TDA7210 Datasheet, PDF (34/52 Pages) Infineon Technologies AG – Wireless Components ASK/FSK Single Conversion Receiver

Uc
Us
TDA7210
Applications
T3
Figure 4-12 Voltage transient on capacitor C13 attached to pin 20
e-Fkt2.WMF
As an example the choice of C18 = 22nF and C13 = 47nF yields
τ₂ = 0.44ms
T₂ = 0.71ms
T₃ = 0.53ms
This means that in this case the inrush current could flow for a duration of
0.64ms but stops already after 0.49ms when the U_Smax limit has been reached.
T3 should always be chosen to be shorter than T2.
It has to be noted finally that during the turn-on duration T2 the overall device
power consumption is increased by the 220µA needed to charge C13.
The precharge circuit may be disabled if C18 is not equipped. This yields a T2
close to zero. Note that the sum of R4 and R5 has to be 600kΩ in order to pro-
duce 3V at the THRES pin as this voltage is internally used also as the refer-
ence for the FSK demodulator.
Wireless Components
4 - 13
Data Sheet, December 2008