LM2734
VIN
VIN
EN
BOOST
SW
FB
GND
V
OUT
C3
L1
C1
C2
R1
R2
D1
D2
ON
OFF
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SNVS288J –SEPTEMBER 2004–REVISED DECEMBER 2014
LM2734 Thin SOT 1-A Load Step-Down DC-DC Regulator
1 Features 3 Description
1
• Thin SOT-6 Package
• 3.0-V to 20-V Input Voltage Range
• 0.8-V to 18-V Output Voltage Range
• 1-A Output Current
• 550-kHz (LM2734Y) and 1.6-MHz (LM2734X)
Switching Frequencies
• 300-mΩ NMOS Switch
• 30-nA Shutdown Current
• 0.8-V, 2% Internal Voltage Reference
• Internal Soft-Start
• Current-Mode, PWM Operation
• WEBENCH®Online Design Tool
• Thermal Shutdown
• LM2734XQ and LM2734YQ are AEC-Q100 Grade
1 Qualified and are Manufactured on an
Automotive Grade Flow.
2 Applications
• Local Point-of-Load Regulation
• Core Power in HDDs
• Set-Top Boxes
• Battery-Powered Devices
• USB Powered Devices
• DSL Modems
• Notebook Computers
• Automotive
Typical Application Circuit
The LM2734 regulator is a monolithic, highfrequency, PWM step-down DC-DC converter in a 6pin Thin SOT package. The device provides all the
active functions to provide local DC-DC conversion
with fast transient response and accurate regulation
in the smallest possible PCB area.
With a minimum of external components and online
design support through WEBENCH, the LM2734
regulator is easy to use. The ability to drive 1-A loads
with an internal 300-mΩ NMOS switch using state-ofthe-art 0.5-µm BiCMOS technology results in the best
power density available. The world-class control
circuitry allows for on-times as low as 13 ns, thus
supporting exceptionally high-frequency conversion
over the entire 3-V to 20-V input operating range
down to the minimum output voltage of 0.8 V.
Switching frequency is internally set to 550 kHz
(LM2734Y) or 1.6 MHz (LM2734X), allowing the use
of extremely small surface-mount inductors and chip
capacitors. Even though the operating frequencies
are very high, efficiencies up to 90% are easy to
achieve. External shutdown is included, featuring an
ultra-low standby current of 30 nA.
The LM2734 regulator uses current-mode control and
internal compensation to provide high-performance
regulation over a wide range of operating conditions.
Additional features include internal soft-start circuitry
to reduce inrush current, pulse-by-pulse current limit,
thermal shutdown, and output overvoltage protection.
Device Information
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.
Efficiency vs Load Current
VIN= 5 V, V
OUT
LM2734
(1)
= 3.3 V
1
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
1 Features.................................................................. 1
2 Applications ........................................................... 1
3 Description............................................................. 1
4 Revision History..................................................... 2
5 Pin Configuration and Functions......................... 3
6 Specifications......................................................... 4
6.1 Absolute Maximum Ratings ...................................... 4
6.2 ESD Ratings.............................................................. 4
6.3 Recommended Operating Conditions....................... 4
6.4 Thermal Information.................................................. 4
6.5 Electrical Characteristics........................................... 5
6.6 Typical Performance Characteristics ........................ 6
7 Detailed Description.............................................. 8
7.1 Overview................................................................... 8
7.2 Functional Block Diagram ......................................... 9
7.3 Feature Description................................................... 9
7.4 Device Functional Modes........................................ 10
8 Application and Implementation ........................ 11
8.1 Application Information............................................ 11
8.2 Typical Applications................................................ 14
9 Power Supply Recommendations...................... 28
10 Layout................................................................... 28
10.1 Layout Guidelines................................................. 28
10.2 Layout Example.................................................... 29
11 Device and Documentation Support................. 30
11.1 Third-Party Products Disclaimer........................... 30
11.2 Trademarks........................................................... 30
11.3 Electrostatic Discharge Caution............................ 30
11.4 Glossary................................................................ 30
12 Mechanical, Packaging, and Orderable
Information........................................................... 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
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1
2
3
6
5
4
BOOST
GND
FB
SW
V
IN
EN
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5 Pin Configuration and Functions
LM2734
SNVS288J –SEPTEMBER 2004–REVISED DECEMBER 2014
See Package Number DDC (R-PDSO-G6)
6-Lead SOT
Top View
Pin Functions
PIN
NAME NO.
BOOST 1 I
GND 2 GND
FB 3 I Feedback pin. Connect FB to the external resistor divider to set output voltage.
EN 4 I
V
IN
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.
I/O DESCRIPTION
Boost voltage that drives the internal NMOS control switch. A bootstrap capacitor is
connected between the BOOST and SW pins.
Signal and Power ground pin. Place the bottom resistor of the feedback network as close as
possible to this pin for accurate regulation.
Enable control input. Logic high enables operation. Do not allow this pin to float or be greater
than VIN+ 0.3 V.
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SNVS288J –SEPTEMBER 2004–REVISED DECEMBER 2014
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6 Specifications
6.1 Absolute Maximum Ratings
over operating free-air temperature (unless otherwise noted)
V
IN
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
T
Storage temperature -65 150 °C
stg
(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
V
Electrostatic discharge Human Body Model (HBM), per ANSI/ESDA/JEDEC JS001
ESD
(1) JEDEC document JEP155 states that 500-V HBM allows safe manufacturing with a standard ESD control process.
(1)(2)
MIN MAX UNIT
-0.5 24 V
VALUE UNIT
(1)
±2000 V
6.3 Recommended Operating Conditions
over operating free-air temperature range (unless otherwise noted)
MIN NOM MAX UNIT
V
IN
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
3 20 V
6.4 Thermal Information
LM2734
THERMAL METRIC
R
θJA
R
θJC(top)
R
θJB
ψ
JT
ψ
JB
R
θJC(bot)
Junction-to-ambient thermal resistance 158.1
Junction-to-case (top) thermal resistance 46.5
Junction-to-board thermal resistance 29.5
Junction-to-top characterization parameter 0.8
Junction-to-board characterization parameter 29.2
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.
(1)
DDC UNIT
6 PINS
°C/W
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6.5 Electrical Characteristics
VIN= 5V, V
statistical analysis.
V
ΔVFB/Δ Feedback Voltage Line VIN= 3V to 20V
V
I
FB
UVLO Undervoltage Lockout VINFalling 2.3 2.0 V
F
D
D
R
I
CL
I
Q
I
BOOST
V
I
EN
I
SW
(1) Specified to Average Outgoing Quality Level (AOQL).
(2) Typicals represent the most likely parametric norm.
Feedback Voltage 0.800 0.784 0.816 V
FB
Regulation
IN
Feedback Input Bias Sink/Source
Current
Undervoltage Lockout VINRising 2.74 2.90
UVLO Hysteresis 0.44 0.30 0.62
Switching Frequency MHz
SW
Maximum Duty Cycle
MAX
Minimum Duty Cycle
MIN
Switch ON Resistance V
DS(ON)
Switch Current Limit V
Quiescent Current Switching 1.5 2.5 mA
Quiescent Current VEN= 0V
(shutdown)
Boost Pin Current mA
Shutdown Threshold VENFalling
Voltage
EN_TH
Enable Threshold VENRising 1.8
Voltage
Enable Pin Current Sink/Source 10 nA
Switch Leakage 40 nA
- VSW= 5V unless otherwise specified. Datasheet min/max specification limits are ensured by design, test, or
BOOST
PARAMETER TEST CONDITIONS UNIT
MIN
TJ= 25°C TJ= -40°C to 125°C
(1)
TYP
(2)
MAX
(1)
MIN TYP MAX
0.01 % / V
10 250 nA
LM2734X 1.6 1.2 1.9
LM2734Y 0.55 0.40 0.66
LM2734X 92 85%
LM2734Y 96 90%
LM2734X 2%
LM2734Y 1%
- VSW= 3V 300 600 mΩ
BOOST
- VSW= 3V 1.7 1.2 2.5 A
BOOST
30 nA
LM2734X (50% Duty
Cycle)
LM2734Y (50% Duty
Cycle)
2.5 3.5
1.0 1.8
0.4
V
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SNVS288J –SEPTEMBER 2004–REVISED DECEMBER 2014
6.6 Typical Performance Characteristics
All curves taken at VIN= 5 V, V
Figure 1. Oscillator Frequency vs Temperature - L1 = 4.7 µH Figure 2. Oscillator Frequency vs Temperature - L1 = 10 μH
- VSW= 5 V and TA= 25°C, unless specified otherwise.
BOOST
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Figure 3. Current Limit vs Temperature Figure 4. Current Limit vs Temperature
VIN= 20 V
Figure 5. VFBvs Temperature Figure 6. R
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vs Temperature
DSON
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Typical Performance Characteristics (continued)
LM2734
SNVS288J –SEPTEMBER 2004–REVISED DECEMBER 2014
All curves taken at VIN= 5 V, V
Figure 7. IQSwitching vs Temperature Figure 8. Line Regulation - L1 = 4.7 µH
- VSW= 5 V and TA= 25°C, unless specified otherwise.
BOOST
V
OUT
= 1.5 V, I
OUT
= 500 mA
Figure 9. Line Regulation - L1 = 10 μH Figure 10. Line Regulation - L1 = 4.7 µH
V
OUT
= 1.5 V, I
= 500 mA V
OUT
OUT
= 3.3 V, I
OUT
= 500 mA
Figure 11. Line Regulation - L1 = 10 μH
V
= 3.3 V, I
OUT
Copyright © 2004–2014, Texas Instruments Incorporated Submit Documentation Feedback 7
OUT
= 500 mA
Product Folder Links: LM2734
0
0
V
IN
V
D
T
ON
t
t
Inductor
Current
D = TON/T
SW
V
SW
T
OFF
T
SW
I
L
I
PK
SW
Voltage
LM2734
SNVS288J –SEPTEMBER 2004–REVISED DECEMBER 2014
www.ti.com
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 currentmode 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 V
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.
. When the PWM comparator output goes high, the output switch turns off until the
REF
Figure 12. LM2734 Waveforms of SW Pin Voltage and Inductor Current
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L
R
1
R
2
D
1
D2
BOOST
Output
Control
Logic
Current
Limit
Thermal
Shutdown
Under
Voltage
Lockout
Corrective Ramp
Reset
Pulse
PWM
Comparator
Current-Sense Amplifier
R
SENSE
+
+
Internal
Regulator
and
Enable
Circuit
Oscillator
Driver
0.3:
Switch
Internal
Compensation
SW
EN
FB
GND
Error Amplifier
-
+
V
REF
0.8V
C
OUT
ON
OFF
V
BOOST
I
L
V
SW
+
-
C
BOOST
V
OUT
C
IN
V
IN
V
IN
I
SENSE
+
-
+
-
+
-
0.88V
-
+
OVP
Comparator
Error
Signal
www.ti.com
7.2 Functional Block Diagram
LM2734
SNVS288J –SEPTEMBER 2004–REVISED DECEMBER 2014
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 VINdrops below 2.3 V
(typical). Hysteresis prevents the part from turning off during power up if VINis 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 V
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.
to increase at a controlled rate during start up. During soft-start, the error amplifier’s
OUT
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BOOST
SW
GND
L
D1
D2
C
OUT
C
BOOST
V
OUT
C
IN
V
IN
V
IN
V
BOOST
LM2734
www.ti.com
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 C
drive voltage to the internal NMOS control switch. To properly drive the internal NMOS switch during its on-time,
V
needs to be at least 1.6 V greater than VSW. Although the LM2734 device will operate with this minimum
BOOST
voltage, it may not have sufficient gate drive to supply large values of output current. Therefore, it is
recommended that V
the maximum operating limit of 5.5 V.
5.5 V > V
BOOST
and diode D2 in Figure 13 are used to generate a voltage V
BOOST
be greater than 2.5 V above VSWfor best efficiency. V
BOOST
– VSW> 2.5 V for best performance.
BOOST
BOOST
. V
- VSWis the gate
BOOST
– VSWshould not exceed
Figure 13. V
Charges C
OUT
BOOST
When the LM2734 device starts up, internal circuitry from the BOOST pin supplies a maximum of 20 mA to
C
source current to C
There are various methods to derive V
. This current charges C
BOOST
to a voltage sufficient to turn the switch on. The BOOST pin will continue to
BOOST
until the voltage at the feedback pin is greater than 0.76 V.
BOOST
:
BOOST
1. From the input voltage (VIN)
2. From the output voltage (V
3. From an external distributed voltage rail (V
OUT
)
)
EXT
4. From a shunt or series Zener diode
In the simplified block diagram of Functional Block Diagram, capacitor C
drive current for the NMOS switch. Capacitor C
cycle, when the internal NMOS control switch is off (T
forward voltage of D2 (V
(V
). Therefore the voltage stored across C
FD1
V
- VSW= VIN- V
BOOST
), during which the current in the inductor (L) forward biases the Schottky diode D1
FD2
BOOST
+ V
FD2
FD1
is charged via diode D2 by VIN. During a normal switching
BOOST
) (refer to Figure 12), V
OFF
is:
and diode D2 supply the gate-
BOOST
equals VINminus the
BOOST
(1)
When the NMOS switch turns on (TON), the switch pin rises to:
VSW= VIN– (R
forcing V
V
BOOST
to rise thus reverse biasing D2. The voltage at V
BOOST
= 2VIN– (R
which is approximately:
2VIN- 0.4 V (4)
Copyright © 2004–2014, Texas Instruments Incorporated Submit Documentation Feedback 11
× IL), (2)
DSON
is then:
BOOST
DSON
× IL) – V
+ V
FD2
FD1
Product Folder Links: LM2734
(3)
LM2734
V
IN
BOOST
SW
GND
C
BOOST
L
D1
D2
D3
C
IN
V
IN
C
OUT
V
OUT
V
BOOST
LM2734
SNVS288J –SEPTEMBER 2004–REVISED DECEMBER 2014
www.ti.com
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 C
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, C
provides a gate drive voltage that is slightly less than V
BOOST
In applications where both VINand V
directly from these voltages. If VINto V
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 V
(V
(V
– VD3) < 5.5 V (6)
INMAX
– VD3) > 1.6 V (7)
INMIN
BOOST
voltage.
is to connect D2 to the output as shown in Figure 13. The output
BOOST
.
OUT
are greater than 5.5 V, or less than 3 V, C
OUT
are greater than 5.5 V, C
OUT
can be charged from VINor V
BOOST
cannot be charged
BOOST
OUT
minus
Figure 14. Zener Reduces Boost Voltage from V
IN
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 V
voltage is maintained during this time.
BOOST
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 (I
) is 1 mA. The current I
ZENER
into the BOOST pin supplies the
BOOST
gate current of the NMOS control switch and varies typically according to the following formula for the X version:
I
= 0.56 × (D + 0.54) × (V
BOOST
I
can be calculated for the Y version using the following:
BOOST
I
= 0.22 × (D + 0.54) × (V
BOOST
where D is the duty cycle, V
ZENER
– VD2) mA (8)
ZENER
- VD2) µA (9)
ZENER
and VD2are in volts, and I
is in milliamps. V
BOOST
is the voltage applied to
ZENER
the anode of the boost diode (D2), and VD2is the average forward voltage across D2. Note that this formula for
I
gives typical current. For the worst case I
BOOST
, increase the current by 40%. In that case, the worst case
BOOST
boost current will be:
I
BOOST-MAX
= 1.4 × I
BOOST
(10)
R3 will then be given by:
R3 = (VIN- V
For example, using the X-version let VIN= 10 V, V
ZENER
) / (1.4 × I
BOOST
+ I
) (11)
ZENER
= 5 V, VD2= 0.7 V, I
ZENER
= 1 mA, and duty cycle D =
ZENER
50%. Then:
I
= 0.56 × (0.5 + 0.54) × (5 - 0.7) mA = 2.5 mA (12)
BOOST
R3 = (10 V - 5 V) / (1.4 × 2.5 mA + 1 mA) = 1.11 kΩ (13)
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LM2734
V
IN
BOOST
SW
GND
L
D1
D2
D3
R3
C4
V
BOOST
C
BOOST
V
Z
V
IN
C
IN
V
OUT
C
OUT
www.ti.com
Application Information (continued)
LM2734
SNVS288J –SEPTEMBER 2004–REVISED DECEMBER 2014
Figure 15. Boost Voltage Supplied from the Shunt Zener on V
IN
Product Folder Links: LM2734
Copyright © 2004–2014, Texas Instruments Incorporated Submit Documentation Feedback 13
D =
VO + V
D
VIN + VD - V
SW
D =
V
O
V
IN
LM2734
VIN
VIN
EN
BOOST
SW
FB
GND
V
OUT
C3
L1
C2
R1
R2
D1
D2
ON
OFF
C1
R3
LM2734
SNVS288J –SEPTEMBER 2004–REVISED DECEMBER 2014
8.2 Typical Applications
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8.2.1 LM2734X (1.6 MHz) V
Figure 16. LM2734X (1.6 MHz) V
Derived from VIN5V to 1.5 V/1 A
BOOST
Derived from VIN5 V to 1.5-V/1-A Schematic
BOOST
8.2.1.1 Design Requirements
Derive charge for V
from the input supply (VIN). V
BOOST
– VSWshould not exceed the maximum operating
BOOST
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):
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:
VSWcan be approximated by:
14 Submit Documentation Feedback Copyright © 2004–2014, Texas Instruments Incorporated
VSW= IOx R
DS(ON)
(14)
(15)
Product Folder Links: LM2734
(16)
I
RMS-IN
= IO x
D x
r
2
12
1-D +
L =
VO + V
D
IO x r x f
S
x (1-D)
r =
'i
L
l
O
www.ti.com
LM2734
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 V
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 (I
I
= IO+ ΔIL/2 (18)
LPK
) in the inductor is calculated as shown in Equation 18:
LPK
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 I
OUT
-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:
D
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 VINdoes 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 (I
RMS-IN
) must be
greater than:
(21)
Copyright © 2004–2014, Texas Instruments Incorporated Submit Documentation Feedback 15
Product Folder Links: LM2734
I
RMS-OUT
= IO x
r
12
'VO = 'iL x (R
ESR
+
1
8 x fS x C
O
)
LM2734
SNVS288J –SEPTEMBER 2004–REVISED DECEMBER 2014
www.ti.com
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 V
circuits derived from voltages less than
BOOST
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.
16 Submit Documentation Feedback Copyright © 2004–2014, Texas Instruments Incorporated
Product Folder Links: LM2734
R1 =
V
O
- 1
V
REF
x R2
LM2734
www.ti.com
8.2.1.2.7 Output Voltage
SNVS288J –SEPTEMBER 2004–REVISED DECEMBER 2014
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 17. Efficiency vs Load Current - L1 = 4.7 µH V
5 V
Figure 19. Efficiency vs Load Current - L1 = 4.7 µH V
3.3 V 3.3 V
=
OUT
= Figure 20. Efficiency vs Load Current - L1 = 10 μH V
OUT
Figure 18. Efficiency vs Load Current - L1 = 10 μH V
V
OUT
OUT
= 5
=
Copyright © 2004–2014, Texas Instruments Incorporated Submit Documentation Feedback 17
Product Folder Links: LM2734
LM2734
SNVS288J –SEPTEMBER 2004–REVISED DECEMBER 2014
www.ti.com
Figure 21. Efficiency vs Load Current - L1 = 4.7 µH V
1.5 V 1.5 V
= Figure 22. Efficiency vs Load Current - L1 = 10 μH V
OUT
OUT
=
18 Submit Documentation Feedback Copyright © 2004–2014, Texas Instruments Incorporated
Product Folder Links: LM2734
LM2734
VIN
EN
BOOST
SW
FB
GND
C3
R1
R2
D1
D2
V
OUT
C
FF
12V
V
IN
3.3V
L1
C1
ON
OFF
R3
C2
www.ti.com
LM2734
SNVS288J –SEPTEMBER 2004–REVISED DECEMBER 2014
8.2.2 LM2734X (1.6 MHz) V
Figure 23. LM2734X (1.6 MHz) V
Derived from V
BOOST
OUT
Derived from V
BOOST
12 V to 3.3 V /1 A
12 V to 3.3 V /1-A Schematic
OUT
8.2.2.1 Design Requirements
Derive charge for V
from the output voltage, (V
BOOST
). The output voltage should be between 2.5 V and 5.5 V.
OUT
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.
Copyright © 2004–2014, Texas Instruments Incorporated Submit Documentation Feedback 19
Product Folder Links: LM2734
LM2734
VIN
V
IN
EN
BOOST
SW
FB
GND
V
OUT
C3
L1
C2
R1
R2
D1
D2
ON
OFF
D3
C4
R4
C1
R3
LM2734
SNVS288J –SEPTEMBER 2004–REVISED DECEMBER 2014
www.ti.com
8.2.3 LM2734X (1.6 MHz) V
Figure 24. LM2734X (1.6 MHz) V
Derived from V
BOOST
SHUNT
Derived from V
BOOST
18 V to 1.5 V /1 A
18 V to 1.5 V /1-A Schematic
SHUNT
8.2.3.1 Design Requirements
An alternative method when VINis 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 V
voltage is maintained during this time.
BOOST
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.
20 Submit Documentation Feedback Copyright © 2004–2014, Texas Instruments Incorporated
Product Folder Links: LM2734
LM2734
VIN
V
IN
EN
BOOST
SW
FB
GND
V
OUT
C3
L1
C2
R1
R2
D1
ON
OFF
D2D3
C1
R3
www.ti.com
LM2734
SNVS288J –SEPTEMBER 2004–REVISED DECEMBER 2014
8.2.4 LM2734X (1.6 MHz) V
Figure 25. LM2734X (1.6 MHz) V
Derived from Series Zener Diode (VIN) 15 V to 1.5 V / 1 A
BOOST
Derived from Series Zener Diode (VIN) 15 V to 1.5 V / 1-A Schematic
BOOST
8.2.4.1 Design Requirements
In applications where both VINand V
directly from these voltages. If VINis greater than 5.5 V, C
are greater than 5.5 V, or less than 3 V, C
OUT
can be charged from VINminus a zener voltage
BOOST
cannot be charged
BOOST
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 V
(V
(V
– VD3) < 5.5 V (26)
INMAX
– VD3) > 1.6 V (27)
INMIN
BOOST
voltage.
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
Copyright © 2004–2014, Texas Instruments Incorporated Submit Documentation Feedback 21
LM2734
VIN
VIN
EN
BOOST
SW
FB
GND
V
OUT
C3
L1
C2
R1
R2
D1
ON
OFF
D2
D3
C1
R3
LM2734
SNVS288J –SEPTEMBER 2004–REVISED DECEMBER 2014
www.ti.com
8.2.5 LM2734X (1.6 MHz) V
Figure 26. LM2734X (1.6 MHz) V
Derived from Series Zener Diode (V
BOOST
Derived from Series Zener Diode (V
BOOST
) 15 V to 9 V /1 A
OUT
) 15 V to 9 V /1-A Schematic
OUT
8.2.5.1 Design Requirements
In applications where both VINand V
directly from these voltages. If VINand V
are greater than 5.5 V, or less than 3 V, C
OUT
are greater than 5.5 V, C
OUT
BOOST
cannot be charged
BOOST
can be charged from V
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
OUT
minus a
8.2.5.3 Application Curves
See Application Curves.
Product Folder Links: LM2734
22 Submit Documentation Feedback Copyright © 2004–2014, Texas Instruments Incorporated
LM2734
VIN
VIN
EN
BOOST
SW
FB
GND
V
OUT
C3
L1
C2
R1
R2
D1
D2
ON
OFF
C1
R3
www.ti.com
LM2734
SNVS288J –SEPTEMBER 2004–REVISED DECEMBER 2014
8.2.6 LM2734Y (550 kHz) V
BOOST
Figure 27. LM2734Y (550 kHz) V
8.2.6.1 Design Requirements
Derive charge for V
from the input supply (VIN). V
BOOST
limit of 5.5 V.
8.2.6.2 Detailed Design Procedure
See Detailed Design Procedure.
Derived from VIN5 V to 1.5 V / 1 A
Derived from VIN5 V to 1.5 V / 1-A Schematic
BOOST
– VSWshould not exceed the maximum operating
BOOST
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
Copyright © 2004–2014, Texas Instruments Incorporated Submit Documentation Feedback 23
LM2734
VIN
EN
BOOST
SW
FB
GND
C3
R1
R2
D1
D2
V
OUT
C
FF
12V
V
IN
3.3V
L1
C1
ON
OFF
R3
C2
LM2734
SNVS288J –SEPTEMBER 2004–REVISED DECEMBER 2014
www.ti.com
8.2.7 LM2734Y (550 kHz) V
Figure 28. LM2734Y (550 kHz) V
Derived from V
BOOST
OUT
Derived from V
BOOST
12 V to 3.3 V / 1 A
12 V to 3.3 V / 1 A Schematic
OUT
8.2.7.1 Design Requirements
Derive charge for V
from the output voltage, (V
BOOST
). The output voltage should be between 2.5 V and 5.5
OUT
V.
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.
24 Submit Documentation Feedback Copyright © 2004–2014, Texas Instruments Incorporated
Product Folder Links: LM2734
LM2734
VIN
V
IN
EN
BOOST
SW
FB
GND
V
OUT
C3
L1
C2
R1
R2
D1
D2
ON
OFF
D3
C4
R4
C1
R3
www.ti.com
LM2734
SNVS288J –SEPTEMBER 2004–REVISED DECEMBER 2014
8.2.8 LM2734Y (550 kHz) V
Figure 29. LM2734Y (550 kHz) V
Derived from V
BOOST
18 V to 1.5 V / 1 A
SHUNT
Derived from V
BOOST
18 V to 1.5 V / 1-A
SHUNT
8.2.8.1 Design Requirements
An alternative method when VINis 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 V
voltage is maintained during this time.
BOOST
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.
Copyright © 2004–2014, Texas Instruments Incorporated Submit Documentation Feedback 25
Product Folder Links: LM2734
LM2734
VIN
V
IN
EN
BOOST
SW
FB
GND
V
OUT
C3
L1
C2
R1
R2
D1
ON
OFF
D2D3
C1
R3
LM2734
SNVS288J –SEPTEMBER 2004–REVISED DECEMBER 2014
www.ti.com
8.2.9 LM2734Y (550 kHz) V
Figure 30. LM2734Y (550 kHz) V
Derived from Series Zener Diode (VIN) 15 V to 1.5 V / 1 A
BOOST
Derived from Series Zener Diode (VIN) 15 V to 1.5 V / 1-A Schematic
BOOST
8.2.9.1 Design Requirements
In applications where both VINand V
directly from these voltages. If VINis greater than 5.5 V, C
are greater than 5.5 V, or less than 3 V, C
OUT
can be charged from VINminus a zener voltage
BOOST
cannot be charged
BOOST
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 V
(V
(V
– VD3) < 5.5 V (28)
INMAX
– VD3) > 1.6 V (29)
INMIN
BOOST
voltage.
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
26 Submit Documentation Feedback Copyright © 2004–2014, Texas Instruments Incorporated
LM2734
VIN
VIN
EN
BOOST
SW
FB
GND
V
OUT
C3
L1
C2
R1
R2
D1
ON
OFF
D2
D3
C1
R3
www.ti.com
LM2734
SNVS288J –SEPTEMBER 2004–REVISED DECEMBER 2014
8.2.10 LM2734Y (550 kHz) V
Figure 31. LM2734Y (550 kHz) V
Derived from Series Zener Diode (V
BOOST
Derived from Series Zener Diode (V
BOOST
) 15 V to 9 V / 1 A
OUT
OUT
) 15 V to 9 V / 1-A
8.2.10.1 Design Requirements
In applications where both VINand V
directly from these voltages. If VINand V
are greater than 5.5 V, or less than 3 V, C
OUT
are greater than 5.5 V, C
OUT
BOOST
cannot be charged
BOOST
can be charged from V
OUT
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
minus a
8.2.10.3 Application Curves
See Application Curves.
Product Folder Links: LM2734
Copyright © 2004–2014, Texas Instruments Incorporated Submit Documentation Feedback 27
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,
V
efficiency V
derived from VINwhere the requirement that V
BOOST
should be at least 2.5-V above VSW.
BOOST
- VSW< 5.5 V should be observed) Also, for best
BOOST
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 C
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 C
connections of CINand 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 V
inductor and any other traces that are switching.
High AC currents flow through the VIN, SW and V
traces, so they should be as short and wide as possible.
OUT
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.
capacitor, which should be near the GND
OUT
trace to R1 should be routed away from the
OUT
IN
28 Submit Documentation Feedback Copyright © 2004–2014, Texas Instruments Incorporated
Product Folder Links: LM2734
EN
BOOST
SW
FB
GND
V
OUT
L1
R1
R2
D1
D2
C1
R5
C3
C2
V
IN
V
IN
V
EN
www.ti.com
10.2 Layout Example
LM2734
SNVS288J –SEPTEMBER 2004–REVISED DECEMBER 2014
Figure 32. Top Layer
Copyright © 2004–2014, Texas Instruments Incorporated Submit Documentation Feedback 29
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.
30 Submit Documentation Feedback Copyright © 2004–2014, Texas Instruments Incorporated
Product Folder Links: LM2734
PACKAGE OPTION ADDENDUM
www.ti.com
11-Dec-2014
PACKAGING INFORMATION
Orderable Device Status
LM2734XMK/NOPB ACTIVE SOT DDC 6 1000 Green (RoHS
LM2734XMKX/NOPB ACTIVE SOT DDC 6 3000 Green (RoHS
LM2734XQMK/NOPB ACTIVE SOT DDC 6 1000 Green (RoHS
LM2734XQMKE/NOPB ACTIVE SOT DDC 6 250 Green (RoHS
LM2734XQMKX/NOPB ACTIVE SOT DDC 6 3000 Green (RoHS
LM2734YMK NRND SOT DDC 6 1000 TBD Call TI Call TI -40 to 125 SFEB
LM2734YMK/NOPB ACTIVE SOT DDC 6 1000 Green (RoHS
LM2734YMKX/NOPB ACTIVE SOT DDC 6 3000 Green (RoHS
LM2734YQMK/NOPB ACTIVE SOT DDC 6 1000 Green (RoHS
LM2734YQMKE/NOPB ACTIVE SOT DDC 6 250 Green (RoHS
LM2734YQMKX/NOPB ACTIVE SOT DDC 6 3000 Green (RoHS
(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.
Package Type Package
(1)
Drawing
Pins Package
Qty
Eco Plan
(2)
& no Sb/Br)
& no Sb/Br)
& no Sb/Br)
& no Sb/Br)
& no Sb/Br)
& no Sb/Br)
& no Sb/Br)
& no Sb/Br)
& no Sb/Br)
& no Sb/Br)
Lead/Ball Finish
(6)
MSL Peak Temp
(3)
Op Temp (°C) Device Marking
CU SN Level-1-260C-UNLIM -40 to 125 SFDB
CU SN Level-1-260C-UNLIM -40 to 125 SFDB
CU SN Level-1-260C-UNLIM -40 to 125 SUKB
CU SN Level-1-260C-UNLIM -40 to 125 SUKB
CU SN Level-1-260C-UNLIM -40 to 125 SUKB
CU SN Level-1-260C-UNLIM -40 to 125 SFEB
CU SN Level-1-260C-UNLIM -40 to 125 SFEB
CU SN Level-1-260C-UNLIM -40 to 125 SVCB
CU SN Level-1-260C-UNLIM -40 to 125 SVCB
CU SN Level-1-260C-UNLIM -40 to 125 SVCB
(4/5)
(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.
Samples
Addendum-Page 1
PACKAGE OPTION ADDENDUM
www.ti.com
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)
11-Dec-2014
(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
•
Addendum-Page 2
PACKAGE MATERIALS INFORMATION
www.ti.com 5-Dec-2014
TAPE AND REEL INFORMATION
*All dimensions are nominal
Device Package
Type
LM2734XMK/NOPB SOT DDC 6 1000 178.0 8.4 3.2 3.2 1.4 4.0 8.0 Q3
LM2734XMKX/NOPB SOT DDC 6 3000 178.0 8.4 3.2 3.2 1.4 4.0 8.0 Q3
LM2734XQMK/NOPB SOT DDC 6 1000 178.0 8.4 3.2 3.2 1.4 4.0 8.0 Q3
LM2734XQMKE/NOPB SOT DDC 6 250 178.0 8.4 3.2 3.2 1.4 4.0 8.0 Q3
LM2734XQMKX/NOPB SOT DDC 6 3000 178.0 8.4 3.2 3.2 1.4 4.0 8.0 Q3
LM2734YMK SOT DDC 6 1000 178.0 8.4 3.2 3.2 1.4 4.0 8.0 Q3
LM2734YMK/NOPB SOT DDC 6 1000 178.0 8.4 3.2 3.2 1.4 4.0 8.0 Q3
LM2734YMKX/NOPB SOT DDC 6 3000 178.0 8.4 3.2 3.2 1.4 4.0 8.0 Q3
LM2734YQMK/NOPB SOT DDC 6 1000 178.0 8.4 3.2 3.2 1.4 4.0 8.0 Q3
LM2734YQMKE/NOPB SOT 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
Drawing
Pins SPQ Reel
Diameter
(mm)
Reel
Width
W1 (mm)
A0
(mm)B0(mm)K0(mm)P1(mm)W(mm)
Quadrant
Pin1
Pack Materials-Page 1
PACKAGE MATERIALS INFORMATION
www.ti.com 5-Dec-2014
*All dimensions are nominal
Device Package Type Package Drawing Pins SPQ Length (mm) Width (mm) Height (mm)
LM2734XMK/NOPB SOT DDC 6 1000 210.0 185.0 35.0
LM2734XMKX/NOPB SOT DDC 6 3000 210.0 185.0 35.0
LM2734XQMK/NOPB SOT DDC 6 1000 210.0 185.0 35.0
LM2734XQMKE/NOPB SOT DDC 6 250 210.0 185.0 35.0
LM2734XQMKX/NOPB SOT DDC 6 3000 210.0 185.0 35.0
LM2734YMK SOT DDC 6 1000 210.0 185.0 35.0
LM2734YMK/NOPB SOT DDC 6 1000 210.0 185.0 35.0
LM2734YMKX/NOPB SOT DDC 6 3000 210.0 185.0 35.0
LM2734YQMK/NOPB SOT DDC 6 1000 210.0 185.0 35.0
LM2734YQMKE/NOPB SOT DDC 6 250 210.0 185.0 35.0
LM2734YQMKX/NOPB SOT DDC 6 3000 210.0 185.0 35.0
Pack Materials-Page 2
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