LM2679S-3.3 - Texas Instruments High-Performance Analog

Voltage

5V/5A

COUT

2 x 180 PF/16V

22 PH

Feedback

Boost

6TQ045S

Ground

Current

VIN

Softstart

1 nF

Voltage

8V to 40V

Input LM2679 - 5.0 Output

Switch

Output

0.01 PF

Limit

Adjust

5.6k

0.47 PF

+++

CIN

3 x 15 PF/50V

= 37,125

RADJ

ICL

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LM2679 SIMPLE SWITCHER

5A Step-Down Voltage Regulator with Adjustable Current

Limit

Check for Samples: LM2679

1FEATURES DESCRIPTION

The LM2679 series of regulators are monolithic

2• 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

• Resistor Programmable Peak Current Limit and load regulation characteristics. High efficiency

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

Over a Range of 3A to 7A. resistance DMOS power switch. The series consists

• 120 mΩDMOS Output Switch of fixed output voltages of 3.3V, 5V and 12V and an

• 3.3V, 5V and 12V Fixed Output and Adjustable adjustable output version.

(1.2V to 37V ) Versions The SIMPLE SWITCHER®concept provides for a

• ±2% Maximum Output Tolerance Over Full complete design using a minimum number of external

Line and Load Conditions components. A high fixed frequency oscillator

• Wide Input Voltage Range: 8V to 40V (260KHz) allows the use of physically smaller sized

components. A family of standard inductors for use

• 260 KHz Fixed Frequency Internal Oscillator with the LM2679 are available from several

• Softstart Capability manufacturers to greatly simplify the design process.

•−40 to +125°C Operating Junction Temperature Other features include the ability to reduce the input

Range surge current at power-ON by adding a softstart

timing capacitor to gradually turn on the regulator.

APPLICATIONS The LM2679 series also has built in thermal

shutdown and resistor programmable current limit of

• Simple to Design, High Efficiency (>90%) Step- the power MOSFET switch to protect the device and

Down Switching Regulators load circuitry under fault conditions. The output

• Efficient System Pre-Regulator for Linear voltage is specified to a ±2% tolerance. The clock

Voltage Regulators frequency is controlled to within a ±11% tolerance.

• Battery Chargers

Typical Application

1Please 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.

Products conform to specifications per the terms of the Texas

Instruments standard warranty. Production processing does not

necessarily include testing of all parameters.

VSW

VIN

CURRENT ADJ

VSW

GND

SOFTSTART

FB 8

VIN VSW

DAP**

*No Connections

** Connect to Pin 9 on PCB

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Connection Diagrams

Figure 1. DDPAK Package Figure 2. TO-220 Package

Top View Top View

See Package Number KTW0007B See Package Number NDZ0007B

Figure 3. VSON-14

Top View

See Package Number NHM0014A

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.

Absolute Maximum Ratings(1)(2)

Input Supply Voltage 45V

Softstart Pin Voltage −0.1V to 6V

Switch Voltage to Ground(3) −1V to VIN

Boost Pin Voltage VSW + 8V

Feedback Pin Voltage −0.3V to 14V

Power Dissipation Internally Limited

ESD(4) 2 kV

Storage Temperature Range −65°C to 150°C

Soldering Temperature Wave 4 sec, 260°C

Infrared 10 sec, 240°C

Vapor Phase 75 sec, 219°C

(1) Absolute Maximum Ratings are limits beyond which damage to the device may occur. Operating Ratings indicate conditions under

which of the device is specified. Operating Ratings do not imply ensure performance limits. For specific performance limits and

associated test condition, see the electrical Characteristics tables.

(2) If Military/Aerospace specified devices are required, please contact the Texas Instruments Sales Office/Distributors for availability and

specifications.

(3) The absolute maximum specification of the 'Switch Voltage to Ground' applies to DC voltage. An extended negative voltage limit of -10V

applies to a pulse of up to 20 ns, -6V of 60 ns and -3V of up to 100 ns.

(4) ESD was applied using the human-body model, a 100pF capacitor discharged through a 1.5 kΩresistor into each pin.

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Operating Ratings

Supply Voltage 8V to 40V

Junction Temperature Range (TJ)−40°C to 125°C

Electrical Characteristics

LM2679-3.3

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. RADJ = 5.6KΩ.

Symbol Parameter Conditions Min(1) Typ(2) Max(1) Units

VOUT Output Voltage VIN = 8V to 40V, 100mA ≤IOUT ≤5A 3.234/3.201 3.3 3.366/3.399 V

ηEfficiency VIN = 12V, ILOAD = 5A 82 %

(1) All limits are specified at room temperature (standard type face) and at temperature extremes (bold type face). All room temperature

limits are 100% tested during production with TA= TJ= 25°C. All limits at temperature extremes are specified via correlation using

standard Quality Control (SQC) methods. All limits are used to calculate Average Outgoing Quality Level (AOQL).

(2) Typical values are determined with TA= TJ= 25°C and represent the most likely norm.

LM2679-5.0

Symbol Parameter Conditions Min(1) Typ(2) Max(1) Units

VOUT Output Voltage VIN = 8V to 40V, 100mA ≤IOUT ≤5A 4.900/4.850 5.0 5.100/5.150 V

ηEfficiency VIN = 12V, ILOAD = 5A 84 %

(1) All limits are specified at room temperature (standard type face) and at temperature extremes (bold type face). All room temperature

limits are 100% tested during production with TA= TJ= 25°C. All limits at temperature extremes are specified via correlation using

standard Quality Control (SQC) methods. All limits are used to calculate Average Outgoing Quality Level (AOQL).

(2) Typical values are determined with TA= TJ= 25°C and represent the most likely norm.

LM2679-12

Symbol Parameter Conditions Min(1) Typ(2) Max(1) Units

VOUT Output Voltage VIN = 15V to 40V, 100mA ≤IOUT ≤5A 11.76/11.64 12 12.24/12.36 V

ηEfficiency VIN = 24V, ILOAD = 5A 92 %

(1) All limits are specified at room temperature (standard type face) and at temperature extremes (bold type face). All room temperature

limits are 100% tested during production with TA= TJ= 25°C. All limits at temperature extremes are specified via correlation using

standard Quality Control (SQC) methods. All limits are used to calculate Average Outgoing Quality Level (AOQL).

(2) Typical values are determined with TA= TJ= 25°C and represent the most likely norm.

LM2679-ADJ

Symbol Parameter Conditions Min(1) Typ(2) Max(1) Units

VFB Feedback VIN = 8V to 40V, 100mA ≤IOUT ≤5A 1.186/1.174 1.21 1.234/1.246 V

Voltage VOUT Programmed for 5V

ηEfficiency VIN = 12V, ILOAD = 5A 84 %

(1) All limits are specified at room temperature (standard type face) and at temperature extremes (bold type face). All room temperature

limits are 100% tested during production with TA= TJ= 25°C. All limits at temperature extremes are specified via correlation using

standard Quality Control (SQC) methods. All limits are used to calculate Average Outgoing Quality Level (AOQL).

(2) Typical values are determined with TA= TJ= 25°C and represent the most likely norm.

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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.

Symbol Parameter Conditions Min Typ Max Units

DEVICE PARAMETERS

IQQuiescent Current VFEEDBACK = 8V 4.2 6 mA

For 3.3V, 5.0V, and ADJ Versions

VFEEDBACK = 15V

For 12V Versions

VADJ Current Limit Adjust 1.181/1.169 1.21 1.229/1.246 V

Voltage

ICL Current Limit RADJ = 5.6KΩ,(1) 5.5/5.3 6.3 7.6/8.1 A

ILOutput Leakage VIN = 40V, Softstart Pin = 0V mA

Current VSWITCH = 0V 1.0 1.5 mA

VSWITCH =−1V 6 15

RDS(ON) Switch On-Resistance ISWITCH = 5A 0.12 0.14/0.225 Ω

fOOscillator Frequency Measured at Switch Pin 225 260 280 kHz

D Duty Cycle Maximum Duty Cycle 91 %

Minimum Duty Cycle 0 %

IBIAS Feedback Bias VFEEDBACK = 1.3V 85 nA

Current ADJ Version Only

VSFST Softstart Threshold 0.53 0.63 0.74 V

Voltage

ISFST Softstart Pin Current Softstart Pin = 0V 3.7 6.9 μA

θJA Thermal Resistance NDZ Package, Junction to Ambient(2) 65

θJA NDZ Package, Junction to Ambient(3) 45

θJC NDZ Package, Junction to Case 2

θJA KTW Package, Junction to Ambient(4) 56 °C/W

θJA KTW Package, Junction to Ambient(5) 35

θJA KTW Package, Junction to Ambient(6) 26

θJC KTW Package, Junction to Case 2 ++

θJA NHM Package, Junction to Ambient(7) 55 °C/W

θJA NHM Package, Junction to Ambient(8) 29

(1) The peak switch current limit is determined by the following relationship: ICL=37,125/ RADJ.

(2) Junction to ambient thermal resistance (no external heat sink) for the 7 lead TO-220 package mounted vertically, with ½ inch leads in a

socket, or on a PC board with minimum copper area.

(3) Junction to ambient thermal resistance (no external heat sink) for the 7 lead TO-220 package mounted vertically, with ½ inch leads

soldered to a PC board containing approximately 4 square inches of (1 oz.) copper area surrounding the leads.

(4) Junction to ambient thermal resistance for the 7 lead DDPAK mounted horizontally against a PC board area of 0.136 square inches (the

same size as the DDPAK package) of 1 oz. (0.0014 in. thick) copper.

(5) Junction to ambient thermal resistance for the 7 lead DDPAK mounted horizontally against a PC board area of 0.4896 square inches

(3.6 times the area of the DDPAK package) of 1 oz. (0.0014 in. thick) copper.

(6) Junction to ambient thermal resistance for the 7 lead DDPAK mounted horizontally against a PC board copper area of 1.0064 square

inches (7.4 times the area of the DDPAK 3 package) of 1 oz. (0.0014 in. thick) copper. Additional copper area will reduce thermal

resistance further. See the thermal model in Switchers Made Simple®software.

(7) Junction to ambient thermal resistance for the 14-lead VSON mounted on a PC board copper area equal to the die attach paddle.

(8) Junction to ambient thermal resistance for the 14-lead VSON mounted on a PC board copper area using 12 vias to a second layer of

copper equal to die attach paddle. Additional copper area will reduce thermal resistance further. For layout recommendations, refer to

Application Note AN-1187 at www.ti.com/lsds/ti/analog/powermanagement/power_portal.page.

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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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Typical Performance Characteristics (continued)

Switching Frequency Feedback Pin Bias Current

Figure 10. Figure 11.

Continuous Mode Switching Waveforms Discontinuous Mode Switching Waveforms

VIN = 20V, VOUT = 5V, ILOAD = 5A VIN = 20V, VOUT = 5V, ILOAD = 500 mA

L = 10 μH, COUT = 400 μF, COUTESR = 13 mΩL = 10 μH, COUT = 400 μF, COUTESR = 13 mΩ

A. VSW Pin Voltage, 10 V/div. A. VSW Pin Voltage, 10 V/div.

B. Inductor Current, 2 A/div B. Inductor Current, 1 A/div

C. Output Ripple Voltage, 20 mV/div AC-Coupled C. Output Ripple Voltage, 20 mV/div AC-Coupled

Figure 12. Horizontal Time Base: 1 μs/div Figure 13. Horizontal Time Base: 1 μs/div

Load Transient Response for Continuous Mode Load Transient Response for Discontinuous Mode

VIN = 20V, VOUT = 5V VIN = 20V, VOUT = 5V,

L = 10 μH, COUT = 400 μF, COUTESR = 13 mΩL = 10 μH, COUT = 400 μF, COUTESR = 13 mΩ

A. Output Voltage, 100 mV/div, AC-Coupled. A. Output Voltage, 100 mV/div, AC-Coupled.

B. Load Current: 500 mA to 5A Load Pulse B. Load Current: 200 mA to 3A Load Pulse

Figure 14. Horizontal Time Base: 100 μs/div Figure 15. Horizontal Time Base: 200 μs/div

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Block Diagram

* Active Inductor Patent Number 5,514,947

† Active Capacitor Patent Number 5,382,918

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APPLICATION HINTS

The LM2679 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 LM2679 is part of the SIMPLE SWITCHER®family of power converters. A complete design uses a minimum

number of external components, which have been pre-determined from a variety of manufacturers. Using either

this data sheet or a design software program called LM267X Made Simple (version 2.0) a complete switching

power supply can be designed quickly. The software is provided free of charge and can be downloaded from

Texas Instruments Internet site located at http://www.ti.com.

SWITCH OUTPUT

This is the output of a power MOSFET switch connected directly to the input voltage. The switch provides energy

to an inductor, an output capacitor and the load circuitry under control of an internal pulse-width-modulator

(PWM). The PWM controller is internally clocked by a fixed 260KHz oscillator. In a standard step-down

application the duty cycle (Time ON/Time OFF) of the power switch is proportional to the ratio of the power

supply output voltage to the input voltage. The voltage on pin 1 switches between Vin (switch ON) and below

ground by the voltage drop of the external Schottky diode (switch OFF).

INPUT

The input voltage for the power supply is connected to pin 2. In addition to providing energy to the load the input

voltage also provides bias for the internal circuitry of the LM2679. For ensured performance the input voltage

must be in the range of 8V to 40V. For best performance of the power supply the input pin should always be

bypassed with an input capacitor located close to pin 2.

C BOOST

A capacitor must be connected from pin 3 to the switch output, pin 1. This capacitor boosts the gate drive to the

internal MOSFET above Vin to fully turn it ON. This minimizes conduction losses in the power switch to maintain

high efficiency. The recommended value for C Boost is 0.01μF.

GROUND

This is the ground reference connection for all components in the power supply. In fast-switching, high-current

applications such as those implemented with the LM2679, it is recommended that a broad ground plane be used

to minimize signal coupling throughout the circuit

CURRENT ADJUST

A key feature of the LM2679 is the ability to tailor the peak switch current limit to a level required by a particular

application. This alleviates the need to use external components that must be physically sized to accommodate

current levels (under shorted output conditions for example) that may be much higher than the normal circuit

operating current requirements.

A resistor connected from pin 5 to ground establishes a current (I(pin 5) = 1.2V / RADJ) that sets the peak current

through the power switch. The maximum switch current is fixed at a level of 37,125 / RADJ.

FEEDBACK

This is the input to a two-stage high gain amplifier, which drives the PWM controller. It is necessary to connect

pin 6 to the actual output of the power supply to set the dc output voltage. For the fixed output devices (3.3V, 5V

and 12V outputs), a direct wire connection to the output is all that is required as internal gain setting resistors are

provided inside the LM2679. For the adjustable output version two external resistors are required to set the dc

output voltage. For stable operation of the power supply it is important to prevent coupling of any inductor flux to

the feedback input.

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SOFTSTART

A capacitor connected from pin 7 to ground allows for a slow turn-on of the switching regulator. The capacitor

sets a time delay to gradually increase the duty cycle of the internal power switch. This can significantly reduce

the amount of surge current required from the input supply during an abrupt application of the input voltage. If

softstart is not required this pin should be left open circuited. Please see the CSS SOFTSTART CAPACITOR

section for further information regarding softstart capacitor values.

DAP (VSON PACKAGE)

The Die Attach Pad (DAP) can and should be connected to PCB Ground plane/island. For CAD and assembly

guidelines refer to Application Note AN-1187 at www.ti.com/lsds/ti/analog/powermanagement/power_portal.page.

DESIGN CONSIDERATIONS

Figure 16. Basic Circuit for Fixed Output Voltage Applications

Figure 17. Basic Circuit for Adjustable Output Voltage Applications

Power supply design using the LM2679 is greatly simplified by using recommended external components. A wide

range of inductors, capacitors and Schottky diodes from several manufacturers have been evaluated for use in

designs that cover the full range of capabilities (input voltage, output voltage and load current) of the LM2679. A

simple design procedure using nomographs and component tables provided in this data sheet leads to a working

design with very little effort. Alternatively, the design software, LM267X Made Simple (version 6.0), can also be

used to provide instant component selection, circuit performance calculations for evaluation, a bill of materials

component list and a circuit schematic.

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The individual components from the various manufacturers called out for use are still just a small sample of the

vast array of components available in the industry. While these components are recommended, they are not

exclusively the only components for use in a design. After a close comparison of component specifications,

equivalent devices from other manufacturers could be substituted for use in an application.

Important considerations for each external component and an explanation of how the nomographs and selection

tables were developed follows.

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). The magnitude of inductance is selected to maintain a maximum ripple current of 30% of the

maximum load current. If the ripple current exceeds this 30% limit the next larger value is selected.

The inductors offered have been specifically manufactured to provide proper operation under all operating

conditions of input and output voltage and load current. Several part types are offered for a given amount of

inductance. Both surface mount and through-hole devices are available. The inductors from each of the three

manufacturers have unique characteristics.

Renco: ferrite stick core inductors; benefits are typically lowest cost and can withstand ripple and transient peak

currents above the rated value. These inductors have an external magnetic field, which may generate EMI.

Pulse Engineering: powdered iron toroid core inductors; these also can withstand higher than rated currents and,

being toroid inductors, will have low EMI.

Coilcraft: ferrite drum core inductors; these are the smallest physical size inductors and are available only as

surface mount components. These inductors also generate EMI but less than stick inductors.

OUTPUT CAPACITOR

The output capacitor acts to smooth the dc output voltage and also provides energy storage. Selection of an

output capacitor, with an associated equivalent series resistance (ESR), impacts both the amount of output ripple

voltage and stability of the control loop.

The output ripple voltage of the power supply is the product of the capacitor ESR and the inductor ripple current.

The capacitor types recommended in the tables were selected for having low ESR ratings.

In addition, both surface mount tantalum capacitors and through-hole aluminum electrolytic capacitors are offered

as solutions.

Impacting frequency stability of the overall control loop, the output capacitance, in conjunction with the inductor,

creates a double pole inside the feedback loop. In addition the capacitance and the ESR value create a zero.

These frequency response effects together with the internal frequency compensation circuitry of the LM2679

modify the gain and phase shift of the closed loop system.

As a general rule for stable switching regulator circuits it is desired to have the unity gain bandwidth of the circuit

to be limited to no more than one-sixth of the controller switching frequency. With the fixed 260KHz switching

frequency of the LM2679, the output capacitor is selected to provide a unity gain bandwidth of 40KHz maximum.

Each recommended capacitor value has been chosen to achieve this result.

In some cases multiple capacitors are required either to reduce the ESR of the output capacitor, to minimize

output ripple (a ripple voltage of 1% of Vout or less is the assumed performance condition), or to increase the

output capacitance to reduce the closed loop unity gain bandwidth (to less than 40KHz). When parallel

combinations of capacitors are required it has been assumed that each capacitor is the exact same part type.

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The RMS current and working voltage (WV) ratings of the output capacitor are also important considerations. In a

typical step-down switching regulator, the inductor ripple current (set to be no more than 30% of the maximum

load current by the inductor selection) is the current that flows through the output capacitor. The capacitor RMS

current rating must be greater than this ripple current. The voltage rating of the output capacitor should be

greater than 1.3 times the maximum output voltage of the power supply. If operation of the system at elevated

temperatures is required, the capacitor voltage rating may be de-rated to less than the nominal room temperature

rating. Careful inspection of the manufacturer's specification for de-rating of working voltage with temperature is

important.

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. The RMS current flowing through the input capacitor is equal to one-half of the maximum dc load current

so the capacitor should be rated to handle this. Paralleling multiple capacitors proportionally increases the

current rating of the total capacitance. The voltage rating should also be selected to be 1.3 times the maximum

input voltage. Depending on the unregulated input power source, under light load conditions the maximum input

voltage could be significantly higher than normal operation and should be considered when selecting an input

capacitor.

The input capacitor should be placed very close to the input pin of the LM2679. Due to relative high current

operation with fast transient changes, the series inductance of input connecting wires or PCB traces can create

ringing signals at the input terminal which could possibly propagate to the output or other parts of the circuitry. It

may be necessary in some designs to add a small valued (0.1μF to 0.47μF) ceramic type capacitor in parallel

with the input capacitor to prevent or minimize any ringing.

CATCH DIODE

When the power switch in the LM2679 turns OFF, the current through the inductor continues to flow. The path for

this current is through the diode connected between the switch output and ground. This forward biased diode

clamps the switch output to a voltage less than ground. This negative voltage must be greater than −1V so a low

voltage drop (particularly at high current levels) Schottky diode is recommended. Total efficiency of the entire

power supply is significantly impacted by the power lost in the output catch diode. The average current through

the catch diode is dependent on the switch duty cycle (D) and is equal to the load current times (1-D). Use of a

diode rated for much higher current than is required by the actual application helps to minimize the voltage drop

and power loss in the diode.

During the switch ON time the diode will be reversed biased by the input voltage. The reverse voltage rating of

the diode should be at least 1.3 times greater than the maximum input voltage.

BOOST CAPACITOR

The boost capacitor creates a voltage used to overdrive the gate of the internal power MOSFET. This improves

efficiency by minimizing the on resistance of the switch and associated power loss. For all applications it is

recommended to use a 0.01μF/50V ceramic capacitor.

RADJ, ADJUSTABLE CURRENT LIMIT

A key feature of the LM2679 is the ability to control the peak switch current. Without this feature the peak switch

current would be internally set to 7A or higher to accommodate 5A load current designs. This requires that both

the inductor (which could saturate with excessively high currents) and the catch diode be able to safely handle

up to 7A which would be conducted under load fault conditions.

If an application only requires a load current of 3A or 4A the peak switch current can be set to a limit just over the

maximum load current with the addition of a single programming resistor. This allows the use of less powerful

and more cost effective inductors and diodes.

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The peak switch current is equal to a factor of 37,125 divided by RADJ. A resistance of 5.6KΩsets the current

limit to typically 6.3A and an RADJ of 8.25KΩreduces the maximum current to approximately 4.4A. For

predictable control of the current limit it is recommended to keep the peak switch current greater than 3A. For

lower current applications a 3A switching regulator with adjustable current limit, the LM2673, is available.

When the power switch reaches the current limit threshold it is immediately turned OFF and the internal switching

frequency is reduced. This extends the OFF time of the switch to prevent a steady state high current condition.

As the switch current falls below the current limit threshold, the switch will turn back ON. If a load fault continues,

the switch will again exceed the threshold and switch back OFF. This will result in a low duty cycle pulsing of the

power switch to minimize the overall fault condition power dissipation.

CSS SOFTSTART CAPACITOR

This optional capacitor controls the rate at which the LM2679 starts up at power on. The capacitor is charged

linearly by an internal current source. This voltage ramp gradually increases the duty cycle of the power switch

until it reaches the normal operating duty cycle defined primarily by the ratio of the output voltage to the input

voltage. The softstart turn-on time is programmable by the selection of Css.

The formula for selecting a softstart capacitor is:

(1)

Where:

ISST = Softstart Current, 3.7μA typical

tSS = Softstart time, from design requirements

VSST = Softstart Threshold Voltage, 0.63V typical

VOUT = Output Voltage, from design requirements

VSCHOTTKY = Schottky Diode Voltage Drop, typically 0.5V

VIN = Maximum Input Voltage, from design requirements

If this feature is not desired, leave the Softstart pin (pin 7) open circuited

With certain softstart capacitor values and operating conditions, the LM2679 can exhibit an overshoot on the

output voltage during turn on. Especially when starting up into no load or low load, the softstart function may not

be effective in preventing a larger voltage overshoot on the output. With larger loads or lower input voltages

during startup this effect is minimized. In particular, avoid using softstart capacitors between 0.033µF and 1µF.

ADDITIONAL APPLICATION INFORMATION

When the output voltage is greater than approximately 6V, and the duty cycle at minimum input voltage is greater

than approximately 50%, the designer should exercise caution in selection of the output filter components. When

an application designed to these specific operating conditions is subjected to a current limit fault condition, it may

be possible to observe a large hysteresis in the current limit. This can affect the output voltage of the device until

the load current is reduced sufficiently to allow the current limit protection circuit to reset itself.

Under current limiting conditions, the LM267x is designed to respond in the following manner:

1. At the moment when the inductor current reaches the current limit threshold, the ON-pulse is immediately

terminated. This happens for any application condition.

2. However, the current limit block is also designed to momentarily reduce the duty cycle to below 50% to avoid

subharmonic oscillations, which could cause the inductor to saturate.

3. Thereafter, once the inductor current falls below the current limit threshold, there is a small relaxation time

during which the duty cycle progressively rises back above 50% to the value required to achieve regulation.

If the output capacitance is sufficiently ‘large’, it may be possible that as the output tries to recover, the output

capacitor charging current is large enough to repeatedly re-trigger the current limit circuit before the output has

fully settled. This condition is exacerbated with higher output voltage settings because the energy requirement of

the output capacitor varies as the square of the output voltage (½CV2), thus requiring an increased charging

current.

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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. It should be noted that even with these components, for a

device’s current limit of ICLIM, the maximum load current under which the possibility of the large current limit

hysteresis can be minimized is ICLIM/2. For example, if the input is 24V and the set output voltage is 18V, then for

a desired maximum current of 1.5A, the current limit of the chosen switcher must be confirmed to be at least 3A.

Under extreme over-current or short circuit conditions, the LM267X employs frequency foldback in addition to the

current limit. If the cycle-by-cycle inductor current increases above the current limit threshold (due to short circuit

or inductor saturation for example) the switching frequency will be automatically reduced to protect the IC.

Frequency below 100 KHz is typical for an extreme short circuit condition.

SIMPLE DESIGN PROCEDURE

Using the nomographs and tables in this data sheet (or use the available design software at http://www.ti.com) a

complete step-down regulator can be designed in a few simple steps.

Step 1: Define the power supply operating conditions:

Required output voltage

Maximum DC input voltage

Maximum output load current

Step 2: Set the output voltage by selecting a fixed output LM2679 (3.3V, 5V or 12V applications) or determine

the required feedback resistors for use with the adjustable LM2679−ADJ

Step 3: Determine the inductor required by using one of the four nomographs, Figure 18 through Figure 21.

Table 1 provides a specific manufacturer and part number for the inductor.

Step 4: Using Table 6 and Table 7 (fixed output voltage) or Table 12 and Table 13 (adjustable output voltage),

determine the output capacitance required for stable operation. Table 3 and Table 4 provide the specific

capacitor type from the manufacturer of choice.

Step 5: Determine an input capacitor from Table 8 and Table 9 for fixed output voltage applications. Use Table 3

and Table 4 to find the specific capacitor type. For adjustable output circuits select a capacitor from Table 3 and

Table 4 with a sufficient working voltage (WV) rating greater than Vin max, and an rms current rating greater than

one-half the maximum load current (2 or more capacitors in parallel may be required).

Step 6: Select a diode from Table 10. The current rating of the diode must be greater than I load max and the

Reverse Voltage rating must be greater than Vin max.

Step 7: Include a 0.01μF/50V capacitor for Cboost in the design and then determine the value of a softstart

capacitor if desired.

Step 8: Define a value for RADJ to set the peak switch current limit to be at least 20% greater than Iout max to

allow for at least 30% inductor ripple current (±15% of Iout). For designs that must operate over the full

temperature range the switch current limit should be set to at least 50% greater than Iout max (1.5 x Iout max).

FIXED OUTPUT VOLTAGE DESIGN EXAMPLE

A system logic power supply bus of 3.3V is to be generated from a wall adapter which provides an unregulated

DC voltage of 13V to 16V. The maximum load current is 4A. A softstart delay time of 50mS is desired. Through-

hole components are preferred.

Step 1: Operating conditions are:

Vout = 3.3V

Vin max = 16V

Iload max = 4A

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Step 2: Select an LM2679T-3.3. The output voltage will have a tolerance of

±2% at room temperature and ±3% over the full operating temperature range.

Step 3: Use the nomograph for the 3.3V device, Figure 18. The intersection of the 16V horizontal line (Vin max)

and the 4A vertical line (Iload max) indicates that L46, a 15μH inductor, is required.

From Table 1, L46 in a through-hole component is available from Renco with part number RL-1283-15-43.

Step 4: Use Table 6 and Table 7 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 and Table 4 provide the actual capacitor characteristics. Any of the

following choices will work in the circuit:

2 x 220μF/10V Sanyo OS-CON (code C5)

2 x 820μF/16V Sanyo MV-GX (code C5)

1 x 3900μF/10V Nichicon PL (code C7)

2 x 560μF/35V Panasonic HFQ (code C5)

Step 5: Use Table 8 and Table 9 to select an input capacitor. With 3.3V output and 15μH there are three

through-hole solutions. These capacitors provide a sufficient voltage rating and an rms current rating greater than

2A (1/2 Iload max). Again using Table 3 and Table 4 for specific component characteristics the following choices

are suitable:

2 x 680μF/63V Sanyo MV-GX (code C13)

1 x 1200μF/63V Nichicon PL (code C25)

1 x 1500μF/63V Panasonic HFQ (code C16)

Step 6: From Table 10, a 5A or more Schottky diode must be selected. For through-hole components only 40V

rated diodes are indicated and 4 part types are suitable:

1N5825

MBR745

80SQ045

6TQ045

Step 7: A 0.01μF capacitor will be used for Cboost. For the 50mS softstart delay the following parameters are to

be used:

ISST: 3.7μA

tSS: 50mS

VSST: 0.63V

VOUT: 3.3V

VSCHOTTKY: 0.5V

VIN: 16V

Using Vin max ensures that the softstart delay time will be at least the desired 50mS.

Using the formula for Css a value of 0.148μF is determined to be required. Use of a standard value 0.22μF

capacitor will produce more than sufficient softstart delay.

Step 8: Determine a value for RADJ to provide a peak switch current limit of at least 4A plus 50% or 6A.

(2)

Use a value of 6.2KΩ.

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ADJUSTABLE OUTPUT DESIGN EXAMPLE

In this example it is desired to convert the voltage from a two battery automotive power supply (voltage range of

20V to 28V, typical in large truck applications) to the 14.8VDC alternator supply typically used to power electronic

equipment from single battery 12V vehicle systems. The load current required is 3.5A maximum. It is also

desired to implement the power supply with all surface mount components. Softstart is not required.

Step 1: Operating conditions are:

Vout = 14.8V

Vin max = 28V

Iload max = 3.5A

Step 2: Select an LM2679S-ADJ. To set the output voltage to 14.9V two resistors need to be chosen (R1 and R2

in Figure 17). For the adjustable device the output voltage is set by the following relationship:

(3)

Where VFB is the feedback voltage of typically 1.21V.

A recommended value to use for R1 is 1K. In this example then R2 is determined to be:

(4)

R2 = 11.23KΩ

The closest standard 1% tolerance value to use is 11.3KΩ

This will set the nominal output voltage to 14.88V which is within 0.5% of the target value.

Step 3: To use the nomograph for the adjustable device, Figure 21, requires a calculation of the inductor

Volt•microsecond constant (E•T expressed in V•μS) from the following formula:

(5)

where VSAT is the voltage drop across the internal power switch which is Rds(ON) times Iload. In this example this

would be typically 0.12Ωx 3.5A or 0.42V and VDis the voltage drop across the forward bisased Schottky diode,

typically 0.5V. The switching frequency of 260KHz is the nominal value to use to estimate the ON time of the

switch during which energy is stored in the inductor.

For this example E•T is found to be:

(6)

(7)

Using Figure 21, the intersection of 27V•μS horizontally and the 3.5A vertical line (Iload max) indicates that L48 , a

47μH inductor, or L49, a 33μH inductor could be used. Either inductor will be suitable, but for this example

selecting the larger inductance will result in lower ripple current.

From Table 1, L48 in a surface mount component is available from Pulse Engineering with part number P0848.

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Step 4: Use Table 12 and Table 13 to determine an output capacitor. With a 14.8V output the 12.5 to 15V row is

used and with a 47μH inductor there are three surface mount output capacitor solutions. Table 3 and Table 4

provide the actual capacitor characteristics based on the C Code number. Any of the following choices can be

used:

1 x 33μF/20V AVX TPS (code C6)

1 x 47μF/20V Sprague 594 (code C8)

1 x 47μF/20V Kemet T495 (code C8)

NOTE

When using the adjustable device in low voltage applications (less than 3V output), if the

nomograph, Figure 21, selects an inductance of 22μH or less, Table 12 and Table 13 do

not provide an output capacitor solution. With these conditions the number of output

capacitors required for stable operation becomes impractical. It is recommended to use

either a 33μH or 47μH inductor and the output capacitors from Table 12 and Table 13.

Step 5: An input capacitor for this example will require at least a 35V WV rating with an rms current rating of

1.75A (1/2 Iout max). From Table 3 and Table 4, it can be seen that C12, a 33μF/35V capacitor from Sprague,

has the highest voltage/current rating of the surface mount components and that two of these capacitor in parallel

will be adequate.

Step 6: From Table 10, a 5A or more Schottky diode must be selected. For surface mount diodes with a margin

of safety on the voltage rating one of two diodes can be used:

MBRD1545CT

6TQ045S

Step 7: A 0.01μF capacitor will be used for Cboost.

The softstart pin will be left open circuited.

Step 8: Determine a value for RADJ to provide a peak switch current limit of at least 3.5A plus 50% or 5.25A.

(8)

Use a value of 7.15KΩ.

VSON PACKAGE DEVICES

The LM2679 is offered in the 14 lead VSON surface mount package to allow for a significantly decreased

footprint with equivalent power dissipation compared to the DDPAK.

The Die Attach Pad (DAP) can and should be connected to PCB Ground plane/island. For CAD and assembly

guidelines refer to Application Note AN-1187 at www.ti.com/lsds/ti/analog/powermanagement/power_portal.page.

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Inductor Selection Guides

For Continuous Mode Operation

Figure 18. LM2679-3.3 Figure 19. LM2679-5.0

Figure 20. LM2679-12 Figure 21. LM2679-ADJ

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Table 1. Inductor Manufacturer Part Numbers

Inductor Renco Pulse Engineering Coilcraft

Inductance Current

Reference Through Hole Surface Mount Through Hole Surface Mount Surface Mount

(µH) (A)

Number

L23 33 1.35 RL-5471-7 RL1500-33 PE-53823 PE-53823S DO3316-333

L24 22 1.65 RL-1283-22-43 RL1500-22 PE-53824 PE-53824S DO3316-223

L25 15 2.00 RL-1283-15-43 RL1500-15 PE-53825 PE-53825S DO3316-153

L29 100 1.41 RL-5471-4 RL-6050-100 PE-53829 PE-53829S DO5022P-104

L30 68 1.71 RL-5471-5 RL6050-68 PE-53830 PE-53830S DO5022P-683

L31 47 2.06 RL-5471-6 RL6050-47 PE-53831 PE-53831S DO5022P-473

L32 33 2.46 RL-5471-7 RL6050-33 PE-53932 PE-53932S DO5022P-333

L33 22 3.02 RL-1283-22-43 RL6050-22 PE-53933 PE-53933S DO5022P-223

L34 15 3.65 RL-1283-15-43 — PE-53934 PE-53934S DO5022P-153

L38 68 2.97 RL-5472-2 — PE-54038 PE-54038S —

L39 47 3.57 RL-5472-3 — PE-54039 PE-54039S —

L40 33 4.26 RL-1283-33-43 — PE-54040 PE-54040S —

L41 22 5.22 RL-1283-22-43 — PE-54041 P0841 —

L44 68 3.45 RL-5473-3 — PE-54044 — —

L45 10 4.47 RL-1283-10-43 — — P0845 DO5022P-103HC

L46 15 5.60 RL-1283-15-43 — — P0846 DO5022P-153HC

L47 10 5.66 RL-1283-10-43 — — P0847 DO5022P-103HC

L48 47 5.61 RL-1282-47-43 — — P0848 —

L49 33 5.61 RL-1282-33-43 — — P0849 —

Table 2. Inductor Manufacturer Contact Numbers

Coilcraft Phone (800) 322-2645

FAX (708) 639-1469

Coilcraft, Europe Phone +44 1236 730 595

FAX +44 1236 730 627

Pulse Engineering Phone (619) 674-8100

FAX (619) 674-8262

Pulse Engineering, Phone +353 93 24 107

Europe FAX +353 93 24 459

Renco Electronics Phone (800) 645-5828

FAX (516) 586-5562

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Capacitor Selection Guides

Table 3. Input and Output Capacitor Codes—Surface Mount

Surface Mount

Capacitor

Reference AVX TPS Series Sprague 594D Series Kemet T495 Series

Code 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 1.35 100 10 1.1

C5 100 16 1.15 47 16 1 150 10 1.1

C6 33 20 0.77 100 16 1.3 220 10 1.1

C7 68 20 0.94 180 16 1.95 33 20 0.78

C8 22 25 0.77 47 20 1.15 47 20 0.94

C9 10 35 0.63 33 25 1.05 68 20 0.94

C10 22 35 0.66 68 25 1.6 10 35 0.63

C11 15 35 0.75 22 35 0.63

C12 33 35 1 4.7 50 0.66

C13 15 50 0.9

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Table 4. Input and Output Capacitor Codes—Through Hole

Through Hole

Capacitor Sanyo OS-CON SA Series Sanyo MV-GX Series Nichicon PL Series Panasonic HFQ Series

Reference Irms Irms Irms Irms

Code C (µF) WV (V) (A) C (µF) WV (V) (A) C (µF) WV (V) (A) C (µF) WV (V) (A)

C1 47 6.3 1 1000 6.3 0.8 680 10 0.8 82 35 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 0.75 1000 10 1.06 220 35 0.76

C4 100 10 1.87 560 16 0.95 1200 10 1.28 330 35 1.01

C5 220 10 2.36 820 16 1.25 2200 10 1.71 560 35 1.4

C6 33 16 0.96 1000 16 1.3 3300 10 2.18 820 35 1.62

C7 100 16 1.92 150 35 0.65 3900 10 2.36 1000 35 1.73

C8 150 16 2.28 470 35 1.3 6800 10 2.68 2200 35 2.8

C9 100 20 2.25 680 35 1.4 180 16 0.41 56 50 0.36

C10 47 25 2.09 1000 35 1.7 270 16 0.55 100 50 0.5

C11 220 63 0.76 470 16 0.77 220 50 0.92

C12 470 63 1.2 680 16 1.02 470 50 1.44

C13 680 63 1.5 820 16 1.22 560 50 1.68

C14 1000 63 1.75 1800 16 1.88 1200 50 2.22

C15 220 25 0.63 330 63 1.42

C16 220 35 0.79 1500 63 2.51

C17 560 35 1.43

C18 2200 35 2.68

C19 150 50 0.82

C20 220 50 1.04

C21 330 50 1.3

C22 100 63 0.75

C23 390 63 1.62

C24 820 63 2.22

C25 1200 63 2.51

Table 5. Capacitor Manufacturer Contact Numbers

Nichicon Phone (847) 843-7500

FAX (847) 843-2798

Panasonic Phone (714) 373-7857

FAX (714) 373-7102

AVX Phone (845) 448-9411

FAX (845) 448-1943

Sprague/Vishay Phone (207) 324-4140

FAX (207) 324-7223

Sanyo Phone (619) 661-6322

FAX (619) 661-1055

Kemet Phone (864) 963-6300

FAX (864) 963-6521

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Table 6. Output Capacitors for Fixed Output Voltage Application—Surface Mount(1)(2)

Surface Mount

Output Voltage (V) Inductance (µH) AVX TPS Series Sprague 594D Series Kemet T495 Series

No. C Code No. C Code No. C Code

10 5 C1 5 C1 5 C2

15 4 C1 4 C1 4 C3

3.3 22 3 C2 2 C7 3 C4

33 1 C1 2 C7 3 C4

10 4 C2 4 C6 4 C4

15 3 C3 2 C7 3 C5

522 3 C2 2 C7 3 C4

33 2 C2 2 C3 2 C4

47 2 C2 1 C7 2 C4

10 4 C5 3 C6 5 C9

15 3 C5 2 C7 4 C9

22 2 C5 2 C6 3 C8

12 33 2 C5 1 C7 3 C8

47 2 C4 1 C6 2 C8

68 1 C5 1 C5 2 C7

100 1 C4 1 C5 1 C8

(1) No. represents the number of identical capacitor types to be connected in parallel.

(2) C Code indicates the Capacitor Reference number in Table 3 and Table 4 for identifying the specific component from the manufacturer.

Table 7. Output Capacitors for Fixed Output Voltage Application—Through Hole(1)(2)

Through Hole

Sanyo OS-CON SA Sanyo MV-GX Panasonic HFQ

Output Voltage (V) Inductance (µH) Nichicon PL Series

Series Series Series

No. C Code No. C Code No. C Code No. C Code

10 2 C5 2 C6 1 C8 2 C6

15 2 C5 2 C5 1 C7 2 C5

3.3 22 1 C5 1 C10 1 C5 1 C7

33 1 C5 1 C10 1 C5 1 C7

10 2 C4 2 C5 1 C6 2 C5

15 1 C5 1 C10 1 C5 1 C7

522 1 C5 1 C9 1 C5 1 C5

33 1 C4 1 C5 1 C4 1 C4

47 1 C4 1 C4 1 C2 2 C4

10 2 C7 1 C10 1 C14 2 C4

15 1 C8 1 C6 1 C17 1 C5

22 1 C7 1 C5 1 C13 1 C5

12 33 1 C7 1 C4 1 C12 1 C4

47 1 C7 1 C3 1 C11 1 C3

68 1 C6 1 C2 1 C10 1 C3

100 1 C6 1 C2 1 C9 1 C1

(1) No. represents the number of identical capacitor types to be connected in parallel.

(2) C Code indicates the Capacitor Reference number in Table 3 and Table 4 for identifying the specific component from the manufacturer.

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Table 8. Input Capacitors for Fixed Output Voltage Application—Surface Mount(1)(2)(3)

Surface Mount

Output Voltage (V) Inductance (µH) AVX TPS Series Sprague 594D Series Kemet T495 Series

No. C Code No. C Code No. C Code

10 3 C7 2 C10 3 C9

15 See(4) See(4) 3 C13 4 C12

3.3 22 See(4) See(4) 2 C13 3 C12

33 See(4) See(4) 2 C13 3 C12

10 3 C4 2 C6 3 C9

15 4 C9 3 C12 4 C10

522 See(4) See(4) 3 C13 4 C12

33 See(4) See(4) 2 C13 3 C12

47 See(4) See(4) 1 C13 2 C12

10 4 C9 2 C10 4 C10

15 4 C8 2 C10 4 C10

22 4 C9 3 C12 4 C10

12 33 See(4) See(4) 3 C13 4 C12

47 See(4) See(4) 2 C13 3 C12

68 See(4) See(4) 2 C13 2 C12

100 See(4) See(4) 1 C13 2 C12

(1) No. represents the number of identical capacitor types to be connected in parallel.

(2) C Code indicates the Capacitor Reference number in Table 3 and Table 4 for identifying the specific component from the manufacturer.

(3) Assumes worst case maximum input voltage and load current for a given inductance value

(4) Check voltage rating of capacitors to be greater than application input voltage.

Table 9. Input Capacitors for Fixed Output Voltage Application—Through Hole(1)(2)(3)

Through Hole

Sanyo OS-CON SA Sanyo MV-GX Panasonic HFQ

Output Voltage (V) Inductance (µH) Nichicon PL Series

Series Series Series

No. C Code No. C Code No. C Code No. C Code

10 2 C9 2 C8 1 C18 1 C8

15 See(4) See(4) 2 C13 1 C25 1 C16

3.3 22 See(4) See(4) 1 C14 1 C24 1 C16

33 See(4) See(4) 1 C14 1 C24 1 C16

10 2 C7 2 C8 1 C25 1 C8

15 See(4) See(4) 2 C8 1 C25 1 C8

522 See(4) See(4) 2 C13 1 C25 1 C16

33 See(4) See(4) 1 C14 1 C23 1 C13

47 See(4) See(4) 1 C12 1 C19 1 C11

10 2 C10 2 C8 1 C18 1 C8

15 2 C10 2 C8 1 C18 1 C8

22 See(4) See(4) 2 C8 1 C18 1 C8

12 33 See(4) See(4) 2 C12 1 C24 1 C14

47 See(4) See(4) 1 C14 1 C23 1 C13

68 See(4) See(4) 1 C13 1 C21 1 C15

100 See(4) See(4) 1 C11 1 C22 1 C11

(1) No. represents the number of identical capacitor types to be connected in parallel.

(2) C Code indicates the Capacitor Reference number in Table 3 and Table 4 for identifying the specific component from the manufacturer.

(3) Assumes worst case maximum input voltage and load current for a given inductance value

(4) Check voltage rating of capacitors to be greater than application input voltage.

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Table 10. Schottky Diode Selection Table

Reverse Surface Mount Through Hole

Voltage (V) 3A 5A or More 3A 5A or More

20V SK32 1N5820

SR302

30V SK33 MBRD835L 1N5821

30WQ03F 31DQ03

40V 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. Diode Manufacturer Contact Numbers

International Rectifier Phone (310) 322-3331

FAX (310) 322-3332

Motorola Phone (800) 521-6274

FAX (602) 244-6609

General Semiconductor Phone (516) 847-3000

FAX (516) 847-3236

Diodes, Inc. Phone (805) 446-4800

FAX (805) 446-4850

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Table 12. Output Capacitors for Adjustable Output Voltage Applications—Surface Mount(1)(2)

Surface Mount

Output Voltage (V) Inductance (µH) AVX TPS Series Sprague 594D Series Kemet T495 Series

No. C Code No. C Code No. C Code

33(3) 7 C1 6 C2 7 C3

1.21 to 2.50 47(3) 5 C1 4 C2 5 C3

33(3) 4 C1 3 C2 4 C3

2.5 to 3.75 47(3) 3 C1 2 C2 3 C3

22 4 C1 3 C2 4 C3

3.75 to 5 33 3 C1 2 C2 3 C3

47 2 C1 2 C2 2 C3

22 3 C2 3 C3 3 C4

33 2 C2 2 C3 2 C4

5 to 6.25 47 2 C2 2 C3 2 C4

68 1 C2 1 C3 1 C4

22 3 C2 1 C4 3 C4

33 2 C2 1 C3 2 C4

6.25 to 7.5 47 1 C3 1 C4 1 C6

68 1 C2 1 C3 1 C4

33 2 C5 1 C6 2 C8

47 1 C5 1 C6 2 C8

7.5 to 10 68 1 C5 1 C6 1 C8

100 1 C4 1 C5 1 C8

33 1 C5 1 C6 2 C8

47 1 C5 1 C6 2 C8

10 to 12.5 68 1 C5 1 C6 1 C8

100 1 C5 1 C6 1 C8

33 1 C6 1 C8 1 C8

47 1 C6 1 C8 1 C8

12.5 to 15 68 1 C6 1 C8 1 C8

100 1 C6 1 C8 1 C8

33 1 C8 1 C10 2 C10

47 1 C8 1 C9 2 C10

15 to 20 68 1 C8 1 C9 2 C10

100 1 C8 1 C9 1 C10

33 2 C9 2 C11 2 C11

47 1 C10 1 C12 1 C11

20 to 30 68 1 C9 1 C12 1 C11

100 1 C9 1 C12 1 C11

10 4 C13 8 C12

15 3 C13 5 C12

22 2 C13 4 C12

30 to 37 No Values Available

33 1 C13 3 C12

47 1 C13 2 C12

68 1 C13 2 C12

(1) No. represents the number of identical capacitor types to be connected in parallel.

(2) C Code indicates the Capacitor Reference number in Table 3 and Table 4 for identifying the specific component from the manufacturer.

(3) Set to a higher value for a practical design solution. See Application Hints section.

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Table 13. Output Capacitors for Adjustable Output Voltage Applications—Through Hole(1)(2)

Through Hole

Sanyo OS-CON SA Sanyo MV-GX Panasonic HFQ

Output Voltage (V) Inductance (µH) Nichicon PL Series

Series Series Series

No. C Code No. C Code No. C Code No. C Code

33(3) 2 C3 5 C1 5 C3 3 C

1.21 to 2.50 47(3) 2 C2 4 C1 3 C3 2 C5

33(3) 1 C3 3 C1 3 C1 2 C5

2.5 to 3.75 47(3) 1 C2 2 C1 2 C3 1 C5

22 1 C3 3 C1 3 C1 2 C5

3.75 to 5 33 1 C2 2 C1 2 C1 1 C5

47 1 C2 2 C1 1 C3 1 C5

22 1 C5 2 C6 2 C3 2 C5

33 1 C4 1 C6 2 C1 1 C5

5 to 6.25 47 1 C4 1 C6 1 C3 1 C5

68 1 C4 1 C6 1 C1 1 C5

22 1 C5 1 C6 2 C1 1 C5

33 1 C4 1 C6 1 C3 1 C5

6.25 to 7.5 47 1 C4 1 C6 1 C1 1 C5

68 1 C4 1 C2 1 C1 1 C5

33 1 C7 1 C6 1 C14 1 C5

47 1 C7 1 C6 1 C14 1 C5

7.5 to 10 68 1 C7 1 C2 1 C14 1 C2

100 1 C7 1 C2 1 C14 1 C2

33 1 C7 1 C6 1 C14 1 C5

47 1 C7 1 C2 1 C14 1 C5

10 to 12.5 68 1 C7 1 C2 1 C9 1 C2

100 1 C7 1 C2 1 C9 1 C2

33 1 C9 1 C10 1 C15 1 C2

47 1 C9 1 C10 1 C15 1 C2

12.5 to 15 68 1 C9 1 C10 1 C15 1 C2

100 1 C9 1 C10 1 C15 1 C2

33 1 C10 1 C7 1 C15 1 C2

47 1 C10 1 C7 1 C15 1 C2

15 to 20 68 1 C10 1 C7 1 C15 1 C2

100 1 C10 1 C7 1 C15 1 C2

33 1 C7 1 C16 1 C2

47 1 C7 1 C16 1 C2

20 to 30 No Values Available

68 1 C7 1 C16 1 C2

100 1 C7 1 C16 1 C2

10 1 C12 1 C20 1 C10

15 1 C11 1 C20 1 C11

22 1 C11 1 C20 1 C10

30 to 37 No Values Available

33 1 C11 1 C20 1 C10

47 1 C11 1 C20 1 C10

68 1 C11 1 C20 1 C10

(1) No. represents the number of identical capacitor types to be connected in parallel.

(2) C Code indicates the Capacitor Reference number in Table 3 and Table 4 for identifying the specific component from the manufacturer.

(3) Set to a higher value for a practical design solution. See Application Hints section.

Product Folder Links: LM2679

LM2679

SNVS026N –MARCH 2000–REVISED APRIL 2013

www.ti.com

REVISION HISTORY

Changes from Revision M (April 2013) to Revision N Page

• Changed layout of National Data Sheet to TI format .......................................................................................................... 26

Product Folder Links: LM2679

PACKAGE OPTION ADDENDUM

www.ti.com 1-Nov-2013

Addendum-Page 1

PACKAGING INFORMATION

Orderable Device Status

(1)

Package Type Package

Drawing Pins Package

Qty Eco Plan

(2)

Lead/Ball Finish

(6)

MSL Peak Temp

(3)

Op Temp (°C) Device Marking

(4/5)

Samples

LM2679S-12/NOPB ACTIVE DDPAK/

TO-263 KTW 7 45 Pb-Free (RoHS

Exempt) CU SN Level-3-245C-168 HR -40 to 125 LM2679

S-12

LM2679S-3.3 NRND DDPAK/

TO-263 KTW 7 45 TBD Call TI Call TI -40 to 125 LM2679

S-3.3

LM2679S-3.3/NOPB ACTIVE DDPAK/

TO-263 KTW 7 45 Pb-Free (RoHS

Exempt) CU SN Level-3-245C-168 HR -40 to 125 LM2679

S-3.3

LM2679S-5.0 NRND DDPAK/

TO-263 KTW 7 45 TBD Call TI Call TI -40 to 125 LM2679

S-5.0

LM2679S-5.0/NOPB ACTIVE DDPAK/

TO-263 KTW 7 45 Pb-Free (RoHS

Exempt) CU SN Level-3-245C-168 HR -40 to 125 LM2679

S-5.0

LM2679S-ADJ NRND DDPAK/

TO-263 KTW 7 45 TBD Call TI Call TI -40 to 125 LM2679

S-ADJ

LM2679S-ADJ/NOPB ACTIVE DDPAK/

TO-263 KTW 7 45 Pb-Free (RoHS

Exempt) CU SN Level-3-245C-168 HR -40 to 125 LM2679

S-ADJ

LM2679SD-12 ACTIVE VSON NHM 14 250 TBD Call TI Call TI -40 to 125 S0003FB

LM2679SD-3.3/NOPB ACTIVE VSON NHM 14 250 Green (RoHS

& no Sb/Br) CU SN Level-1-260C-UNLIM -40 to 125 S0003HB

LM2679SD-5.0 NRND VSON NHM 14 250 TBD Call TI Call TI -40 to 125 S0003JB

LM2679SD-5.0/NOPB ACTIVE VSON NHM 14 250 Green (RoHS

& no Sb/Br) CU SN Level-1-260C-UNLIM -40 to 125 S0003JB

LM2679SD-ADJ/NOPB ACTIVE VSON NHM 14 250 Green (RoHS

& no Sb/Br) CU SN Level-1-260C-UNLIM -40 to 125 S0003KB

LM2679SDX-3.3/NOPB ACTIVE VSON NHM 14 2500 Green (RoHS

& no Sb/Br) CU SN Level-1-260C-UNLIM -40 to 125 S0003HB

LM2679SDX-ADJ/NOPB ACTIVE VSON NHM 14 2500 Green (RoHS

& no Sb/Br) CU SN Level-1-260C-UNLIM -40 to 125 S0003KB

LM2679SX-12/NOPB ACTIVE DDPAK/

TO-263 KTW 7 500 Pb-Free (RoHS

Exempt) CU SN Level-3-245C-168 HR -40 to 125 LM2679

S-12

LM2679SX-3.3/NOPB ACTIVE DDPAK/

TO-263 KTW 7 500 Pb-Free (RoHS

Exempt) CU SN Level-3-245C-168 HR -40 to 125 LM2679

S-3.3

LM2679SX-5.0 NRND DDPAK/

TO-263 KTW 7 500 TBD Call TI Call TI -40 to 125 LM2679

S-5.0

PACKAGE OPTION ADDENDUM

www.ti.com 1-Nov-2013

Addendum-Page 2

Orderable Device Status

(1)

Package Type Package

Drawing Pins Package

Qty Eco Plan

(2)

Lead/Ball Finish

(6)

MSL Peak Temp

(3)

Op Temp (°C) Device Marking

(4/5)

Samples

LM2679SX-5.0/NOPB ACTIVE DDPAK/

TO-263 KTW 7 500 Pb-Free (RoHS

Exempt) CU SN Level-3-245C-168 HR -40 to 125 LM2679

S-5.0

LM2679SX-ADJ NRND DDPAK/

TO-263 KTW 7 500 TBD Call TI Call TI -40 to 125 LM2679

S-ADJ

LM2679SX-ADJ/NOPB ACTIVE DDPAK/

TO-263 KTW 7 500 Pb-Free (RoHS

Exempt) CU SN Level-3-245C-168 HR -40 to 125 LM2679

S-ADJ

LM2679T-12/NOPB ACTIVE TO-220 NDZ 7 45 Green (RoHS

& no Sb/Br) CU SN Level-1-NA-UNLIM -40 to 125 LM2679

T-12

LM2679T-3.3/NOPB ACTIVE TO-220 NDZ 7 45 Green (RoHS

& no Sb/Br) CU SN Level-1-NA-UNLIM -40 to 125 LM2679

T-3.3

LM2679T-5.0 NRND TO-220 NDZ 7 45 TBD Call TI Call TI -40 to 125 LM2679

T-5.0

LM2679T-5.0/NOPB ACTIVE TO-220 NDZ 7 45 Green (RoHS

& no Sb/Br) CU SN Level-1-NA-UNLIM -40 to 125 LM2679

T-5.0

LM2679T-ADJ/NOPB ACTIVE TO-220 NDZ 7 45 Green (RoHS

& no Sb/Br) CU SN Level-1-NA-UNLIM -40 to 125 LM2679

T-ADJ

(1) The marketing status values are defined as follows:

ACTIVE: Product device recommended for new designs.

LIFEBUY: TI has announced that the device will be discontinued, and a lifetime-buy period is in effect.

NRND: Not recommended for new designs. Device is in production to support existing customers, but TI does not recommend using this part in a new design.

PREVIEW: Device has been announced but is not in production. Samples may or may not be available.

OBSOLETE: TI has discontinued the production of the device.

(2) Eco Plan - The planned eco-friendly classification: Pb-Free (RoHS), Pb-Free (RoHS Exempt), or Green (RoHS & no Sb/Br) - please check http://www.ti.com/productcontent for the latest availability

information and additional product content details.

TBD: The Pb-Free/Green conversion plan has not been defined.

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.

Pb-Free (RoHS Exempt): This component has a RoHS exemption for either 1) lead-based flip-chip solder bumps used between the die and package, or 2) lead-based die adhesive used between

the die and leadframe. The component is otherwise considered Pb-Free (RoHS compatible) as defined above.

Green (RoHS & no Sb/Br): TI defines "Green" to mean Pb-Free (RoHS compatible), and free of Bromine (Br) and Antimony (Sb) based flame retardants (Br or Sb do not exceed 0.1% by weight

in homogeneous material)

(3) MSL, Peak Temp. - The Moisture Sensitivity Level rating according to the JEDEC industry standard classifications, and peak solder temperature.

(4) There may be additional marking, which relates to the logo, the lot trace code information, or the environmental category on the device.

PACKAGE OPTION ADDENDUM

www.ti.com 1-Nov-2013

Addendum-Page 3

(5) Multiple Device Markings will be inside parentheses. Only one Device Marking contained in parentheses and separated by a "~" will appear on a device. If a line is indented then it is a continuation

of the previous line and the two combined represent the entire Device Marking for that device.

(6) Lead/Ball Finish - Orderable Devices may have multiple material finish options. Finish options are separated by a vertical ruled line. Lead/Ball Finish values may wrap to two lines if the finish

value exceeds the maximum column width.

Important Information and Disclaimer:The information provided on this page represents TI's knowledge and belief as of the date that it is provided. TI bases its knowledge and belief on information

provided by third parties, and makes no representation or warranty as to the accuracy of such information. Efforts are underway to better integrate information from third parties. TI has taken and

continues to take reasonable steps to provide representative and accurate information but may not have conducted destructive testing or chemical analysis on incoming materials and chemicals.

TI and TI suppliers consider certain information to be proprietary, and thus CAS numbers and other limited information may not be available for release.

In no event shall TI's liability arising out of such information exceed the total purchase price of the TI part(s) at issue in this document sold by TI to Customer on an annual basis.

TAPE AND REEL INFORMATION

*All dimensions are nominal

Device Package

Type Package

Drawing Pins SPQ Reel

Diameter

(mm)

Reel

Width

W1 (mm)

(mm) B0

(mm) K0

(mm) P1

(mm) W

(mm) Pin1

Quadrant

LM2679SD-12 VSON NHM 14 250 178.0 16.4 5.3 6.3 1.5 12.0 16.0 Q1

LM2679SD-3.3/NOPB VSON NHM 14 250 178.0 16.4 5.3 6.3 1.5 12.0 16.0 Q1

LM2679SD-5.0 VSON NHM 14 250 178.0 16.4 5.3 6.3 1.5 12.0 16.0 Q1

LM2679SD-5.0/NOPB VSON NHM 14 250 178.0 16.4 5.3 6.3 1.5 12.0 16.0 Q1

LM2679SD-ADJ/NOPB VSON NHM 14 250 178.0 16.4 5.3 6.3 1.5 12.0 16.0 Q1

LM2679SDX-3.3/NOPB VSON NHM 14 2500 330.0 16.4 5.3 6.3 1.5 12.0 16.0 Q1

LM2679SDX-ADJ/NOPB VSON NHM 14 2500 330.0 16.4 5.3 6.3 1.5 12.0 16.0 Q1

LM2679SX-12/NOPB DDPAK/

TO-263 KTW 7 500 330.0 24.4 10.75 14.85 5.0 16.0 24.0 Q2

LM2679SX-3.3/NOPB DDPAK/

TO-263 KTW 7 500 330.0 24.4 10.75 14.85 5.0 16.0 24.0 Q2

LM2679SX-5.0 DDPAK/

TO-263 KTW 7 500 330.0 24.4 10.75 14.85 5.0 16.0 24.0 Q2

LM2679SX-5.0/NOPB DDPAK/

TO-263 KTW 7 500 330.0 24.4 10.75 14.85 5.0 16.0 24.0 Q2

LM2679SX-ADJ DDPAK/

TO-263 KTW 7 500 330.0 24.4 10.75 14.85 5.0 16.0 24.0 Q2

LM2679SX-ADJ/NOPB DDPAK/

TO-263 KTW 7 500 330.0 24.4 10.75 14.85 5.0 16.0 24.0 Q2

PACKAGE MATERIALS INFORMATION

www.ti.com 11-Oct-2013

Pack Materials-Page 1

*All dimensions are nominal

Device Package Type Package Drawing Pins SPQ Length (mm) Width (mm) Height (mm)

LM2679SD-12 VSON NHM 14 250 210.0 185.0 35.0

LM2679SD-3.3/NOPB VSON NHM 14 250 210.0 185.0 35.0

LM2679SD-5.0 VSON NHM 14 250 210.0 185.0 35.0

LM2679SD-5.0/NOPB VSON NHM 14 250 210.0 185.0 35.0

LM2679SD-ADJ/NOPB VSON NHM 14 250 210.0 185.0 35.0

LM2679SDX-3.3/NOPB VSON NHM 14 2500 367.0 367.0 35.0

LM2679SDX-ADJ/NOPB VSON NHM 14 2500 367.0 367.0 35.0

LM2679SX-12/NOPB DDPAK/TO-263 KTW 7 500 367.0 367.0 45.0

LM2679SX-3.3/NOPB DDPAK/TO-263 KTW 7 500 367.0 367.0 45.0

LM2679SX-5.0 DDPAK/TO-263 KTW 7 500 367.0 367.0 45.0

LM2679SX-5.0/NOPB DDPAK/TO-263 KTW 7 500 367.0 367.0 45.0

LM2679SX-ADJ DDPAK/TO-263 KTW 7 500 367.0 367.0 45.0

LM2679SX-ADJ/NOPB DDPAK/TO-263 KTW 7 500 367.0 367.0 45.0

PACKAGE MATERIALS INFORMATION

www.ti.com 11-Oct-2013

Pack Materials-Page 2

MECHANICAL DATA

NDZ0007B

www.ti.com

TA07B (Rev E)

MECHANICAL DATA

NHM0014A

www.ti.com

SRC14A (Rev A)

MECHANICAL DATA

KTW0007B

www.ti.com

BOTTOM SIDE OF PACKAGE

TS7B (Rev E)

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