STEVAL-IHT005V2 schematic
UM1631
22/27
DocID024503 Rev 1
Assumptions for calculation
V
DD_Min
is minimum supply voltage (typically 3 V for 3.3 V power supply taking into
account dispersion of resistors at LM337).
V
GT_Max
= 1.0 V (maximum gate voltage that must be applied between gate and A1 or
COM).
V
OL
= 0.4 V maximum MCU I/O port voltage when turned to low level (given by the
datasheet (0.4 V for STM32F100)).
Note:
V
OL
value of 0.4 V is used also for BC547B buffer transistor control.
R
g_tol
is tolerance of used resistor (typically 1% or 5%).
I
G
(0 °C)
is gate current for minimum ambient temperature (normally 0 °C) (refer to
Triac family datasheet curve).
Standard resistor choices, according to the above equation and assumptions, are shown in
In the STEVAL-IHT005V2 demonstration board tolerance resistors of 1% are used.
Table 8. Gate resistor definition for each device
Tolerance of R
g
(%)
R
g
(
)
R
g
standard (
)
T1635H
1
31.7
2 x 15
5
30.4
2 x 15
ACST16
1
31.7
2 x 15
5
30.4
2 x 15
ACS108
1
112.2
2 x 56
5
107.8
2 x 51
Z0109
1
112.2
2 x 56
5
107.8
2 x 51
