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LM2840, LM2841, LM2842
SNVS540K – MARCH 2009 – REVISED APRIL 2019
LM284x SIMPLE SWITCHER® 4.5-V to 42-V Input, 0.1-, 0.3-, or
0.6-A Output Step-Down DC/DC Regulator in Thin SOT
1 Features
3 Description
•
•
The LM284x SIMPLE SWITCHER™ devices are
PWM DC/DC buck (step-down) regulators. With an
input range from 4.5 V to 42 V, they are suitable for a
wide range of applications, such as power
conditioning from unregulated sources. They feature
a low RDSON (0.9‑Ω typical) internal switch for
maximum efficiency (85% typical). Operating
frequency is fixed at 550 kHz (X option) and
1.25 MHz (Y option), allowing the use of small
external components while still being able to have low
output voltage ripple. Soft start can be implemented
using the shutdown (SHDN) pin with an external RC
circuit allowing the user to tailor the soft-start time to
a specific application.
1
•
•
•
•
•
•
•
•
Input voltage 4.5 V to 42 V
Output current options of 100 mA, 300 mA, and
600 mA
Feedback pin voltage of 0.765 V
550-kHz (X) or 1.25-MHz (Y) switching frequency
Low shutdown IQ: 16-µA typical
Short-circuit protected
Internally compensated
Soft-start circuitry
Small overall solution size (SOT-6L package)
Create a custom design using the LM2840 (or
LM2841/42) with the WEBENCH® Power Designer
The LM2840 is optimized for up to 100 mA, the
LM2841 for up to 300 mA, and the LM2842 for up to
600‑mA load currents. They all have a 0.765-V
nominal feedback voltage.
2 Applications
•
•
•
•
Battery-powered equipment
Industrial distributed power applications
Portable media players
Portable hand-held instruments
Additional features include: thermal shutdown, VIN
undervoltage lockout, and gate-drive undervoltage
lockout. The LM284x are available in a low-profile
SOT-6L package.
Device Information(1)
PART NUMBER
LM2840, LM2841,
LM2842
PACKAGE
SOT (6)
BODY SIZE (NOM)
1.60 mm × 2.90 mm
(1) For all available packages, see the orderable addendum at
the end of the data sheet.
Typical Application Circuit
CBOOT
L1
VOUT
LM2840/1/2-ADJL
VIN
VIN
CB
SHDN
SW
GND
FB
D1
R1
CIN
R2
COUT
Copyright © 2016, Texas Instruments Incorporated
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.
LM2840, LM2841, LM2842
SNVS540K – MARCH 2009 – REVISED APRIL 2019
www.ti.com
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
4
6.1
6.2
6.3
6.4
6.5
6.6
4
4
4
4
5
7
Absolute Maximum Ratings .....................................
ESD Ratings..............................................................
Recommended Operating Conditions.......................
Thermal Information ..................................................
Electrical Characteristics ..........................................
Typical Characteristics ..............................................
Detailed Description .............................................. 9
7.1
7.2
7.3
7.4
Overview ................................................................... 9
Functional Block Diagram ......................................... 9
Feature Description................................................... 9
Device Functional Modes........................................ 10
8
Application and Implementation ........................ 11
8.1 Application Information............................................ 11
8.2 Typical Applications ................................................ 11
9 Power Supply Recommendations...................... 16
10 Layout................................................................... 16
10.1 Layout Guidelines ................................................. 16
10.2 Layout Example .................................................... 16
11 Device and Documentation Support ................. 17
11.1
11.2
11.3
11.4
11.5
11.6
11.7
11.8
Device Support......................................................
Documentation Support ........................................
Related Links ........................................................
Receiving Notification of Documentation Updates
Community Resources..........................................
Trademarks ...........................................................
Electrostatic Discharge Caution ............................
Glossary ................................................................
17
17
17
17
18
18
18
18
12 Mechanical, Packaging, and Orderable
Information ........................................................... 18
4 Revision History
NOTE: Page numbers for previous revisions may differ from page numbers in the current version.
Changes from Revision J (February 2017) to Revision K
Page
•
Split automotive data sheet to separate document (SNVSBE5) and remove automotive-specific content from SNVS540 .. 1
•
Added SIMPLE SWITCHER® to data sheet title ................................................................................................................... 1
Changes from Revision I (September 2016) to Revision J
Page
•
Added new text for Pin 4 ........................................................................................................................................................ 3
•
Added this new line of text in Shutdown Operation section ................................................................................................. 13
Changes from Revision H (April 2013) to Revision I
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
•
Added Thermal Information table ........................................................................................................................................... 4
Changes from Revision G (April 2013) to Revision H
•
2
Page
Changed layout of National Semiconductor data sheet to TI format...................................................................................... 1
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SNVS540K – MARCH 2009 – REVISED APRIL 2019
5 Pin Configuration and Functions
DDC Package
6-Pin SOT
Top View
CB
1
6
SW
GND
2
5
FB
3
4
VIN
SHDN
Not to scale
Pin Functions
PIN
NO.
NAME
I/O
DESCRIPTION
1
CB
I
2
GND
—
SW FET gate bias voltage. Connect CBOOT capacitor between CB and SW.
3
FB
I
Feedback pin: Set feedback voltage divider ratio with VOUT = VFB (1 + (R1 / R2)). Resistors must be from
100 Ω to 10 kΩ to avoid input bias errors.
4
SHDN
I
Logic level shutdown input. Pull to GND to disable the device and pull high to enable the device. If this function
is not used tie to VIN . DO NOT ALLOW TO FLOAT.
5
VIN
I
Power input voltage pin: 4.5-V to 42-V normal operating range.
6
SW
O
Power FET output: Connect to inductor, diode, and CBOOT capacitor.
Ground connection
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6 Specifications
6.1 Absolute Maximum Ratings
(1) (2)
See
MIN
MAX
UNIT
VIN
–0.3
45
V
SHDN
–0.3
(VIN + 0.3 V) < 45
V
SW voltage
–0.3
45
V
7
V
5
V
CB voltage above SW voltage
FB voltage
–0.3
Power dissipation (3)
Internally Limited
Maximum junction temperature
Storage temperature, Tstg
(1)
(2)
(3)
–65
150
°C
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, contact the Texas Instruments 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, RθJA, and the ambient temperature, TA. The maximum allowable power dissipation at any ambient temperature is calculated
using: PD (MAX) = (TJ(MAX) − TA) / RθJA. Exceeding the maximum allowable power dissipation causes excessive die temperature, and
the regulator goes into thermal shutdown. Internal thermal shutdown circuitry protects the device from permanent damage. Thermal
shutdown engages at TJ=175°C (typical) and disengages at TJ= 155°C (typical).
6.2 ESD Ratings
V(ESD)
(1)
Electrostatic discharge
VALUE
UNIT
±2000
V
Human-body model (HBM), per ANSI/ESDA/JEDEC JS-001 (1)
JEDEC document JEP155 states that 500-V HBM allows safe manufacturing with a standard ESD control process.
6.3 Recommended Operating Conditions
over operating free-air temperature range (unless otherwise noted)
MIN
MAX
UNIT
Operating junction temperature (1)
–40
125
°C
Input voltage VIN
4.5
42
V
42
V
SW voltage
(1)
All limits specified at room temperature (TA = 25°C) unless otherwise specified. All room temperature limits are 100% production tested.
All limits at temperature extremes are ensured through correlation using standard Statistical Quality Control (SQC) methods. All limits
are used to calculate Average Outgoing Quality Level (AOQL).
6.4 Thermal Information
LM284x
THERMAL METRIC (1)
DDC (SOT)
UNIT
6 PINS
RθJA
Junction-to-ambient thermal resistance (2) (3)
121
°C/W
RθJC(top)
Junction-to-case (top) thermal resistance
94
°C/W
(1)
(2)
(3)
4
For more information about traditional and new thermal metrics, see the Semiconductor and IC Package Thermal Metrics application
report.
The package thermal impedance is calculated in accordance to JESD 51-7.
Thermal Resistances were simulated on a 4-layer, JEDEC board
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SNVS540K – MARCH 2009 – REVISED APRIL 2019
6.5 Electrical Characteristics
Specifications are for TJ = 25°C unless otherwise specified. Minimum and Maximum limits are specified 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. Unless otherwise stated the following conditions apply: VIN = 12 V. (1) (2) (3)
PARAMETER
TEST CONDITIONS
SHDN = 0 V
IQ
Quiescent current
Device ON, not switching
Device ON, no load
Switch ON resistance
See
ILSW
Switch leakage current
VIN = 42 V
LM2841 (5)
LM2842 (5)
IFB
Feedback pin bias current
VFB
FB Pin reference voltage
tON(min)
Minimum ON-time
LM284[0,1,2] (6)
See
X option, VFB = 0.5 V
1.75
1.35
TJ = −40°C to 125°C
1.6
0
TJ = −40°C to 125°C
0.5
525
TJ = −40°C to 125°C
900
525
TJ = −40°C to 125°C
900
1.15
TJ = −40°C to 125°C
1.7
0.1
TJ = −40°C to 125°C
1
0.747
DMAX
Maximum duty cycle
Y option
(1)
(2)
(3)
(4)
(5)
(6)
(7)
0.782
100
TJ = −40°C to 125°C
150
110
TJ = −40°C to 125°C
370
104
TJ = −40°C to 125°C
200
mA
Ω
µA
mA
mA
A
µA
V
ns
ns
ns
550
TJ = −40°C to 125°C
325
750
kHz
1.5
MHz
140
1.25
TJ = −40°C to 125°C
0.95
Y option, VFB = 0 V
X option
µA
1.85
0.9
X option, VFB = 0 V
Y option, VFB = 0.5 V
UNIT
1.3
(7)
Minimum OFF-time
Switching frequency
40
TJ = −40°C to 125°C
TJ = −40°C to 125°C
Y option
fSW
MAX
0.765
X option
tOFF(min)
TJ = −40°C to 125°C
TJ = −40°C to 125°C
LM2840 (5)
Switch current limit
TYP
16
(4)
RDSON
ICL
MIN
0.35
94%
TJ = −40°C to 125°C
88%
87%
TJ = −40°C to 125°C
81%
All limits specified at room temperature (TA = 25°C) unless otherwise noted. Room temperature limits are production tested. Limits at
temperature extremes are ensured through correlation using standard Statistical Quality Control (SQC) methods. Limits are used to
calculate Average Outgoing Quality Level (AOQL).
Typical numbers are at 25°C and represent the most likely norm.
The part numbers in this table represent both the Q1 and non-Q1 versions of the respective parts.
Includes the bond wires, RDSON from VIN pin to SW pin.
Current limit at 0% duty cycle. May be lower at higher duty cycle or input voltages below 6 V.
Bias currents flow into pin.
Minimum ON-time specified by design and simulation.
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Electrical Characteristics (continued)
Specifications are for TJ = 25°C unless otherwise specified. Minimum and Maximum limits are specified 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. Unless otherwise stated the following conditions apply: VIN = 12 V.(1)(2)(3)
PARAMETER
TEST CONDITIONS
On threshold
VUVP
Undervoltage lockout
thresholds
Off threshold
Device ON
V SHDN
Shutdown threshold
Device OFF
VSHDN = 2.3 V (6)
ISHDN
Shutdown pin input bias
current
VSHDN = 0 V
6
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MIN
TYP
MAX
UNIT
3.7
TJ = −40°C to 125°C
4.4
V
3.5
TJ = −40°C to 125°C
3.25
1
TJ = −40°C to 125°C
2.3
V
0.9
TJ = −40°C to 125°C
0.3
0.05
TJ = −40°C to 125°C
1.5
0.02
TJ = −40°C to 125°C
µA
1.5
Copyright © 2009–2019, Texas Instruments Incorporated
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6.6 Typical Characteristics
The part numbers in this section represent both the Q1 and non-Q1 versions of the respective parts.
100
100
VIN = 12V
VIN = 12V
80
EFFICIENCY (%)
EFFICIENCY (%)
80
VIN = 36V
60
VIN = 24V
40
20
0
0.0
VIN = 36V
60
VIN = 24V
40
20
0.1
0.2
0.3
0.4
0.5
0
0.0
0.6
0.1
LM2842X
0.2
0.3
LOAD CURRENT (A)
LOAD CURRENT (A)
VOUT = 3.3 V
LM2841X
Figure 1. Efficiency vs Load Current
VOUT = 3.3 V
Figure 2. Efficiency vs Load Current
100
VIN = 12V
90
EFFICIENCY (%)
80
VIN = 24V
70
60
50
40
30
20
10
0
0
20
40
60
80
100
120
LOAD CURRENT (mA)
LM2840X
VOUT = 8 V
X option
Figure 3. Efficiency vs Load Current
Figure 4. Switching Frequency vs Temperature
SWITCH CURRENT LIMIT (mA)
800
600
400
200
0
1.0
1.6
2.2
2.8
3.4
4.0
SHDN PIN VOLTAGE (V)
Soft-Start Implementation
Figure 5. Input UVLO Voltage vs Temperature
LM284[0,1]
Figure 6. Switch Current Limit vs SHDN Pin Voltage
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Typical Characteristics (continued)
The part numbers in this section represent both the Q1 and non-Q1 versions of the respective parts.
SWITCH CURRENT LIMIT (A)
1.2
1.0
0.9
0.7
0.6
0.4
1.1
1.7
2.3
2.8
3.4
4.0
SHDN PIN VOLTAGE (V)
Soft-Start Implementation
LM2842
Figure 7. Switch Current Limit vs SHDN Pin Voltage
8
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Figure 8. SHDN Pin Current vs SHDN Pin Voltage
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7 Detailed Description
7.1 Overview
The LM284x SIMPLE SWITCHER® regulators are easy-to-use, non-synchronous, step-down DC/DC converters
with a wide input voltage range up to 42 V. The devices are capable of delivering up to 100‑mA, 300-mA, or 600mA DC load current with excellent line and load regulation. These devices are available in fixed frequency of 550
kHz and 1.25 MHz. The family requires few external components, and the pin arrangement was designed for
simple, optimum PCB layout.
7.2 Functional Block Diagram
CB
+
+
OSC
SET
FB
+
PWM
Comp
Error
Amp
+
Bandgap
VIN
Max Duty
Cycle Limit
RESET
Inductor
Current
Measurement
DC
LIMIT
BUCK
DRIVE
FET
Driver
SW
UVLO
TSD
UVLO
Comp
Thermal
Shutdown
Soft
Start
BG
Voltage
Regulator
GND
SHDN
Copyright © 2016, Texas Instruments Incorporated
7.3 Feature Description
7.3.1 Protection
The LM284x have dedicated protection circuitry running during normal operation to protect the IC. The thermal
shutdown circuitry turns off the power device when the die temperature reaches excessive levels. The UVLO
comparator protects the power device during supply power start-up and shutdown to prevent operation at
voltages less than the minimum input voltage. A gate drive (CB) undervoltage lockout is included to ensure that
there is enough gate drive voltage to drive the MOSFET before the device tries to start switching. The LM284x
also feature a shutdown mode decreasing the supply current to approximately 16 µA.
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7.4 Device Functional Modes
7.4.1 Continuous Conduction Mode
The LM284x contain a current-mode, PWM buck regulator. A buck regulator steps the input voltage down to a
lower output voltage. In continuous conduction mode (when the inductor current never reaches zero at steadystate operation), the buck regulator operates in two cycles. The power switch is connected between VIN and SW.
In the first cycle of operation the transistor is closed and the diode is reverse biased. Energy is collected in the
inductor and the load current is supplied by COUT and the rising current through the inductor. During the second
cycle the transistor is open and the diode is forward biased due to the fact that the inductor current cannot
instantaneously change direction. The energy stored in the inductor is transferred to the load and output
capacitor. The ratio of these two cycles determines the output voltage. The output voltage is defined
approximately as shown in Equation 1.
D = VOUT / VIN
D’ = (1 – D)
(1)
where
•
D is the duty cycle of the switch
(2)
D and D' are required for design calculations.
10
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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 LM284x are step-down DC/DC regulators. They are typically used to convert a higher DC voltage to a lower
DC voltage with a maximum output current of 100 mA, 300 mA, or 600 mA. The following design procedure can
be used to select components for the LM284x . Alternately, the WEBENCH® software may be used to generate
complete designs. When generating a design, the WEBENCH software uses iterative design procedure and
accesses comprehensive databases of components. See ti.com and Detailed Design Procedure for more details
8.2 Typical Applications
L1
15 PH
CBOOT
LM2840/1/2-ADJL
C
VIN
B
SHDN
SW
4.5V to 42V IN
3.3V OUT
0.1 PF
D1
MA2YD26
R1
FB
GND
3.4k
R2
1.02k
CIN
2.2 PF
COUT
10 PF
Copyright © 2016, Texas Instruments Incorporated
Figure 9. Application Circuit With 3.3-V Output Voltage at 100 mA
8.2.1 Design Requirements
Table 1 lists the design parameters for this example.
Table 1. Design Parameters
DESIGN PARAMETER
EXAMPLE VALUE
Input voltage
4.5 V to 42 V
Output voltage
3.3 V
Output current
0.1 A
8.2.2 Detailed Design Procedure
8.2.2.1 Custom Design With WEBENCH® Tools
Click here to create a custom design using the LM2840 device with the WEBENCH® Power Designer.
1. Start by entering the input voltage (VIN), output voltage (VOUT), and output current (IOUT) requirements.
2. Optimize the design for key parameters such as efficiency, footprint, and cost using the optimizer dial.
3. Compare the generated design with other possible solutions from Texas Instruments.
The WEBENCH Power Designer provides a customized schematic along with a list of materials with real-time
pricing and component availability.
In most cases, these actions are available:
• Run electrical simulations to see important waveforms and circuit performance
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•
•
•
www.ti.com
Run thermal simulations to understand board thermal performance
Export customized schematic and layout into popular CAD formats
Print PDF reports for the design, and share the design with colleagues
Get more information about WEBENCH tools at www.ti.com/WEBENCH.
This section presents guidelines for selecting external components.
8.2.2.2 Setting the Output Voltage
The output voltage is set using the feedback pin and a resistor divider connected to the output as shown in
Typical Application Circuit. The feedback pin voltage 0.765 V, so the ratio of the feedback resistors sets the
output voltage according to Equation 3:
VOUT = 0.765 V (1 + (R1 / R2))
(3)
Typically R2 is given as 100 Ω to 10 kΩ for a starting value. To solve for R1 given R2 and VOUT, use Equation 4:
R1 = R2 ((VOUT / 0.765 V) – 1)
(4)
8.2.2.3 Inductor Selection
The most critical parameters for the inductor are the inductance, peak current, and the DC resistance. The
inductance is related to the peak-to-peak inductor ripple current, the input and the output voltages.
L=
(VIN - VOUT)VOUT
VIN x IRIPPLE x fSW
(5)
A higher value of ripple current reduces inductance, but increases the conductance loss, core loss, and current
stress for the inductor and switch devices. It also requires a bigger output capacitor for the same output voltage
ripple requirement. A reasonable value is setting the ripple current to be 30% of the DC output current. Because
the ripple current increases with the input voltage, the maximum input voltage is always used to determine the
inductance. The DC resistance of the inductor is a key parameter for the efficiency. Lower DC resistance is
available with a bigger winding area. A good tradeoff between the efficiency and the core size is letting the
inductor copper loss equal 2% of the output power. See Selecting Inductors for Buck Converters for more
information on selecting inductors. A good starting point for most applications is a 10 µH to 22 µH with 1.1 A or
greater current rating for the LM2842 or a 0.7 A or greater current rating for the LM284x . Using such a rating
enables the device to current limit without saturating the inductor. This is preferable to the device going into
thermal shutdown mode and the possibility of damaging the inductor if the output is shorted to ground or other
long-term overload.
Table 2. Recommended Inductors
MANUFACTURER
INDUCTOR
CONTACT INFORMATION
Coilcraft
LPS4018, DO1608C, DO3308, and LPO2506 series
www.coilcraft.com
800-3222645
MuRata
LQH55D and LQH66S series
www.murata.com
Coiltronics
MP2 and MP2A series
www.cooperbussman.com
8.2.2.4 Input Capacitor
A low ESR ceramic capacitor (CIN) is needed between the VIN pin and GND pin. This capacitor prevents large
voltage transients from appearing at the input. Use a 2.2-µF to 10-µF value with X5R or X7R dielectric.
Depending on construction, a ceramic capacitor’s value can decrease up to 50% of its nominal value when rated
voltage is applied. Consult with the capacitor manufacturer's data sheet for information on capacitor derating over
voltage and temperature.
12
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8.2.2.5 Output Capacitor
The selection of COUT is driven by the maximum allowable output voltage ripple. The output ripple in the constant
frequency, PWM mode is approximated by Equation 6.
VRIPPLE = IRIPPLE (ESR + (1 / (8fSWCOUT)))
(6)
The ESR term usually plays the dominant role in determining the voltage ripple. Low-ESR ceramic capacitors are
recommended. Capacitors in the range of 22 µF to 100 µF are a good starting point with an ESR of 0.1 Ω or
less.
Table 3. Recommended Input and Output Capacitors
MANUFACTURER
CAPACITOR
CONTACT INFORMATION
Vishay Sprague
293D, 592D, and 595D series tantalum
www.vishay.com
407-324-4140
Taiyo Yuden
High capacitance MLCC ceramic
www.t-yuden.com
408-573-4150
Cornell Dubilier
ESRD seriec Polymer Aluminum Electrolytic
SPV and AFK series V-chip series
www.cde.com
MuRata
High capacitance MLCC ceramic
www.murata.com
8.2.2.6 Bootstrap Capacitor
A 0.15-µF ceramic capacitor or larger is recommended for the bootstrap capacitor CBOOT). For applications where
the input voltage is less than twice the output voltage a larger capacitor is recommended, generally 0.15 µF to 1
µF to ensure plenty of gate drive for the internal switches and a consistently low RDSON.
8.2.2.7 Soft-Start Components
The devices have circuitry that is used in conjunction with the SHDN pin to limit the inrush current on start-up of
the DC/DC switching regulator. The SHDN pin in conjunction with a RC filter is used to tailor the soft start for a
specific application. When a voltage applied to the SHDN pin is between 0 V and up to 2.3 V it causes the cycleby-cycle current limit in the power stage to be modulated for minimum current limit at 0 V up to the rated current
limit at 2.3 V. Thus controlling the output rise time and inrush current at start-up. The resistor value must be
selected so the current injected into the SHDN pin is greater then the leakage current of the SHDN pin (1.5 µA)
when the voltage at SHDN is equal or greater then 2.3 V.
8.2.2.8 Shutdown Operation
The SHDN pin of the LM284x is designed so that it may be controlled using 2.3 V or higher logic signals. If the
shutdown function is not to be used the SHDN pin may be tied to VIN. This input must not be allowed to float
The maximum voltage to the SHDN pin should not exceed 42 V. If the use of a higher voltage is desired due to
system or other constraints it may be used; however, a 100 kΩ or larger resistor is recommended between the
applied voltage and the SHDN pin to protect the device.
8.2.2.9 Schottky Diode
The breakdown voltage rating of the diode (D1) is preferred to be 25% higher than the maximum input voltage.
The current rating for the diode must be equal to the maximum output current for best reliability in most
applications. In cases where the duty cycle is greater than 50%, the average diode current is lower. In this case it
is possible to use a diode with a lower average current rating, approximately (1 – D)IOUT; however, the peak
current rating should be higher than the maximum load current. A 0.5-A to 1-A rated diode is a good starting
point.
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8.2.3 Application Curves
VIN = 12 V
VOUT = 3.3 V
T = 1 µs/div
IOUT = 200 mA
Top trace: VOUT, 10 mV/div, AC-Coupled
Bottom trace: SW, 5 V/div, DC-Coupled
VIN = 12 V
VOUT = 3.3 V
T = 200 µs/div
Figure 10. Switching Node and Output Voltage Waveforms
VIN = 12 V
VOUT = 3.3 V
T = 40 µs/div
IOUT = 300 mA to 200 mA to 300 mA
Top trace: VOUT, 20 mV/div, AC-Coupled
Bottom trace: IOUT, 100 mA/div, DC-Coupled
Figure 11. Load Transient Waveforms
IOUT = 50 mA
Top trace: VOUT, 1V/div, DC-Coupled
Bottom trace: SHDN, 2V/div, DC-Coupled
Figure 12. Start-Up Waveform
8.2.4 Other Application Circuits
Figure 13 to Figure 16 show application circuit examples using the LM284x devices. Customers must fully
validate and test these circuits before implementing a design based on these examples. Unless otherwise noted,
the design procedures in are applicable to these designs.
L1
15 PH
CBOOT
LM2840/1/2-ADJL
7V to 42V IN
VIN
0.15 PF
D1
MA2YD26
CB
SHDN
SW
GND
FB
5V OUT
R1
5.62k
CIN
R2
1.02k
2.2 PF
COUT
47 PF
Copyright © 2016, Texas Instruments Incorporated
Figure 13. Step-Down Converter With 5-V Output Voltage
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SNVS540K – MARCH 2009 – REVISED APRIL 2019
L1
47 PH
CBOOT
LM2840/1/2-ADJL
15V to 42V IN
VIN
CB
SHDN
SW
GND
FB
12V OUT
0.15 PF
D1
MA2YD26
R1
14.7k
R2
1k
CIN
2.2 PF
COUT
22 PF
Copyright © 2016, Texas Instruments Incorporated
Figure 14. Step-Down Converter With 12-V Output Voltage
L1
47 PH
CBOOT
LM2840/1/2-ADJL
18V to 42V IN
VIN
CB
SHDN
SW
GND
FB
15V OUT
0.15 PF
D1
MA2YD26
R1
28k
CIN
COUT
22 PF
R2
1.5k
2.2 PF
Copyright © 2016, Texas Instruments Incorporated
Figure 15. Step-Down Converter With 15-V Output Voltage
L1
10 PH
CBOOT
LM2840/1/2-ADJL
4.5V to 12V IN
VIN
CB
SHDN
SW
GND
FB
0.8V OUT
0.15 PF
D1
MA2YD26
R1
30.9
CIN
COUT
100 PF
R2
787
2.2 PF
Copyright © 2016, Texas Instruments Incorporated
Figure 16. Step-Down Converter With 0.8-V Output Voltage
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9 Power Supply Recommendations
The LM284x are designed to operate from an input voltage supply range between 4 V and 42 V. This input
supply must be able to withstand the maximum input current and maintain a voltage above 4.5 V. The resistance
of the input supply rail must be low enough that an input current transient does not cause a drop at the device
supply voltage high enough to cause a false UVLO fault triggering and system reset. If the input supply is located
more than a few inches from the device, additional bulk capacitance may be required in addition to the ceramic
input capacitors.
10 Layout
10.1 Layout Guidelines
To reduce problems with conducted noise pickup, the ground side of the feedback network should be connected
directly to the GND pin with its own connection. The feedback network, resistors R1 and R2, must be kept close
to the FB pin, and away from the inductor to minimize coupling noise into the feedback pin. The input bypass
capacitor CIN must be placed close to the VIN pin. This reduces copper trace resistance, which effects input
voltage ripple of the IC. The inductor L1 must be placed close to the SW pin to reduce EMI and capacitive
coupling. The output capacitor, COUT must be placed close to the junction of L1 and the diode D1. The L1, D1,
and COUT trace must be as short as possible to reduce conducted and radiated noise and increase overall
efficiency. The ground connection for the diode, CIN, and COUT must be as small as possible and tied to the
system ground plane in only one spot (preferably at the COUT ground point) to minimize conducted noise in the
system ground plane. See Layout Guidelines for Switching Power Supplies for more detail on switching power
supply layout considerations.
10.2 Layout Example
Figure 17. Recommended Layout
16
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LM2840, LM2841, LM2842
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SNVS540K – MARCH 2009 – REVISED APRIL 2019
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.
11.1.2 Development Support
11.1.2.1 Custom Design With WEBENCH® Tools
Click here to create a custom design using the LM2840 device with the WEBENCH® Power Designer.
1. Start by entering the input voltage (VIN), output voltage (VOUT), and output current (IOUT) requirements.
2. Optimize the design for key parameters such as efficiency, footprint, and cost using the optimizer dial.
3. Compare the generated design with other possible solutions from Texas Instruments.
The WEBENCH Power Designer provides a customized schematic along with a list of materials with real-time
pricing and component availability.
In most cases, these actions are available:
• Run electrical simulations to see important waveforms and circuit performance
• Run thermal simulations to understand board thermal performance
• Export customized schematic and layout into popular CAD formats
• Print PDF reports for the design, and share the design with colleagues
Get more information about WEBENCH tools at www.ti.com/WEBENCH.
11.2 Documentation Support
11.2.1 Related Documentation
For related documentation, see the following:
• AN-1197 Selecting Inductors for Buck Converters (SNVA038)
• AN-1149 Layout Guidelines for Switching Power Supplies (SNVA021)
11.3 Related Links
The table below lists quick access links. Categories include technical documents, support and community
resources, tools and software, and quick access to order now.
Table 4. Related Links
PARTS
PRODUCT FOLDER
ORDER NOW
TECHNICAL
DOCUMENTS
TOOLS &
SOFTWARE
SUPPORT &
COMMUNITY
LM2840
Click here
Click here
Click here
Click here
Click here
LM2841
Click here
Click here
Click here
Click here
Click here
LM2842
Click here
Click here
Click here
Click here
Click here
11.4 Receiving Notification of Documentation Updates
To receive notification of documentation updates, navigate to the device product folder on ti.com. In the upper
right corner, click on Alert me to register and receive a weekly digest of any product information that has
changed. For change details, review the revision history included in any revised document.
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Product Folder Links: LM2840 LM2841 LM2842
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11.5 Community Resources
The following links connect to TI community resources. Linked contents are provided "AS IS" by the respective
contributors. They do not constitute TI specifications and do not necessarily reflect TI's views; see TI's Terms of
Use.
TI E2E™ Online Community TI's Engineer-to-Engineer (E2E) Community. Created to foster collaboration
among engineers. At e2e.ti.com, you can ask questions, share knowledge, explore ideas and help
solve problems with fellow engineers.
Design Support TI's Design Support Quickly find helpful E2E forums along with design support tools and
contact information for technical support.
11.6 Trademarks
SIMPLE SWITCHER, E2E are trademarks of Texas Instruments.
WEBENCH, SIMPLE SWITCHER are registered trademarks of Texas Instruments.
All other trademarks are the property of their respective owners.
11.7 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.
11.8 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
10-Dec-2020
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)
LM2840XMK-ADJL/NOPB
ACTIVE
SOT-23-THIN
DDC
6
1000
RoHS & Green
SN
Level-1-260C-UNLIM
-40 to 125
SE8B
LM2840XMKX-ADJL/NOPB
ACTIVE
SOT-23-THIN
DDC
6
3000
RoHS & Green
SN
Level-1-260C-UNLIM
-40 to 125
SE8B
LM2840YMK-ADJL/NOPB
ACTIVE
SOT-23-THIN
DDC
6
1000
RoHS & Green
SN
Level-1-260C-UNLIM
-40 to 125
SF1B
LM2841XMK-ADJL/NOPB
ACTIVE
SOT-23-THIN
DDC
6
1000
RoHS & Green
SN
Level-1-260C-UNLIM
-40 to 125
STFB
LM2841XMKX-ADJL/NOPB
ACTIVE
SOT-23-THIN
DDC
6
3000
RoHS & Green
SN
Level-1-260C-UNLIM
-40 to 125
STFB
LM2841YMK-ADJL/NOPB
ACTIVE
SOT-23-THIN
DDC
6
1000
RoHS & Green
SN
Level-1-260C-UNLIM
-40 to 125
STTB
LM2841YMKX-ADJL/NOPB
ACTIVE
SOT-23-THIN
DDC
6
3000
RoHS & Green
SN
Level-1-260C-UNLIM
-40 to 125
STTB
LM2842XMK-ADJL/NOPB
ACTIVE
SOT-23-THIN
DDC
6
1000
RoHS & Green
SN
Level-1-260C-UNLIM
-40 to 125
STVB
LM2842XMKX-ADJL/NOPB
ACTIVE
SOT-23-THIN
DDC
6
3000
RoHS & Green
SN
Level-1-260C-UNLIM
-40 to 125
STVB
LM2842YMK-ADJL/NOPB
ACTIVE
SOT-23-THIN
DDC
6
1000
RoHS & Green
SN
Level-1-260C-UNLIM
-40 to 125
STXB
LM2842YMKX-ADJL/NOPB
ACTIVE
SOT-23-THIN
DDC
6
3000
RoHS & Green
SN
Level-1-260C-UNLIM
-40 to 125
STXB
(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
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