mount 1.35 RL-5471-7 RL1500-33 PE-53823 PE-53823S DO3316-333 1.65 RL-1283-22-43 RL1500-22 PE-53824 PE-53824S DO3316-223 15 2.00 RL-1283-15-43 RL1500-15 PE-53825 PE-53825S DO3316-153 L29 100 1.
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LM2678 SNVS029I – MARCH 2000 – REVISED APRIL 2013 www.ti.com Capacitor Selection Guides Table 3. Input and Output Capacitor Codes—Surface Mount Capacitor Reference Code 18 Surface Mount AVX TPS Series Sprague 594D Series Kemet T495 Series C (µF) WV (V) Irms (A) C (µF) WV (V) Irms (A) C (µF) WV (V) Irms (A) C1 330 6.3 1.15 120 6.3 1.1 100 6.3 0.82 C2 100 10 1.1 220 6.3 1.4 220 6.3 1.1 C3 220 10 1.15 68 10 1.05 330 6.3 1.1 C4 47 16 0.89 150 10 1.
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LM2678 www.ti.com SNVS029I – MARCH 2000 – REVISED APRIL 2013 Table 4. Input and Output Capacitor Codes—Through Hole Capacitor Reference Code Through Hole Sanyo OS-CON SA Series Sanyo MV-GX Series Nichicon PL Series Panasonic HFQ Series C (µF) WV (V) Irms (A) C (µF) WV (V) Irms (A) C (µF) WV (V) Irms (A) C (µF) WV (V) C1 47 6.3 1 1000 6.3 0.8 680 10 0.8 82 35 Irms (A) 0.4 C2 150 6.3 1.95 270 16 0.6 820 10 0.98 120 35 0.44 C3 330 6.3 2.45 470 16 0.
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LM2678 SNVS029I – MARCH 2000 – REVISED APRIL 2013 www.ti.com Table 6. Output Capacitors for Fixed Output Voltage Application—Surface Mount (1) (2) Surface Mount Output Voltage (V) Inductance (µH) 3.3 5 12 (1) (2) AVX TPS Series Sprague 594D Series Kemet T495 Series No. C Code No. C Code No.
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LM2678 www.ti.com SNVS029I – MARCH 2000 – REVISED APRIL 2013 Table 8. Input Capacitors for Fixed Output Voltage Application—Surface Mount (1) (2) (3) Surface Mount Output Voltage (V) Inductance (µH) 3.3 5 12 (1) (2) (3) (4) AVX TPS Series Sprague 594D Series Kemet T495 Series No. C Code No. C Code No.
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LM2678 SNVS029I – MARCH 2000 – REVISED APRIL 2013 www.ti.com Table 10. Schottky Diode Selection Table Reverse Voltage (V) Surface Mount 3A 20V SK32 30V SK33 Through Hole 5A or More 3A 5A or More 1N5820 SR302 MBRD835L 1N5821 30WQ03F 40V 31DQ03 SK34 MBRD1545CT 1N5822 1N5825 30BQ040 6TQ045S MBR340 MBR745 30WQ04F 31DQ04 80SQ045 MBRS340 SR403 6TQ045 MBRD340 50V or More SK35 MBR350 30WQ05F 31DQ05 SR305 Table 11.
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LM2678 www.ti.com SNVS029I – MARCH 2000 – REVISED APRIL 2013 Table 12. Output Capacitors for Adjustable Output Voltage Applications—Surface Mount (1) (2) Surface Mount Output Voltage (V) 1.21 to 2.50 2.5 to 3.75 3.75 to 5 5 to 6.25 6.25 to 7.5 7.5 to 10 10 to 12.5 12.5 to 15 15 to 20 20 to 30 30 to 37 (1) (2) (3) Inductance (µH) AVX TPS Series Sprague 594D Series Kemet T495 Series No. C Code No. C Code No.
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LM2678 SNVS029I – MARCH 2000 – REVISED APRIL 2013 www.ti.com Table 13. Output Capacitors for Adjustable Output Voltage Applications—Through Hole (1) (2) Through Hole Output Voltage (V) 1.21 to 2.50 2.5 to 3.75 3.75 to 5 5 to 6.25 6.25 to 7.5 7.5 to 10 10 to 12.5 12.5 to 15 15 to 20 Inductance (µH) Sanyo OS-CON SA Series 30 to 37 (1) (2) (3) 24 Nichicon PL Series Panasonic HFQ Series No. C Code No. C Code No. C Code No.
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LM2678 www.ti.com SNVS029I – MARCH 2000 – REVISED APRIL 2013 REVISION HISTORY Changes from Revision H (April 2013) to Revision I • Page Changed layout of National Data Sheet to TI format ..........................................................................................................
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PACKAGE OPTION ADDENDUM www.ti.com 1-Nov-2013 PACKAGING INFORMATION Orderable Device Status (1) Package Type Package Pins Package Drawing Qty Eco Plan Lead/Ball Finish MSL Peak Temp (2) (6) (3) Op Temp (°C) Device Marking (4/5) LM2678S-12 NRND DDPAK/ TO-263 KTW 7 45 TBD Call TI Call TI -40 to 125 LM2678 S-12 LM2678S-12/NOPB ACTIVE DDPAK/ TO-263 KTW 7 45 Pb-Free (RoHS Exempt) CU SN Level-3-245C-168 HR -40 to 125 LM2678 S-12 LM2678S-3.
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PACKAGE OPTION ADDENDUM www.ti.com 1-Nov-2013 Orderable Device Status (1) Package Type Package Pins Package Drawing Qty Eco Plan Lead/Ball Finish MSL Peak Temp (2) (6) (3) Op Temp (°C) Device Marking (4/5) LM2678SX-12/NOPB ACTIVE DDPAK/ TO-263 KTW 7 500 Pb-Free (RoHS Exempt) CU SN Level-3-245C-168 HR -40 to 125 LM2678 S-12 LM2678SX-3.3/NOPB ACTIVE DDPAK/ TO-263 KTW 7 500 Pb-Free (RoHS Exempt) CU SN Level-3-245C-168 HR -40 to 125 LM2678 S-3.3 LM2678SX-5.
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PACKAGE OPTION ADDENDUM www.ti.com 1-Nov-2013 Pb-Free (RoHS): TI's terms "Lead-Free" or "Pb-Free" mean semiconductor products that are compatible with the current RoHS requirements for all 6 substances, including the requirement that lead not exceed 0.1% by weight in homogeneous materials. Where designed to be soldered at high temperatures, TI Pb-Free products are suitable for use in specified lead-free processes.
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PACKAGE MATERIALS INFORMATION www.ti.com 11-Oct-2013 TAPE AND REEL INFORMATION *All dimensions are nominal Device Package Package Pins Type Drawing SPQ Reel Reel A0 Diameter Width (mm) (mm) W1 (mm) B0 (mm) K0 (mm) P1 (mm) W Pin1 (mm) Quadrant LM2678SD-12 VSON NHM 14 250 178.0 16.4 5.3 6.3 1.5 12.0 16.0 Q1 LM2678SD-12/NOPB VSON NHM 14 250 178.0 16.4 5.3 6.3 1.5 12.0 16.0 Q1 LM2678SD-3.3/NOPB VSON NHM 14 250 178.0 16.4 5.3 6.3 1.5 12.0 16.0 Q1 LM2678SD-5.
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PACKAGE MATERIALS INFORMATION www.ti.com 11-Oct-2013 Device Package Package Pins Type Drawing SPQ Reel Reel A0 Diameter Width (mm) (mm) W1 (mm) B0 (mm) K0 (mm) P1 (mm) W Pin1 (mm) Quadrant 14.85 5.0 16.0 24.0 TO-263 LM2678SX-ADJ/NOPB DDPAK/ TO-263 KTW 7 500 330.0 24.4 10.75 Q2 *All dimensions are nominal Device Package Type Package Drawing Pins SPQ Length (mm) Width (mm) Height (mm) LM2678SD-12 VSON NHM 14 250 210.0 185.0 35.
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PACKAGE MATERIALS INFORMATION www.ti.com 11-Oct-2013 Device Package Type Package Drawing Pins SPQ Length (mm) Width (mm) Height (mm) LM2678SX-ADJ DDPAK/TO-263 KTW 7 500 367.0 367.0 45.0 LM2678SX-ADJ/NOPB DDPAK/TO-263 KTW 7 500 367.0 367.0 45.
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MECHANICAL DATA NDZ0007B TA07B (Rev E) www.ti.
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MECHANICAL DATA NHM0014A SRC14A (Rev A) www.ti.
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MECHANICAL DATA KTW0007B TS7B (Rev E) BOTTOM SIDE OF PACKAGE www.ti.
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