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BST

COMP

SSRAMP

OUT

GND

LM25005

OUT

SYNC

LM25005

www.ti.com

SNVS411C –JANUARY 2006–REVISED MARCH 2013

LM25005 42V, 2.5A Step-Down Switching Regulator

Check for Samples: LM25005

FEATURES

DESCRIPTION

The LM25005 switching regulator features all of the

• Integrated 42V, 160mΩ N-Channel MOSFET

functions necessary to implement an efficient, high

• Ultra-Wide Input Voltage Range from 7V to 42V

voltage buck regulator using a minimum of external

• Internal Bias Regulator

components. This easy to use regulator includes a

42V, 160mΩ, N-channel MOSFET, with an output

• Adjustable Output Voltage from 1.225V

current capability of 2.5 Amps. The regulator control

• 1.5% Feedback Reference Accuracy

method is based upon current mode control utilizing

• Current Mode Control with Emulated Inductor

an emulated current ramp. Current mode control

Current Ramp

provides inherent line voltage feed-forward, cycle-by-

cycle current limiting and ease of loop compensation.

• Single Resistor Oscillator Frequency Setting

The use of an emulated control ramp reduces noise

• Oscillator Synchronization Input

sensitivity of the pulse-width modulation circuit,

• Programmable Soft-Start

allowing reliable control of very small duty cycles

necessary in high input voltage applications. The

• Shutdown / Standby Input

operating frequency is programmable from 50kHz to

• Wide Bandwidth Error Amplifier

500kHz. An oscillator synchronization pin allows

• Thermal Shutdown

multiple LM25005 regulators to self-synchronize or to

be synchronized to an external clock. Additional

protection features include: current limit, thermal

shutdown and remote shutdown capability. The

device is available in a power enhanced HTSSOP

package featuring an exposed die attach pad to aid

thermal dissipation.

Package

• HTSSOP (Exposed Pad)

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 (28 pages)

PAGE 1
LM25005 www.ti.com SNVS411C – JANUARY 2006 – REVISED MARCH 2013 LM25005 42V, 2.5A Step-Down Switching Regulator Check for Samples: LM25005 FEATURES DESCRIPTION • • • • • • The LM25005 switching regulator features all of the functions necessary to implement an efficient, high voltage buck regulator using a minimum of external components. This easy to use regulator includes a 42V, 160mΩ, N-channel MOSFET, with an output current capability of 2.5 Amps.
PAGE 2
LM25005 SNVS411C – JANUARY 2006 – REVISED MARCH 2013 www.ti.com Connection Diagram 1 VCC BST SD PRE VIN SW VIN SW 2 3 4 5 6 7 8 9 10 SYNC IS COMP IS FB PGND RT PGND RAMP OUT AGND SS 20 19 18 17 16 15 14 13 12 11 Figure 1. Top View 20-Lead HTSSOP PIN DESCRIPTIONS Pin(S) 1 2 Name VCC 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.
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LM25005 www.ti.com SNVS411C – JANUARY 2006 – REVISED MARCH 2013 PIN DESCRIPTIONS (continued) Pin(S) Name Description Application Information 15, 16 IS Current sense Current measurement connection for the re-circulating diode. An internal sense resistor and a sample/hold circuit sense the diode current near the conclusion of the off-time. This current measurement provides the DC level of the emulated current ramp. 17, 18 SW Switching node The source terminal of the internal buck switch.
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LM25005 SNVS411C – JANUARY 2006 – REVISED MARCH 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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LM25005 www.ti.com SNVS411C – JANUARY 2006 – REVISED MARCH 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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LM25005 SNVS411C – JANUARY 2006 – REVISED MARCH 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 RT (k:) 100 125 o TEMPERATURE ( C) Figure 2. Figure 3. Soft Start Current vs Temperature VCC vs ICC, VIN = 12V 8 6 1.05 VCC (V) NORMALIZED SOFTSTART CURRENT 1.10 1.
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LM25005 www.ti.com SNVS411C – JANUARY 2006 – REVISED MARCH 2013 Typical Performance Characteristics (continued) Demoboard Efficiency vs IOUT and VIN 100 EFFICIENCY (%) 80 VIN = 7V 60 VIN = 24V 40 20 0 0.0 0.5 1.0 1.5 2.0 2.5 IOUT (A) Figure 8.
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LM25005 SNVS411C – JANUARY 2006 – REVISED MARCH 2013 www.ti.com Typical Application Circuit and Block Diagram VIN 7V ± 42V C1 2.2 3, 4 VIN C2 2.2 7V REGULATOR 5 PA R1 OPEN LM25005 1.225V 2 SD STANDBY VCC 0.7V C12 OPEN R2 OPEN 11 SS BST UVLO C7 0.022 DRIVER S Q 1.225V 20 VIN DIS CLK 10 PA C4 0.01 C8 0.47 THERMAL SHUTDOWN UVLO SHUTDOWN SD 1 R Q LEVEL SHIFT L1 33 PH SW 17, 18 PWM 0.7V C11 330p PRE 19 C_LIMIT 7 FB C6 open C5 0.01 R4 49.9k ERROR AMP 1.75V 0.
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LM25005 www.ti.com SNVS411C – JANUARY 2006 – REVISED MARCH 2013 Detailed Operating Description The LM25005 switching regulator features all of the functions necessary to implement an efficient high voltage buck regulator using a minimum of external components. This easy to use regulator integrates a 42V N-Channel buck switch with an output current capability of 2.5 Amps. The regulator control method is based on current mode control utilizing an emulated current ramp.
PAGE 10
LM25005 SNVS411C – JANUARY 2006 – REVISED MARCH 2013 www.ti.com Shutdown / Standby The LM25005 contains a dual level Shutdown (SD) circuit. When the SD pin voltage is below 0.7V, the regulator is in a low current shutdown mode. When the SD pin voltage is greater than 0.7V but less than 1.225V, the regulator is in standby mode. In standby mode the Vcc regulator is active but the output switch is disabled. When the SD pin voltage exceeds 1.225V, the output switch is enabled and normal operation begins.
PAGE 11
LM25005 www.ti.com SNVS411C – JANUARY 2006 – REVISED MARCH 2013 5V SYNC 10k I = f(RT) 2.5V Q S Q R DEADTIME ONE-SHOT Figure 12. Simplified Oscillator Block Diagram and SYNC I/O Circuit 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).
PAGE 12
LM25005 SNVS411C – JANUARY 2006 – REVISED MARCH 2013 www.ti.com RAMP (5P x (VIN ± VOUT) + 25P) x tON CRAMP Sample and Hold DC Level 0.5V/A TON Figure 13. Composition of Current Sense Signal The Sample and Hold DC level illustrated in Figure 13. is derived from a measurement of the re-circulating Schottky diode anode current. The re-circulating diode anode should be connected to the IS pin. The diode current flows through an internal current sense resistor between the IS and PGND pins.
PAGE 13
LM25005 www.ti.com SNVS411C – JANUARY 2006 – REVISED MARCH 2013 VCC RRAMP RAMP CRAMP Figure 14. RRAMP to VCC for VOUT > 7.5V Current Limit The LM25005 contains a unique current monitoring scheme for control and over-current protection. When set correctly, the emulated current sense signal provides a signal which is proportional to the buck switch current with a scale factor of 0.5 V / A. The emulated ramp signal is applied to the current limit comparator. If the emulated ramp signal exceeds 1.75V (3.
PAGE 14
LM25005 SNVS411C – JANUARY 2006 – REVISED MARCH 2013 www.ti.com APPLICATION INFORMATION EXTERNAL COMPONENTS The procedure for calculating the external components is illustrated with the following design example. The Bill of Materials for this design is listed in 5V, 2.5A Demo Board Bill of Materials.
PAGE 15
LM25005 www.ti.com SNVS411C – JANUARY 2006 – REVISED MARCH 2013 C3 (CRAMP) With the inductor value selected, the value of C3 (CRAMP) necessary for the emulation ramp circuit is: CRAMP = L x 10-5 where • L is in Henrys (With L1 selected for 33µH the recommended value for C3 is 330pF) (6) C9, C10 The output capacitors C9, and C10, smooth the inductor ripple current and provide a source of charge for transient loading conditions.
PAGE 16
LM25005 SNVS411C – JANUARY 2006 – REVISED MARCH 2013 www.ti.com C7 The bootstrap capacitor between the BST and the SW pins supplies the gate current to charge the buck switch gate at turn-on. The recommended value of C7 is 0.022 µF, and should be a good quality, low ESR, ceramic capacitor. C4 The capacitor at the SS pin determines the soft-start time, i.e. the time for the reference voltage and the output voltage, to reach the final regulated value. The time is determined from: C4 x 1.
PAGE 17
LM25005 www.ti.com SNVS411C – JANUARY 2006 – REVISED MARCH 2013 R4, C5, C6 These components configure the error amplifier gain characteristics to accomplish a stable overall loop gain. One advantage of current mode control is the ability to close the loop with only two feedback components, R4 and C5. The overall loop gain is the product of the modulator gain and the error amplifier gain.
PAGE 18
LM25005 SNVS411C – JANUARY 2006 – REVISED MARCH 2013 www.ti.com REF LEVEL 0.000 dB 0.0 deg /DIV 10.000 dB 45.000 deg PHASE GAIN 0 100 1k START 50.000 Hz 10k STOP 50 000.000 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 50.000 Hz 10k STOP 50 000.000 Hz Figure 18.
PAGE 19
LM25005 www.ti.com SNVS411C – JANUARY 2006 – REVISED MARCH 2013 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 20
LM25005 SNVS411C – JANUARY 2006 – REVISED MARCH 2013 www.ti.com PCB LAYOUT AND THERMAL CONSIDERATIONS The circuit in theTypical Application Circuit and Block Diagram serves as both a block diagram of the LM25005 and a typical application board schematic for the LM25005. 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 21
LM25005 www.ti.com SNVS411C – JANUARY 2006 – REVISED MARCH 2013 PCB Layout Figure 21. Component Side Figure 22. Solder Side Figure 23.
PAGE 22
LM25005 SNVS411C – JANUARY 2006 – REVISED MARCH 2013 www.ti.com REVISION HISTORY Changes from Revision B (March 2013) to Revision C • 22 Page Changed layout of National Data Sheet to TI format ..........................................................................................................
PAGE 23
PACKAGE OPTION ADDENDUM www.ti.
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PACKAGE OPTION ADDENDUM www.ti.com 1-Nov-2013 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.
PAGE 25
PACKAGE MATERIALS INFORMATION www.ti.com 23-Sep-2013 TAPE AND REEL INFORMATION *All dimensions are nominal Device LM25005MHX/NOPB Package Package Pins Type Drawing SPQ HTSSOP 2500 PWP 20 Reel Reel A0 Diameter Width (mm) (mm) W1 (mm) 330.0 16.4 Pack Materials-Page 1 6.95 B0 (mm) K0 (mm) P1 (mm) 7.1 1.6 8.0 W Pin1 (mm) Quadrant 16.
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PACKAGE MATERIALS INFORMATION www.ti.com 23-Sep-2013 *All dimensions are nominal Device Package Type Package Drawing Pins SPQ Length (mm) Width (mm) Height (mm) LM25005MHX/NOPB HTSSOP PWP 20 2500 367.0 367.0 35.
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MECHANICAL DATA PWP0020A MXA20A (Rev C) www.ti.
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