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LM2734

SNVS288J –SEPTEMBER 2004–REVISED DECEMBER 2014

LM2734 Thin SOT 1-A Load Step-Down DC-DC Regulator

1 Features 3 Description

The LM2734 regulator is a monolithic, high-

1• Thin SOT-6 Package frequency, PWM step-down DC-DC converter in a 6-

• 3.0-V to 20-V Input Voltage Range pin Thin SOT package. The device provides all the

• 0.8-V to 18-V Output Voltage Range active functions to provide local DC-DC conversion

with fast transient response and accurate regulation

• 1-A Output Current in the smallest possible PCB area.

• 550-kHz (LM2734Y) and 1.6-MHz (LM2734X)

Switching Frequencies With a minimum of external components and online

design support through WEBENCH, the LM2734

• 300-mΩNMOS Switch regulator is easy to use. The ability to drive 1-A loads

• 30-nA Shutdown Current with an internal 300-mΩNMOS switch using state-of-

• 0.8-V, 2% Internal Voltage Reference the-art 0.5-µm BiCMOS technology results in the best

power density available. The world-class control

• Internal Soft-Start circuitry allows for on-times as low as 13 ns, thus

• Current-Mode, PWM Operation supporting exceptionally high-frequency conversion

• WEBENCH®Online Design Tool over the entire 3-V to 20-V input operating range

down to the minimum output voltage of 0.8 V.

• Thermal Shutdown Switching frequency is internally set to 550 kHz

• LM2734XQ and LM2734YQ are AEC-Q100 Grade (LM2734Y) or 1.6 MHz (LM2734X), allowing the use

1 Qualified and are Manufactured on an of extremely small surface-mount inductors and chip

Automotive Grade Flow. capacitors. Even though the operating frequencies

are very high, efficiencies up to 90% are easy to

2 Applications achieve. External shutdown is included, featuring an

ultra-low standby current of 30 nA.

• Local Point-of-Load Regulation

• Core Power in HDDs The LM2734 regulator uses current-mode control and

internal compensation to provide high-performance

• Set-Top Boxes regulation over a wide range of operating conditions.

• Battery-Powered Devices Additional features include internal soft-start circuitry

• USB Powered Devices to reduce inrush current, pulse-by-pulse current limit,

thermal shutdown, and output overvoltage protection.

• DSL Modems

• Notebook Computers Device Information(1)

• Automotive PART NUMBER PACKAGE BODY SIZE (NOM)

LM2734 SOT (6) 2.90 mm x 1.60 mm

(1) For all available packages, see the orderable addendum at

the end of the datasheet.

Typical Application Circuit Efficiency vs Load Current

VIN =5V,VOUT = 3.3 V

An IMPORTANT NOTICE at the end of this data sheet addresses availability, warranty, changes, use in safety-critical applications,

intellectual property matters and other important disclaimers. PRODUCTION DATA.

LM2734

SNVS288J –SEPTEMBER 2004–REVISED DECEMBER 2014

www.ti.com

Table of Contents

7.3 Feature Description................................................... 9

1 Features.................................................................. 17.4 Device Functional Modes........................................ 10

2 Applications ........................................................... 18 Application and Implementation ........................ 11

3 Description............................................................. 18.1 Application Information............................................ 11

4 Revision History..................................................... 28.2 Typical Applications ................................................ 14

5 Pin Configuration and Functions......................... 39 Power Supply Recommendations...................... 28

6 Specifications......................................................... 410 Layout................................................................... 28

6.1 Absolute Maximum Ratings ...................................... 410.1 Layout Guidelines ................................................. 28

6.2 ESD Ratings.............................................................. 410.2 Layout Example .................................................... 29

6.3 Recommended Operating Conditions....................... 411 Device and Documentation Support................. 30

6.4 Thermal Information.................................................. 411.1 Third-Party Products Disclaimer ........................... 30

6.5 Electrical Characteristics........................................... 511.2 Trademarks........................................................... 30

6.6 Typical Performance Characteristics ........................ 611.3 Electrostatic Discharge Caution............................ 30

7 Detailed Description.............................................. 811.4 Glossary................................................................ 30

7.1 Overview................................................................... 812 Mechanical, Packaging, and Orderable

7.2 Functional Block Diagram......................................... 9Information ........................................................... 30

4 Revision History

Changes from Revision I (April 2013) to Revision J Page

• Added ESD Ratings table, Feature Description section, Device Functional Modes,Application and Implementation

section, Power Supply Recommendations section, Layout section, Device and Documentation Support section, and

Mechanical, Packaging, and Orderable Information section.................................................................................................. 1

Product Folder Links: LM2734

BOOST

GND

VIN

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SNVS288J –SEPTEMBER 2004–REVISED DECEMBER 2014

5 Pin Configuration and Functions

See Package Number DDC (R-PDSO-G6)

6-Lead SOT

Top View

Pin Functions

PIN I/O DESCRIPTION

NAME NO.

Boost voltage that drives the internal NMOS control switch. A bootstrap capacitor is

BOOST 1 I connected between the BOOST and SW pins.

Signal and Power ground pin. Place the bottom resistor of the feedback network as close as

GND 2 GND possible to this pin for accurate regulation.

FB 3 I Feedback pin. Connect FB to the external resistor divider to set output voltage.

Enable control input. Logic high enables operation. Do not allow this pin to float or be greater

EN 4 I than VIN + 0.3 V.

VIN 5 I Input supply voltage. Connect a bypass capacitor to this pin.

SW 6 O Output switch. Connects to the inductor, catch diode, and bootstrap capacitor.

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6 Specifications

6.1 Absolute Maximum Ratings

over operating free-air temperature (unless otherwise noted)(1)(2)

MIN MAX UNIT

VIN -0.5 24 V

SW Voltage -0.5 24 V

Boost Voltage -0.5 30 V

Boost to SW Voltage -0.5 6.0 V

FB Voltage -0.5 0.3 V

EN Voltage -0.5 VIN + 0.3 V

Junction Temperature 150 °C

Soldering Information Reflow Peak Pkg. Temp.(15s) 260 °C

Tstg Storage temperature -65 150 °C

(1) Stresses beyond those listed under Absolute Maximum Ratings may cause permanent damage to the device. These are stress ratings

only, which do not imply functional operation of the device at these or any other conditions beyond those indicated under Recommended

Operating Conditions. Exposure to absolute-maximum-rated conditions for extended periods may affect device reliability.

(2) If Military/Aerospace specified devices are required, please contact the Texas Instruments Sales Office/ Distributors for availability and

specifications.

6.2 ESD Ratings VALUE UNIT

VESD Electrostatic discharge Human Body Model (HBM), per ANSI/ESDA/JEDEC JS001(1) ±2000 V

(1) JEDEC document JEP155 states that 500-V HBM allows safe manufacturing with a standard ESD control process.

6.3 Recommended Operating Conditions

over operating free-air temperature range (unless otherwise noted) MIN NOM MAX UNIT

VIN 3 20 V

SW Voltage -0.5 20 V

Boost Voltage -0.5 25 V

Boost to SW Voltage 1.6 5.5 V

Junction Temperature Range −40 125 °C

6.4 Thermal Information LM2734

THERMAL METRIC(1) DDC UNIT

6 PINS

RθJA Junction-to-ambient thermal resistance 158.1

RθJC(top) Junction-to-case (top) thermal resistance 46.5

RθJB Junction-to-board thermal resistance 29.5 °C/W

ψJT Junction-to-top characterization parameter 0.8

ψJB Junction-to-board characterization parameter 29.2

RθJC(bot) Junction-to-case (bottom) thermal resistance n/a

(1) For more information about traditional and new thermal metrics, see the IC Package Thermal Metrics application report, SPRA953.

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SNVS288J –SEPTEMBER 2004–REVISED DECEMBER 2014

6.5 Electrical Characteristics

VIN = 5V, VBOOST - VSW = 5V unless otherwise specified. Datasheet min/max specification limits are ensured by design, test, or

statistical analysis. TJ= 25°C TJ= -40°C to 125°C

PARAMETER TEST CONDITIONS UNIT

MIN(1) TYP(2) MAX(1) MIN TYP MAX

VFB Feedback Voltage 0.800 0.784 0.816 V

ΔVFB/ΔFeedback Voltage Line VIN = 3V to 20V 0.01 % / V

VIN Regulation

Feedback Input Bias Sink/Source

IFB 10 250 nA

Current

Undervoltage Lockout VIN Rising 2.74 2.90

UVLO Undervoltage Lockout VIN Falling 2.3 2.0 V

UVLO Hysteresis 0.44 0.30 0.62

LM2734X 1.6 1.2 1.9

FSW Switching Frequency MHz

LM2734Y 0.55 0.40 0.66

LM2734X 92 85%

DMAX Maximum Duty Cycle LM2734Y 96 90%

LM2734X 2%

DMIN Minimum Duty Cycle LM2734Y 1%

RDS(ON) Switch ON Resistance VBOOST - VSW = 3V 300 600 mΩ

ICL Switch Current Limit VBOOST - VSW = 3V 1.7 1.2 2.5 A

IQQuiescent Current Switching 1.5 2.5 mA

Quiescent Current VEN = 0V 30 nA

(shutdown) LM2734X (50% Duty 2.5 3.5

Cycle)

IBOOST Boost Pin Current mA

LM2734Y (50% Duty 1.0 1.8

Cycle)

Shutdown Threshold VEN Falling 0.4

Voltage

VEN_TH V

Enable Threshold VEN Rising 1.8

Voltage

IEN Enable Pin Current Sink/Source 10 nA

ISW Switch Leakage 40 nA

(1) Specified to Average Outgoing Quality Level (AOQL).

(2) Typicals represent the most likely parametric norm.

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6.6 Typical Performance Characteristics

All curves taken at VIN = 5 V, VBOOST - VSW = 5 V and TA= 25°C, unless specified otherwise.

Figure 1. Oscillator Frequency vs Temperature - L1 = 4.7 µH Figure 2. Oscillator Frequency vs Temperature - L1 = 10 μH

Figure 3. Current Limit vs Temperature Figure 4. Current Limit vs Temperature

VIN = 20 V

Figure 5. VFB vs Temperature Figure 6. RDSON vs Temperature

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Typical Performance Characteristics (continued)

All curves taken at VIN = 5 V, VBOOST - VSW = 5 V and TA= 25°C, unless specified otherwise.

Figure 7. IQSwitching vs Temperature Figure 8. Line Regulation - L1 = 4.7 µH

VOUT = 1.5 V, IOUT = 500 mA

Figure 9. Line Regulation - L1 = 10 μH Figure 10. Line Regulation - L1 = 4.7 µH

VOUT = 1.5 V, IOUT = 500 mA VOUT = 3.3 V, IOUT = 500 mA

Figure 11. Line Regulation - L1 = 10 μH

VOUT = 3.3 V, IOUT = 500 mA

Product Folder Links: LM2734

VIN

TON

Inductor

Current

D = TON/TSW

VSW

TOFF

TSW

IPK

Voltage

LM2734

SNVS288J –SEPTEMBER 2004–REVISED DECEMBER 2014

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7 Detailed Description

7.1 Overview

The LM2734 device is a constant frequency PWM buck regulator IC that delivers a 1-A load current. The

regulator has a preset switching frequency of either 550 kHz (LM2734Y) or 1.6 MHz (LM2734X). These high

frequencies allow the LM2734 device to operate with small surface-mount capacitors and inductors, resulting in

DC-DC converters that require a minimum amount of board space. The LM2734 device is internally

compensated, so it is simple to use, and requires few external components. The LM2734 device uses current-

mode control to regulate the output voltage.

The following operating description of the LM2734 device will refer to the Simplified Block Diagram () and to the

waveforms in Figure 12. The LM2734 device supplies a regulated output voltage by switching the internal NMOS

control switch at constant frequency and variable duty cycle. A switching cycle begins at the falling edge of the

reset pulse generated by the internal oscillator. When this pulse goes low, the output control logic turns on the

internal NMOS control switch. During this on-time, the SW pin voltage (VSW) swings up to approximately VIN, and

the inductor current (IL) increases with a linear slope. ILis measured by the current-sense amplifier, which

generates an output proportional to the switch current. The sense signal is summed with the regulator’s

corrective ramp and compared to the error amplifier’s output, which is proportional to the difference between the

feedback voltage and VREF. When the PWM comparator output goes high, the output switch turns off until the

next switching cycle begins. During the switch off-time, inductor current discharges through Schottky diode D1,

which forces the SW pin to swing below ground by the forward voltage (VD) of the catch diode. The regulator

loop adjusts the duty cycle (D) to maintain a constant output voltage.

Figure 12. LM2734 Waveforms of SW Pin Voltage and Inductor Current

Product Folder Links: LM2734

BOOST

Output

Control

Logic

Current

Limit

Thermal

Shutdown

Under

Voltage

Lockout

Corrective Ramp

Reset

Pulse

PWM

Comparator

Current-Sense Amplifier RSENSE

Internal

Regulator

and

Enable

Circuit

Oscillator

Driver 0.3:

Switch

Internal

Compensation

GND

Error Amplifier -

+VREF

0.8V

COUT

OFF

VBOOST

VSW

CBOOST

VOUT

CIN

VIN

ISENSE

-0.88V

OVP

Comparator

Error

Signal

LM2734

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SNVS288J –SEPTEMBER 2004–REVISED DECEMBER 2014

7.2 Functional Block Diagram

7.3 Feature Description

7.3.1 Output Overvoltage Protection

The overvoltage comparator compares the FB pin voltage to a voltage that is 10% higher than the internal

reference Vref. Once the FB pin voltage goes 10% above the internal reference, the internal NMOS control

switch is turned off, which allows the output voltage to decrease toward regulation.

7.3.2 Undervoltage Lockout

Undervoltage lockout (UVLO) prevents the LM2734 from operating until the input voltage exceeds 2.74 V

(typical).

The UVLO threshold has approximately 440 mV of hysteresis, so the part will operate until VIN drops below 2.3 V

(typical). Hysteresis prevents the part from turning off during power up if VIN is nonmonotonic.

7.3.3 Current Limit

The LM2734 device uses cycle-by-cycle current limiting to protect the output switch. During each switching cycle,

a current limit comparator detects if the output switch current exceeds 1.7 A (typical), and turns off the switch

until the next switching cycle begins.

7.3.4 Thermal Shutdown

Thermal shutdown limits total power dissipation by turning off the output switch when the IC junction temperature

exceeds 165°C. After thermal shutdown occurs, the output switch does not turn on until the junction temperature

drops to approximately 150°C.

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7.4 Device Functional Modes

7.4.1 Enable Pin / Shutdown Mode

The LM2734 device has a shutdown mode that is controlled by the enable pin (EN). When a logic low voltage is

applied to EN, the part is in shutdown mode and its quiescent current drops to typically 30 nA. Switch leakage

adds another 40 nA from the input supply. The voltage at this pin should never exceed VIN + 0.3 V.

7.4.2 Soft-Start

This function forces VOUT to increase at a controlled rate during start up. During soft-start, the error amplifier’s

reference voltage ramps from 0 V to its nominal value of 0.8 V in approximately 200 µs. This forces the regulator

output to ramp up in a more linear and controlled fashion, which helps reduce inrush current. Under some

circumstances at start-up, an output voltage overshoot may still be observed. This may be due to a large output

load applied during start up. Large amounts of output external capacitance can also increase output voltage

overshoot. A simple solution is to add a feed forward capacitor with a value between 470 pf and 1000 pf across

the top feedback resistor (R1). See Figure 23 for further detail.

Product Folder Links: LM2734

LM2734

BOOST

GND

COUT

CBOOST

VOUT

CIN

VIN

VBOOST

LM2734

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SNVS288J –SEPTEMBER 2004–REVISED DECEMBER 2014

8 Application and Implementation

NOTE

Information in the following applications sections is not part of the TI component

specification, and TI does not warrant its accuracy or completeness. TI’s customers are

responsible for determining suitability of components for their purposes. Customers should

validate and test their design implementation to confirm system functionality.

8.1 Application Information

8.1.1 Boost Function

Capacitor CBOOST and diode D2 in Figure 13 are used to generate a voltage VBOOST. VBOOST - VSW is the gate

drive voltage to the internal NMOS control switch. To properly drive the internal NMOS switch during its on-time,

VBOOST needs to be at least 1.6 V greater than VSW. Although the LM2734 device will operate with this minimum

voltage, it may not have sufficient gate drive to supply large values of output current. Therefore, it is

recommended that VBOOST be greater than 2.5 V above VSW for best efficiency. VBOOST – VSW should not exceed

the maximum operating limit of 5.5 V.

5.5 V > VBOOST – VSW > 2.5 V for best performance.

Figure 13. VOUT Charges CBOOST

When the LM2734 device starts up, internal circuitry from the BOOST pin supplies a maximum of 20 mA to

CBOOST. This current charges CBOOST to a voltage sufficient to turn the switch on. The BOOST pin will continue to

source current to CBOOST until the voltage at the feedback pin is greater than 0.76 V.

There are various methods to derive VBOOST:

1. From the input voltage (VIN)

2. From the output voltage (VOUT)

3. From an external distributed voltage rail (VEXT)

4. From a shunt or series Zener diode

In the simplified block diagram of Functional Block Diagram, capacitor CBOOST and diode D2 supply the gate-

drive current for the NMOS switch. Capacitor CBOOST is charged via diode D2 by VIN. During a normal switching

cycle, when the internal NMOS control switch is off (TOFF) (refer to Figure 12), VBOOST equals VIN minus the

forward voltage of D2 (VFD2), during which the current in the inductor (L) forward biases the Schottky diode D1

(VFD1). Therefore the voltage stored across CBOOST is:

VBOOST - VSW = VIN - VFD2 + VFD1 (1)

When the NMOS switch turns on (TON), the switch pin rises to:

VSW = VIN – (RDSON × IL), (2)

forcing VBOOST to rise thus reverse biasing D2. The voltage at VBOOST is then:

VBOOST = 2VIN – (RDSON × IL) – VFD2 + VFD1 (3)

which is approximately:

2VIN - 0.4 V (4)

Product Folder Links: LM2734

LM2734

VIN BOOST

GND

CBOOST

CIN

VIN

COUT

VOUT

VBOOST

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Application Information (continued)

for many applications. Thus the gate-drive voltage of the NMOS switch is approximately:

VIN - 0.2 V (5)

An alternate method for charging CBOOST is to connect D2 to the output as shown in Figure 13. The output

voltage should be from 2.5 V and 5.5 V, so that proper gate voltage will be applied to the internal switch. In this

circuit, CBOOST provides a gate drive voltage that is slightly less than VOUT.

In applications where both VIN and VOUT are greater than 5.5 V, or less than 3 V, CBOOST cannot be charged

directly from these voltages. If VIN to VOUT are greater than 5.5 V, CBOOST can be charged from VIN or VOUT minus

a Zener voltage by placing a Zener diode D3 in series with D2, as shown in Figure 14. When using a series

Zener diode from the input, ensure that the regulation of the input supply does not create a voltage that falls

outside the recommended VBOOST voltage.

(VINMAX – VD3) < 5.5 V (6)

(VINMIN – VD3) > 1.6 V (7)

Figure 14. Zener Reduces Boost Voltage from VIN

An alternative method is to place the Zener diode D3 in a shunt configuration as shown in Figure 15. A small 350

mW to 500 mW 5.1-V Zener diode in a SOT or SOD package can be used for this purpose. A small ceramic

capacitor such as a 6.3 V, 0.1-µF capacitor (C4) should be placed in parallel with the Zener diode. When the

internal NMOS switch turns on, a pulse of current is drawn to charge the internal NMOS gate capacitance. The

0.1-µF parallel shunt capacitor ensures that the VBOOST voltage is maintained during this time.

Resistor R3 should be chosen to provide enough RMS current to the Zener diode (D3) and to the BOOST pin. A

recommended choice for the Zener current (IZENER) is 1 mA. The current IBOOST into the BOOST pin supplies the

gate current of the NMOS control switch and varies typically according to the following formula for the X version:

IBOOST = 0.56 × (D + 0.54) × (VZENER – VD2) mA (8)

IBOOST can be calculated for the Y version using the following:

IBOOST = 0.22 × (D + 0.54) × (VZENER - VD2) µA (9)

where D is the duty cycle, VZENER and VD2 are in volts, and IBOOST is in milliamps. VZENER is the voltage applied to

the anode of the boost diode (D2), and VD2 is the average forward voltage across D2. Note that this formula for

IBOOST gives typical current. For the worst case IBOOST, increase the current by 40%. In that case, the worst case

boost current will be:

IBOOST-MAX = 1.4 × IBOOST (10)

R3 will then be given by:

R3 = (VIN - VZENER) / (1.4 × IBOOST + IZENER) (11)

For example, using the X-version let VIN = 10 V, VZENER =5V,VD2 = 0.7 V, IZENER = 1 mA, and duty cycle D =

50%. Then:

IBOOST = 0.56 × (0.5 + 0.54) × (5 - 0.7) mA = 2.5 mA (12)

R3 = (10 V - 5 V) / (1.4 × 2.5 mA + 1 mA) = 1.11 kΩ(13)

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LM2734

VIN BOOST

GND

VBOOST

CBOOST

VIN

CIN

VOUT

COUT

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SNVS288J –SEPTEMBER 2004–REVISED DECEMBER 2014

Application Information (continued)

Figure 15. Boost Voltage Supplied from the Shunt Zener on VIN

Product Folder Links: LM2734

D = VO + VD

VIN + VD - VSW

D = VO

VIN

LM2734

VIN VIN

BOOST

GND

VOUT

C3 L1

OFF

C1 R3

LM2734

SNVS288J –SEPTEMBER 2004–REVISED DECEMBER 2014

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8.2 Typical Applications

8.2.1 LM2734X (1.6 MHz) VBOOST Derived from VIN 5V to 1.5 V/1 A

Figure 16. LM2734X (1.6 MHz) VBOOST Derived from VIN 5 V to 1.5-V/1-A Schematic

8.2.1.1 Design Requirements

Derive charge for VBOOST from the input supply (VIN ). VBOOST – VSW should not exceed the maximum operating

limit of 5.5V.

8.2.1.2 Detailed Design Procedure

Table 1. Bill of Materials for Figure 16

PART ID PART VALUE MANUFACTURER PART NUMBER

U1 1-A Buck Regulator Texas Instruments LM2734X

C1, Input Cap 10 µF, 6.3V, X5R TDK C3216X5ROJ106M

C2, Output Cap 10 µF, 6.3V, X5R TDK C3216X5ROJ106M

C3, Boost Cap 0.01 uF, 16V, X7R TDK C1005X7R1C103K

D1, Catch Diode 0.3 VFSchottky 1 A, 10 VR ON Semi MBRM110L

D2, Boost Diode 1VF@ 50-mA Diode Diodes, Inc. 1N4148W

L1 4.7µH, 1.7A, TDK VLCF4020T- 4R7N1R2

R1 8.87 kΩ, 1% Vishay CRCW06038871F

R2 10.2 kΩ, 1% Vishay CRCW06031022F

R3 100 kΩ, 1% Vishay CRCW06031003F

8.2.1.2.1 Inductor Selection

The Duty Cycle (D) can be approximated quickly using the ratio of output voltage (VO) to input voltage (VIN):

(14)

The catch diode (D1) forward voltage drop and the voltage drop across the internal NMOS must be included to

calculate a more accurate duty cycle. Calculate D by using the following formula:

(15)

VSW can be approximated by:

VSW = IOx RDS(ON) (16)

Product Folder Links: LM2734

IRMS-IN = IO x D x r2

1-D +

L = VO + VD

IO x r x fSx (1-D)

r = 'iL

LM2734

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SNVS288J –SEPTEMBER 2004–REVISED DECEMBER 2014

The diode forward drop (VD) can range from 0.3 V to 0.7 V depending on the quality of the diode. The lower VD

is, the higher the operating efficiency of the converter.

The inductor value determines the output ripple current. Lower inductor values decrease the size of the inductor,

but increase the output ripple current. An increase in the inductor value will decrease the output ripple current.

The ratio of ripple current (ΔiL) to output current (IO) is optimized when it is set between 0.3 and 0.4 at 1 A. The

ratio r is defined as:

(17)

One must also ensure that the minimum current limit (1.2 A) is not exceeded, so the peak current in the inductor

must be calculated. The peak current (ILPK) in the inductor is calculated as shown in Equation 18:

ILPK = IO+ΔIL/2 (18)

If r = 0.5 at an output of 1 A, the peak current in the inductor will be 1.25 A. The minimum specified current limit

over all operating conditions is 1.2 A. One can either reduce r to 0.4 resulting in a 1.2-A peak current, or make

the engineering judgement that 50 mA over will be safe enough with a 1.7-A typical current limit and 6 sigma

limits. When the designed maximum output current is reduced, the ratio r can be increased. At a current of 0.1 A,

r can be made as high as 0.9. The ripple ratio can be increased at lighter loads because the net ripple is actually

quite low, and if r remains constant the inductor value can be made quite large. An equation empirically

developed for the maximum ripple ratio at any current less than 2 A is:

r = 0.387 x IOUT-0.3667 (19)

Note that this is just a guideline.

The LM2734 device operates at frequencies allowing the use of ceramic output capacitors without compromising

transient response. Ceramic capacitors allow higher inductor ripple without significantly increasing output ripple.

See Output Capacitor for more details on calculating output voltage ripple.

Now that the ripple current or ripple ratio is determined, the inductance is calculated as shown in Equation 20:

where

• fsis the switching frequency

• IOis the output current. (20)

When selecting an inductor, make sure that it is capable of supporting the peak output current without saturating.

Inductor saturation will result in a sudden reduction in inductance and prevent the regulator from operating

correctly. Because of the speed of the internal current limit, it necessary to specify the peak current of the

inductor only for the required maximum output current. For example, if the designed maximum output current is

0.5 A and the peak current is 0.7 A, then the inductor should be specified with a saturation current limit of >0.7 A.

There is no need to specify the saturation or peak current of the inductor at the 1.7-A typical switch current limit.

The difference in inductor size is a factor of 5. Because of the operating frequency of the LM2734, ferrite based

inductors are preferred to minimize core losses. This presents little restriction because the variety of ferrite based

inductors is huge. Lastly, inductors with lower series resistance (DCR) will provide better operating efficiency. For

recommended inductors see example circuits.

8.2.1.2.2 Input Capacitor

An input capacitor is necessary to ensure that VIN does not drop excessively during switching transients. The

primary specifications of the input capacitor are capacitance, voltage, RMS current rating, and ESL (Equivalent

Series Inductance). The recommended input capacitance is 10 µF, although 4.7 µF is sufficient for input voltages

below 6 V. The input voltage rating is specifically stated by the capacitor manufacturer. Make sure to check any

recommended deratings and also verify if there is any significant change in capacitance at the operating input

voltage and the operating temperature. The input capacitor maximum RMS input current rating (IRMS-IN) must be

greater than:

(21)

Product Folder Links: LM2734

IRMS-OUT = IO x r

'VO = 'iL x (RESR + 1

8 x fS x CO)

LM2734

SNVS288J –SEPTEMBER 2004–REVISED DECEMBER 2014

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From Equation 21 from the above equation that maximum RMS capacitor current occurs when D = 0.5. Always

calculate the RMS at the point where the duty cycle, D, is closest to 0.5. The ESL of an input capacitor is usually

determined by the effective cross sectional area of the current path. A large leaded capacitor will have high ESL

and a 0805 ceramic chip capacitor will have very low ESL. At the operating frequencies of the LM2734 device,

certain capacitors may have an ESL so large that the resulting impedance (2πfL) will be higher than that required

to provide stable operation. As a result, surface-mount capacitors are strongly recommended. Sanyo POSCAP,

Tantalum or Niobium, Panasonic SP or Cornell Dubilier ESR, and multilayer ceramic capacitors (MLCC) are all

good choices for both input and output capacitors and have very low ESL. For MLCCs it is recommended to use

X7R or X5R dielectrics. Consult the capacitor manufacturer data sheet to see how rated capacitance varies over

operating conditions.

8.2.1.2.3 Output Capacitor

The output capacitor is selected based upon the desired output ripple and transient response. The initial current

of a load transient is provided mainly by the output capacitor. The output ripple of the converter is:

(22)

When using MLCCs, the ESR is typically so low that the capacitive ripple may dominate. When this occurs, the

output ripple will be approximately sinusoidal and 90° phase shifted from the switching action. Given the

availability and quality of MLCCs and the expected output voltage of designs using the LM2734 device, there is

really no need to review any other capacitor technologies. Another benefit of ceramic capacitors is their ability to

bypass high frequency noise. A certain amount of switching edge noise will couple through parasitic

capacitances in the inductor to the output. A ceramic capacitor will bypass this noise while a tantalum will not.

Because the output capacitor is one of the two external components that control the stability of the regulator

control loop, most applications will require a minimum at 10 µF of output capacitance. Capacitance can be

increased significantly with little detriment to the regulator stability. Like the input capacitor, recommended

multilayer ceramic capacitors are X7R or X5R. Again, verify actual capacitance at the desired operating voltage

and temperature.

Check the RMS current rating of the capacitor. The RMS current rating of the capacitor chosen must also meet

the following condition:

(23)

8.2.1.2.4 Catch Diode

The catch diode (D1) conducts during the switch off-time. A Schottky diode is recommended for its fast switching

times and low forward voltage drop. The catch diode should be chosen so that its current rating is greater than:

ID1 = IOx (1-D) (24)

The reverse breakdown rating of the diode must be at least the maximum input voltage plus appropriate margin.

To improve efficiency choose a Schottky diode with a low forward voltage drop.

8.2.1.2.5 Boost Diode

A standard diode such as the 1N4148 type is recommended. For VBOOST circuits derived from voltages less than

3.3 V, a small-signal Schottky diode is recommended for greater efficiency. A good choice is the BAT54 small

signal diode.

8.2.1.2.6 Boost Capacitor

A ceramic 0.01-µF capacitor with a voltage rating of at least 16 V is sufficient. The X7R and X5R MLCCs provide

the best performance.

Product Folder Links: LM2734

R1 =VO- 1

VREF x R2

LM2734

www.ti.com

SNVS288J –SEPTEMBER 2004–REVISED DECEMBER 2014

8.2.1.2.7 Output Voltage

The output voltage is set using the following equation where R2 is connected between the FB pin and GND, and

R1 is connected between VOand the FB pin. A good value for R2 is 10 kΩ.

(25)

8.2.1.3 Application Curves

Figure 18. Efficiency vs Load Current - L1 = 10 μH VOUT = 5

Figure 17. Efficiency vs Load Current - L1 = 4.7 µH VOUT =V

5 V

Figure 19. Efficiency vs Load Current - L1 = 4.7 µH VOUT = Figure 20. Efficiency vs Load Current - L1 = 10 μH VOUT =

3.3 V 3.3 V

Product Folder Links: LM2734

LM2734

SNVS288J –SEPTEMBER 2004–REVISED DECEMBER 2014

www.ti.com

Figure 21. Efficiency vs Load Current - L1 = 4.7 µH VOUT = Figure 22. Efficiency vs Load Current - L1 = 10 μH VOUT =

1.5 V 1.5 V

Product Folder Links: LM2734

LM2734

VIN

BOOST

GND

VOUT

CFF

12V

VIN

3.3V

OFF

LM2734

www.ti.com

SNVS288J –SEPTEMBER 2004–REVISED DECEMBER 2014

8.2.2 LM2734X (1.6 MHz) VBOOST Derived from VOUT 12 V to 3.3 V /1 A

Figure 23. LM2734X (1.6 MHz) VBOOST Derived from VOUT 12 V to 3.3 V /1-A Schematic

8.2.2.1 Design Requirements

Derive charge for VBOOST from the output voltage, (VOUT). The output voltage should be between 2.5 V and 5.5 V.

8.2.2.2 Detailed Design Procedure

See Detailed Design Procedure.

Table 2. Bill of Materials for Figure 23

PART ID PART VALUE MANUFACTURER PART NUMBER

U1 1-A Buck Regulator Texas Instruments LM2734X

C1, Input Cap 10 µF, 25 V, X7R TDK C3225X7R1E106M

C2, Output Cap 22 µF, 6.3 V, X5R TDK C3216X5ROJ226M

C3, Boost Cap 0.01 µF, 16 V, X7R TDK C1005X7R1C103K

CFF 1000 pF 25 V TDK C0603X5R1E102K

D1, Catch Diode 0.34 VFSchottky 1 A, 30 VR Vishay SS1P3L

D2, Boost Diode 1 VF@ 50-mA Diode Diodes, Inc. 1N4148W

L1 4.7µH, 1.7 A TDK VLCF4020T- 4R7N1R2

R1 31.6 kΩ, 1% Vishay CRCW06033162F

R2 10 kΩ, 1% Vishay CRCW06031002F

R3 100 kΩ, 1% Vishay CRCW06031003F

8.2.2.3 Application Curves

See Application Curves.

Product Folder Links: LM2734

LM2734

VIN VIN

BOOST

GND

VOUT

C3 L1

OFF

C1 R3

LM2734

SNVS288J –SEPTEMBER 2004–REVISED DECEMBER 2014

www.ti.com

8.2.3 LM2734X (1.6 MHz) VBOOST Derived from VSHUNT 18 V to 1.5 V /1 A

Figure 24. LM2734X (1.6 MHz) VBOOST Derived from VSHUNT 18 V to 1.5 V /1-A Schematic

8.2.3.1 Design Requirements

An alternative method when VIN is greater than 5.5 V is to place the zener diode D3 in a shunt configuration. A

small 350 mW to 500 mW 5.1 V zener in a SOT or SOD package can be used for this purpose. A small ceramic

capacitor such as a 6.3 V, 0.1 μF capacitor (C4) should be placed in parallel with the zener diode. When the

internal NMOS switch turns on, a pulse of current is drawn to charge the internal NMOS gate capacitance. The

0.1 μF parallel shunt capacitor ensures that the VBOOST voltage is maintained during this time.

8.2.3.2 Detailed Design Procedure

See Detailed Design Procedure.

Table 3. Bill of Materials for Figure 24

PART ID PART VALUE MANUFACTURER PART NUMBER

U1 1-A Buck Regulator Texas Instruments LM2734X

C1, Input Cap 10 µF, 25 V, X7R TDK C3225X7R1E106M

C2, Output Cap 22 µF, 6.3 V, X5R TDK C3216X5ROJ226M

C3, Boost Cap 0.01 µF, 16 V, X7R TDK C1005X7R1C103K

C4, Shunt Cap 0.1 µF, 6.3 V, X5R TDK C1005X5R0J104K

D1, Catch Diode 0.4 VFSchottky 1 A, 30 VR Vishay SS1P3L

D2, Boost Diode 1 VF@ 50-mA Diode Diodes, Inc. 1N4148W

D3, Zener Diode 5.1 V 250 Mw SOT Vishay BZX84C5V1

L1 6.8 µH, 1.6 A, TDK SLF7032T-6R8M1R6

R1 8.87 kΩ, 1% Vishay CRCW06038871F

R2 10.2 kΩ, 1% Vishay CRCW06031022F

R3 100 kΩ, 1% Vishay CRCW06031003F

R4 4.12 kΩ, 1% Vishay CRCW06034121F

8.2.3.3 Application Curves

See Application Curves.

Product Folder Links: LM2734

LM2734

VIN VIN

BOOST

GND

VOUT

C3 L1

OFF

D2D3

C1 R3

LM2734

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SNVS288J –SEPTEMBER 2004–REVISED DECEMBER 2014

8.2.4 LM2734X (1.6 MHz) VBOOST Derived from Series Zener Diode (VIN)15Vto1.5V/1A

Figure 25. LM2734X (1.6 MHz) VBOOST Derived from Series Zener Diode (VIN) 15 V to 1.5 V / 1-A Schematic

8.2.4.1 Design Requirements

In applications where both VIN and VOUT are greater than 5.5 V, or less than 3 V, CBOOST cannot be charged

directly from these voltages. If VIN is greater than 5.5 V, CBOOST can be charged from VIN minus a zener voltage

by placing a zener diode D3 in series with D2. When using a series zener diode from the input, ensure that the

regulation of the input supply doesn’t create a voltage that falls outside the recommended VBOOST voltage.

(VINMAX – VD3) < 5.5 V (26)

(VINMIN – VD3) > 1.6 V (27)

8.2.4.2 Detailed Design Procedure

See Detailed Design Procedure.

Table 4. Bill of Materials for Figure 25

PART ID PART VALUE MANUFACTURER PART NUMBER

U1 1-A Buck Regulator Texas Instruments LM2734X

C1, Input Cap 10 µF, 25V, X7R TDK C3225X7R1E106M

C2, Output Cap 22 µF, 6.3 V, X5R TDK C3216X5ROJ226M

C3, Boost Cap 0.01 µF, 16 V, X7R TDK C1005X7R1C103K

D1, Catch Diode 0.4 VFSchottky 1 A, 30 VR Vishay SS1P3L

D2, Boost Diode 1 VF@ 50-mA Diode Diodes, Inc. 1N4148W

D3, Zener Diode 11 V 350 Mw SOT Diodes, Inc. BZX84C11T

L1 6.8 µH, 1.6 A, TDK SLF7032T-6R8M1R6

R1 8.87 kΩ, 1% Vishay CRCW06038871F

R2 10.2 kΩ, 1% Vishay CRCW06031022F

R3 100 kΩ, 1% Vishay CRCW06031003F

8.2.4.3 Application Curves

See Application Curves.

Product Folder Links: LM2734

LM2734

VIN VIN

BOOST

GND

VOUT

C3 L1

OFF

D2 D3

C1 R3

LM2734

SNVS288J –SEPTEMBER 2004–REVISED DECEMBER 2014

www.ti.com

8.2.5 LM2734X (1.6 MHz) VBOOST Derived from Series Zener Diode (VOUT)15Vto9V/1A

Figure 26. LM2734X (1.6 MHz) VBOOST Derived from Series Zener Diode (VOUT) 15 V to 9 V /1-A Schematic

8.2.5.1 Design Requirements

In applications where both VIN and VOUT are greater than 5.5 V, or less than 3 V, CBOOST cannot be charged

directly from these voltages. If VIN and VOUT are greater than 5.5 V, CBOOST can be charged from VOUT minus a

zener voltage by placing a zener diode D3 in series with D2.

8.2.5.2 Detailed Design Procedure

See Detailed Design Procedure.

Table 5. Bill of Materials for Figure 26

PART ID PART VALUE MANUFACTURER PART NUMBER

U1 1-A Buck Regulator Texas Instruments LM2734X

C1, Input Cap 10 µF, 25 V, X7R TDK C3225X7R1E106M

C2, Output Cap 22 µF, 16 V, X5R TDK C3216X5R1C226M

C3, Boost Cap 0.01 µF, 16 V, X7R TDK C1005X7R1C103K

D1, Catch Diode 0.4 VFSchottky 1 A, 30 VR Vishay SS1P3L

D2, Boost Diode 1 VF@ 50-mA Diode Diodes, Inc. 1N4148W

D3, Zener Diode 4.3 V 350-mw SOT Diodes, Inc. BZX84C4V3

L1 6.8 µH, 1.6 A, TDK SLF7032T-6R8M1R6

R1 102 kΩ, 1% Vishay CRCW06031023F

R2 10.2 kΩ, 1% Vishay CRCW06031022F

R3 100 kΩ, 1% Vishay CRCW06031003F

8.2.5.3 Application Curves

See Application Curves.

Product Folder Links: LM2734

LM2734

VIN VIN

BOOST

GND

VOUT

C3 L1

OFF

C1 R3

LM2734

www.ti.com

SNVS288J –SEPTEMBER 2004–REVISED DECEMBER 2014

8.2.6 LM2734Y (550 kHz) VBOOST Derived from VIN 5Vto1.5V/1A

Figure 27. LM2734Y (550 kHz) VBOOST Derived from VIN 5 V to 1.5 V / 1-A Schematic

8.2.6.1 Design Requirements

Derive charge for VBOOST from the input supply (VIN ). VBOOST – VSW should not exceed the maximum operating

limit of 5.5 V.

8.2.6.2 Detailed Design Procedure

See Detailed Design Procedure.

Table 6. Bill of Materials for Figure 27

PART ID PART VALUE MANUFACTURER PART NUMBER

U1 1-A Buck Regulator Texas Instruments LM2734Y

C1, Input Cap 10 µF, 6.3 V, X5R TDK C3216X5ROJ106M

C2, Output Cap 22 µF, 6.3 V, X5R TDK C3216X5ROJ226M

C3, Boost Cap 0.01 µF, 16 V, X7R TDK C1005X7R1C103K

D1, Catch Diode 0.3 VFSchottky 1 A, 10 VR ON Semi MBRM110L

D2, Boost Diode 1 VF@ 50-mA Diode Diodes, Inc. 1N4148W

L1 10 µH, 1.6 A, TDK SLF7032T-100M1R4

R1 8.87 kΩ, 1% Vishay CRCW06038871F

R2 10.2 kΩ, 1% Vishay CRCW06031022F

R3 100 kΩ, 1% Vishay CRCW06031003F

8.2.6.3 Application Curves

See Application Curves.

Product Folder Links: LM2734

LM2734

VIN

BOOST

GND

VOUT

CFF

12V

VIN

3.3V

OFF

LM2734

SNVS288J –SEPTEMBER 2004–REVISED DECEMBER 2014

www.ti.com

8.2.7 LM2734Y (550 kHz) VBOOST Derived from VOUT 12Vto3.3V/1A

Figure 28. LM2734Y (550 kHz) VBOOST Derived from VOUT 12 V to 3.3 V / 1 A Schematic

8.2.7.1 Design Requirements

Derive charge for VBOOST from the output voltage, (VOUT ). The output voltage should be between 2.5 V and 5.5

8.2.7.2 Detailed Design Procedure

See Detailed Design Procedure.

Table 7. Bill of Materials for Figure 28

PART ID PART VALUE MANUFACTURER PART NUMBER

U1 1-A Buck Regulator Texas Instruments LM2734Y

C1, Input Cap 10 µF, 25 V, X7R TDK C3225X7R1E106M

C2, Output Cap 22 µF, 6.3 V, X5R TDK C3216X5ROJ226M

C3, Boost Cap 0.01 µF, 16 V, X7R TDK C1005X7R1C103K

D1, Catch Diode 0.34 VFSchottky 1 A, 30VR Vishay SS1P3L

D2, Boost Diode 0.6 VF@ 30-mA Diode Vishay BAT17

L1 10 µH, 1.6 A TDK SLF7032T-100M1R4

R1 31.6 kΩ, 1% Vishay CRCW06033162F

R2 10.0 kΩ, 1% Vishay CRCW06031002F

R3 100 kΩ, 1% Vishay CRCW06031003F

8.2.7.3 Application Curves

See Application Curves.

Product Folder Links: LM2734

LM2734

VIN VIN

BOOST

GND

VOUT

C3 L1

OFF

C1 R3

LM2734

www.ti.com

SNVS288J –SEPTEMBER 2004–REVISED DECEMBER 2014

8.2.8 LM2734Y (550 kHz) VBOOST Derived from VSHUNT 18Vto1.5V/1A

Figure 29. LM2734Y (550 kHz) VBOOST Derived from VSHUNT 18 V to 1.5 V / 1-A

8.2.8.1 Design Requirements

An alternative method when VIN is greater than 5.5 V is to place the zener diode D3 in a shunt configuration. A

small 350 mW to 500 mW 5.1 V zener in a SOT or SOD package can be used for this purpose. A small ceramic

capacitor such as a 6.3 V, 0.1 μF capacitor (C4) should be placed in parallel with the zener diode. When the

internal NMOS switch turns on, a pulse of current is drawn to charge the internal NMOS gate capacitance. The

0.1 μF parallel shunt capacitor ensures that the VBOOST voltage is maintained during this time.

8.2.8.2 Detailed Design Procedure

See Detailed Design Procedure.

Table 8. Bill of Materials for Figure 29

PART ID PART VALUE MANUFACTURER PART NUMBER

U1 1-A Buck Regulator Texas Instruments LM2734Y

C1, Input Cap 10 µF, 25 V, X7R TDK C3225X7R1E106M

C2, Output Cap 22 µF, 6.3 V, X5R TDK C3216X5ROJ226M

C3, Boost Cap 0.01 µF, 16 V, X7R TDK C1005X7R1C103K

C4, Shunt Cap 0.1 µF, 6.3 V, X5R TDK C1005X5R0J104K

D1, Catch Diode 0.4 VFSchottky 1 A, 30VR Vishay SS1P3L

D2, Boost Diode 1 VF@ 50-mA Diode Diodes, Inc. 1N4148W

D3, Zener Diode 5.1 V 250 Mw SOT Vishay BZX84C5V1

L1 15 µH, 1.5 A TDK SLF7045T-150M1R5

R1 8.87 kΩ, 1% Vishay CRCW06038871F

R2 10.2 kΩ, 1% Vishay CRCW06031022F

R3 100 kΩ, 1% Vishay CRCW06031003F

R4 4.12 kΩ, 1% Vishay CRCW06034121F

8.2.8.3 Application Curves

See Application Curves.

Product Folder Links: LM2734

LM2734

VIN VIN

BOOST

GND

VOUT

C3 L1

OFF

D2D3

C1 R3

LM2734

SNVS288J –SEPTEMBER 2004–REVISED DECEMBER 2014

www.ti.com

8.2.9 LM2734Y (550 kHz) VBOOST Derived from Series Zener Diode (VIN)15Vto1.5V/1A

Figure 30. LM2734Y (550 kHz) VBOOST Derived from Series Zener Diode (VIN) 15 V to 1.5 V / 1-A Schematic

8.2.9.1 Design Requirements

In applications where both VIN and VOUT are greater than 5.5 V, or less than 3 V, CBOOST cannot be charged

directly from these voltages. If VIN is greater than 5.5 V, CBOOST can be charged from VIN minus a zener voltage

by placing a zener diode D3 in series with D2. When using a series zener diode from the input, ensure that the

regulation of the input supply doesn’t create a voltage that falls outside the recommended VBOOST voltage.

(VINMAX – VD3) < 5.5 V (28)

(VINMIN – VD3) > 1.6 V (29)

8.2.9.2 Detailed Design Procedure

See Detailed Design Procedure.

Table 9. Bill of Materials for Figure 30

PART ID PART VALUE MANUFACTURER PART NUMBER

U1 1-A Buck Regulator Texas Instruments LM2734Y

C1, Input Cap 10 µF, 25 V, X7R TDK C3225X7R1E106M

C2, Output Cap 22 µF, 6.3 V, X5R TDK C3216X5ROJ226M

C3, Boost Cap 0.01 µF, 16 V, X7R TDK C1005X7R1C103K

D1, Catch Diode 0.4 VFSchottky 1 A, 30 VR Vishay SS1P3L

D2, Boost Diode 1 VF@ 50-mA Diode Diodes, Inc. 1N4148W

D3, Zener Diode 11 V 350 Mw SOT Diodes, Inc. BZX84C11T

L1 15 µH, 1.5 A, TDK SLF7045T-150M1R5

R1 8.87 kΩ, 1% Vishay CRCW06038871F

R2 10.2 kΩ, 1% Vishay CRCW06031022F

R3 100 kΩ, 1% Vishay CRCW06031003F

8.2.9.3 Application Curves

See Application Curves.

Product Folder Links: LM2734

LM2734

VIN VIN

BOOST

GND

VOUT

C3 L1

OFF

D2 D3

C1 R3

LM2734

www.ti.com

SNVS288J –SEPTEMBER 2004–REVISED DECEMBER 2014

8.2.10 LM2734Y (550 kHz) VBOOST Derived from Series Zener Diode (VOUT)15Vto9V/1A

Figure 31. LM2734Y (550 kHz) VBOOST Derived from Series Zener Diode (VOUT)15Vto9V/1-A

8.2.10.1 Design Requirements

In applications where both VIN and VOUT are greater than 5.5 V, or less than 3 V, CBOOST cannot be charged

directly from these voltages. If VIN and VOUT are greater than 5.5 V, CBOOST can be charged from VOUT minus a

zener voltage by placing a zener diode D3 in series with D2.

8.2.10.2 Detailed Design Procedure

See Detailed Design Procedure.

Table 10. Bill of Materials for Figure 31

PART ID PART VALUE MANUFACTURER PART NUMBER

U1 1-A Buck Regulator Texas Instruments LM2734Y

C1, Input Cap 10 µF, 25 V, X7R TDK C3225X7R1E106M

C2, Output Cap 22 µF, 16 V, X5R TDK C3216X5R1C226M

C3, Boost Cap 0.0 1 µF, 16 V, X7R TDK C1005X7R1C103K

D1, Catch Diode 0.4 VFSchottky 1 A, 30 VR Vishay SS1P3L

D2, Boost Diode 1 VF@ 50-mA Diode Diodes, Inc. 1N4148W

D3, Zener Diode 4.3 V 350 Mw SOT Diodes, Inc. BZX84C4V3

L1 22 µH, 1.4 A, TDK SLF7045T-220M1R3-1PF

R1 102 kΩ, 1% Vishay CRCW06031023F

R2 10.2kΩ, 1% Vishay CRCW06031022F

R3 100kΩ, 1% Vishay CRCW06031003F

8.2.10.3 Application Curves

See Application Curves.

Product Folder Links: LM2734

LM2734

SNVS288J –SEPTEMBER 2004–REVISED DECEMBER 2014

www.ti.com

9 Power Supply Recommendations

Input voltage is rated as 3 V to 18 V; however, care must be taken in certain circuit configurations (for example,

VBOOST derived from VIN where the requirement that VBOOST - VSW < 5.5 V should be observed) Also, for best

efficiency VBOOST should be at least 2.5-V above VSW.

The voltage on the Enable pin should not exceed VIN by more than 0.3 V.

10 Layout

10.1 Layout Guidelines

When planning layout there are a few things to consider when trying to achieve a clean, regulated output. The

most important consideration when completing the layout is the close coupling of the GND connections of the CIN

capacitor and the catch diode D1. These ground ends should be close to one another and be connected to the

GND plane with at least two through-holes. Place these components as close to the IC as possible. Next in

importance is the location of the GND connection of the COUT capacitor, which should be near the GND

connections of CIN and D1.

There should be a continuous ground plane on the bottom layer of a two-layer board except under the switching

node island.

The FB pin is a high-impedance node and care should be taken to make the FB trace short to avoid noise pickup

and inaccurate regulation. The feedback resistors should be placed as close as possible to the IC, with the GND

of R2 placed as close as possible to the GND of the IC. The VOUT trace to R1 should be routed away from the

inductor and any other traces that are switching.

High AC currents flow through the VIN, SW and VOUT traces, so they should be as short and wide as possible.

However, making the traces wide increases radiated noise, so the designer must make this trade-off. Radiated

noise can be decreased by choosing a shielded inductor.

The remaining components should also be placed as close as possible to the IC. See Application Note AN-1229

(SNVA054) for further considerations and the LM2734 demo board as an example of a four-layer layout.

Product Folder Links: LM2734

BOOST

GND

VOUT

C1 R5

VIN

VEN

LM2734

www.ti.com

SNVS288J –SEPTEMBER 2004–REVISED DECEMBER 2014

10.2 Layout Example

Figure 32. Top Layer

Figure 33. Layout Schematic

Product Folder Links: LM2734

LM2734

SNVS288J –SEPTEMBER 2004–REVISED DECEMBER 2014

www.ti.com

11 Device and Documentation Support

11.1 Third-Party Products Disclaimer

TI'S PUBLICATION OF INFORMATION REGARDING THIRD-PARTY PRODUCTS OR SERVICES DOES NOT

CONSTITUTE AN ENDORSEMENT REGARDING THE SUITABILITY OF SUCH PRODUCTS OR SERVICES

OR A WARRANTY, REPRESENTATION OR ENDORSEMENT OF SUCH PRODUCTS OR SERVICES, EITHER

ALONE OR IN COMBINATION WITH ANY TI PRODUCT OR SERVICE.

11.2 Trademarks

WEBENCH is a registered trademark of Texas Instruments.

All other trademarks are the property of their respective owners.

11.3 Electrostatic Discharge Caution

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.

11.4 Glossary

SLYZ022 —TI Glossary.

This glossary lists and explains terms, acronyms, and definitions.

12 Mechanical, Packaging, and Orderable Information

The following pages include mechanical, packaging, and orderable information. This information is the most

current data available for the designated devices. This data is subject to change without notice and revision of

this document. For browser-based versions of this data sheet, refer to the left-hand navigation.

Product Folder Links: LM2734

PACKAGE OPTION ADDENDUM

www.ti.com 28-Feb-2017

Addendum-Page 1

PACKAGING INFORMATION

Orderable Device Status

(1)

Package Type Package

Drawing Pins Package

Qty Eco Plan

(2)

Lead/Ball Finish

(6)

MSL Peak Temp

(3)

Op Temp (°C) Device Marking

(4/5)

Samples

LM2734XMK/NOPB ACTIVE SOT-23-THIN DDC 6 1000 Green (RoHS

& no Sb/Br) CU SN Level-1-260C-UNLIM -40 to 125 SFDB

LM2734XMKX/NOPB ACTIVE SOT-23-THIN DDC 6 3000 Green (RoHS

& no Sb/Br) CU SN Level-1-260C-UNLIM -40 to 125 SFDB

LM2734XQMK/NOPB ACTIVE SOT-23-THIN DDC 6 1000 Green (RoHS

& no Sb/Br) CU SN Level-1-260C-UNLIM -40 to 125 SUKB

LM2734XQMKE/NOPB ACTIVE SOT-23-THIN DDC 6 250 Green (RoHS

& no Sb/Br) CU SN Level-1-260C-UNLIM -40 to 125 SUKB

LM2734XQMKX/NOPB ACTIVE SOT-23-THIN DDC 6 3000 Green (RoHS

& no Sb/Br) CU SN Level-1-260C-UNLIM -40 to 125 SUKB

LM2734YMK NRND SOT-23-THIN DDC 6 1000 TBD Call TI Call TI -40 to 125 SFEB

LM2734YMK/NOPB ACTIVE SOT-23-THIN DDC 6 1000 Green (RoHS

& no Sb/Br) CU SN Level-1-260C-UNLIM -40 to 125 SFEB

LM2734YMKX/NOPB ACTIVE SOT-23-THIN DDC 6 3000 Green (RoHS

& no Sb/Br) CU SN Level-1-260C-UNLIM -40 to 125 SFEB

LM2734YQMK/NOPB ACTIVE SOT-23-THIN DDC 6 1000 Green (RoHS

& no Sb/Br) CU SN Level-1-260C-UNLIM -40 to 125 SVCB

LM2734YQMKE/NOPB ACTIVE SOT-23-THIN DDC 6 250 Green (RoHS

& no Sb/Br) CU SN Level-1-260C-UNLIM -40 to 125 SVCB

LM2734YQMKX/NOPB ACTIVE SOT-23-THIN DDC 6 3000 Green (RoHS

& no Sb/Br) CU SN Level-1-260C-UNLIM -40 to 125 SVCB

(1) The marketing status values are defined as follows:

ACTIVE: Product device recommended for new designs.

LIFEBUY: TI has announced that the device will be discontinued, and a lifetime-buy period is in effect.

NRND: Not recommended for new designs. Device is in production to support existing customers, but TI does not recommend using this part in a new design.

PREVIEW: Device has been announced but is not in production. Samples may or may not be available.

OBSOLETE: TI has discontinued the production of the device.

(2) Eco Plan - The planned eco-friendly classification: Pb-Free (RoHS), Pb-Free (RoHS Exempt), or Green (RoHS & no Sb/Br) - please check http://www.ti.com/productcontent for the latest availability

information and additional product content details.

TBD: The Pb-Free/Green conversion plan has not been defined.

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.

Pb-Free (RoHS Exempt): This component has a RoHS exemption for either 1) lead-based flip-chip solder bumps used between the die and package, or 2) lead-based die adhesive used between

the die and leadframe. The component is otherwise considered Pb-Free (RoHS compatible) as defined above.

PACKAGE OPTION ADDENDUM

www.ti.com 28-Feb-2017

Addendum-Page 2

Green (RoHS & no Sb/Br): TI defines "Green" to mean Pb-Free (RoHS compatible), and free of Bromine (Br) and Antimony (Sb) based flame retardants (Br or Sb do not exceed 0.1% by weight

in homogeneous material)

(3) MSL, Peak Temp. - The Moisture Sensitivity Level rating according to the JEDEC industry standard classifications, and peak solder temperature.

(4) There may be additional marking, which relates to the logo, the lot trace code information, or the environmental category on the device.

(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. Lead/Ball Finish values may wrap to two lines if the finish

value exceeds the maximum column width.

Important Information and Disclaimer:The information provided on this page represents TI's knowledge and belief as of the date that it is provided. TI bases its knowledge and belief on information

provided by third parties, and makes no representation or warranty as to the accuracy of such information. Efforts are underway to better integrate information from third parties. TI has taken and

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.

In no event shall TI's liability arising out of such information exceed the total purchase price of the TI part(s) at issue in this document sold by TI to Customer on an annual basis.

OTHER QUALIFIED VERSIONS OF LM2734, LM2734-Q1 :

•Catalog: LM2734

•Automotive: LM2734-Q1

NOTE: Qualified Version Definitions:

•Catalog - TI's standard catalog product

•Automotive - Q100 devices qualified for high-reliability automotive applications targeting zero defects

TAPE AND REEL INFORMATION

*All dimensions are nominal

Device Package

Type Package

Drawing Pins SPQ Reel

Diameter

(mm)

Reel

Width

W1 (mm)

(mm) B0

(mm) K0

(mm) P1

(mm) W

(mm) Pin1

Quadrant

LM2734XMK/NOPB SOT-

23-THIN DDC 6 1000 178.0 8.4 3.2 3.2 1.4 4.0 8.0 Q3

LM2734XMKX/NOPB SOT-

23-THIN DDC 6 3000 178.0 8.4 3.2 3.2 1.4 4.0 8.0 Q3

LM2734XQMK/NOPB SOT-

23-THIN DDC 6 1000 178.0 8.4 3.2 3.2 1.4 4.0 8.0 Q3

LM2734XQMKE/NOPB SOT-

23-THIN DDC 6 250 178.0 8.4 3.2 3.2 1.4 4.0 8.0 Q3

LM2734XQMKX/NOPB SOT-

23-THIN DDC 6 3000 178.0 8.4 3.2 3.2 1.4 4.0 8.0 Q3

LM2734YMK SOT-

23-THIN DDC 6 1000 178.0 8.4 3.2 3.2 1.4 4.0 8.0 Q3

LM2734YMK/NOPB SOT-

23-THIN DDC 6 1000 178.0 8.4 3.2 3.2 1.4 4.0 8.0 Q3

LM2734YMKX/NOPB SOT-

23-THIN DDC 6 3000 178.0 8.4 3.2 3.2 1.4 4.0 8.0 Q3

LM2734YQMK/NOPB SOT-

23-THIN DDC 6 1000 178.0 8.4 3.2 3.2 1.4 4.0 8.0 Q3

LM2734YQMKE/NOPB SOT-

23-THIN DDC 6 250 178.0 8.4 3.2 3.2 1.4 4.0 8.0 Q3

LM2734YQMKX/NOPB SOT- DDC 6 3000 178.0 8.4 3.2 3.2 1.4 4.0 8.0 Q3

PACKAGE MATERIALS INFORMATION

www.ti.com 3-Mar-2017

Pack Materials-Page 1

Device Package

Type Package

Drawing Pins SPQ Reel

Diameter

(mm)

Reel

Width

W1 (mm)

(mm) B0

(mm) K0

(mm) P1

(mm) W

(mm) Pin1

Quadrant

23-THIN

*All dimensions are nominal

Device Package Type Package Drawing Pins SPQ Length (mm) Width (mm) Height (mm)

LM2734XMK/NOPB SOT-23-THIN DDC 6 1000 210.0 185.0 35.0

LM2734XMKX/NOPB SOT-23-THIN DDC 6 3000 210.0 185.0 35.0

LM2734XQMK/NOPB SOT-23-THIN DDC 6 1000 210.0 185.0 35.0

LM2734XQMKE/NOPB SOT-23-THIN DDC 6 250 210.0 185.0 35.0

LM2734XQMKX/NOPB SOT-23-THIN DDC 6 3000 210.0 185.0 35.0

LM2734YMK SOT-23-THIN DDC 6 1000 210.0 185.0 35.0

LM2734YMK/NOPB SOT-23-THIN DDC 6 1000 210.0 185.0 35.0

LM2734YMKX/NOPB SOT-23-THIN DDC 6 3000 210.0 185.0 35.0

LM2734YQMK/NOPB SOT-23-THIN DDC 6 1000 210.0 185.0 35.0

LM2734YQMKE/NOPB SOT-23-THIN DDC 6 250 210.0 185.0 35.0

LM2734YQMKX/NOPB SOT-23-THIN DDC 6 3000 210.0 185.0 35.0

PACKAGE MATERIALS INFORMATION

www.ti.com 3-Mar-2017

Pack Materials-Page 2

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Click to View Pricing, Inventory, Delivery & Lifecycle Information:

Texas Instruments:

LM2734XQMK/NOPB LM2734XQMKE/NOPB LM2734XQMKX/NOPB LM2734YQMK/NOPB LM2734YQMKE/NOPB

LM2734YQMKX/NOPB