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LM22674-ADJ

VIN

BOOT

GND

VIN

VOUT

LM22674

www.ti.com

SNVS590L –SEPTEMBER 2008–REVISED APRIL 2013

LM22674/LM22674-Q1 42V, 500 mA SIMPLE SWITCHER® Step-Down Voltage Regulator

with Features

Check for Samples: LM22674

FEATURES

DESCRIPTION

The LM22674 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

• 200 mΩ N-Channel MOSFET

capable of providing up to 500mA 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

• Precision Enable Pin

good transient response. A precision enable input

• Integrated Boot-Strap Diode

allows simplification of regulator control and system

power sequencing. In shutdown mode the regulator

• Integrated Soft-Start

draws only 25 µA (typ.). Built in soft-start (500µs, typ)

• Fully WEBENCH

Enabled

saves external components. The LM22674 also has

• LM22674-Q1 is an Automotive Grade product

built in thermal shutdown, and current limiting to

that is AEC-Q100 Grade 1 Qualified (-40°C to

protect against accidental overloads.

+125°C Operating Junction Temperature)

The LM22674 is a member of Texas Instruments'

SIMPLE SWITCHER™ family. The SIMPLE

PACKAGE

SWITCHER™ concept provides for an easy to use

• SO PowerPAD (Exposed Pad)

complete design using a minimum number of external

components and the TI WEBENCH

design tool. TI's

WEBENCH

tool includes features such as external

APPLICATIONS

component calculation, electrical simulation, thermal

• Industrial Control

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

• Telecom and Datacom Systems

• Embedded Systems

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

Input Rails

Simplified Application Schematic

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 (22 pages)

PAGE 1
LM22674 www.ti.com SNVS590L – SEPTEMBER 2008 – REVISED APRIL 2013 LM22674/LM22674-Q1 42V, 500 mA SIMPLE SWITCHER® Step-Down Voltage Regulator with Features Check for Samples: LM22674 FEATURES DESCRIPTION • • • • • The LM22674 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
LM22674 SNVS590L – SEPTEMBER 2008 – REVISED APRIL 2013 www.ti.com Connection Diagram BOOT 1 8 SW NC 2 7 VIN NC 3 6 GND FB 4 5 EN Exposed Pad Connect to GND Figure 1. 8-Lead Plastic SO PowerPAD Package Package Number DDA0008B PIN DESCRIPTIONS Pins Name Description Application Information 1 BOOT Bootstrap input Provides the gate voltage for the high side NFET. 2, 3 NC Not Connected Pins are not electrically connected to die. Pins do function as thermal conductor.
PAGE 3
LM22674 www.ti.com SNVS590L – SEPTEMBER 2008 – REVISED APRIL 2013 Operating Ratings (1) Supply Voltage (VIN) 4.5V to 42V Junction Temperature Range (1) -40°C to +125°C Absolute Maximum Ratings indicate limits beyond which damage to the device may occur, including inoperability and degradation of device reliability and/or performance.
PAGE 4
LM22674 SNVS590L – SEPTEMBER 2008 – REVISED APRIL 2013 www.ti.com Typical Performance Characteristics Unless otherwise specified the following conditions apply: Vin = 12V, TJ = 25°C. 4 Efficiency vs IOUT and VIN VOUT = 3.3V Normalized Switching Frequency vs Temperature Figure 2. Figure 3. Current Limit vs Temperature Normalized RDS(ON) vs Temperature Figure 4. Figure 5. Feedback Bias Current vs Temperature Normalized Enable Threshold Voltage vs Temperature Figure 6. Figure 7.
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LM22674 www.ti.com SNVS590L – SEPTEMBER 2008 – REVISED APRIL 2013 Typical Performance Characteristics (continued) Unless otherwise specified the following conditions apply: Vin = 12V, TJ = 25°C. Standby Quiescent Current vs Input Voltage Normalized Feedback Voltage vs Temperature Figure 8. Figure 9. Normalized Feedback Voltage vs Input Voltage Figure 10.
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LM22674 SNVS590L – SEPTEMBER 2008 – REVISED APRIL 2013 www.ti.com SIMPLIFIED BLOCK DIAGRAM VIN VIN Vcc BOOT INT REG, EN,UVLO EN ILimit PWM Cmp. FB + TYPE III COMP + - LOGIC Error Amp. VOUT SW OSC 1.285V & Soft-start GND Figure 11. Simplified Block Diagram Detailed Operating Description The LM22674 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.
PAGE 7
LM22674 www.ti.com SNVS590L – SEPTEMBER 2008 – REVISED APRIL 2013 Although an internal pull-up is provided on the EN pin, it is good practice to pull the input high, when this feature is not used, especially in noisy environments. This can most easily be done by connecting a resistor between VIN and the EN pin. The resistor is required, since the internal zener diode, at the EN pin, will conduct for voltages above about 6V. The current in this zener must be limited to less than 100 µA.
PAGE 8
LM22674 SNVS590L – SEPTEMBER 2008 – REVISED APRIL 2013 www.ti.com The second limitation is the maximum duty cycle before the output voltage will "dropout" of regulation. The following equation can be used to approximate the minimum input voltage before dropout occurs: (4) The values of TOFF and RDS(ON) are found in the Electrical Characteristics table. The worst case here occurs at the highest load. In this equation, RL is the D.C. inductor resistance.
PAGE 9
LM22674 www.ti.com SNVS590L – SEPTEMBER 2008 – REVISED APRIL 2013 45 INPUT VOLTAGE (v) 40 35 30 25 SAFE OPERATING AREA 20 15 10 5 0.0 0.2 0.4 0.6 0.8 1.0 SHORT CIRCUIT VOLTAGE (v) 1.2 Figure 13. SOA 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 is fixed and can not be changed.
PAGE 10
LM22674 SNVS590L – SEPTEMBER 2008 – REVISED APRIL 2013 www.ti.com (9) The Q factor depends on the parasitic resistance of the power stage components and is not typically in the control of the designer. Of course, loop compensation is only one consideration when selecting power stage components; see the Application Information section for more details. COMPENSATOR GAIN (dB) 40 -ADJ -5.0 35 30 25 20 15 10 5 0 100 1k 10k 100k 1M FREQUENCY (Hz) 10M Figure 14.
PAGE 11
LM22674 www.ti.com SNVS590L – SEPTEMBER 2008 – REVISED APRIL 2013 INDUCTOR The inductor value is determined based on the load current, ripple current, and the minimum and maximum input voltages. To keep the application in continuous conduction mode (CCM), the maximum ripple current, IRIPPLE , should be less than twice the minimum load current.
PAGE 12
LM22674 SNVS590L – SEPTEMBER 2008 – REVISED APRIL 2013 www.ti.com It is good practice to include a high frequency bypass capacitor as close as possible to the LM22674. This small case size, low ESR, ceramic capacitor should be connected directly to the VIN and GND pins with the shortest possible PCB traces. Values in the range of 0.47 µF to 1 µF are appropriate. This capacitor helps to provide a low impedance supply to sensitive internal circuitry.
PAGE 13
LM22674 www.ti.com SNVS590L – SEPTEMBER 2008 – REVISED APRIL 2013 Vout RFBT FB RFBB Figure 16. Resistive Feedback Divider A maximum value of 10 kΩ is recommended for the sum of RFBB and RFBT to maintain good output voltage accuracy for the -ADJ option. A maximum of 2 kΩ is recommended for the -5.0 option. For the -5.0 option, the total internal divider resistance is typically 9.93 kΩ.
PAGE 14
LM22674 SNVS590L – SEPTEMBER 2008 – REVISED APRIL 2013 www.ti.com Figure 17. Current Flow in a Buck Application Thermal Considerations The components with the highest power dissipation are the power diode and the power MOSFET internal to the LM22674 regulator. The easiest method to determine the power dissipation within the LM22674 is to measure the total conversion losses then subtract the power losses in the diode and inductor.
PAGE 15
LM22674 www.ti.com SNVS590L – SEPTEMBER 2008 – REVISED APRIL 2013 PCB Layout Example RFBB 2.55 k: VIN 5.5V to 35V VIN FB LM22674-ADJ BOOT EN C2 22 PF + C1 2.2 PF C6 4.7 PF VOUT C3 10 nF L1 10 PH RFBT 7.32 k: SW GND D1 60V 1A C4 120 PF VOUT -5V Figure 18.
PAGE 16
LM22674 SNVS590L – SEPTEMBER 2008 – REVISED APRIL 2013 www.ti.com REVISION HISTORY Changes from Revision K (April 2013) to Revision L • 16 Page Changed layout of National Data Sheet to TI format ..........................................................................................................
PAGE 17
PACKAGE OPTION ADDENDUM www.ti.com 11-Apr-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) Top-Side Markings (3) (4) LM22674MR-5.0/NOPB ACTIVE SO PowerPAD DDA 8 95 Green (RoHS & no Sb/Br) CU SN Level-3-260C-168 HR -40 to 125 L22674 5.0 LM22674MR-ADJ/NOPB ACTIVE SO PowerPAD DDA 8 95 Green (RoHS & no Sb/Br) CU SN Level-3-260C-168 HR -40 to 125 L22674 ADJ LM22674MRE-5.
PAGE 18
PACKAGE OPTION ADDENDUM www.ti.com 11-Apr-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.
PAGE 19
PACKAGE MATERIALS INFORMATION www.ti.com 8-Apr-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 LM22674MRE-5.0/NOPB SO Power PAD DDA 8 250 178.0 12.4 6.5 5.4 2.0 8.0 12.0 Q1 LM22674MRE-ADJ/NOPB SO Power PAD DDA 8 250 178.0 12.4 6.5 5.4 2.0 8.0 12.0 Q1 LM22674MRX-5.0/NOPB SO Power PAD DDA 8 2500 330.0 12.4 6.5 5.4 2.
PAGE 20
PACKAGE MATERIALS INFORMATION www.ti.com 8-Apr-2013 Device B 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 Power PAD *All dimensions are nominal Device Package Type Package Drawing Pins SPQ Length (mm) Width (mm) Height (mm) LM22674MRE-5.0/NOPB SO PowerPAD DDA 8 250 213.0 191.0 55.0 LM22674MRE-ADJ/NOPB SO PowerPAD DDA 8 250 213.0 191.0 55.0 LM22674MRX-5.
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MECHANICAL DATA DDA0008B MRA08B (Rev B) www.ti.
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