Datasheet

ManualsBrandsTEXAS INSTRUMENTS ManualsPMICsPMIC - DC/DC voltage regulator Holder TSSOP 16

BST

COMP

RAMP

VCC

VIN

OUT

GND

LM25574

VIN

VOUT

SYNC

LM25574, LM25574-Q1

www.ti.com

SNVS483G –JANUARY 2007–REVISED APRIL 2013

LM25574/LM25574-Q1 SIMPLE SWITCHER® 42V, 0.5A Step-Down Switching Regulator

Check for Samples: LM25574, LM25574-Q1

FEATURES

DESCRIPTION

The LM25574 is an easy to use SIMPLE

• LM25574-Q1 is an Automotive Grade Product

SWITCHER® buck regulator which allows design

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

engineers to design and optimize a robust power

125°C Operating Junction Temperature)

supply using a minimum set of components.

• Integrated 42V, 750mΩ N-channel MOSFET

Operating with an input voltage range of 6 - 42V, the

LM25574 delivers 0.5A of continuous output current

• Ultra-wide Input Voltage Range from 6V to 42V

with an integrated 750mΩ N-Channel MOSFET. The

• Adjustable Output Voltage as Low as 1.225V

regulator utilizes an Emulated Current Mode

• 1.5% Feedback Reference Accuracy

architecture which provides inherent line regulation,

• Operating Frequency Adjustable Between

tight load transient response, and ease of loop

compensation without the usual limitation of low-duty

50kHz and 1MHz with Single Resistor

cycles associated with current mode regulators. The

• Master or Slave Frequency Synchronization

operating frequency is adjustable from 50kHz to

• Adjustable Soft-Start

1MHz to allow optimization of size and efficiency. To

• Emulated Current Mode Control Architecture reduce EMI, a frequency synchronization pin allows

multiple IC’s from the LM(2)557x family to self-

• Wide Bandwidth Error Amplifier

synchronize or to synchronize to an external clock.

• Built-in Protection

The LM25574 guarantees robustness with cycle-by-

• Automotive Grade Product Datasheet that is

cycle current limit, short-circuit protection, thermal

shut-down, and remote shut-down. The device is

AEC-Q100 Grade 0 Qualified is Available Upon

available in a TSSOP-16 package. The LM25574 is

Request.

supported by the full suite of WEBENCH

On-Line

– (−40°C to + 150°C Operating Junction

design tools.

Temperature)

PACKAGE

APPLICATIONS

• TSSOP-16

• Automotive

• Industrial

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.

2WEBENCH is a registered trademark 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 (29 pages)

PAGE 1
LM25574, LM25574-Q1 www.ti.com SNVS483G – JANUARY 2007 – REVISED APRIL 2013 LM25574/LM25574-Q1 SIMPLE SWITCHER® 42V, 0.5A Step-Down Switching Regulator Check for Samples: LM25574, LM25574-Q1 FEATURES DESCRIPTION • The LM25574 is an easy to use SIMPLE SWITCHER® buck regulator which allows design engineers to design and optimize a robust power supply using a minimum set of components. Operating with an input voltage range of 6 - 42V, the LM25574 delivers 0.
PAGE 2
LM25574, LM25574-Q1 SNVS483G – JANUARY 2007 – REVISED APRIL 2013 www.ti.com Connection Diagram 1 VCC BST SD PRE VIN SW 2 3 4 5 6 7 8 SYNC IS COMP PGND FB OUT RT SS RAMP AGND 16 15 14 13 12 11 10 9 Figure 1. Top View 16-Lead TSSOP PIN DESCRIPTIONS 2 Pin(s) Name 1 VCC 2 Description Application Information Output of the bias regulator Vcc tracks Vin up to 9V. Beyond 9V, Vcc is regulated to 7 Volts. A 0.1uF to 1uF ceramic decoupling capacitor is required. An external voltage (7.
PAGE 3
LM25574, LM25574-Q1 www.ti.com SNVS483G – JANUARY 2007 – REVISED APRIL 2013 PIN DESCRIPTIONS (continued) Pin(s) Name 15 PRE Pre-charge assist for the bootstrap capacitor Description This open drain output can be connected to SW pin to aid charging the bootstrap capacitor during very light load conditions or in applications where the output may be pre-charged before the LM25574 is enabled.
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LM25574, LM25574-Q1 SNVS483G – JANUARY 2007 – REVISED APRIL 2013 www.ti.com Electrical Characteristics Specifications with standard typeface are for TJ = 25°C, and those with boldface type apply over full Operating Junction Temperature range. VIN = 24V, RT = 32.4kΩ unless otherwise stated. (1) Symbol Parameter Conditions Min Typ Max Units 6.85 7.15 7.
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LM25574, LM25574-Q1 www.ti.com SNVS483G – JANUARY 2007 – REVISED APRIL 2013 Electrical Characteristics (continued) Specifications with standard typeface are for TJ = 25°C, and those with boldface type apply over full Operating Junction Temperature range. VIN = 24V, RT = 32.4kΩ unless otherwise stated.(1) Symbol Parameter Conditions Min Typ Max 1.207 1.225 1.
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LM25574, LM25574-Q1 SNVS483G – JANUARY 2007 – REVISED APRIL 2013 www.ti.com Typical Performance Characteristics Oscillator Frequency vs Temperature FOSC = 200kHz Oscillator Frequency vs RT NORMALIZED OSCILLATOR FREQUENCY OSCILLATOR FREQUENCY (kHz) 1000 100 10 1 10 100 1000 1.010 1.005 1.000 0.995 0.990 -50 -25 0 25 50 75 100 125 RT (k:) o TEMPERATURE ( C) Figure 2. Figure 3. Soft Start Current vs Temperature VCC vs ICC VIN = 12V 8 6 1.
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LM25574, LM25574-Q1 www.ti.com SNVS483G – JANUARY 2007 – REVISED APRIL 2013 Typical Performance Characteristics (continued) Demoboard Efficiency vs IOUT and VIN 100 VIN = 7V 90 EFFICIENCY (%) 80 70 VIN = 24V 60 50 40 30 20 10 0 0.1 0.2 0.3 0.4 0.5 IOUT (A) Figure 8.
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LM25574, LM25574-Q1 SNVS483G – JANUARY 2007 – REVISED APRIL 2013 www.ti.com TYPICAL APPLICATION CIRCUIT AND BLOCK DIAGRAM VIN 7V ± 42V C1 1.0 VIN 3 7V REGULATOR 5 PA R1 OPEN LM25574 1.225V 2 SD STANDBY VCC SHUTDOWN SD 0.7V C2 OPEN R2 OPEN 10 SS BST UVLO C7 0.022 DRIVER S Q 1.225V 16 VIN DIS CLK 10 PA C4 0.01 C8 0.47 THERMAL SHUTDOWN UVLO 1 R Q LEVEL SHIFT SW 14 L1 100 PH 5V PWM 0.7V PRE 15 C_LIMIT 6 FB C6 open C5 0.022 R4 24.9k ERROR AMP 1.
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LM25574, LM25574-Q1 www.ti.com SNVS483G – JANUARY 2007 – REVISED APRIL 2013 An auxiliary supply voltage can be applied to the Vcc pin to reduce the IC power dissipation. If the auxiliary voltage is greater than 7.3V, the internal regulator will essentially shut off, reducing the IC power dissipation. The Vcc regulator series pass transistor includes a diode between Vcc and Vin that should not be forward biased in normal operation. Therefore the auxiliary Vcc voltage should never exceed the Vin voltage.
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LM25574, LM25574-Q1 SNVS483G – JANUARY 2007 – REVISED APRIL 2013 www.ti.com LM25574 SYNC SW SYNC AGND CLK SW 500 ns Figure 10. Sync from External Clock LM25574 SYNC LM25574 SYNC UP TO 5 TOTAL DEVICES Figure 11. Sync from Multiple Devices Multiple LM25574 devices can be synchronized together simply by connecting the SYNC pins together. In this configuration all of the devices will be synchronized to the highest frequency device.
PAGE 11
LM25574, LM25574-Q1 www.ti.com SNVS483G – JANUARY 2007 – REVISED APRIL 2013 Error Amplifier and PWM Comparator The internal high gain error amplifier generates an error signal proportional to the difference between the regulated output voltage and an internal precision reference (1.225V). The output of the error amplifier is connected to the COMP pin allowing the user to provide loop compensation components, generally a type II network, as illustrated in Typical Application Circuit and Block Diagram.
PAGE 12
LM25574, LM25574-Q1 SNVS483G – JANUARY 2007 – REVISED APRIL 2013 www.ti.com For duty cycles greater than 50%, peak current mode control circuits are subject to sub-harmonic oscillation. Sub-harmonic oscillation is normally characterized by observing alternating wide and narrow pulses at the switch node. Adding a fixed slope voltage ramp (slope compensation) to the current sense signal prevents this oscillation.
PAGE 13
LM25574, LM25574-Q1 www.ti.com SNVS483G – JANUARY 2007 – REVISED APRIL 2013 Soft-Start The soft-start feature allows the regulator to gradually reach the initial steady state operating point, thus reducing start-up stresses and surges. The internal soft-start current source, set to 10µA, gradually increases the voltage of an external soft-start capacitor connected to the SS pin. The soft-start capacitor voltage is connected to the reference input of the error amplifier.
PAGE 14
LM25574, LM25574-Q1 SNVS483G – JANUARY 2007 – REVISED APRIL 2013 www.ti.com L1 The inductor value is determined based on the operating frequency, load current, ripple current, and the minimum and maximum input voltage (VIN(min), VIN(max)). L1 Current IPK+ IRIPPLE IO IPK- 1/Fs 0 mA Figure 15. Inductor Current Waveform To keep the circuit in continuous conduction mode (CCM), the maximum ripple current IRIPPLE should be less than twice the minimum load current, or 0.2Ap-p.
PAGE 15
LM25574, LM25574-Q1 www.ti.com SNVS483G – JANUARY 2007 – REVISED APRIL 2013 The forward voltage drop has a significant impact on the conversion efficiency, especially for applications with a low output voltage. “Rated” current for diodes vary widely from various manufacturers. The worst case is to assume a short circuit load condition. In this case the diode will carry the output current almost continuously. For the LM25574 this current can be as high as 0.7A.
PAGE 16
LM25574, LM25574-Q1 SNVS483G – JANUARY 2007 – REVISED APRIL 2013 www.ti.com Capacitor C2 provides filtering for the divider. The voltage at the SD pin should never exceed 8V, when using an external set-point divider it may be necessary to clamp the SD pin at high input voltage conditions. The reference design utilizes the full range of the LM25574 (6V to 42V); therefore these components can be omitted. With the SD pin open circuit the LM25574 responds once the Vcc UVLO threshold is satisfied.
PAGE 17
LM25574, LM25574-Q1 www.ti.com SNVS483G – JANUARY 2007 – REVISED APRIL 2013 REF LEVEL 0.000 dB 0.0 deg /DIV 10.000 dB 45.000 deg PHASE GAIN 0 100 1k START 100.000 Hz 10k 100k STOP 100 000.000 Hz Figure 17. Error Amplifier Gain and Phase The overall loop can be predicted as the sum (in dB) of the modulator gain and the error amp gain. REF LEVEL 0.000 dB 0.0 deg /DIV 10.000 dB 45.000 deg GAIN PHASE 0 100 1k START 100.000 Hz 10k 100k STOP 100 000.000 Hz Figure 18.
PAGE 18
LM25574, LM25574-Q1 SNVS483G – JANUARY 2007 – REVISED APRIL 2013 www.ti.com BIAS POWER DISSIPATION REDUCTION Buck regulators operating with high input voltage can dissipate an appreciable amount of power for the bias of the IC. The VCC regulator must step-down the input voltage VIN to a nominal VCC level of 7V. The large voltage drop across the VCC regulator translates into a large power dissipation within the Vcc regulator.
PAGE 19
LM25574, LM25574-Q1 www.ti.com SNVS483G – JANUARY 2007 – REVISED APRIL 2013 PCB LAYOUT AND THERMAL CONSIDERATIONS The circuit in Typical Application Circuit and Block Diagram serves as both a block diagram of the LM25574 and a typical application board schematic for the LM25574. In a buck regulator there are two loops where currents are switched very fast. The first loop starts from the input capacitors, to the regulator VIN pin, to the regulator SW pin, to the inductor then out to the load.
PAGE 20
LM25574, LM25574-Q1 SNVS483G – JANUARY 2007 – REVISED APRIL 2013 www.ti.com Table 1. 5V, 0.5A Demo Board Bill of Materials ITEM 20 PART NUMBER DESCRIPTION VALUE C 1 C3225X7R2A105M CAPACITOR, CER, TDK C 2 OPEN NOT USED C 3 C0805A471K1GAC CAPACITOR, CER, KEMET 470p, 100V C 4 C2012X7R2A103K CAPACITOR, CER, TDK 0.01µ, 100V C 5 C2012X7R2A223K CAPACITOR, CER, TDK 0.022µ, 100V C 6 OPEN NOT USED C 7 C2012X7R2A223K CAPACITOR, CER, TDK 0.
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LM25574, LM25574-Q1 www.ti.com SNVS483G – JANUARY 2007 – REVISED APRIL 2013 PCB Layout Figure 21. Component Side Figure 22. Solder Side Figure 23.
PAGE 22
LM25574, LM25574-Q1 SNVS483G – JANUARY 2007 – REVISED APRIL 2013 www.ti.com Typical Schematic for High Frequency (1MHz) Application BST 9 - 32V 0.022P VIN 22 P 3.3V, 0.5A SD 1P SW SYNC 5.11k LM25574 CMSH2-40 COMP 22P IS 24.9k 3.01k GND 0.022P OUT FB RAMP RT SS VCC 3.57k 0.1P 100p 0.
PAGE 23
LM25574, LM25574-Q1 www.ti.com SNVS483G – JANUARY 2007 – REVISED APRIL 2013 REVISION HISTORY Changes from Revision F (April 2013) to Revision G • Page Changed layout of National Data Sheet to TI format ..........................................................................................................
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PACKAGE OPTION ADDENDUM www.ti.
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PACKAGE OPTION ADDENDUM www.ti.com 7-Nov-2013 (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.
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PACKAGE MATERIALS INFORMATION www.ti.com 9-Nov-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 LM25574Q0MTX/NOPB TSSOP PW 16 2500 330.0 12.4 6.95 8.3 1.6 8.0 12.0 Q1 LM25574QMTX/NOPB TSSOP PW 16 2500 330.0 12.4 6.95 8.3 1.6 8.0 12.
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PACKAGE MATERIALS INFORMATION www.ti.com 9-Nov-2013 *All dimensions are nominal Device Package Type Package Drawing Pins SPQ Length (mm) Width (mm) Height (mm) LM25574Q0MTX/NOPB TSSOP PW 16 2500 367.0 367.0 35.0 LM25574QMTX/NOPB TSSOP PW 16 2500 367.0 367.0 35.
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