U211B Datasheet, PDF (9/30 Pages) ATMEL Corporation – Phase Control IC with Overload Limitation for Tacho Applications

U211B
7.4 Design Hints
Practical trials are normally needed for the exact determination of the values of the relevant
components for load limiting. To make this evaluation easier, the following table shows the effect
of the circuitry on the important parameters for load limiting and summarizes the general
tendencies.
Table 7-1. Load Limiting Parameters
Component
Component
Component
Parameters
P_max
P_min
P_max/min
t_d
t_r
P_max
P_min
t_d
t_r
n.e.
R₁₀ Increasing
Increases
R₉ Increasing
Decreases
C₉ Increasing
n.e.
Increases
Decreases
n.e.
Increases
n.e.
n.e.
n.e.
Increases
Increases
n.e.
Increases
Increases
- Maximum continuous power dissipationP₁ = f_(n) n ≠ 0
- Power dissipation with no rotation
P₁ = f_(n) n = 0
- Operation delay time
- Recovery time
- No effect
7.5 Pulse-output Stage
The pulse-output stage is short-circuit protected and can typically deliver currents of 125 mA.
For the design of smaller triggering currents, the function I_GT = f(R_GT) can be taken from Figure
10-12 on page 18.
7.6 Automatic Retriggering
The variable automatic retriggering prevents half cycles without current flow, even if the triac has
been turned off earlier, e.g., due to a collector which is not exactly centered (brush lifter) or in the
event of unsuccessful triggering. If necessary, another triggering pulse is generated after a time
lapse which is determined by the repetition rate set by resistance between pin 5 and pin 3 (R_5-3).
With the maximum repetition rate (pin 5 directly connected to pin 3), the next attempt to trigger
comes after a pause of 4.5 t_p and this is repeated until either the triac fires or the half cycle fin-
ishes. If pin 5 is not connected, only one trigger pulse per half cycle is generated. Since the
value of R_5-3 determines the charging current of C₂, any repetition rate set using R_5-3 is only valid
for a fixed value of C₂.
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4752B–INDCO–09/05