TI LM27313 Lm27313/-q1 1.6-mhz boost converter with 30-v internal fet switch in sot-23 Datasheet

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LM27313, LM27313-Q1
SNVS487E – DECEMBER 2006 – REVISED JANUARY 2015
LM27313/-Q1 1.6-MHz Boost Converter With 30-V Internal FET Switch in SOT-23
1 Features
3 Description
•
The LM27313/-Q1 switching regulator is a currentmode boost converter with a fixed operating
frequency of 1.6 MHz.
1
•
•
•
•
•
•
•
•
•
•
LM27313-Q1 is an Automotive-Grade Product that
is AEC-Q100 Grade 1 Qualified (–40°C to +125°C
Operating Junction Temperature)
30-V DMOS FET Switch
1.6-MHz Switching Frequency
Low RDS(ON) DMOS FET
Switch Current up to 800 mA
Wide Input Voltage Range (2.7 V to 14 V)
Low Shutdown Current (< 1 µA)
5-Lead SOT-23 Package
Uses Tiny Capacitors and Inductors
Cycle-by-Cycle Current Limiting
Internally Compensated
The use of the SOT-23 package, made possible by
the minimal losses of the 800-mA switch, and the
small inductors and capacitors result in extremely
high power density. The 30-V internal switch makes
these solutions perfect for boosting to voltages of 5 V
to 28 V.
This device has a logic-level shutdown pin that can
be used to reduce quiescent current and extend
battery life.
Protection is provided through cycle-by-cycle current
limiting and thermal shutdown. Internal compensation
simplifies design and reduces component count.
2 Applications
•
•
•
•
•
Device Information(1)
White LED Current Source
PDAs and Palm-Top Computers
Digital Cameras
Portable Phones, Games, and Media Players
GPS Devices
Typical Application Circuit
VIN
SHDN
R3
51k
C1
2.2 PF
GND
U1
BODY SIZE (NOM)
SOT-23 (5)
2.90 mm x 1.60 mm
(1) For all available packages, see the orderable addendum at
the end of the data sheet.
Efficiency vs. Load Current
SW
LM27313
SHDN
GND
LM27313-Q1
PACKAGE
D1
MBR0520
L1/10 PH
5 VIN
PART NUMBER
LM27313
R1/117k
FB
R2
13.3k
CF
220 pF
12V
OUT
260 mA
(TYP)
C2
4.7 PF
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.
LM27313, LM27313-Q1
SNVS487E – DECEMBER 2006 – REVISED JANUARY 2015
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Table of Contents
1
2
3
4
5
6
7
Features ..................................................................
Applications ...........................................................
Description .............................................................
Revision History.....................................................
Pin Configuration and Functions .........................
Specifications.........................................................
1
1
1
2
3
3
6.1
6.2
6.3
6.4
6.5
6.6
6.7
3
3
4
4
4
5
6
Absolute Maximum Ratings ......................................
ESD Ratings: LM27313 ............................................
ESD Ratings: LM27313-Q1 ......................................
Recommended Operating Conditions.......................
Thermal Information ..................................................
Electrical Characteristics...........................................
Typical Characteristics ..............................................
Detailed Description .............................................. 8
7.1 Overview ................................................................... 8
7.2 Functional Block Diagram ......................................... 8
7.3 Feature Description................................................... 8
7.4 Device Functional Modes.......................................... 9
8
Application and Implementation ........................ 10
8.1 Application Information............................................ 10
8.2 Typical Applications ................................................ 10
9 Power Supply Recommendations...................... 17
10 Layout................................................................... 17
10.1 Layout Guidelines ................................................. 17
10.2 Layout Example .................................................... 17
10.3 Thermal Considerations ........................................ 17
11 Device and Documentation Support ................. 18
11.1
11.2
11.3
11.4
11.5
Device Support......................................................
Related Links ........................................................
Trademarks ...........................................................
Electrostatic Discharge Caution ............................
Glossary ................................................................
18
18
18
18
18
12 Mechanical, Packaging, and Orderable
Information ........................................................... 18
4 Revision History
Changes from Revision D (April 2013) to Revision E
•
Page
Added Pin Configuration and Functions section, 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
Changes from Revision C (April 2013) to Revision D
•
2
Page
Changed layout of National Data Sheet to TI format ........................................................................................................... 15
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SNVS487E – DECEMBER 2006 – REVISED JANUARY 2015
5 Pin Configuration and Functions
SOT-23 Package
5-Pin
(Top View)
Pin Functions
PIN
NO.
(1)
NAME
I/O (1)
DESCRIPTION
1
SW
O
Drain of the internal FET switch.
2
GND
G
Analog and power ground.
3
FB
I
Feedback point that connects to external resistive divider to set VOUT.
4
SHDN
I
Shutdown control input. Connect to VIN if this feature is not used.
5
VIN
I/P
Analog and power input.
I: Input Pin, O: Output Pin, P: Power Pin, G: Ground Pin
6 Specifications
6.1 Absolute Maximum Ratings (1) (2)
MIN
MAX
UNIT
FB Pin Voltage
−0.4
6
V
SW Pin Voltage
−0.4
30
V
Input Supply Voltage
−0.4
14.5
V
Shutdown
Input Voltage
−0.4
14.5
V
300
°C
(Survival)
Lead Temp. (Soldering, 5 s)
Power Dissipation
Internally Limited
Storage temperature, Tstg
−65
(1)
(2)
150
°C
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.
If Military/Aerospace specified devices are required, please contact the Texas Instruments Sales Office/ Distributors for availability and
specifications.
6.2 ESD Ratings: LM27313
VALUE
V(ESD)
(1)
(2)
Electrostatic discharge
Human body model (HBM), per ANSI/ESDA/JEDEC JS-001, all pins (1)
±2000
Charged device model (CDM), per JEDEC specification JESD22-C101, all
pins (2)
±1000
UNIT
V
JEDEC document JEP155 states that 500-V HBM allows safe manufacturing with a standard ESD control process.
JEDEC document JEP157 states that 250-V CDM allows safe manufacturing with a standard ESD control process.
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6.3 ESD Ratings: LM27313-Q1
VALUE
Human body model (HBM), per AEC Q100-002 (1)
V(ESD)
(1)
Electrostatic discharge
Charged device model (CDM), per
AEC Q100-011
UNIT
±2000
Corner pins (1, 3, 4, and 5)
±1000
Other pins
±1000
V
AEC Q100-002 indicates HBM stressing is done in accordance with the ANSI/ESDA/JEDEC JS-001 specification.
6.4 Recommended Operating Conditions
MIN
VIN
NOM
2.7
VSW(MAX)
VSHDN
Junction Temperature, TJ
MAX UNIT
14
V
30
V
0
VIN
V
–40
125
°C
6.5 Thermal Information
THERMAL METRIC
LM27313,
LM27313-Q1
(1)
DBV
UNIT
5 PINS
RθJA
Junction-to-ambient thermal resistance
166.3
RθJC(top)
Junction-to-case (top) thermal resistance
71.8
RθJB
Junction-to-board thermal resistance
28.1
ψJT
Junction-to-top characterization parameter
2.1
ψJB
Junction-to-board characterization parameter
27.7
RθJC(bot)
Junction-to-case (bottom) thermal resistance
N/A
(1)
4
°C/W
For more information about traditional and new thermal metrics, see the IC Package Thermal Metrics application report, SPRA953.
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6.6 Electrical Characteristics
Unless otherwise specified: VIN = 5 V, VSHDN = 5 V, IL = 0 mA, and TJ = 25°C. Minimum and Maximum limits are ensured
through test, design, or statistical correlation. Typical values represent the most likely parametric norm at TJ = 25°C, and are
provided for reference purposes only.
PARAMETER
TEST CONDITIONS
VIN
Input Voltage
−40°C ≤ TJ ≤ +125°C
ISW
Switch Current Limit
See (1)
RDS(ON)
Switch ON Resistance
ISW = 100 mA
MIN
ISHDN
Shutdown Threshold
UNIT
V
1.25
500
A
650
mΩ
1.5
Device OFF, −40°C ≤ TJ ≤
+125°C
Shutdown Pin Bias Current
MAX
14
0.80
Device ON, −40°C ≤ TJ ≤ +125°C
VSHDN(TH)
TYP
2.7
V
0.50
VSHDN = 0
0
VSHDN = 5 V
0
2
µA
VSHDN = 5 V, −40°C ≤ TJ ≤
+125°C
VFB
Feedback Pin Reference Voltage
IFB
Feedback Pin Bias Current
VIN = 3 V
VIN = 3 V, −40°C ≤ TJ ≤ +125°C
1.230
1.205
VFB = 1.23 V
60
VSHDN = 5 V, Switching
2.1
VSHDN = 5 V, Switching, −40°C ≤
TJ ≤ +125°C
IQ
Quiescent Current
VSHDN = 5 V, Not Switching
fSW
Switching Frequency
DMAX
Maximum Duty Cycle
IL
Switch Leakage
(1)
mA
400
500
VSHDN = 0
0.024
2.7 V ≤ VIN ≤ 14 V
FB Voltage Line Regulation
nA
3.0
VSHDN = 5 V, Not Switching,
−40°C ≤ TJ ≤ +125°C
ΔVFB/ΔVIN
V
1.255
1
0.02
%/V
1.6
−40°C ≤ TJ ≤ +125°C
1.15
−40°C ≤ TJ ≤ +125°C
80%
µA
1.90
MHz
88%
Not Switching, VSW = 5 V
1
µA
Switch current limit is dependent on duty cycle. Limits shown are for duty cycles ≤ 50%. See Figure 15.
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6.7 Typical Characteristics
Unless otherwise specified: VIN = 5 V, SHDN pin is tied to VIN, TJ = 25°C.
Figure 1. Iq VIN (Active) vs Temperature
Figure 2. Oscillator Frequency vs Temperature
88.5
MAX DUTY CYCLE (%)
88.4
88.3
88.2
88.1
88.0
87.9
87.8
-40
-25
0
25
50
75
100
125
o
TEMPERATURE ( C)
6
Figure 3. Max. Duty Cycle vs Temperature
Figure 4. Feedback Voltage vs Temperature
Figure 5. RDS(ON) vs Temperature
Figure 6. Current Limit vs Temperature
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Typical Characteristics (continued)
Unless otherwise specified: VIN = 5 V, SHDN pin is tied to VIN, TJ = 25°C.
Figure 7. RDS(ON) vs VIN
Figure 8. Efficiency vs Load Current (VOUT = 12 V)
100
100
90
90
VIN = 10V
VIN = 5V
70
VIN = 3.3V
60
50
40
30
50
40
30
10
10
0
200
400
800
600
1000
VIN = 3.3V
60
20
0
VIN = 5V
70
20
0
VIN = 10V
80
EFFICIENCY (%)
EFFICIENCY (%)
80
0
100
200
300 400
500
600 700
LOAD CURRENT (mA)
LOAD CURRENT (mA)
Figure 9. Efficiency vs Load Current (VOUT = 15 V)
Figure 10. Efficiency vs Load Current (VOUT = 20 V)
100
90
VIN = 10V
EFFICIENCY (%)
80
70
VIN = 5V
60
50
40
30
20
10
0
0
50
100 150 200 250 300 350 400
LOAD CURRENT (mA)
Figure 11. Efficiency vs Load Current (VOUT = 25 V)
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7 Detailed Description
7.1 Overview
The LM27313 is a switching converter IC that operates at a fixed frequency of 1.6 MHz using current-mode
control for fast transient response over a wide input voltage range and incorporate pulse-by-pulse current limiting
protection. Because this is current mode control, a 50-mΩ sense resistor in series with the switch FET is used to
provide a voltage (which is proportional to the FET current) to both the input of the pulse width modulation
(PWM) comparator and the current limit amplifier.
At the beginning of each cycle, the S-R latch turns on the FET. As the current through the FET increases, a
voltage (proportional to this current) is summed with the ramp coming from the ramp generator and then fed into
the input of the PWM comparator. When this voltage exceeds the voltage on the other input (coming from the
Gm amplifier), the latch resets and turns the FET off. Because the signal coming from the Gm amplifier is derived
from the feedback (which samples the voltage at the output), the action of the PWM comparator constantly sets
the correct peak current through the FET to keep the output voltage in regulation.
Q1 and Q2 along with R3 - R6 form a bandgap voltage reference used by the IC to hold the output in regulation.
The currents flowing through Q1 and Q2 will be equal, and the feedback loop will adjust the regulated output to
maintain this. Because of this, the regulated output is always maintained at a voltage level equal to the voltage at
the FB node "multiplied up" by the ratio of the output resistive divider.
The current limit comparator feeds directly into the flip-flop, that drives the switch FET. If the FET current reaches
the limit threshold, the FET is turned off and the cycle terminated until the next clock pulse. The current limit
input terminates the pulse regardless of the status of the output of the PWM comparator.
7.2 Functional Block Diagram
7.3 Feature Description
This device is designed as a current mode boost converter for a wide input voltage range. It features a very small
package and operates at a high switching frequency. This allows for use of small passive components (inductors
and capacitors), enabling small solution size. The device features also logic level shutdown, making it ideal for
applications where low power consumption is desired. Control loop compensation is internal and no additional
external components are required. Additional protection features are provided by deploying cycle-by-cycle current
limiting and thermal shutdown.
8
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7.4 Device Functional Modes
In normal operational mode, the device regulates output voltage to the value set with resistive divider. In addition,
this device has a logic level shutdown pin (SHDN) that allows user to turn the device on/off by driving this pin
high/low. Default setup is that this pin is connected to VIN through pullup resistor (typically 50 kΩ). When
shutdown pin is low, the device is in shutdown mode consuming typically only 24 nA, making it ideal for
applications where low power consumption is desirable.
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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
The device operates with input voltage in the range of 2.7 V to 14 V and provides regulated output voltage. This
device is optimized for high-efficiency operation with minimum number of external components. Also, high
switching frequency allows use of small surface mount components, enabling very small solution size. For
component selection, refer to Detailed Design Procedure.
8.2 Typical Applications
8.2.1 Application Circuit VIN=5.0 V, VOUT=12.0 V, Iload=250 mA
VIN
SHDN
R3
51k
C1
2.2 PF
GND
D1
MBR0520
L1/10 PH
5 VIN
U1
SW
LM27313
SHDN
GND
R1/117k
FB
R2
13.3k
CF
220 pF
12V
OUT
260 mA
(TYP)
C2
4.7 PF
Figure 12. Typical Application Circuit
Figure 13. Efficiency vs. Load Current
8.2.1.1 Design Requirements
The device must be able to operate at any voltage within input voltage range.
Load Current must be defined in order to properly size the inductor, input and output capacitors. The inductor
should be able to handle full expected load current as well as the peak current generated during load transients
and start up. Inrush current at startup will depend on the output capacitor selection. More details are provided in
Detailed Design Procedure.
Device has a shutdown pin (SHDN) that is used to enable and disable device. This pin is active low and should
be tied to VIN if not used in application.
10
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Typical Applications (continued)
8.2.1.2 Detailed Design Procedure
8.2.1.2.1 Selecting the External Capacitors
The LM27313 requires ceramic capacitors at the input and output to accommodate the peak switching currents
the part needs to operate. Electrolytic capacitors have resonant frequencies which are below the switching
frequency of the device, and therefore can not provide the currents needed to operate. Electrolytics may be used
in parallel with the ceramics for bulk charge storage which will improve transient response.
When selecting a ceramic capacitor, only X5R and X7R dielectric types should be used. Other types such as
Z5U and Y5F have such severe loss of capacitance due to effects of temperature variation and applied voltage,
they may provide as little as 20% of rated capacitance in many typical applications. Always consult capacitor
manufacturer’s data curves before selecting a capacitor. High-quality ceramic capacitors can be obtained from
Taiyo-Yuden, AVX, and Murata.
8.2.1.2.2 Selecting the Output Capacitor
A single ceramic capacitor of value 4.7 µF to 10 µF provides sufficient output capacitance for most applications.
For output voltages below 10 V, a 10 µF capacitance is required. If larger amounts of capacitance are desired for
improved line support and transient response, tantalum capacitors can be used in parallel with the ceramics.
Aluminum electrolytics with ultra low ESR such as Sanyo Oscon can be used, but are usually prohibitively
expensive. Typical AI electrolytic capacitors are not suitable for switching frequencies above
500 kHz due to significant ringing and temperature rise due to self-heating from ripple current. An output
capacitor with excessive ESR can also reduce phase margin and cause instability.
8.2.1.2.3 Selecting the Input Capacitor
An input capacitor is required to serve as an energy reservoir for the current which must flow into the inductor
each time the switch turns ON. This capacitor must have extremely low ESR and ESL, so ceramic must be used.
We recommend a nominal value of 2.2 µF, but larger values can be used. Because this capacitor reduces the
amount of voltage ripple seen at the input pin, it also reduces the amount of EMI passed back along that line to
other circuitry.
8.2.1.2.4 Feed-Forward Compensation
Although internally compensated, the feed-forward capacitor Cf is required for stability (see Equation 1). Adding
this capacitor puts a zero in the loop response of the converter. Without it, the regulator loop can oscillate. The
recommended frequency for the zero fz should be approximately 8 kHz. Cf can be calculated using the formula:
Cf = 1 / (2 x π x R1 x fz)
(1)
8.2.1.2.5 Selecting Diodes
The external diode used in the typical application should be a Schottky diode. If the switch voltage is less than
15V, a 20V diode such as the MBR0520 is recommended. If the switch voltage is between 15 V and 25 V, a 30V diode such as the MBR0530 is recommended. If the switch voltage exceeds 25V, a 40V diode such as the
MBR0540 should be used.
The MBR05xx series of diodes are designed to handle a maximum average current of 500 mA. For applications
with load currents to 800 mA, a Microsemi UPS5817 can be used.
8.2.1.2.6 Setting the Output Voltage
The output voltage is set using the external resistors R1 and R2 (see Equation 2). A value of 13.3 kΩ is
recommended for R2 to establish a divider current of approximately 92 µA. R1 is calculated using the formula:
R1 = R2 x ( (VOUT / VFB) − 1 )
(2)
8.2.1.2.7 Duty Cycle
The maximum duty cycle of the switching regulator determines the maximum boost ratio of output-to-input
voltage that the converter can attain in continuous mode of operation. The duty cycle for a given boost
application is defined as:
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Typical Applications (continued)
VOUT + VDIODE - VIN
Duty Cycle =
VOUT + VDIODE - VSW
(3)
This applies for continuous mode operation.
The equation shown for calculating duty cycle incorporates terms for the FET switch voltage and diode forward
voltage. The actual duty cycle measured in operation will also be affected slightly by other power losses in the
circuit such as wire losses in the inductor, switching losses, and capacitor ripple current losses from self-heating.
Therefore, the actual (effective) duty cycle measured may be slightly higher than calculated to compensate for
these power losses. A good approximation for effective duty cycle is:
DC (eff) = (1 - Efficiency x (VIN / VOUT))
where
•
the efficiency can be approximated from the curves provided.
(4)
8.2.1.2.8 Inductance Value
The first question we are usually asked is: “How small can I make the inductor?” (because they are the largest
sized component and usually the most costly). The answer is not simple and involves trade-offs in performance.
More inductance means less inductor ripple current and less output voltage ripple (for a given size of output
capacitor). More inductance also means more load power can be delivered because the energy stored during
each switching cycle is:
E = L/2 x (lp)2
where
•
lp is the peak inductor current.
(5)
An important point to observe is that the LM27313 will limit its switch current based on peak current. This means
that because lp(max) is fixed, increasing L will increase the maximum amount of power available to the load.
Conversely, using too little inductance may limit the amount of load current which can be drawn from the output.
Best performance is usually obtained when the converter is operated in “continuous” mode at the load current
range of interest, typically giving better load regulation and less output ripple. Continuous operation is defined as
not allowing the inductor current to drop to zero during the cycle. It should be noted that all boost converters shift
over to discontinuous operation as the output load is reduced far enough, but a larger inductor stays “continuous”
over a wider load current range.
To better understand these tradeoffs, a typical application circuit (5V to 12V boost with a 10 µH inductor) will be
analyzed.
Because the LM27313 typical switching frequency is 1.6 MHz, the typical period is equal to 1/fSW(TYP), or
approximately 0.625 µs.
We will assume: VIN = 5 V, VOUT = 12 V, VDIODE = 0.5 V, VSW = 0.5 V. The duty cycle is:
Duty Cycle = ((12 V + 0.5 V - 5 V) / (12 V + 0.5 V - 0.5 V)) = 62.5%
(6)
The typical ON time of the switch is:
(62.5% x 0.625 µs) = 0.390 µs
(7)
It should be noted that when the switch is ON, the voltage across the inductor is approximately 4.5 V.
Use the equation:
V = L (di/dt)
(8)
Then, calculate the di/dt rate of the inductor which is found to be 0.45 A/µs during the ON time. Using these
facts, we can then show what the inductor current will look like during operation:
12
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Typical Applications (continued)
Figure 14. 10 µH Inductor Current, 5 V – 12 V Boost
During the 0.390-µs ON time, the inductor current ramps up 0.176 A and ramps down an equal amount during
the OFF time. This is defined as the inductor “ripple current”. It can also be seen that if the load current drops to
about 33 mA, the inductor current will begin touching the zero axis which means it will be in discontinuous mode.
A similar analysis can be performed on any boost converter, to make sure the ripple current is reasonable and
continuous operation will be maintained at the typical load current values.
8.2.1.2.9 Maximum Switch Current
The maximum FET switch current available before the current limiter cuts in is dependent on duty cycle of the
application. This is illustrated in Figure 15 which shows typical values of switch current as a function of effective
(actual) duty cycle:
SWITCH CURRENT LIMIT (mA)
1600
1400
1200
1000
VIN = 5V
VIN = 3.3V
800
600
VIN = 2.7V
400
200
0
0
20
40
60
80
100
DUTY CYCLE (%) = [1 - EFF*(VIN/VOUT))]
Figure 15. Switch Current Limit vs Duty Cycle
8.2.1.2.10 Calculating Load Current
As shown in Figure 14 which depicts inductor current, the load current is related to the average inductor current
by the relation:
ILOAD = IIND(AVG) x (1 - DC)
where
•
DC is the duty cycle of the application.
(9)
The switch current can be found by:
ISW = IIND(AVG) + ½ (IRIPPLE)
(10)
Inductor ripple current is dependent on inductance, duty cycle, input voltage and frequency:
IRIPPLE = DC x (VIN - VSW) / (fSW x L)
(11)
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Typical Applications (continued)
Combining all terms, we can develop an expression which allows the maximum available load current to be
calculated:
ILOAD(max) = (1 - DC) x (ISW(max) - DC (VIN - VSW))
2fL
(12)
The equation shown to calculate maximum load current takes into account the losses in the inductor or turn-OFF
switching losses of the FET and diode. For actual load current in typical applications, we took bench data for
various input and output voltages and displayed the maximum load current available for a typical device in graph
form:
Figure 16. Max. Load Current vs VIN
8.2.1.2.11 Design Parameters VSW and ISW
The value of the FET ON voltage (referred to as VSW in the equations) is dependent on load current. A good
approximation can be obtained by multiplying the "ON Resistance" of the FET times the average inductor
current.
FET ON resistance increases at VIN values below 5V, because the internal N-FET has less gate voltage in this
input voltage range (see Typical Characteristics). Above VIN = 5 V, the FET gate voltage is internally clamped to
5V.
The maximum peak switch current the device can deliver is dependent on duty cycle. The minimum switch
current value (ISW) is ensured to be at least 800 mA at duty cycles below 50%. For higher duty cycles, see
Typical Characteristics.
8.2.1.2.12 Minimum Inductance
In some applications where the maximum load current is relatively small, it may be advantageous to use the
smallest possible inductance value for cost and size savings. The converter will operate in discontinuous mode in
such a case.
The minimum inductance should be selected such that the inductor (switch) current peak on each cycle does not
reach the 800 mA current limit maximum. To understand how to do this, an example will be presented.
In this example, the LM27313 nominal switching frequency is 1.6 MHz, and the minimum switching frequency is
1.15 MHz. This means the maximum cycle period is the reciprocal of the minimum frequency:
TON(max) = 1/1.15M = 0.870 µs
(13)
Assume: VIN = 5 V, VOUT = 12 V, VSW = 0.2 V, and VDIODE = 0.3 V. The duty cycle is:
Duty Cycle = ((12 V + 0.3 V - 5 V) / (12 V + 0.3 V - 0.2 V)) = 60.3%
(14)
Therefore, the maximum switch ON time is:
(60.3% x 0.870 µs) = 0.524 µs
14
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SNVS487E – DECEMBER 2006 – REVISED JANUARY 2015
Typical Applications (continued)
An inductor should be selected with enough inductance to prevent the switch current from reaching 800 mA in
the 0.524 µs ON time interval (see Figure 17):
Figure 17. Discontinuous Design, 5 V – 12 V Boost
The voltage across the inductor during ON time is 4.8 V. Minimum inductance value is found by:
L = V x (dt/dl)
L = 4.8 V x (0.524 µs / 0.8 mA) = 3.144 µH
(16)
(17)
In this case, a 3.3-µH inductor could be used, assuming it provided at least that much inductance up to the 800mA current value. This same analysis can be used to find the minimum inductance for any boost application.
8.2.1.2.13 Inductor Suppliers
Some of the recommended suppliers of inductors for this product include, but are not limited to, Sumida,
Coilcraft, Panasonic, TDK and Murata. When selecting an inductor, make certain that the continuous current
rating is high enough to avoid saturation at peak currents. A suitable core type must be used to minimize core
(switching) losses, and wire power losses must be considered when selecting the current rating.
8.2.1.2.14 Shutdown Pin Operation
The device is turned off by pulling the shutdown pin low. If this function is not going to be used, the pin should be
tied directly to VIN. If the SHDN function will be needed, a pullup resistor must be used to VIN (50 kΩ to 100 kΩ is
recommended), or the pin must be actively driven high and low. The SHDN pin must not be left unterminated.
8.2.1.3 Application Curves
Figure 18. Typical Startup Waveform for Vin = 3.3 V, Vout
= 12 V
Figure 19. Typical Startup Waveform for Vin = 5.0 V, Vout
= 12 V
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Typical Applications (continued)
8.2.2 Application Circuit VIN=5.0V, VOUT=20.0V, Iload=150mA
VIN
SHDN
R3
51k
C1
2.2 PF
GND
D1
MBR0530
L1/10 PH
5 VIN
U1
SW
R1/205k
LM27313
SHDN
GND
FB
R2
13.3k
CF
120 pF
20V
OUT
130 mA
(TYP)
C2
4.7 PF
Figure 20. Typical Application Circuit
Figure 21. Efficiency vs. Load Current
8.2.2.1 Design Requirements
See Design Requirements.
8.2.2.2 Detailed Design Procedure
See Detailed Design Procedure.
8.2.2.3 Application Curves
See Application Curves.
16
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SNVS487E – DECEMBER 2006 – REVISED JANUARY 2015
9 Power Supply Recommendations
The LM27313 is designed to operate from an input voltage supply range from 2.7 V to 14 V. This input supply
should be able to withstand the maximum input current and maintain a voltage above 2.7 V. In cases where input
supply is located farther away (more than a few inches) from LM27313, additional bulk capacitance may be
required in addition to the ceramic bypass capacitors.
10 Layout
10.1 Layout Guidelines
High-frequency switching regulators require very careful layout of components in order to get stable operation
and low noise. All components must be as close as possible to the LM27313 device. It is recommended that a 4layer PCB be used so that internal ground planes are available.
Some additional guidelines to be observed:
1. Keep the path between L1, D1, and C2 extremely short. Parasitic trace inductance in series with D1 and C2
will increase noise and ringing.
2. The feedback components R1, R2 and CF must be kept close to the FB pin of the LM27313 to prevent noise
injection on the high impedance FB pin.
3. If internal ground planes are available (recommended) use vias to connect directly to the LM27313 ground at
device pin 2, as well as the negative sides of capacitors C1 and C2.
10.2 Layout Example
Figure 22. Recommended PCB Component Layout
10.3 Thermal Considerations
At higher duty cycles, the increased ON time of the FET means the maximum output current will be determined
by power dissipation within the LM27313 FET switch. The switch power dissipation from ON-state conduction is
calculated by:
PSW = DC x IIND(AVG)2 x RDS(ON)
(18)
There will be some switching losses as well, so some derating needs to be applied when calculating IC power
dissipation.
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LM27313, LM27313-Q1
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www.ti.com
11 Device and Documentation Support
11.1 Device Support
11.1.1 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 Related Links
The table below lists quick access links. Categories include technical documents, support and community
resources, tools and software, and quick access to sample or buy.
Table 1. Related Links
PARTS
PRODUCT FOLDER
SAMPLE & BUY
TECHNICAL
DOCUMENTS
TOOLS &
SOFTWARE
SUPPORT &
COMMUNITY
LM27313
Click here
Click here
Click here
Click here
Click here
LM27313-Q1
Click here
Click here
Click here
Click here
Click here
11.3 Trademarks
All trademarks are the property of their respective owners.
11.4 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.
11.5 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.
18
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PACKAGE OPTION ADDENDUM
www.ti.com
11-Dec-2014
PACKAGING INFORMATION
Orderable Device
Status
(1)
Package Type Package Pins Package
Drawing
Qty
Eco Plan
Lead/Ball Finish
MSL Peak Temp
(2)
(6)
(3)
Op Temp (°C)
Device Marking
(4/5)
LM27313XMF/NOPB
ACTIVE
SOT-23
DBV
5
1000
Green (RoHS
& no Sb/Br)
CU SN
Level-1-260C-UNLIM
-40 to 125
SRPB
LM27313XMFX/NOPB
ACTIVE
SOT-23
DBV
5
3000
Green (RoHS
& no Sb/Br)
CU SN
Level-1-260C-UNLIM
-40 to 125
SRPB
LM27313XQMF/NOPB
ACTIVE
SOT-23
DBV
5
1000
Green (RoHS
& no Sb/Br)
CU SN
Level-1-260C-UNLIM
-40 to 125
SD3B
LM27313XQMFX/NOPB
ACTIVE
SOT-23
DBV
5
3000
Green (RoHS
& no Sb/Br)
CU SN
Level-1-260C-UNLIM
-40 to 125
SD3B
(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.
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.
Addendum-Page 1
Samples
PACKAGE OPTION ADDENDUM
www.ti.com
11-Dec-2014
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 LM27313, LM27313-Q1 :
• Catalog: LM27313
• Automotive: LM27313-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
22-Jul-2015
TAPE AND REEL INFORMATION
*All dimensions are nominal
Device
Package Package Pins
Type Drawing
SPQ
Reel
Reel
A0
Diameter Width (mm)
(mm) W1 (mm)
LM27313XMF/NOPB
SOT-23
DBV
5
1000
178.0
8.4
B0
(mm)
K0
(mm)
P1
(mm)
W
Pin1
(mm) Quadrant
3.2
3.2
1.4
4.0
8.0
Q3
LM27313XMFX/NOPB
SOT-23
DBV
5
3000
178.0
8.4
3.2
3.2
1.4
4.0
8.0
Q3
LM27313XQMF/NOPB
SOT-23
DBV
5
1000
178.0
8.4
3.2
3.2
1.4
4.0
8.0
Q3
LM27313XQMFX/NOPB
SOT-23
DBV
5
3000
178.0
8.4
3.2
3.2
1.4
4.0
8.0
Q3
Pack Materials-Page 1
PACKAGE MATERIALS INFORMATION
www.ti.com
22-Jul-2015
*All dimensions are nominal
Device
Package Type
Package Drawing
Pins
SPQ
Length (mm)
Width (mm)
Height (mm)
LM27313XMF/NOPB
SOT-23
DBV
5
1000
210.0
185.0
35.0
LM27313XMFX/NOPB
SOT-23
DBV
5
3000
210.0
185.0
35.0
LM27313XQMF/NOPB
SOT-23
DBV
5
1000
210.0
185.0
35.0
LM27313XQMFX/NOPB
SOT-23
DBV
5
3000
210.0
185.0
35.0
Pack Materials-Page 2
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