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LM22679/LM22679Q

www.ti.com

SNVS581K –FEBRUARY 2013–REVISED NOVEMBER 2012

LM22679/LM22679Q 42V, 5A SIMPLE SWITCHER® Step-Down Voltage Regulator with

Features

Check for Samples: LM22679/LM22679Q

FEATURES

DESCRIPTION

The LM22679 switching regulator provides all of the

• Wide Input Voltage Range: 4.5V to 42V

functions necessary to implement an efficient high

• Internally Compensated Voltage Mode Control

voltage step-down (buck) regulator using a minimum

• Stable with Low ESR Ceramic Capacitors

of external components. This easy to use regulator

incorporates a 42V N-channel MOSFET switch

• 100 mΩ N-Channel MOSFET

capable of providing up to 5A of load current.

• Output Voltage Options:

Excellent line and load regulation along with high

– ADJ (Outputs as Low as 1.285V)

efficiency (>90%) are featured. Voltage mode control

offers short minimum on-time, allowing the widest

– 5.0 (Output Fixed to 5V)

ratio between input and output voltages. Internal loop

• ±1.5% Feedback Reference Accuracy

compensation means that the user is free from the

• Switching Frequency of 500 kHz

tedious task of calculating the loop compensation

components. Fixed 5V output and adjustable output

• -40°C to 125°C Operating Junction

voltage options are available. A switching frequency

Temperature Range

of 500 kHz allows for small external components and

• Adjustable Soft-Start

good transient response. An adjustable soft-start

• Adjustable Current Limit

feature is provided through the selection of a single

external capacitor. In addition, the switch current limit

• Integrated Boot-Strap Diode

can be programmed with a single external resistor,

• Fully WEBENCH

Enabled

allowing solution optimization. The LM22679 also has

• LM22679Q is AEC-Q100 qualified and

built in thermal shutdown, and current limiting to

manufactured on an Automotive Grade Flow

protect against accidental overloads.

The LM22679 is a member of Texas Instruments'

PACKAGE

SIMPLE SWITCHER™ family. The SIMPLE

• PFM (Exposed Pad)

SWITCHER™ concept provides for an easy to use

complete design using a minimum number of external

components and the TI WEBENCH

design tool. TI's

APPLICATIONS

WEBENCH

tool includes features such as external

• Industrial Control

component calculation, electrical simulation, thermal

• Telecom and Datacom Systems

simulation, and Build-It boards for easy design-in.

• Embedded Systems

• Conversions from Standard 24V, 12V and 5V

Input Rails

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.

2All 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 (23 pages)

PAGE 1
LM22679/LM22679Q www.ti.com SNVS581K – FEBRUARY 2013 – REVISED NOVEMBER 2012 LM22679/LM22679Q 42V, 5A SIMPLE SWITCHER® Step-Down Voltage Regulator with Features Check for Samples: LM22679/LM22679Q FEATURES DESCRIPTION • • • • • The LM22679 switching regulator provides all of the functions necessary to implement an efficient high voltage step-down (buck) regulator using a minimum of external components.
PAGE 2
LM22679/LM22679Q SNVS581K – FEBRUARY 2013 – REVISED NOVEMBER 2012 www.ti.com Simplified Application Schematic VIN VIN FB LM22679-ADJ BOOT VOUT IADJ SS GND SW Connection Diagram 7 SS 6 FB 5 IADJ 4 GND 3 BOOT 2 VIN 1 SW Exposed Pad Connect to GND Figure 1. Connection Diagram Package Number NDR0007A PIN DESCRIPTIONS Pin Name Description 1 SW Switch Output Switching output of regulator. Supply input to regulator.
PAGE 3
LM22679/LM22679Q www.ti.com SNVS581K – FEBRUARY 2013 – REVISED NOVEMBER 2012 Absolute Maximum Ratings (1) (2) VIN to GND 43V SS, IADJ Pin Voltage -0.5V to 7V SW to GND (3) -5V to VIN Boot Pin Voltage VSW + 7V FB Pin Voltage -0.
PAGE 4
LM22679/LM22679Q SNVS581K – FEBRUARY 2013 – REVISED NOVEMBER 2012 www.ti.com Electrical Characteristics (continued) Limits in standard type are for TJ = 25°C only; limits in boldface type apply over the junction temperature (TJ) range of -40°C to +125°C. Minimum and Maximum limits are guaranteed through test, design, or statistical correlation. Typical values represent the most likely parametric norm at TA = TJ = 25°C, and are provided for reference purposes only. Unless otherwise specified: VIN = 12V.
PAGE 5
LM22679/LM22679Q www.ti.com SNVS581K – FEBRUARY 2013 – REVISED NOVEMBER 2012 Typical Performance Characteristics Unless otherwise specified the following conditions apply: Vin = 12V, TJ = 25°C. Efficiency vs IOUT and VIN (VOUT = 3.3V) Current Limit vs Temperature Figure 2. Figure 3. Normalized Switching Frequency vs Temperature Feedback Bias Current vs Temperature Figure 4. Figure 5. Normalized Feedback Voltage vs Temperature Normalized RDS(ON) vs Temperature Figure 6. Figure 7.
PAGE 6
LM22679/LM22679Q SNVS581K – FEBRUARY 2013 – REVISED NOVEMBER 2012 www.ti.com Typical Performance Characteristics (continued) Unless otherwise specified the following conditions apply: Vin = 12V, TJ = 25°C. Normalized Feedback Voltage vs Input Voltage Soft-start Current vs Temperature Figure 8. Figure 9. Current Limit vs IADJ Resistor Figure 10.
PAGE 7
LM22679/LM22679Q www.ti.com SNVS581K – FEBRUARY 2013 – REVISED NOVEMBER 2012 Simplified Block Diagram VIN VIN BOOT Vcc INT REG, EN, UVLO ILimit IADJ PWM Cmp. FB TYPE III COMP + + - LOGIC Error Amp. VOUT SW OSC 1.285V & Soft-start SS GND Figure 11.
PAGE 8
LM22679/LM22679Q SNVS581K – FEBRUARY 2013 – REVISED NOVEMBER 2012 www.ti.com Detailed Operating Description The LM22679 incorporates a voltage mode constant frequency PWM architecture. In addition, input voltage feedforward is used to stabilize the loop gain against variations in input voltage. This allows the loop compensation to be optimized for transient performance.
PAGE 9
LM22679/LM22679Q www.ti.com SNVS581K – FEBRUARY 2013 – REVISED NOVEMBER 2012 When the LM22679 enters current limit, the output voltage will drop and the peak inductor current will be fixed at ICL at the end of each cycle. The switching frequency will remain constant while the duty cycle drops. The load current will not remain constant, but will depend on the severity of the overload and the output voltage.
PAGE 10
LM22679/LM22679Q SNVS581K – FEBRUARY 2013 – REVISED NOVEMBER 2012 www.ti.com Figure 13. Current Limit vs IADJ Resistor Soft-Start The soft-start feature allows the regulator to gradually reach steady-state operation, thus reducing start-up stresses. The internal soft-start feature brings the output voltage up in about 500 µs. This time can be extended by using an external capacitor connected to the SS pin. Values in the range of 100 nF to 1 µF are recommended.
PAGE 11
LM22679/LM22679Q www.ti.com SNVS581K – FEBRUARY 2013 – REVISED NOVEMBER 2012 The complete transfer function for the regulator loop is found by combining the compensation and power stage transfer functions. The LM22679 has internal type III loop compensation, as detailed in Internal Loop Compensation section. This is the approximate "straight line" function from the FB pin to the input of the PWM modulator. The power stage transfer function consists of a D.C.
PAGE 12
LM22679/LM22679Q SNVS581K – FEBRUARY 2013 – REVISED NOVEMBER 2012 www.ti.com APPLICATION INFORMATION TYPICAL BUCK REGULATOR APPLICATION Figure 15 shows an example of converting an input voltage range of 5.5V to 42V, to an output of 3.3v at 5A. See AN-1891 for more information. RFBB 976: VIN 4.5V to 42V C2 22 PF + C1 6.8 PF C7 6.8 PF C6 1 PF FB VIN C3 LM22679-ADJ 10 nF SS BOOT IADJ R3 GND RFBT 1.54 k: L1 4.7 PH SW D1 60V, 5A VOUT 3.3V C4 180 PF GND + GND Figure 15.
PAGE 13
LM22679/LM22679Q www.ti.com SNVS581K – FEBRUARY 2013 – REVISED NOVEMBER 2012 INPUT CAPACITOR The input capacitor selection is based on both input voltage ripple and RMS current. Good quality input capacitors are necessary to limit the ripple voltage at the VIN pin while supplying most of the regulator current during switch on-time. Low ESR ceramic capacitors are preferred. Larger values of input capacitance are desirable to reduce voltage ripple and noise on the input supply.
PAGE 14
LM22679/LM22679Q SNVS581K – FEBRUARY 2013 – REVISED NOVEMBER 2012 www.ti.com OUTPUT VOLTAGE DIVIDER SELECTION For output voltages between about 1.285V and 5V, the -ADJ option should be used, with an appropriate voltage divider as shown in Figure 16. The following equation can be used to calculate the resistor values of this divider: (14) A good value for RFBB is 1k Ω. This will help to provide some of the minimum load current requirement and reduce susceptibility to noise pick-up.
PAGE 15
LM22679/LM22679Q www.ti.com SNVS581K – FEBRUARY 2013 – REVISED NOVEMBER 2012 Circuit Board Layout Board layout is critical for the proper operation of switching power supplies. First, the ground plane area must be sufficient for thermal dissipation purposes. Second, appropriate guidelines must be followed to reduce the effects of switching noise. Switch mode converters are very fast switching devices.
PAGE 16
LM22679/LM22679Q SNVS581K – FEBRUARY 2013 – REVISED NOVEMBER 2012 www.ti.com The regulator has an exposed thermal pad to aid power dissipation. Adding multiple vias under the device to the ground plane will greatly reduce the regulator junction temperature. Selecting a diode with an exposed pad will also aid the power dissipation of the diode. The most significant variables that affect the power dissipation of the regulator are output current, input voltage and operating frequency.
PAGE 17
LM22679/LM22679Q www.ti.com SNVS581K – FEBRUARY 2013 – REVISED NOVEMBER 2012 RFBB 2.55 k: VIN 5.5V to 35V VIN FB LM22679-ADJ SS C2 22 PF + BOOT C6 4.7 PF C1 2.2 PF IADJ GND VOUT C3 10 nF RFBT 7.32 k: L1 10 PH SW D1 60V 5A C4 120 PF + VOUT -5V Figure 18.
PAGE 18
PACKAGE OPTION ADDENDUM www.ti.com 20-Jul-2013 PACKAGING INFORMATION Orderable Device Status (1) Package Type Package Pins Package Drawing Qty Eco Plan Lead/Ball Finish (2) MSL Peak Temp Op Temp (°C) Device Marking (3) (4/5) LM22679QTJ-5.0/NOPB ACTIVE TO-263 NDR 7 1000 Green (RoHS & no Sb/Br) CU SN Level-1-260C-UNLIM LM22679 QTJ-5.0 LM22679QTJ-ADJ/NOPB ACTIVE TO-263 NDR 7 1000 Green (RoHS & no Sb/Br) CU SN Level-1-260C-UNLIM LM22679 QTJ-ADJ LM22679QTJE-5.
PAGE 19
PACKAGE OPTION ADDENDUM www.ti.com (4) 20-Jul-2013 There may be additional marking, which relates to the logo, the lot trace code information, or the environmental category on the device. (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.
PAGE 20
PACKAGE MATERIALS INFORMATION www.ti.com 20-Jul-2013 TAPE AND REEL INFORMATION *All dimensions are nominal Device LM22679QTJ-5.0/NOPB 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 TO-263 NDR 7 1000 330.0 24.4 10.6 15.4 2.45 12.0 24.0 Q2 LM22679QTJ-ADJ/NOPB TO-263 NDR 7 1000 330.0 24.4 10.6 15.4 2.45 12.0 24.0 Q2 LM22679QTJE-5.0/NOPB TO-263 NDR 7 250 178.0 24.4 10.6 15.4 2.45 12.
PAGE 21
PACKAGE MATERIALS INFORMATION www.ti.com 20-Jul-2013 *All dimensions are nominal Device Package Type Package Drawing Pins SPQ Length (mm) Width (mm) Height (mm) LM22679QTJ-5.0/NOPB TO-263 NDR 7 1000 367.0 367.0 35.0 LM22679QTJ-ADJ/NOPB TO-263 NDR 7 1000 367.0 367.0 35.0 LM22679QTJE-5.0/NOPB TO-263 NDR 7 250 210.0 185.0 35.0 LM22679QTJE-ADJ/NOPB TO-263 NDR 7 250 210.0 185.0 35.0 LM22679TJ-5.0/NOPB TO-263 NDR 7 1000 367.0 367.0 35.
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MECHANICAL DATA NDR0007A BOTTOM SIDE OF PACKAGE TOP SIDE OF PACKAGE TJ7A (Rev D) www.ti.
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