U211B Datasheet, PDF (11/30 Pages) ATMEL Corporation – Phase Control IC with Overload Limitation for Tacho Applications

U211B
7.8 Design Calculations for Main Supply
The following equations can be used for the evaluation of the series resistor R₁ for worst case
conditions:
R_1max
=
0.85
-^V----^M----^m----ⁱ-ⁿ----–----^V-----^S---^m----^a---^x
2 I_tot
R_1min
=
V_{-----M-----–-----}V_{----S---m----i-n-}
2 I_Smax
P _{( R1max )}
=
(_---V_{----M----m----a---x----–----}V_{----S----m----i-n---})_--²_-
2 R₁
where:
V_M
V_S
I_tot
I_Smax
I_p
I_x
= Mains voltage
= Supply voltage on pin 3
= Total DC current requirement of the circuit
= I_S + I_p + I_x
= Current requirement of the IC in mA
= Average current requirement of the triggering pulse
= Current requirement of other peripheral components
R₁ can be easily evaluated from the Figure 10-14 on page 19, Figure 10-15 on page 19 and
Figure 10-16 on page 20.
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4752B–INDCO–09/05