LM2703
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SNVS172F – FEBRUARY 2002 – REVISED MAY 2013
LM2703 Micropower Step-Up DC/DC Converter with 350mA Peak Current Limit
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FEATURES
DESCRIPTION
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The LM2703 is a micropower step-up DC/DC in a
small 5-lead SOT-23 package. A current limited, fixed
off-time control scheme conserves operating current
resulting in high efficiency over a wide range of load
conditions. The 22V switch allows for output voltages
as high as 21V. The low 400ns off-time permits the
use of tiny, low profile inductors and capacitors to
minimize footprint and cost in space-conscious
portable applications. The LM2703 is ideal for LCD
panels requiring low current and high efficiency as
well as white LED applications for cellular phone
back-lighting. The LM2703 can drive up to 4 white
LEDs from a single Li-Ion battery.
1
2
350mA, 0.7Ω, Internal Switch
Uses Small Surface Mount Components
Adjustable Output Voltage up to 21V
2.2V to 7V Input Range
Input Undervoltage Lockout
0.01µA Shutdown Current
Small 5-Lead SOT-23 Package
APPLICATIONS
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LCD Bias Supplies
White LED Back-Lighting
Handheld Devices
Digital Cameras
Portable Applications
Typical Application Circuit
L
10 PH
VIN = Li-Ion
5
1
SW
VIN
CIN
4.7 PF
4
20V
15 mA
D
R1
510k
LM2703
3
FB
SHDN
GND
2
COUT
1 PF
R2
33k
CIN: Taiyo Yuden Ceramic
COUT: Taiyo Yuden Ceramic
L: Coilcraft DT1608C-103 or Murata
LQY33PN100M02
(low profile)
D: Motorola MBRM130LT3
Figure 1. Typical 20V Application
1
2
Please be aware that an important notice concerning availability, standard warranty, and use in critical applications of
Texas Instruments semiconductor products and disclaimers thereto appears at the end of this data sheet.
All trademarks are the property of their respective owners.
PRODUCTION DATA information is current as of publication date.
Products conform to specifications per the terms of the Texas
Instruments standard warranty. Production processing does not
necessarily include testing of all parameters.
Copyright © 2002–2013, Texas Instruments Incorporated
LM2703
SNVS172F – FEBRUARY 2002 – REVISED MAY 2013
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Connection Diagram
Top View
SW
VIN
GND
FB
SHDN
The maximum allowable power dissipation is a function of the maximum junction temperature, TJ(MAX), the junctionto-ambient thermal resistance, θJA, and the ambient temperature, TA. See the Electrical Characteristics table for the
thermal resistance. The maximum allowable power dissipation at any ambient temperature is calculated using: PD
(MAX) = (TJ(MAX) − TA)/θJA. Exceeding the maximum allowable power dissipation will cause excessive die
temperature.
Figure 2. SOT23-5
TJmax = 125°C, θJA = 220°C/W
PIN DESCRIPTIONS
Pin
Name
1
SW
Power Switch input.
2
GND
Ground.
3
FB
4
SHDN
5
VIN
Function
Output voltage feedback input.
Shutdown control input, active low.
Analog and Power input.
SW (Pin 1): Switch Pin.
This is the drain of the internal NMOS power switch. Minimize the metal trace area
connected to this pin to minimize EMI.
GND (Pin 2): Ground Pin.
Tie directly to ground plane.
FB (Pin 3): Feedback Pin.
Set the output voltage by selecting values for R1 and R2 using:
R1 = R2
VOUT
-1
1.237V
(1)
Connect the ground of the feedback network to an AGND plane which should be tied directly
to the GND pin.
SHDN (Pin 4): Shutdown Pin.
The shutdown pin is an active low control. Tie this pin above 1.1V to enable the device. Tie
this pin below 0.3V to turn off the device.
VIN (Pin 5): Input Supply Pin.
Bypass this pin with a capacitor as close to the device as possible.
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.
2
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Absolute Maximum Ratings
(1) (2)
VIN
7.5V
SW Voltage
22.5V
FB Voltage
2V
SHDN Voltage
7.5V
Maximum Junction Temp. TJ (3)
150°C
Lead Temperature
(Soldering 10 sec.)
300°C
Vapor Phase
(60 sec.)
215°C
Infrared
(15 sec.)
220°C
(4)
ESD Ratings
Human Body Model
Machine Model (5)
(1)
2kV
200V
Absolute maximum ratings are limits beyond which damage to the device may occur. Operating Ratings are conditions for which the
device is intended to be functional, but device parameter specifications may not be ensured. For ensured specifications and test
conditions, see the Electrical Characteristics.
If Military/Aerospace specified devices are required, please contact the TI Sales Office/Distributors for availability and specifications.
The maximum allowable power dissipation is a function of the maximum junction temperature, TJ(MAX), the junction-to-ambient thermal
resistance, θJA, and the ambient temperature, TA. See the Electrical Characteristics table for the thermal resistance. The maximum
allowable power dissipation at any ambient temperature is calculated using: PD (MAX) = (TJ(MAX) − TA)/θJA. Exceeding the maximum
allowable power dissipation will cause excessive die temperature.
The human body model is a 100 pF capacitor discharged through a 1.5 kΩ resistor into each pin. The machine model is a 200 pF
capacitor discharged directly into each pin.
ESD susceptibility using the machine model is 150V for SW pin.
(2)
(3)
(4)
(5)
Operating Conditions
Junction Temperature
(1)
−40°C to +125°C
Supply Voltage
2.2V to 7V
SW Voltage Max.
(1)
22V
All limits ensured at room temperature and at temperature extremes. All room temperature limits are 100% production tested or
ensured through statistical analysis. All limits at temperature extremes are ensured via correlation using standard Statistical Quality
Control (SQC) methods. All limits are used to calculate Average Outgoing Quality Level (AOQL).
Electrical Characteristics
Specifications in standard type face are for TJ = 25°C and those in boldface type apply over the full Operating Temperature
Range (TJ = −40°C to +125°C). Unless otherwise specified. VIN =2.2V.
Symbol
IQ
Parameter
Min
Conditions
(1)
Typ
Max
40
70
(2)
(1)
Device Disabled
FB = 1.3V
Device Enabled
FB = 1.2V
235
300
Shutdown
SHDN = 0V
0.01
2.5
Units
µA
VFB
FeedbackTrip Point
1.189
1.237
1.269
V
ICL
Switch Current Limit
275
260
350
400
400
mA
30
120
nA
7.0
V
IB
FB Pin Bias Current
VIN
Input Voltage Range
RDSON
Switch RDSON
0.7
TOFF
Switch Off Time
400
(1)
(2)
(3)
FB = 1.23V
(3)
2.2
1.6
Ω
ns
All limits ensured at room temperature and at temperature extremes. All room temperature limits are 100% production tested or
ensured through statistical analysis. All limits at temperature extremes are ensured via correlation using standard Statistical Quality
Control (SQC) methods. All limits are used to calculate Average Outgoing Quality Level (AOQL).
Typical numbers are at 25°C and represent the most likely norm.
Feedback current flows into the pin.
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Electrical Characteristics (continued)
Specifications in standard type face are for TJ = 25°C and those in boldface type apply over the full Operating Temperature
Range (TJ = −40°C to +125°C). Unless otherwise specified. VIN =2.2V.
Symbol
ISD
Parameter
SHDN Pin Current
Typ
Max
SHDN = VIN, TJ = 25°C
0
80
SHDN = VIN, TJ = 125°C
15
SHDN = GND
0
Conditions
Min
(1)
(2)
(1)
Units
nA
IL
Switch Leakage Current
VSW = 22V
0.05
UVP
Input Undervoltage Lockout
ON/OFF Threshold
1.8
V
VFB
Hysteresis
Feedback Hysteresis
8
mV
SHDN
Threshold
SHDN low
θJA
Thermal Resistance
4
0.7
SHDN High
1.1
0.7
220
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5
0.3
µA
V
°C/W
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Typical Performance Characteristics
Enable Current
vs
VIN
(Part Switching)
Disable Current
vs
VIN
(Part Not Switching)
Figure 3.
Figure 4.
Efficiency
vs
Load Current
Efficiency
vs
Load Current
95
V OUT = 20V
V IN = 4.2V
85
EFFICIENCY (%)
V IN = 3.3V
75
V
IN
= 2.5V
65
55
45
35
0.05
2
6
10
14
18
22
26
LOAD CURRENT (mA)
Figure 5.
Figure 6.
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Typical Performance Characteristics (continued)
6
Efficiency
vs
Load Current
SHDN Threshold
vs
VIN
Figure 7.
Figure 8.
Switch Current Limit
vs
VIN
Switch RDSON
vs
VIN
Figure 9.
Figure 10.
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Typical Performance Characteristics (continued)
FB Trip Point and FB Pin Current
vs
Temperature
12.20
50
12.15
124
45
40
123
35
122
30
nA
25
121
20
120
-40
-20
0
20
40
60
15
80 100 120
OUTPUT VOLTAGE (V)
FEEDBACK TRIP POINT (V)
V
55
FEEDBACK BIAS CURRENT (nA)
125
Output Voltage
vs
Load Current
C
= 1uF
OUT
V
= 12V
OUT
V
12.10
12.05
V
IN
= 2.5V
V
11.95
IN
= 3.3V
V
11.90
11.85
0.05 2
IN
= 5V
6 10 14 18 22 26 30 38 55 75
LOAD CURRENT (mA)
Figure 12.
Step Response
Figure 13.
= 4.2V
12.00
JUNCTION TEMPERATURE (°C)
Figure 11.
VOUT = 20V, VIN = 2.5V
1) Load, 1mA to 10mA to 1mA, DC
2) VOUT, 200mV/div, AC
3) IL, 200mA/div, DC
T = 50µs/div
IN
Start-Up/Shutdown
VOUT = 20V, VIN = 2.5V
1) SHDN, 1V/div, DC
2) IL, 200mA/div, DC
3) VOUT, 20V/div, DC
T = 400µs/div
RL = 1.8kΩ
Figure 14.
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OPERATION
V
C
V
IN
5
SW
IN
R1
50k
V
R2
50k
C
OUT
Enable
FB
3
R
OUT
Q1
Q2
10x
+
F1
1
V
Enable
Comp
OUT
+
R
D
L
IN
CL
Comp
F2
-
R3
30k
Current Sensing
Circuitry
CL Adjust
R4
140k
400ns
One Shot
Driver
Logic
Under Voltage
Lockout
4
2
GND
SHDN
Figure 15. LM2703 Block Diagram
VOUT = 20V, VIN = 2.5V
1) VSW, 20V/div, DC
2) Inductor Current, 200mA/div, DC
3) VOUT, 200mV/div, AC
T = 4µs/div
Figure 16. Typical Switching Waveform
The LM2703 features a constant off-time control scheme. Operation can be best understood by referring to
Figure 15 and Figure 16. Transistors Q1 and Q2 and resistors R3 and R4 of Figure 15 form a bandgap reference
used to control the output voltage. When the voltage at the FB pin is less than 1.237V, the Enable Comp in
Figure 15 enables the device and the NMOS switch is turned on pulling the SW pin to ground. When the NMOS
switch is on, current begins to flow through inductor L while the load current is supplied by the output capacitor
COUT. Once the current in the inductor reaches the current limit, the CL Comp trips and the 400ns One Shot turns
8
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SNVS172F – FEBRUARY 2002 – REVISED MAY 2013
off the NMOS switch.The SW voltage will then rise to the output voltage plus a diode drop and the inductor
current will begin to decrease as shown in Figure 16. During this time the energy stored in the inductor is
transferred to COUT and the load. After the 400ns off-time the NMOS switch is turned on and energy is stored in
the inductor again. This energy transfer from the inductor to the output causes a stepping effect in the output
ripple as shown in Figure 16.
This cycle is continued until the voltage at FB reaches 1.237V. When FB reaches this voltage, the enable
comparator then disables the device turning off the NMOS switch and reducing the Iq of the device to 40uA. The
load current is then supplied solely by COUT indicated by the gradually decreasing slope at the output as shown
in Figure 16. When the FB pin drops slightly below 1.237V, the enable comparator enables the device and
begins the cycle described previously. The SHDN pin can be used to turn off the LM2703 and reduce the Iq to
0.01µA. In shutdown mode the output voltage will be a diode drop lower than the input voltage.
APPLICATION INFORMATION
INDUCTOR SELECTION
The appropriate inductor for a given application is calculated using the following equation:
L=
VOUT - VIN(min) + VD
ICL
TOFF
(2)
where VD is the schottky diode voltage, ICL is the switch current limit found in the Typical Performance
Characteristics section, and TOFF is the switch off time. When using this equation be sure to use the minimum
input voltage for the application, such as for battery powered applications. For the LM2703 constant-off time
control scheme, the NMOS power switch is turned off when the current limit is reached. There is approximately a
200ns delay from the time the current limit is reached in the NMOS power switch and when the internal logic
actually turns off the switch. During this 200ns delay, the peak inductor current will increase. This increase in
inductor current demands a larger saturation current rating for the inductor. This saturation current can be
approximated by the following equation:
IPK = ICL +
VIN(max)
L
200ns
(3)
Choosing inductors with low ESR decrease power losses and increase efficiency.
Care should be taken when choosing an inductor. For applications that require an input voltage that approaches
the output voltage, such as when converting a Li-Ion battery voltage to 5V, the 400ns off time may not be enough
time to discharge the energy in the inductor and transfer the energy to the output capacitor and load. This can
cause a ramping effect in the inductor current waveform and an increased ripple on the output voltage. Using a
smaller inductor will cause the IPK to increase and will increase the output voltage ripple further. This can be
solved by adding a 4.7pF capacitor across the RF1 feedback resistor (Figure 15) and slightly increasing the
output capacitor. A smaller inductor can then be used to ensure proper discharge in the 400ns off time.
DIODE SELECTION
To maintain high efficiency, the average current rating of the schottky diode should be larger than the peak
inductor current, IPK. Schottky diodes with a low forward drop and fast switching speeds are ideal for increasing
efficiency in portable applications. Choose a reverse breakdown of the schottky diode larger than the output
voltage.
CAPACITOR SELECTION
Choose low ESR capacitors for the output to minimize output voltage ripple. Multilayer ceramic capacitors are the
best choice. For most applications, a 1µF ceramic capacitor is sufficient. For some applications a reduction in
output voltage ripple can be achieved by increasing the output capacitor.
Local bypassing for the input is needed on the LM2703. Multilayer ceramic capacitors are a good choice for this
as well. A 4.7µF capacitor is sufficient for most applications. For additional bypassing, a 100nF ceramic capacitor
can be used to shunt high frequency ripple on the input.
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LAYOUT CONSIDERATIONS
The input bypass capacitor CIN, as shown in Figure 1, must be placed close to the IC. This will reduce copper
trace resistance which effects input voltage ripple of the IC. For additional input voltage filtering, a 100nF bypass
capacitor can be placed in parallel with CIN to shunt any high frequency noise to ground. The output capacitor,
COUT, should also be placed close to the IC. Any copper trace connections for the Cout capacitor can increase
the series resistance, which directly effects output voltage ripple. The feedback network, resistors R1 and R2,
should be kept close to the FB pin to minimize copper trace connections that can inject noise into the system.
The ground connection for the feedback resistor network should connect directly to an analog ground plane. The
analog ground plane should tie directly to the GND pin. If no analog ground plane is available, the ground
connection for the feedback network should tie directly to the GND pin. Trace connections made to the inductor
and schottky diode should be minimized to reduce power dissipation and increase overall efficiency.
L
10 PH
VIN
2.5V-4.2V
D
5
1
VIN
SW
CIN
4.7 PF
Ceramic
COUT
1 PF
Ceramic
LM2703
>1.1V
0V
4
SHDN
GND
FB 3
2
R2
82:
CIN: Taiyo Yuden Ceramic
COUT: Taiyo Yuden Ceramic
L: Coilcraft DT1608C-103 or Murata
LQY33PN100M02 (low profile)
D: Motorola MBRM130LT3
Figure 17. White LED Application
Figure 18. Li-Ion 5V Application
10
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L
10PH
VIN
2.54.2V
5
1
VIN
CIN
4
4.7PF
12V
22 mA
D
R1
240k
SW
COUT
1PF
LM2703
3
FB
SHDN
R2
27k
GND
2
Figure 19. Li-Ion 12V Application
L
10PH
VIN
5V
5
1
VIN
CIN
4
4.7PF
12V
70 mA
D
SW
R1
240k
COUT
4.7PF
LM2703
3
FB
SHDN
GND
2
R2
27k
Figure 20. 5V to 12V Application
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REVISION HISTORY
Changes from Revision E (May 2013) to Revision F
•
12
Page
Changed layout of National Data Sheet to TI format .......................................................................................................... 11
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PACKAGE OPTION ADDENDUM
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30-Sep-2021
PACKAGING INFORMATION
Orderable Device
Status
(1)
Package Type Package Pins Package
Drawing
Qty
Eco Plan
(2)
Lead finish/
Ball material
MSL Peak Temp
Op Temp (°C)
Device Marking
(3)
(4/5)
(6)
LM2703MF-ADJ
NRND
SOT-23
DBV
5
1000
Non-RoHS
& Green
Call TI
Level-1-260C-UNLIM
-40 to 85
S48B
LM2703MF-ADJ/NOPB
ACTIVE
SOT-23
DBV
5
1000
RoHS & Green
SN
Level-1-260C-UNLIM
-40 to 85
S48B
LM2703MFX-ADJ/NOPB
ACTIVE
SOT-23
DBV
5
3000
RoHS & Green
SN
Level-1-260C-UNLIM
-40 to 85
S48B
(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)
RoHS: TI defines "RoHS" to mean semiconductor products that are compliant with the current EU RoHS requirements for all 10 RoHS substances, including the requirement that RoHS substance
do not exceed 0.1% by weight in homogeneous materials. Where designed to be soldered at high temperatures, "RoHS" products are suitable for use in specified lead-free processes. TI may
reference these types of products as "Pb-Free".
RoHS Exempt: TI defines "RoHS Exempt" to mean products that contain lead but are compliant with EU RoHS pursuant to a specific EU RoHS exemption.
Green: TI defines "Green" to mean the content of Chlorine (Cl) and Bromine (Br) based flame retardants meet JS709B low halogen requirements of