TDA7210V_10 Datasheet, PDF (19/44 Pages) Infineon Technologies AG – ASK/FSK Single Conversion Receiver

TDA7210V
Applications
3.2
Data Filter Design
Utilising the on-board voltage follower and the two 100 kΩ on-chip resistors a 2nd order Sallen-Key low pass data
filter can be constructed by adding 2 external capacitors between pins 18 (SLP) and 22 (FFB) and to pin 20 (OPP)
as depicted in the following figure and described in the following formulas¹⁾.
C₁₄
C₁₂
Pins:
22
20
18
R
R
100k
100k
Figure 7 Data Filter Design
C12 =
b
4QR πf _{3 dB}
(1)
C14 = ^{2Q b}
R2πf_3dB
(2)
with
Q= ^b
a
(3)
the quality factor of the poles, where in case of a Bessel filter a = 1.3617, b = 0.618
and thus Q = 0.577
and in case of a Butterworth filter a = 1.414, b = 1
and thus Q = 0.71
Example
Butterworth filter with f_3dB = 5 kHz and R = 100 kΩ:
C14 = 450 pF, C12 = 225 pF
1) Taken from Tietze/Schenk: Halbleiterschaltungstechnik, Springer Berlin, 1999.
Data Sheet
19
Revision 1.1, 2010-06-18