FP38 Datasheet, PDF (3/5 Pages) Power-One – Filter & Ring Core Chokes

Accessories
Filter & Ring Core Chokes FP, L and LP Series
Typical Application
The example in figure Reduction of voltage interference by
FP filters shows a switching regulator operating from a bat-
tery (R_i < 0.5 Ω) with long supply lines (e.g. 2 m). The result-
ing superimposed interference voltage U_SL may be meas-
ured at the regulators input. The connection of a filter in
front of the power supply will reduce this interference ac-
cordingly:
1. The regulator's source impedance is mainly inductive
because of the low battery impedance and the long sup-
ply lines. It can be calculated as follows:
l Z_Line l ≅ 2 π • f_S • L_Line • 2 l
l Z_Line l ≅ 2 π • (150 • 10³) • 10^-6 • 2 • 2 ≅ 3.8 Ω
f_S: Switching frequency (150 kHz)
L_Line : Supply line inductance (typically 1µH/m)
l : Length of single supply line (twice for posi-
tive and negative path)
2. This example shows, that with an inductive source im-
pedance of 3.8 Ω, the insertion of the filter results in an
interference voltage reduction of approx. 18 dB (see
fig.: Interference voltage reduction with FP filters at f =
150 kHz).
3. The original superimposed interference voltage will be
reduced by a factor of approx. 8:
U_SF = U_SL • 10^–18/20 [V]
2•l
Uii _Filter Uio _Vi+
Vo+
12011
U
U_s Z_Line
Gi
PSR
U_o R_L
Gi–
Go–
Fig. 3
Reduction of voltage interference by FP filters
Low-Loss Ring Core Chokes L/LP-Series
The ring core chokes, in combination with a capacitor, may
easily be used for application specific LC filters at the input
or output of switched mode power supplies. All chokes are
suitable for PCB mounting. They are either moulded into
plastic cases or isolated from the PCB by means of an iso-
lation pad.
Series L/LP20-7 and LP34-3 are intended for use as differ-
ential mode filters and the current compensated choke
LP183 enables attenuation of common mode interference.
L /L_o [%]
100
80
75
60
40
LP183
12012
LP34-3
L/LP20-7
Fig. 4
Choke inductance versus current
20
0
0
2 34
6 7 8 10
12 14 ^{IL [A]}
Electrical Data Ring Core Chokes
General Condition: T_A = 25°C unless otherwise specified
Table 3: Ring core chokes
Characteristics
I_Ln Rated current ¹
R_L Ohmic resistance
L_o No load inductance
D_TI Current specific case
temp. increase ¹
T_A Amb. temperature ¹
T_C Case temperature
T_S Storage temperature
Conditions
L = 0.75 L_o
I_L = 0, T_{C min}...T_{C max}
I_L = I_Ln
L20-7/LP 20-7
min typ max
7
5 5.5 6
18 20 22
0.082
–40
106
–40
110
–40
110
LP34-3
min typ max
3
18 20 22
30 34 38
0.68
LP183
min typ max
8
2×2.9 2×4.2 2×5.5
2×95 2×183 2×245
0.19
Unit
A DC
mý
µH
K/A²
–40
104 –40
98
°C
–40
110
–40
110
–40
110
–40
110
1 _{If the choke is not operating at the rated current ILn, the maximum ambient temperature TA max and the maximum direct current IL max}
change according to the following equations: _{IL max =} T_{C max} –T_{A max}
T_{A max} = T_{C max} – I_{L2 max} • D _TI
D_TI
REV. SEP 29, 2003
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