Introduction to Digital Power Conversion
XMC4000/1000 Family
Modulation
Application Guide
63
V1.0, 2015-01
6.4
Blanking, Filtering and Clamping
Blanking
Blanking compare mode is essential to avoid prematurely switching off the MOSFET because of noise
that is induced when it is turned on.
A dedicated blanking timer, in single-shot mode, is one way to create a time window to disable the
comparator output and get a peak-detection accept window.
Note:
The HRPWM has an embedded blanking timer.
Figure 47
Blanking (principle)
– Example
Filtering
A filter on the analog comparator output rejects unwanted OFF-switching due to EMI noise during
switch-ON signal sensing. This filter performs filtering during a few clock cycles of the comparator
output signal, so rejecting some line noise or long settling time of the analog input signal to interfere.
Clamping
There is an output clamping control input on the analog comparator that can clamp the comparator
output at the required passive level, for a certain time, that should be consistent with the ultimate
minimum ON-time (t
ON_min
), as specified in the MOSFET datasheet (to avoid destruction).
