MOTOROLA ANALOG IC DEVICE DATA
Ramps Generator – (Pin 6) If only a high acceleration ramp is
needed, connect Pin 6 to ground.
When a Distribute ramp should occur, preset a voltage on Pin 6
which corresponds to the motor speed starting ramp point.
Distribution (or low ramp) will continue up to the moment the motor
speed would have reached twice the starting value.
The ratio of two is imposed by the IC. Nevertheless, it could be
externally changed downwards (Figure 6) or upwards (Figure 7).
The distribution ramp can be shortened by an external resistor from
VCC charging CPin 7, adding its current to the internal 5.0 µA
Triac Triggering pulse amplitude must be determined by Pin 13
resistor according to the needs in Quadrant IV. Trigger pulse duration
can be disturbed by noise signals generated by the triac itself, which
interfere within Pins 14 and 16, precisely those which determine it.
While easily visible, this effect is harmless.
The triac must be protected from high AC line dV/dt during external
disturbances by 100 nF x 100
Shunt resistor must be as non–inductive as possible. It can be made
locally by using constantan alloy wire.
When the load is a DC fed universal motor through a rectifier bridge,
the triac must be protected from commutating dV/dt by a 1.0 to
2.0 mH coil in series with MT2.
Synchronization functions are performed by resistors sensing AC
line and triac conduction. 820 k values are normal but could be
reduced down to 330 k in order to detect the “zeros” with accuracy
and to reduce the residual DC line component below 20 mA.
The current limiter starts to discharge Pin 7 capacitor (reference
speed) as the motor current reaches the designed threshold level.
The loop gain is determined by the resistor connecting Pin 3 to the
series shunt. Experience has shown that its optimal value for a
10 Arms limitation is within 2.0 k
Ω. Pin 3 input has a sensitivity in
current which is limited to reasonable values and should not react to
If not used, Pin 3 must be connected to a maximum positive voltage
of 5.0 V rather than be left open.
The Pin 16 network is predominant and must be adjusted
experimentally during module development. The values indicated in
Figure 4 are typical for washing machine applications but accept
large modifications from one model to another. R16 (the sole
restriction) should not go below 33 k, otherwise slew rate limitation
will cause large transient errors for load steps.
Figure 2. Acceleration Ramp
Figure 3. Programmable Double
VPin 6 = VDS
VPin 5 fixed set value
VDF = 2 VDS