One example of noise detection mode is shown in the following figure. in this figure the
TSI is working in capacitive mode until 30uS when it is changed to noise detection mode.
In noise detection mode the selected pad is biased with 0.815V and all AC waveform in
this pad is caused by a noise source external to IC.
It is possible to observe in the following figure that, in noise detection mode, the clkref
output has the peak detection and the number of detected peaks can be counted or used by
digital block. The clkext output has the internal oscillator output and can be used to set
the maximum noise detection time window.
The waveform of the following figure shows two operations during noise detection mode:
• The V(vp) and V(vm) thresholds are changed in 34.4 µs.
• The Rs series resistance value is changed between 184 kΩ (iext<2:0>=011) and 32
kΩ (iext<2:0>=101). Because of this Rs change the amplitude of noise waveform
change also.
Figure 42-16. TSI noise detection mode waveform
Functional description
KL25 Sub-Family Reference Manual, Rev. 3, September 2012
802 Freescale Semiconductor, Inc.
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