U209B_07 Datasheet, PDF (8/19 Pages) ATMEL Corporation – Phase Control IC for Tacho Applications

3.6 Control Amplifier
The integrated control amplifier with differential input compares the set value (pin 10) with the
instantaneous value on pin 9, and generates a regulating voltage on the output pin 11 (together
with external circuitry on pin 12). This pin always tries to keep the real voltage at the value of the
set voltages. The amplifier has a transmittance of typically 110 µA/V and a bipolar current
source output on pin 11 which operates with typically ±100 µA. The amplification and frequency
response are determined by R₇, C₇, C₈ and R₈ (can be left out). For operation as a power divider,
C₄, C₅, R₆, C₆, R₇, C₇, C₈ and R₈ can be left out. Pin 9 should be connected with pin 11 and pin 7
with pin 2. The phase angle of the triggering pulse can be adjusted using the voltage on pin 10.
An internal limiting circuit prevents the voltage on pin 11 from becoming more negative than V13
+ 1 V.
3.7 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
6-8 on page 15.
3.8 Automatic Retriggering
The automatic retriggering prevents half cycles without current flow, even if the triacs have been
turned off earlier, e.g., due to not exactly centered collector (brush lifter) or in the event of unsuc-
cessful triggering. If necessary, another triggering pulse is generated after a time lapse of
t_PP = 4.5 t_P and this is repeated until either the triac fires or the half cycle finishes.
3.9 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 6 and pin 2 should be as short as possible, and the connec-
tion 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.
8 U209B
4765C–INDCO–02/07