UM1494 Datasheet, PDF (19/23 Pages) STMicroelectronics – The STEVAL-IHT007V1 demonstration board is designed for the home appliance market

UM1494
STEVAL-IHT007V1 demonstration board
Figure 9. PCB silkscreen - bottom side
A.3
Gate current consumption
Gate current consumption is based on Equation 3. Values used for the calculation are
shown in the datasheet for the AC switch or Triac.
Equation 3 Gate resistor calculation
R_g
≤₁-----+-----_{R----------g----------}¹_-t---_{o------l----e-----r}----_a-----_{n------c------e--}
⎛
⎜
⎝
V_{CC Min} – V_{GT Max} – V_{CE(Sat)⎞}
----------------------------_I--_G----₍--₁----₀----_°---_C-----₎----------------------------_⎠⎟
100
where R_{g_tolerance} is the tolerance of the used resistor (typically 1% or 5%), V_{CC_Min} is the
minimum supply voltage (typically 5 V for capacitive power supply with 5.6 V Zener diode),
V_{GT_Max} is maximum gate voltage that appears between the gate and A1 or the COM pin
(typically 0.8 V), I_G gate current for the minimum ambient temperature (normally 0 or 10 °C
for household applications) is given in the datasheet, V_CE(Sat) is saturation voltage of the
opto-coupler [maximum value is given by the PC817 datasheet (0.2 V)]. Standard resistor
choice is shown in Table 4.
Please note that the STEVAL-IHT007V1 demonstration board uses gate resistors with 1%
dispersion.
Doc ID 022519 Rev 1
19/23