TDA5204E1 Infineon Technologies, TDA5204E1 Datasheet - Page 23

• Manufacturer Part Number: TDA5204E1
• Description: ASK Single Conversion Receiver 390MHz
• Manufacturer: Infineon Technologies

Wireless Components
4.2 Data Filter Design
Utilising the on-board voltage follower and the two 100k Ω on-chip resistors a
2nd order Sallen-Key low pass data filter can be constructed by adding 2 exter-
nal capacitors between pins 19 (SLP) and 22 (FFB) and to pin 21 (OPP) as
depicted in the following figure and described in the following formulas
Figure 4-3
(1)
with
where
in case of a Bessel filter
and thus
and in case of a Butterworth filter
and thus
Example: Butterworth filter with f
C
1
Q
1. taken from Tietze/Schenk: Halbleiterschaltungstechnik, Springer Berlin, 1999
=
=
C
------------------------ -
R 2πf
1
------ -
2 Q b
a
= 450pF, C
⋅
b
⋅
Data Filter Design
3dB
Pins:
2
4 - 4
= 225pF
100k
R
(2)
C2
22
C
1
=
3dB
100k
--------------------------------- -
4Q R πf
R
= 5kHz and R = 100k Ω :
C
21
⋅
2
(3)
a = 1.3617, b = 0.618
Q = 0.577
a = 1.41, b = 1
Q = 0.71
⋅
b
the quality factor of the poles
3dB
19
Specification, January 2001
TDA 5204 E1
Applications
preliminary
Filter_Design.wmf
1
.