psa242.5 Power-One, psa242.5 Datasheet - Page 2

• Manufacturer Part Number: psa242.5
• Description: Accessories Filter & Ring Core Chokes Fp, L And Lp Series
• Manufacturer: Power-One

REV. SEP 29, 2003
Electrical Data Filter Blocks
General Condition: T
Table 2: Filter blocks FP
For currents I
Input Interference Reduction
An AC ripple current can be measured at the input of any
switching regulator, even if they are equipped with an input
filter. Depending on the types of filters used, common and/
or differential mode interferences can be reduced. They will
also help to further increase the surge and burst immunity
of the power supplies.
The FP filters considerably increase the source impedance
of the regulators superimposed interference, to a value
which is normally high in comparison to the impedance of
the source ( Z
practically independent of their source impedance. The fil-
ter will reduce these currents by approximately 25 dB at a
frequency of 150 kHz.
The interference voltages at the filter input are due to the
remaining interference currents flowing through the source
impedance. The resulting interference voltage reduction
can be seen in the following figure. For frequencies above
the regulator switching frequency the attenuation will in-
crease (up to 2 MHz approx.).
Parallel operation: When several switching regulator inputs
are connected in parallel, each regulator should be
equipped with a separate input filter. Interconnections
should only be made in front of the filter or at its input Uii
(i. e. the central ground point should be before or at the filter
and under no circumstances at the regulator input).
Characteristics
I
U
R
L
T
T
T
Fn
o
A
C
S
Fn
F
40
30
20
10
Att. [dB]
Rated current
Rated voltage
Ohmic resistance
No load inductance
Ambient temperature
Case temperature
Storage temperature
0
0
F
> 4 A the following derating takes place: T
Line
1
). The interference currents are therefore
A
Source impedance
2
inductive
resistive
capacitive
= 25°C unless otherwise specified
3
Conditions
L = 0.75 L
T
I
I
L
F
C min
= 0, T
= I
Fn
... T
4
C min
C max
o
... T
5
C max
12009
6
min
–40
–40
–40
Filter & Ring Core Chokes FP, L and LP Series
18
30
5
Z
A max
Line
Page 2 of 5
[ ]
FP38
= 100 – 1.3 • I
typ
20
34
4
max
100
Reduction of Output Ripple
Even though switching regulators have an inherently low
output ripple, certain sensitive applications need even fur-
ther reduction. In such cases, the filters designed to reduce
disturbances at the input, can also be used for reducing the
ripple on the output voltage (even better results with regard
to the ripple and dynamic control deviation can be achieved
by using low-loss ring core chokes in combination with an
external capacitor, see below).
The output ripple can be reduced by the use of filter blocks
by about 24 dB. The formula for the ripple u
is as follows:
(Ripple voltage u
responding data section).
Consider, that the filter not only affects the output ripple but
can also influence the voltage across the load R
event of load changes. The static load regulation increases
with the ohmic resistance of the choke i.e. 24 mV/A for the
FP 38 and FP 80 filters and 95 mV/A for the FP 144 filter.
Fig. 1
Interference voltage reduction with FP filters at f = 150 kHz
40
22
38
80
92
U
Fig. 2
Reduction of voltage interference by FP filters
F
2
u
min
–40
–40
–40
[°C], T
R
18
30
5
= 0.063 • u
Vi+
Gi–
FP80
C max
typ
20
34
4
PSR
o
is given for specific regulators in the cor-
= 100 – 0.49 • I
max
Go–
100
o
Vo+
80
22
38
80
92
U
Uii
min
–40
–40
–55
o
15
90
88
F
Filter
2
FP144
[°C]
100
typ
Gi
95
2
Accessories
Uio
max
144
100
112
100
95
98
R
at the load R
U
R
L
12010
A DC
V DC
Unit
mý
µH
°C
in the
R
L
L