Datasheet

ManualsBrandsTEXAS INSTRUMENTS ManualsPMICsPMIC - DC/DC voltage regulator Boost SOT 23 5

Efficiency vs Load Current

EFFICIENCY (%)

LOAD CURRENT (mA)

3.3 -5V Boost

^z_sŒ•]}v

200

400

600

800

100

LM2731 ³<´

GND

SHDN

51K

SHDN

GND

3.3 V

2.2PF

13.3K

470pF

MBR0520

R1/40.5K

L1/6.8PH

22PF

OUT

700mA

(TYP)

Efficiency vs Load Current

EFFICIENCY (%)

LOAD CURRENT (mA)

100

200

300

400

100

LM2731 ³;´

GND

SHDN

51K

SHDN

GND

5 V

2.2PF

13.3K

220pF

MBR0520

R1/117K

L1/10PH

4.7PF

12V

OUT

500mA

(TYP)

500

5 - 12V Boost

^y_sŒ•]}v

TI Confidential - NDA Restrictions

LM2731

www.ti.com

SNVS217F –MAY 2004–REVISED NOVEMBER 2012

LM2731 0.6/1.6 MHz Boost Converters With 22V Internal FET Switch in SOT-23

Check for Samples: LM2731

FEATURES

DESCRIPTION

The LM2731 switching regulators are current-mode

• 22V DMOS FET Switch

boost converters operating at fixed frequencies of 1.6

• 1.6 MHz (“X”), 0.6 MHz (“Y”) Switching

MHz (“X” option) and 600 kHz (“Y” option).

Frequency

The use of SOT-23 package, made possible by the

• Low R

(ON) DMOS FET

minimal power loss of the internal 1.8A switch, and

• Switch Current up to 1.8A

use of small inductors and capacitors result in the

industry's highest power density. The 22V internal

• Wide Input Voltage Range (2.7V–14V)

switch makes these solutions perfect for boosting to

• Low Shutdown Current (<1 µA)

voltages up to 20V.

• 5-Lead SOT-23 Package

These parts have a logic-level shutdown pin that can

• Uses Tiny Capacitors and Inductors

be used to reduce quiescent current and extend

• Cycle-by-Cycle Current Limiting

battery life.

• Internally Compensated

Protection is provided through cycle-by-cycle current

limiting and thermal shutdown. Internal compensation

APPLICATIONS

simplifies design and reduces component count.

• White LED Current Source

Table 1. Switch Frequency

• PDA’s and Palm-Top Computers

X Y

• Digital Cameras

1.6 MHz 0.6 MHz

• Portable Phones and Games

• Local Boost Regulator

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 (16 pages)

PAGE 1
TI Confidential - NDA Restrictions LM2731 www.ti.com SNVS217F – MAY 2004 – REVISED NOVEMBER 2012 LM2731 0.6/1.6 MHz Boost Converters With 22V Internal FET Switch in SOT-23 Check for Samples: LM2731 FEATURES DESCRIPTION • • The LM2731 switching regulators are current-mode boost converters operating at fixed frequencies of 1.6 MHz (“X” option) and 600 kHz (“Y” option). 1 2 • • • • • • • • 22V DMOS FET Switch 1.6 MHz (“X”), 0.
PAGE 2
TI Confidential - NDA Restrictions LM2731 SNVS217F – MAY 2004 – REVISED NOVEMBER 2012 www.ti.com Efficiency vs Load Current U1 VIN R3 51K SW R1/117K LM2731 ³<´ FB SHDN GND GND EFFICIENCY (%) 3.3 VIN SHDN D1 MBR0520 L1/6.8PH C1 2.2PF CF 270pF R2 13.3K 12V OUT 230mA (TYP) C2 10PF 100 90 80 70 60 50 40 30 20 10 0 3.3 -12V Boost ^z_ s Œ•]}v 50 100 150 200 250 0 LOAD (mA) R3 51K U1 GND SW R1/84K LM2731 ³;´ SHDN GND C1 2.
PAGE 3
TI Confidential - NDA Restrictions LM2731 www.ti.com SNVS217F – MAY 2004 – REVISED NOVEMBER 2012 PIN DESCRIPTIONS Pin Name 1 SW 2 GND 3 FB 4 SHDN 5 VIN Function Drain of the internal FET switch. Analog and power ground. Feedback point that connects to external resistive divider. Shutdown control input. Connect to Vin if the feature is not used. Analog and power input. These devices have limited built-in ESD protection.
PAGE 4
TI Confidential - NDA Restrictions LM2731 SNVS217F – MAY 2004 – REVISED NOVEMBER 2012 www.ti.com Electrical Characteristics Limits in standard typeface are for TJ = 25°C, and limits in boldface type apply over the full operating temperature range (−40°C ≤ TJ ≤ +125°C). Unless otherwise specified: VIN = 5V, VSHDN = 5V, IL = 0A. Parameter VIN Test Conditions Input Voltage VOUT (MIN) Minimum Output Voltage Under Load Min (1) Typ (2) 2.7 RL = 43Ω X Option (3) VIN = 2.7V 5.4 7 VIN = 3.
PAGE 5
TI Confidential - NDA Restrictions LM2731 www.ti.com SNVS217F – MAY 2004 – REVISED NOVEMBER 2012 Typical Performance Characteristics Unless otherwise specified: VIN = 5V, SHDN pin tied to VIN. Iq Vin (Active) vs Temperature - "Y" 2.2 1.25 2.15 1.2 2.1 1.15 IQ VIN ACTIVE (mA) IQ VIN ACTIVE (mA) Iq Vin (Active) vs Temperature - "X" 2.05 2 1.95 1.1 1.05 1 1.9 0.95 1.85 1.8 -50 -25 0 25 50 75 0.9 -50 100 125 150 -25 50 75 100 125 150 Figure 3. Figure 4.
PAGE 6
TI Confidential - NDA Restrictions LM2731 SNVS217F – MAY 2004 – REVISED NOVEMBER 2012 www.ti.com Typical Performance Characteristics (continued) Unless otherwise specified: VIN = 5V, SHDN pin tied to VIN. Iq Vin (Idle) vs Temperature Feedback Bias Current vs Temperature 0.09 375 0.08 FEEDBACK BIAS CURRENT (PA) 380 IQ VIN (IDLE) (PA) 370 365 360 355 350 345 340 -50 0 -25 50 25 0.07 0.06 0.05 0.04 0.03 0.02 0.01 0 -50 75 100 125 150 -25 75 100 125 150 Figure 10.
PAGE 7
TI Confidential - NDA Restrictions LM2731 www.ti.com SNVS217F – MAY 2004 – REVISED NOVEMBER 2012 Typical Performance Characteristics (continued) Unless otherwise specified: VIN = 5V, SHDN pin tied to VIN. Efficiency vs Load Current - "X" VIN = 2.7V, VOUT = 5V 100 100 90 80 80 EFFICIENCY (%) 90 EFFICIENCY (%) 70 60 50 40 70 60 50 40 30 30 20 20 10 10 0 0 100 50 200 150 250 Efficiency vs Load Current - "X" VIN = 3.
PAGE 8
TI Confidential - NDA Restrictions LM2731 SNVS217F – MAY 2004 – REVISED NOVEMBER 2012 www.ti.com Typical Performance Characteristics (continued) Unless otherwise specified: VIN = 5V, SHDN pin tied to VIN. Efficiency vs Load Current - "X" VIN = 5V, VOUT = 18V 100 90 90 80 80 EFFICIENCY (%) EFFICIENCY (%) 100 Efficiency vs Load Current - "Y" VIN = 2.
PAGE 9
TI Confidential - NDA Restrictions LM2731 www.ti.com SNVS217F – MAY 2004 – REVISED NOVEMBER 2012 Typical Performance Characteristics (continued) Unless otherwise specified: VIN = 5V, SHDN pin tied to VIN. Efficiency vs Load Current - "Y" VIN = 5V, VOUT = 12V 100 90 EFFICIENCY (%) 80 70 60 50 40 30 20 10 0 0 100 200 300 400 500 600 LOAD (mA) Figure 27.
PAGE 10
TI Confidential - NDA Restrictions LM2731 SNVS217F – MAY 2004 – REVISED NOVEMBER 2012 www.ti.com THEORY OF OPERATION The LM2731 is a switching converter IC that operates at a fixed frequency (0.6 or 1.6 MHz) for fast transient response over a wide input voltage range and incorporates pulse-by-pulse current limiting protection.
PAGE 11
TI Confidential - NDA Restrictions LM2731 www.ti.com SNVS217F – MAY 2004 – REVISED NOVEMBER 2012 FEED-FORWARD COMPENSATION Although internally compensated, the feed-forward capacitor Cf is required for stability (see Figure 29). Adding this capacitor puts a zero in the loop response of the converter. The recommended frequency for the zero fz should be approximately 6 kHz.
PAGE 12
TI Confidential - NDA Restrictions LM2731 SNVS217F – MAY 2004 – REVISED NOVEMBER 2012 www.ti.com SWITCHING FREQUENCY The LM2731 is provided with two switching frequencies: the “X” version is typically 1.6 MHz, while the “Y” version is typically 600 kHz. The best frequency for a specific application must be determined based on the trade-offs involved: Higher switching frequency means the inductors and capacitors can be made smaller and cheaper for a given output voltage and current.
PAGE 13
TI Confidential - NDA Restrictions LM2731 www.ti.com SNVS217F – MAY 2004 – REVISED NOVEMBER 2012 Using the equation: V = L (di/dt) (6) We can then calculate the di/dt rate of the inductor which is found to be 0.45 A/µs during the ON time. Using these facts, we can then show what the inductor current will look like during operation: Figure 30. 10 µH Inductor Current, 5V–12V Boost (LM2731X) During the 0.390 µs ON time, the inductor current ramps up 0.
PAGE 14
TI Confidential - NDA Restrictions LM2731 SNVS217F – MAY 2004 – REVISED NOVEMBER 2012 www.ti.com CALCULATING LOAD CURRENT As shown in the figure which depicts inductor current, the load current is related to the average inductor current by the relation: ILOAD = IIND(AVG) x (1 - DC) (7) Where "DC" is the duty cycle of the application.
PAGE 15
TI Confidential - NDA Restrictions LM2731 www.ti.com SNVS217F – MAY 2004 – REVISED NOVEMBER 2012 DESIGN PARAMETERS VSW AND ISW The value of the FET "ON" voltage (referred to as VSW in the equations) is dependent on load current. A good approximation can be obtained by multiplying the "ON Resistance" of the FET times the average inductor current.
PAGE 16
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