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TDA1085 Datasheet(PDF) 6 Page - Motorola, Inc |
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TDA1085 Datasheet(HTML) 6 Page - Motorola, Inc |
6 / 12 page ![]() TDA1085C 6 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 generator. Power Circuits 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 Ω network. 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. Current Limitation 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 spikes. If not used, Pin 3 must be connected to a maximum positive voltage of 5.0 V rather than be left open. Loop Stability 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 Acceleration Ramp V VPin 5 VPin 7 t 0 VPin 6 = VDS 0 VDS VDF High Acceleration Ramp Distribution Low Acceleration Ramp High Acceleration Ramp VPin 5 fixed set value Speeds t VPin 4 VDF = 2 VDS |
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