LM3519MKEV National Semiconductor, LM3519MKEV Datasheet - Page 12

• Manufacturer Part Number: LM3519MKEV
• Description: BOARD EVALUATION LM3519MK
• Manufacturer: National Semiconductor
• Series: PowerWise®r

Specifications of LM3519MKEV

• Current - Output / Channel: 20mA
• Outputs And Type: 1, Non-Isolated
• Features: Dimmable
• Voltage - Input: 2.7 ~ 5.5V
• Utilized Ic / Part: LM3519
• Lead Free Status / RoHS Status: Not applicable / Not applicable
• Voltage - Output: -

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Application Information
CAPACITOR SELECTION
To minimize output and input voltage ripple, low equivalent
series resistance (ESR) ceramic capacitors are the best
choice to use for the input and output filters. For most display
applications, a 4.7µF capacitor is recommended for C
1µF for C
Larger output capacitors can be used to reduce ripple volt-
age. To guarantee good performance, a minimum of 0.47µF
C
must be taken to account for the true capacitance of a
multilayer ceramic capacitor. Smaller case size capacitors
typically have less capacitance for a given bias voltage as
compared to a larger case size capacitor with the same bias
voltage. Please confirm with capacitor manufacturer data
before selecting the capacitor.
INDUCTOR SELECTION
In order to maintain sufficient inductance, the saturation
current rating of the inductor used with the LM3519 should
be higher than the peak inductor current in the target appli-
cation. Inductors with low DCR values have less power loss
and higher efficiency. Larger inductor values such as 2.2µH
and 3.3µH can be used to optimize efficiency, frequency and
peak current. If 1µH is used, the peak inductor current,
frequency will be higher and the efficiency will be lower. Note
that the switching frequency ranges will be higher at lower
inductance. Typical frequency range is between 4 to 8MHz
for 1µH, 2 to 5MHz for 2.2µH and 2 to 4MHz for 3.3µH over
the input range. Below is a sample list of low profile induc-
tors.
LPO3310-102ML
LPO3310-222ML
LPO3310-332ML
Some recommended capacitor manufacturers include but
are not limited to:
Some recommended inductor manufacturers include but
are not limited to:
OUT
Manufacturer
Manufacturer
DO3314-102
DO3314-222
DO3314-332
SD3114-2R2
SD3114-3R3
SD31121R0
Taiyo Yuden
CoilCraft:
Coilcraft:
Cooper:
muRata
is required to trade off for large ripple voltage. Care
TDK
AVX
OUT
.
06033D105MAT-25V
06036D475MAT-6.3V
C2012X5R1A475M-10V
TMK212BJ105KG-J
EM212BJ475MG-16V
GRM40-034B105K25
GRM39X5R475K6.3
2.2µH
3.3µH
2.2µH
3.3µH
2.2µH
3.3uH
1µH
1µH
1µH
L
Description
3.3x3.3x1.0 mm
3.1x3.1x1.4 mm
3.3x3.3x1.4mm
Case Size
Case Size
0603
0603
0805
0805
0805
0805
0603
0.95A
2.07A
1.48A
1.15A
2.1A
1.6A
1.4A
1.6A
1.1A
I
SAT
IN
and
12
DIODE SELECTION
Diodes with low forward voltage ratings (V
capacitance magnitudes (C
high efficiency. The chosen diode must have a reverse
breakdown voltage rating (V
than the output voltage. The following criteria should be
followed when choosing a diode:
1. V
2. I
3. I
PWM DIMMING
The LED current is set internally by the LM3519 to 20mA
(typical); dimming control may be realized by applying a
pulse width modulated(PWM) signal to the En pin. For ex-
ample, a 50% duty cycle waveform will produce an average
current of 10mA. A control signal frequency between 17kHz
and 30kHz is suitable for dimming.
Although the LM3519 is capable of operation outside this
frequency range, it is not recommended to operate below
17kHz for the following reasons: 1) frequency below 100Hz
is likely to cause visible flicker in the light emitted by the LED
string. 2) frequency below 17kHz may induce audible noise
due to combinations of some capacitance/PCB. A PWM
frequency above 30kHz is possible but the current linearity
vs duty cycle will be affected.
If it is not possible to operate the dimming control above
17kHz, audible noise emission may be minimized by using
capacitors with low susceptibility to piezoelectric induced
stresses, such as poly film designs. Minimum audible noise
is most likely to occur when the PWM frequency is less than
2kHz. It is recommended that any application using a PWM
control signal below 17kHz be thoroughly evaluated for un-
desirable audible or visible noise.
DRIVING 2 LEDs
The LM3519 is optimized to drive up to 4LEDs. When driving
2LEDs, a minimum inductance of 2.2µH is required to main-
tain good loop regulation and current accuracy. If a smaller
inductor is used, the LED current will have more variation
with input voltage than a typical application. The following
curve illustrates the behavior.
Some recommended diode manufacturers include but are
not limited to:
NR3015T2R2M
NR3015T3R3M
NR3015T1R0N
Central Semiconductor
Taiyo Yuden:
Peak Repetitive Reverse Voltage Rating)
put Voltage)
(Load Current)
I
F
FRM
Lpeak
R
or I
Maufacturer
(Diode Blocking Voltage Range) and V
(Diode Peak Repetitive Forward Current Rating) ≥
O
ONSemi
(Peak Inductor Current)
Vishay
(Diode Average Forward Current Rating) ≥ I
2.2µH
3.3µH
1µH
J
Description
SS12(1A/20V)
SS14(1A/40V)
SS16(1A/60V)
CMSH1- 40M(1A/40V)
MBRS1540T3(1.5A/40V)
or C
R
3.0x3.0x1.5 mm
and/or V
T
or C
D
RRM
F
) are conducive to
) and low junction
) that is larger
>
RRM
V
OUT
1.48A
1.21A
2.1A
(Diode
(Out-
LOAD