Board immunity performances
UM1631
14/27
DocID024503 Rev 1
6
Board immunity performances
6.1 Hardware
and
software
features to increase immunity
Software features
Software features to improve board immunity are
Filtering procedure for button and potentiometer control
Software watchdog
Hardware features to improve board immunity are
Input varistor
ACS-ACST technology and Transil™ as an option for T1635H-6T
47 nF input X2 capacitor
Noise suppressor circuits are implemented (10 nF X2 capacitor and 75
resistor)
R-C-R filter on gate implemented (RG/2, 10 nF, RG/2)
Layout golden rules for immunity improvement
Power tracks far from signal tracks
V
SS
map
Noise suppressor and R-C-R gate filter close to AC switches and Triacs
Input MCU pins have implemented filter capacitor 10 nF
Any branch in the V
DD
map has implemented a capacitor to decrease the V
DD
variation
6.2
Surge tests results
Standard IEC 61000-4-5 tests were performed with surge level of 2 kV, which is required for
home appliances. Mains voltage used for the tests was 230 Vrms/50 Hz.
The ACST16 device is protected against overvoltage spikes up to 2 kV with implemented
crowbar technology. See the ACST16 datasheet for further details.
ACS devices are protected against overvoltage spikes up to 2 kV with implemented crowbar
technology. See the ACS108-8S datasheet for further details.
The Z01 Triac is protected thanks to the noise suppressor circuit and high impedance of the
load (refer to the AN437 application note for snubber design).
The T1635H is protected with Transil P6KE400CA. This is a different implementation of the
crowbar technology. The purpose here is to propose overvoltage protection with a crowbar
technology. This method presents the advantage of not aging contrary to the varistor
technology.
