DocID024503 Rev 1
9/27
UM1631
Getting started
3.3 MCU
programming
Once the demonstration board has the mains cable and load cable correctly connected, it
can be powered on. The STEVAL-IHT005V2 demonstration board goes to wait-for-signal
mode immediately after powering it on.
A JTAG connector for MCU programming is used when software modifications are
necessary.
Warning:
Programming device has to be galvanically isolated from
mains when programmed directly on mains.
3.4
Load and gate control fitting
Gate current pulse is generated by the MCU. The length of the pulse is set by software.
Gate current pulse length is important. Its value must be set according to the minimum load
current. The load current has to reach the AC switch latching current value to keep the
device ON after the gate pulse is removed. Latching current (I
L
) is specified in the AC switch
datasheet - ACS108-8S. It is important to check this point for low power loads when RMS
current is low and it takes a long time to reach the latching current level. When gate current
is removed before the load current reaches latching current, the device may turn off. Refer
to the AN302 application note for further information on latching current.
The maximum value and length of the gate current the board can provide depends on power
supply rating. The power supply used in the demonstration board is able to provide 120 mA
continuously in full range of the operating voltage.
