U211B Datasheet, PDF (10/30 Pages) ATMEL Corporation – Phase Control IC with Overload Limitation for Tacho Applications

7.7 General Hints and Explanation of Terms
To ensure safe and trouble-free operation, the following points should be taken into consider-
ation when circuits are being constructed or in the design of printed circuit boards.
• The connecting lines from C₂ to pin 7 and pin 2 should be as short as possible. The
connection to pin 2 should not carry any additional high current such as the load current.
When selecting C₂, a low temperature coefficient is desirable.
• The common (earth) connections of the set-point generator, the tacho generator and the final
interference suppression capacitor C₄ of the f/V converter should not carry load current.
• The tacho generator should be mounted without influence by strong stray fields from the
motor.
• The connections from R₁₀ and C₅ should be as short as possible.
To achieve a high noise immunity, a maximum ramp voltage of 6 V should be used. The typical
resistance R_ϕ can be calculated from I_ϕ as follows:
R_ϕ( k Ω)
=
T_-----(_--m_-----s_---)_----×_------1_---._--1_---3_----(_--V_-----)_---×_------1_---0_----³_-
C(nF) × 6(V)
T=
Period duration for mains frequency (10 ms at 50 Hz)
C_ϕ =
Ramp capacitor, maximum ramp voltage 6 V and constant voltage drop at
R_ϕ = 1.13 V
A 10% lower value of R_ϕ (under worst case conditions) is recommended.
Figure 7-2. Explanation of Terms in Phase Relationship
V
Mains
Supply
π/2
π
3/2π
2π
V_GT
Trigger
Pulse
t_p
t_pp = 4.5 t_p
V_L
Load
Voltage
10 U211B
IL
Load
Current
ϕ
Φ
4752B–INDCO–09/05