Datasheet

ManualsBrandsTEXAS INSTRUMENTS ManualsPMICsPMIC - voltage regulators - DC DC switch controllers SOT 23 5

OUT

= 2.5V/2A

OUT

FB1

FB2

10 PF

100 PF

10 PH

2.15k

Si2343

LM3475

GND

PGATE

1 nF

= 5V

LM3475

www.ti.com

SNVS239B –OCTOBER 2004–REVISED MARCH 2013

LM3475 Hysteretic PFET Buck Controller

Check for Samples: LM3475

FEATURES

DESCRIPTION

• Easy to Use Control Methodology

The LM3475 is a hysteretic P-FET buck controller

• 0.8V to V

Adjustable Output Range

designed to support a wide range of high efficiency

• High Efficiency (90% Typical)

applications in a very small SOT-23-5 package. The

hysteretic control scheme has several advantages,

• ±0.9% (±1.5% Over Temp) Feedback Voltage

including simple system design with no external

• 100% Duty Cycle Capable

compensation, stable operation with a wide range of

• Maximum Operating Frequency up to 2MHz

components, and extremely fast transient response.

Hysteretic control also provides high efficiency

• Internal Soft-Start

operation, even at light loads. The PFET architecture

• Enable Pin

allows for low component count as well as 100% duty

• SOT-23-5 Package

cycle and ultra-low dropout operation.

APPLICATIONS

• TFT Monitor

• Auto PC

• Vehicle Security

• Navigation Systems

• Notebook Standby Supply

• Battery Powered Portable Applications

• Distributed Power Systems

Typical Application Circuit

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)

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LM3475 www.ti.com SNVS239B – OCTOBER 2004 – REVISED MARCH 2013 LM3475 Hysteretic PFET Buck Controller Check for Samples: LM3475 FEATURES 1 • • • • • • • • • 2 DESCRIPTION Easy to Use Control Methodology 0.8V to VIN Adjustable Output Range High Efficiency (90% Typical) ±0.9% (±1.
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LM3475 SNVS239B – OCTOBER 2004 – REVISED MARCH 2013 www.ti.com Connection Diagram 1 2 3 FB PGATE 5 GND 4 EN VIN Figure 1. Top View 5 Lead Plastic SOT-23-5 See Package Number DBV0005A PIN DESCRIPTION 2 Pin Name Pin Number Description FB 1 Feedback input. Connect to a resistor divider between the output and GND. GND 2 Ground. EN 3 Enable. Pull this pin above 1.5V (typical) for normal operation. When EN is low, the device enters shutdown mode. VIN 4 Power supply input.
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LM3475 www.ti.com SNVS239B – OCTOBER 2004 – REVISED MARCH 2013 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) VIN −0.3V to 16V PGATE −0.3V to 16V −0.3V to 5V FB −0.3V to 16V EN Storage Temperature −65°C to 150°C (3) 440mW Power Dissipation ESD Susceptibilty Human Body Model (4) 2.
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LM3475 SNVS239B – OCTOBER 2004 – REVISED MARCH 2013 www.ti.com Electrical Characteristics (continued) Specifications in Standard type face are for TJ = 25°C, and in bold type face apply over the full Operating Temperature Range (TJ = −40°C to +125°C). Unless otherwise specified, VIN = EN = 5.0V. Datasheet min/max specification limits are specified by design, test, or statistical analysis. Symbol IPGATE Parameter Driver Output Current Conditions Typ 0.475 Sink VPGATE = 3.5V CPGATE = 1nF 1.
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LM3475 www.ti.com SNVS239B – OCTOBER 2004 – REVISED MARCH 2013 Typical Performance Characteristics Unless specified otherwise, all curves taken at VIN = 5V, VOUT = 2.5V, L = 10 µH, COUT = 100 µF, ESR = 100mΩ, and TA = 25°C. Quiescent Current vs Input Voltage Feedback Voltage vs Temperature Figure 2. Figure 3. Hysteresis Voltage vs Input Voltage Hysteresis Voltage vs Temperature Figure 4. Figure 5.
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LM3475 SNVS239B – OCTOBER 2004 – REVISED MARCH 2013 www.ti.com Typical Performance Characteristics (continued) Unless specified otherwise, all curves taken at VIN = 5V, VOUT = 2.5V, L = 10 µH, COUT = 100 µF, ESR = 100mΩ, and TA = 25°C. 1 ms/DIV 6 VSW 2.5V/DIV VRIPPLE Output Ripple Voltage 20 mV/DIV VIN 2V/DIV VOUT 1V/DIV Start Up 2 Ps/DIV Figure 8. Figure 9.
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LM3475 www.ti.com SNVS239B – OCTOBER 2004 – REVISED MARCH 2013 Block Diagram reset Internal Regulator Level Shift PGATE UVD-Disable + VCC EN Pdrive en VIN en UVD Comp Blanking Timer FB UVD-Disable 70% VREF Band Gap Reference Hysteretic Comp + - VREF Vref Ramp Current Bias reset Soft-Start GND OPERATION DESCRIPTION OVERVIEW The LM3475 is a buck (step-down) DC-DC controller that uses a hysteretic control architecture, which results in Pulse Frequency Modulated (PFM) regulation.
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LM3475 SNVS239B – OCTOBER 2004 – REVISED MARCH 2013 www.ti.com VIN tON tOFF -VD Switch Voltage Iout 'IL Inductor Current td VOUT VOUT ripple (DC) VHYST td Output Voltage Figure 12. Hysteretic Waveforms The LM3475 operates in discontinuous conduction mode at light load current and continuous conduction mode at heavy load current. In discontinuous conduction mode, current through the inductor starts at zero and ramps up to the peak, then ramps down to zero.
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LM3475 www.ti.com SNVS239B – OCTOBER 2004 – REVISED MARCH 2013 At very low or very high duty cycle operation, maximum frequency will be limited by the blanking time.
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LM3475 SNVS239B – OCTOBER 2004 – REVISED MARCH 2013 www.ti.com SETTING OPERATING FREQUENCY AND OUTPUT RIPPLE Although hysteretic control is a simple control scheme, the operating frequency and other performance characteristics depend on external conditions and components. If the inductance, output capacitance, ESR, VIN, or Cff is changed, there will be a change in the operating frequency and possibly output ripple.
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LM3475 www.ti.com SNVS239B – OCTOBER 2004 – REVISED MARCH 2013 OUTPUT CAPACITOR SELECTION Once the desired operating frequency and inductance value are selected, ESR must be selected based on Equation 4. This process may involve a few iterations to select standard ESR and inductance values. In general, the ESR of the output capacitor and the inductor ripple current create the output ripple of the regulator. However, the comparator hysteresis sets the first order value of this ripple.
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LM3475 SNVS239B – OCTOBER 2004 – REVISED MARCH 2013 www.ti.com DIODE SELECTION The catch diode provides the current path to the load during the PFET off time. Therefore, the current rating of the diode must be higher than the average current through the diode, which be calculated as shown: ID_AVE = IOUT x (1 − D) (11) The peak voltage across the catch diode is approximately equal to the input voltage. Therefore, the diode’s peak reverse voltage rating should be greater than 1.3 times the input voltage.
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LM3475 www.ti.com SNVS239B – OCTOBER 2004 – REVISED MARCH 2013 MOSFETs are very fast switching devices. The fast increase in PFET current coupled with parasitic trace inductance can create unwanted noise spikes at both the switch node and at VIN. Switching noise will increase with load current and input voltage. This noise can also propagate through the ground plane, sometimes causing unpredictable device performance.
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LM3475 SNVS239B – OCTOBER 2004 – REVISED MARCH 2013 www.ti.com Table 1. Bill of Materials Designator Description Part Number Vendor CIN 10µF, 16V, X5R EMK325BJ106MN TAIYO YUDEN COUT 100µF, 6V, Ta TPSY107M006R0100 AVX CFF 1nF, 25V, X7R VJ1206Y102KXXA Vishay D1 Schottky, 20V, 2A CMSH2-20L Central Semiconductor L1 10µH, 3.1A CDRH103R100 Sumida 30V, 2.5A Si2343 Vishay 1kΩ, 0805, 1% CRW08051001F Vishay RFB1 2.
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LM3475 www.ti.com SNVS239B – OCTOBER 2004 – REVISED MARCH 2013 REVISION HISTORY Changes from Revision A (March 2013) to Revision B • 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 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.
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PACKAGE MATERIALS INFORMATION www.ti.com 23-Sep-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) LM3475MF SOT-23 DBV 5 1000 178.0 8.4 LM3475MF/NOPB SOT-23 DBV 5 1000 178.0 LM3475MFX/NOPB SOT-23 DBV 5 3000 178.0 3.2 3.2 1.4 4.0 8.0 Q3 8.4 3.2 3.2 1.4 4.0 8.0 Q3 8.4 3.2 3.2 1.4 4.0 8.
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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) LM3475MF SOT-23 DBV 5 1000 210.0 185.0 35.0 LM3475MF/NOPB SOT-23 DBV 5 1000 210.0 185.0 35.0 LM3475MFX/NOPB SOT-23 DBV 5 3000 210.0 185.0 35.
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