LM3554TMEEV National Semiconductor, LM3554TMEEV Datasheet - Page 35

• Manufacturer Part Number: LM3554TMEEV
• Description: BOARD EVAL FOR LM3554
• Manufacturer: National Semiconductor

Specifications of LM3554TMEEV

• Current - Output / Channel: 600mA
• Outputs And Type: 2, Non-Isolated
• Voltage - Output: 5V
• Features: Camera Flash and Torch Modes, Dimmable, I²C Interface
• Voltage - Input: 2.7 ~ 5.5 V
• Utilized Ic / Part: LM3554
• Lead Free Status / RoHS Status: Not applicable / Not applicable
• Other names: LM3554TMEV; LM3554TMEV

Applications Information
OUTPUT CAPACITOR SELECTION
The LM3554 is designed to operate with a at least a 4.7µF
ceramic output capacitor in LED mode and a 10µF output ca-
pacitor in Voltage Output Mode. When the boost converter is
running the output capacitor supplies the load current during
the boost converters on-time. When the NMOS switch turns
off the inductor energy is discharged through the internal
PMOS switch supplying power to the load and restoring
charge to the output capacitor. This causes a sag in the output
voltage during the on-time and a rise in the output voltage
during the off-time. The output capacitor is therefore chosen
to limit the output ripple to an acceptable level depending on
load current and input/output voltage differentials and also to
ensure the converter remains stable.
For proper LED operation the output capacitor must be at
least a 4.7µF ceramic (10µF in Voltage Output Mode). Larger
capacitors such as 10µF or 22µF can be used if lower output
voltage ripple is desired. To estimate the output voltage ripple
considering the ripple due to capacitor discharge (ΔV
the ripple due to the capacitors ESR (ΔV
equations:
For continuous conduction mode, the output voltage ripple
due to the capacitor discharge is:
INDUCTOR SELECTION
The LM3554 is designed to use a 2.2µH inductor.
lists various inductors and their manufacturers that can work
well with the LM3554. When the device is boosting (V
V
loss in the circuit. Therefore, choosing an inductor with the
lowest possible series resistance is important. Additionally,
the saturation rating of the inductor should be greater than the
maximum operating peak current of the LM3554. This pre-
vents excess efficiency loss that can occur with inductors that
operate in saturation and prevents over heating of the induc-
tor and possible damage. For proper inductor operation and
IN
) the inductor will typically be the biggest area of efficiency
TDK Corporation
TDK Corporation
TDK Corporation
TDK Corporation
TDK Corporation
Manufacturer
Manufacturer
Coilcraft
Murata
Murata
Murata
Murata
TOKO
TDK
GRM21BR60J226ME39L
GRM21BR61C475KA88
GRM21BR61A106KE19
GRM188R60J475KE19
TABLE 10. Recommended Input/Output Capacitors (X5R Dielectric)
C2012JB1A106M
C1608JB0J106M
C2012JB1C475K
C2012JB0J226M
C1608JB0J475K
Part Number
2.2µH
2.2µH
2.2µH
L
ESR
) use the following
TABLE 11. Recommended Inductors
Table 11
VLS252012T-2R2M1R3
Q
OUT
) and
FDSE0312-2R2M
LPS4018-222ML
Part Number
>
Value
4.7µF
4.7µF
4.7µF
4.7µF
10µF
10µF
22µF
10µF
22µF
35
The output voltage ripple due to the output capacitors ESR is
found by:
In ceramic capacitors the ESR is very low so assume that 80%
of the output voltage ripple is due to capacitor discharge and
20% from ESR.
ious output capacitors and their case sizes suitable for use
with the LM3554.
INPUT CAPACITOR SELECTION
Choosing the correct size and type of input capacitor helps
minimize the voltage ripple caused by the switching of the
LM3554’s boost converter and reduces noise on the devices
input terminal that can feed through and disrupt internal ana-
log signals. In the Typical Application Circuit a 4.7µF ceramic
input capacitor works well. It is important to place the input
capacitor as close as possible to the LM3554’s input (IN) ter-
minals. This reduces the series resistance and inductance
that can inject noise into the device due to the input switching
currents.
ommended for use with the LM3554.
circuit performance ensure that the inductor saturation and
the peak current limit setting of the LM3554 is greater than
I
ƒ
Characteristics plots.
PEAK
SW
= 2MHz; η can be found in the Typical Performance
0805(2mm×1.25mm×1.25mm)
0805(2mm×1.25mm×1.25mm)
0805(2mm×1.25mm×1.25mm)
0805(2mm×1.25mm×1.25mm)
0805(2mm×1.25mm×1.25mm)
0805(2mm×1.25mm×1.25mm)
can be calculated by:
0603(1.6mm×0.8mm×0.8mm)
0603(1.6mm×0.8mm×0.8mm)
0603(1.6mm×0.8mm×0.8mm)
Table 10
3.9mmx3.9mmx1.7mm
Dimensions (L×W×H)
2mm×2.5mm×1.2mm
3mm×3mm×1.2mm
Case Size
Table 10
lists various input capacitors that or rec-
lists different manufacturers for var-
Voltage Rating
1.5A
2.3A
I
SAT
2A
6.3V
6.3V
6.3V
6.3V
6.3V
16V
10V
16V
10V
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