U211B Datasheet, PDF (7/30 Pages) ATMEL Corporation – Phase Control IC with Overload Limitation for Tacho Applications

U211B
7.1 Pulse Blocking
The output of pulses can be blocked by using pin 18 (standby operation) and the system reset
via the voltage monitor if V₁₈ ≥ -1.25 V. After cycling through the switching point hysteresis, the
output is released when V₁₈ ≤-1.5 V, followed by a soft start such as after turn-on.
Monitoring of the rotation can be carried out by connecting an RC network to pin 18. In the event
of a short or open circuit, the triac triggering pulses are cut off by the time delay which is deter-
mined by R and C. The capacitor C is discharged via an internal resistance R_i = 2 kΩ with each
charge transfer process of the f/V converter. If there are no more charge transfer processes, C is
charged up via R until the switch-off threshold is exceeded and the triac triggering pulses are cut
off. For operation without trigger pulse blocking or monitoring of the rotation, pin 18 and pin 16
must be connected together.
Figure 7-1. Operation Delay
C = 1 µF
10 V
18 17 16 15
R = 1 MΩ
1
2
3
4
7.2 Control Amplifier
The integrated control amplifier (see Figure 10-17 on page 21) with differential input compares
the set value (pin 11) with the instantaneous value on pin 10, and generates a regulating voltage
on the output pin 12 (together with the external circuitry on pin 12). This pin always tries to keep
the actual voltage at the value of the set voltages. The amplifier has a transmittance of typically
1000 µA/V and a bipolar current source output on pin 12 which operates with typically ±110 µA.
The amplification and frequency response are determined by R₇, C₇, C₈ and R₁₁ (can be left
out). For open-loop operation, C₄, C₅, R₆, R₇, C₇, C₈ and R₁₁ can be omitted. Pin 10 should be
connected with pin 12 and pin 8 with pin 2. The phase angle of the triggering pulse can be
adjusted by using the voltage on pin 11. An internal limitation circuit prevents the voltage on
pin 12 from becoming more negative than V₁₆ + 1 V.
7.3 Load Limitation
The load limitation, with standard circuitry, provides full protection against overloading of the
motor. The function of load limiting takes account of the fact that motors operating at higher
speeds can safely withstand larger power dissipations than at lower speeds due to the increased
action of the cooling fan. Similarly, considerations have been made for short-term overloads for
the motor which are, in practice, often required. These behaviors are not damaging and can be
tolerated.
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4752B–INDCO–09/05