LM3410
PowerWise® 525kHz/1.6MHz, Constant Current Boost and
SEPIC LED Driver with Internal Compensation
LM3410 PowerWise
Internal Compensation
General Description
The LM3410 constant current LED driver is a monolithic, high
frequency, PWM DC/DC converter in 5-pin SOT23, 6-pin LLP,
& 8-pin eMSOP packages. With a minimum of external components the LM3410 is easy to use. It can drive 2.8A typical
peak currents with an internal 170 mΩ NMOS switch. Switching frequency is internally set to either 525 kHz or 1.60 MHz,
allowing the use of extremely small surface mount inductors
and chip capacitors. Even though the operating frequency is
high, efficiencies up to 88% are easy to achieve. External
shutdown is included, featuring an ultra-low standby current
of 80 nA. The LM3410 utilizes current-mode control and internal compensation to provide high-performance over a wide
range of operating conditions. Additional features include
dimming, cycle-by-cycle current limit, and thermal shutdown.
Typical Boost Application Circuit
Features
Space Saving SOT23-5 & 6-LLP Package
■
Input voltage range of 2.7V to 5.5V
■
Output voltage range of 3V to 24V
■
2.8A Typical Switch Current
■
High Switching Frequency
■
525 KHz (LM3410-Y)
—
1.6 MHz (LM3410-X)
—
170 mΩ NMOS Switch
■
190 mV Internal Voltage Reference
■
Internal Soft-Start
■
Current-Mode, PWM Operation
■
Thermal Shutdown
■
Applications
LED Backlight Current Source
■
LiIon Backlight OLED & HB LED Driver
■
Handheld Devices
■
LED Flash Driver
■
®
525kHz/1.6MHz, Constant Current Boost and SEPIC LED Driver with
Order NumberFrequencyPackage TypePackage DrawingSupplied As
LM3410YMF
LM3410YMFX3000 units Tape & Reel
LM3410YMFE250 units Tape & Reel
LM3410YSD
LM3410YSDX4500 units Tape & Reel
LM3410YSDE250 units Tape & Reel
LM3410YMY
LM3410YMYX3500 units Tape & Reel
LM3410YMYE250 units Tape & Reel
LM3410XMF
LM3410XMFX3000 units Tape & Reel
LM3410XMFE250 units Tape & Reel
LM3410XSD
LM3410XSDX4500 units Tape & Reel
LM3410XSDE250 units Tape & Reel
LM3410XMY
LM3410XMYX3500 units Tape & Reel
LM3410XMYE250 units Tape & Reel
525 kHz
1.6 MHz
SOT23-5MF05A
LLP-6SDE06A
eMSOP-8MUY08A
SOT23-5MF05A
LLP-6SDE06A
eMSOP-8MUY08A
1000 units Tape & Reel
1000 units Tape & Reel
1000 units Tape & Reel
1000 units Tape & Reel
1000 units tape & reel
1000 units Tape & Reel
30038505
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Pin Descriptions - 5-Pin SOT23
PinNameFunction
1SWOutput switch. Connect to the inductor, output diode.
2GND
3FBFeedback pin. Connect FB to external resistor divider to set output voltage.
4DIM
5VINSupply voltage pin for power stage, and input supply voltage.
Signal and power ground pin. Place the bottom resistor of the feedback network as close as possible to this
pin.
Dimming & shutdown control input. Logic high enables operation. Duty Cycle from 0 to 100%. Do not allow
this pin to float or be greater than VIN + 0.3V.
Pin Descriptions - 6-Pin LLP
PinNameFunction
1PGNDPower ground pin. Place PGND and output capacitor GND close together.
2VINSupply voltage for power stage, and input supply voltage.
3DIM
4FBFeedback pin. Connect FB to external resistor divider to set output voltage.
5AGND
6SWOutput switch. Connect to the inductor, output diode.
DAPGND
Dimming & shutdown control input. Logic high enables operation. Duty Cycle from 0 to 100%. Do not allow
this pin to float or be greater than VIN + 0.3V.
Signal ground pin. Place the bottom resistor of the feedback network as close as possible to this pin & pin
4.
Signal & Power ground. Connect to pin 1 & pin 5 on top layer. Place 4-6 vias from DAP to bottom layer GND
plane.
LM3410
Pin Descriptions - 8-Pin eMSOP
PinNameFunction
1-No Connect
2PGNDPower ground pin. Place PGND and output capacitor GND close together.
3VINSupply voltage for power stage, and input supply voltage.
4DIM
5FBFeedback pin. Connect FB to external resistor divider to set output voltage.
6AGNDSignal ground pin. Place the bottom resistor of the feedback network as close as possible to this pin & pin 5
7SWOutput switch. Connect to the inductor, output diode.
8-No Connect
DAPGND
Dimming & shutdown control input. Logic high enables operation. Duty Cycle from 0 to 100%. Do not allow
this pin to float or be greater than VIN + 0.3V.
Signal & Power ground. Connect to pin 2 & pin 6 on top layer. Place 4-6 vias from DAP to bottom layer GND
plane.
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Absolute Maximum Ratings (Note 1)
If Military/Aerospace specified devices are required,
LM3410
please contact the National Semiconductor Sales Office/
Distributors for availability and specifications.
V
IN
SW Voltage-0.5V to 26.5V
FB Voltage-0.5V to 3.0V
DIM Voltage-0.5V to 7.0V
ESD Susceptibility (Note 4)
Human Body Model2kV
Junction Temperature (Note 2)150°C
-0.5V to 7V
Storage Temp. Range-65°C to 150°C
Soldering Information
Infrared/Convection Reflow (15sec)220°C
Operating Ratings (Note 1)
V
IN
V
(Note 5)0V to V
DIM
V
SW
Junction Temperature Range-40°C to 125°C
Power Dissipation
(Internal) SOT23-5400 mW
2.7V to 5.5V
3V to 24V
IN
Electrical Characteristics Limits in standard type are for T
= 25°C only; limits in boldface type apply over the
J
junction temperature (TJ) range of -40°C to 125°C. Minimum and Maximum limits are guaranteed 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.
VIN = 5V, unless otherwise indicated under the Conditions column.
SymbolParameterConditionsMinTypMaxUnits
V
FB
ΔVFB/V
I
FB
F
SW
D
MAX
D
MIN
R
DS(ON)
I
CL
Feedback Voltage178190202mV
Feedback Voltage Line Regulation
IN
VIN = 2.7V to 5.5V
-0.06-%/V
Feedback Input Bias Current-0.11µA
Switching Frequency
Maximum Duty Cycle
Minimum Duty Cycle
Switch On Resistance
LM3410-X120016002000
LM3410-Y360525680
LM3410-X8892-
LM3410-Y9095-
LM3410-X-5-
LM3410-Y-2-
SOT23-5 and eMSOP-8-170330
LLP-6190350
Switch Current Limit2.12.80-A
kHz
%
%
mΩ
SUStart Up Time-20-µs
I
Q
Quiescent Current (switching)
Quiescent Current (shutdown)
UVLOUndervoltage Lockout
V
DIM_H
I
SW
I
DIM
Shutdown Threshold Voltage--0.4
Enable Threshold Voltage1.8--
Switch Leakage
Dimming Pin CurrentSink/Source-100-nA
LM3410-X VFB = 0.25
LM3410-Y VFB = 0.25
All Options V
DIM
= 0V
VIN Rising
VIN Falling
VSW = 24V
-7.011
-3.47
-80-nA
-2.32.65
1.71.9-
-1.0-µA
mA
V
V
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SymbolParameterConditionsMinTypMaxUnits
θ
JA
θ
JC
T
SD
Note 1: Absolute Maximum Ratings indicate limits beyond which damage to the device may occur. Operating Ratings indicate conditions for which the device is
intended to be functional, but does not guarantee specific performance limits. For guaranteed specifications and conditions, see the Electrical Characteristics.
Note 2: Thermal shutdown will occur if the junction temperature exceeds the maximum junction temperature of the device.
Note 3: Applies for packages soldered directly onto a 3” x 3” PC board with 2oz. copper on 4 layers in still air.
Note 4: The human body model is a 100 pF capacitor discharged through a 1.5 kΩ resistor into each pin. Test method is per JESD22-A114.
Note 5: Do not allow this pin to float or be greater than VIN +0.3V.
Junction to Ambient
0 LFPM Air Flow (Note 3)
Junction to Case (Note 3)
Thermal Shutdown Temperature (Note 2) -165-°C
LLP-6 and eMSOP-8 Package-80-
SOT23-5 Package-118-
LLP-6 and eMSOP-8 Package-18-
SOT23-5 Package-60-
°C/W
°C/W
LM3410
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Typical Performance Characteristics All curves taken at V
= 5.0V with configuration in typical
IN
application circuit shown in Application Information section of this datasheet. TJ = 25C, unless otherwise specified.
LM3410
LM3410-X Efficiency vs VIN (R
SET
= 4Ω)
LM3410-X Start-Up Signature
30038502
4 x 3.3V LEDs 500 Hz DIM FREQ D = 50%
30038508
Current Limit vs Temperature
DIM Freq & Duty Cycle vs Avg I-LED
R
vs Temperature
DSON
30038507
30038509
30038510
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30038511
LM3410
Oscillator Frequency vs Temperature - "X"
30038512
VFB vs Temperature
Oscillator Frequency vs Temperature - "Y"
30038513
30038580
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Simplified Internal Block Diagram
LM3410
FIGURE 1. Simplified Block Diagram
Application Information
THEORY OF OPERATION
The LM3410 is a constant frequency PWM, boost regulator
IC. It delivers a minimum of 2.1A peak switch current. The
device operates very similar to a voltage regulated boost converter except that it regulates the output current through
LEDs. The current magnitude is set with a series resistor. This
series resistor multiplied by the LED current creates the feedback voltage (190 mV) which the converter regulates to. The
regulator has a preset switching frequency of either 525 kHz
or 1.60 MHz. This high frequency allows the LM3410 to operate with small surface mount capacitors and inductors,
resulting in a DC/DC converter that requires a minimum
amount of board space. The LM3410 is internally compensated, so it is simple to use, and requires few external components. The LM3410 uses current-mode control to regulate
the LED current. The following operating description of the
LM3410 will refer to the Simplified Block Diagram (Figure 1)
the simplified schematic (Figure 2), and its associated waveforms (Figure 3). The LM3410 supplies a regulated LED
current by switching the internal NMOS control switch at constant frequency and variable duty cycle. A switching cycle
30038514
begins at the falling edge of the reset pulse generated by the
internal oscillator. When this pulse goes low, the output control logic turns on the internal NMOS control switch. During
this on-time, the SW pin voltage (VSW) decreases to approximately GND, and the inductor current (IL) increases with a
linear slope. IL is measured by the current sense amplifier,
which generates an output proportional to the switch current.
The sensed signal is summed with the regulator’s corrective
ramp and compared to the error amplifier’s output, which is
proportional to the difference between the feedback voltage
and V
output switch turns off until the next switching cycle begins.
During the switch off-time, inductor current discharges
through diode D1, which forces the SW pin to swing to the
output voltage plus the forward voltage (VD) of the diode. The
regulator loop adjusts the duty cycle (D) to maintain a regulated LED current.
. When the PWM comparator output goes high, the
REF
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30038515
FIGURE 2. Simplified Boost Topology Schematic
LM3410
Design Guide
SETTING THE LED CURRENT
30038517
FIGURE 4. Setting I
LED
The LED current is set using the following equation:
where R
is connected between the FB pin and GND.
SET
DIM PIN / SHUTDOWN MODE
The average LED current can be controlled using a PWM
signal on the DIM pin. The duty cycle can be varied between
0 & 100% to either increase or decrease LED brightness.
PWM frequencies in the range of 1 Hz to 25 kHz can be used.
For controlling LED currents down to the µA levels, it is best
to use a PWM signal frequency between 200-1 kHz. The
maximum LED current would be achieved using a 100% duty
cycle, i.e. the DIM pin always high.
LED-DRIVE CAPABILITY
When using the LM3410 in the typical application configuration, with LEDs stacked in series between the VOUT and FB
pin, the maximum number of LEDs that can be placed in series is dependent on the maximum LED forward voltage
(VF
).
MAX
(VF
x N
MAX
When inserting a value for maximum VF
voltage variation over the operating temperature range
) + 190 mV < 24V
LEDs
the LED forward
MAX
should be considered.
30038516
FIGURE 3. Typical Waveforms
CURRENT LIMIT
The LM3410 uses cycle-by-cycle current limiting to protect
the internal NMOS switch. It is important to note that this current limit will not protect the output from excessive current
during an output short circuit. The input supply is connected
to the output by the series connection of an inductor and a
diode. If a short circuit is placed on the output, excessive current can damage both the inductor and diode.
THERMAL SHUTDOWN
Thermal shutdown limits total power dissipation by turning off
the output switch when the IC junction temperature exceeds
165°C. After thermal shutdown occurs, the output switch
doesn’t turn on until the junction temperature drops to approximately 150°C.
INDUCTOR SELECTION
The inductor value determines the input ripple current. Lower
inductor values decrease the physical size of the inductor, but
increase the input ripple current. An increase in the inductor
value will decrease the input ripple current.
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LM3410
From the previous equations, the inductor value is then obtained.
30038519
FIGURE 5. Inductor Current
The Duty Cycle (D) for a Boost converter can be approximated by using the ratio of output voltage (V
(VIN).
) to input voltage
OUT
Therefore:
Power losses due to the diode (D1) forward voltage drop, the
voltage drop across the internal NMOS switch, the voltage
drop across the inductor resistance (R
losses must be included to calculate a more accurate duty
) and switching
DCR
cycle (See Calculating Efficiency and Junction Tempera-ture for a detailed explanation). A more accurate formula for
calculating the conversion ratio is:
Where η equals the efficiency of the LM3410 application.
Or:
Therefore:
Where
1/TS = f
SW
One must also ensure that the minimum current limit (2.1A)
is not exceeded, so the peak current in the inductor must be
calculated. The peak current (Lpk I) in the inductor is calculated by:
I
= IIN + ΔIL or I
Lpk
Lpk
= I
OUT
/D' + Δi
L
When selecting an inductor, make sure that it is capable of
supporting the peak input current without saturating. Inductor
saturation will result in a sudden reduction in inductance and
prevent the regulator from operating correctly. Because of the
speed of the internal current limit, the peak current of the inductor need only be specified for the required maximum input
current. For example, if the designed maximum input current
is 1.5A and the peak current is 1.75A, then the inductor should
be specified with a saturation current limit of >1.75A. There is
no need to specify the saturation or peak current of the inductor at the 2.8A typical switch current limit.
Because of the operating frequency of the LM3410, ferrite
based inductors are preferred to minimize core losses. This
presents little restriction since the variety of ferrite-based inductors is huge. Lastly, inductors with lower series resistance
(DCR) will provide better operating efficiency. For recommended inductors see Example Circuits.
INPUT CAPACITOR
An input capacitor is necessary to ensure that VIN does not
drop excessively during switching transients. The primary
specifications of the input capacitor are capacitance, voltage,
RMS current rating, and ESL (Equivalent Series Inductance).
The recommended input capacitance is 2.2 µF to 22 µF depending on the application. The capacitor manufacturer
specifically states the input voltage rating. Make sure to check
any recommended deratings and also verify if there is any
significant change in capacitance at the operating input voltage and the operating temperature. The ESL of an input
capacitor is usually determined by the effective cross sectional area of the current path. At the operating frequencies
of the LM3410, certain capacitors may have an ESL so large
that the resulting impedance (2πfL) will be higher than that
required to provide stable operation. As a result, surface
mount capacitors are strongly recommended. Multilayer ceramic capacitors (MLCC) are good choices for both input and
output capacitors and have very low ESL. For MLCCs it is
recommended to use X7R or X5R dielectrics. Consult capacitor manufacturer datasheet to see how rated capacitance
varies over operating conditions.
Inductor ripple in a LED driver circuit can be greater than what
would normally be allowed in a voltage regulator Boost &
Sepic design. A good design practice is to allow the inductor
to produce 20% to 50% ripple of maximum load. The increased ripple shouldn’t be a problem when illuminating
LEDs.
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OUTPUT CAPACITOR
The LM3410 operates at frequencies allowing the use of ceramic output capacitors without compromising transient response. Ceramic capacitors allow higher inductor ripple
without significantly increasing output ripple. The output capacitor is selected based upon the desired output ripple and
transient response. The initial current of a load transient is
provided mainly by the output capacitor. The output
impedance will therefore determine the maximum voltage
perturbation. The output ripple of the converter is a function
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