поискавой системы для электроныых деталей |
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UC3717 датащи(PDF) 5 Page - Texas Instruments |
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UC3717 датащи(HTML) 5 Page - Texas Instruments |
5 / 9 page Overload Protection: The circuit is equipped with a thermal shutdown function, which will limit the junction temperature by reducing the output current. It should be noted however, that a short circuit of the output is not permitted. Operation: When the voltage is applied across the motor winding the current rises linearly and appears across the external sense resistor as an analog voltage. This volt- age is fed through a low pass filter RC, CC to the voltage comparator (pin 10). At the moment the voltage rises be- yond the comparator threshold voltage the monostable is triggered and its output turns off the sink transistors. The current then circulates through the source transistor and the appropriate Schottky diode. After the one shot has timed out, the sink transistsor is turned on again and the procedure repeated until a current reverse command is given. By reversing the logic level of the phase input (pin 8), both active transistors are being turned off and the opposite pair turned on. When this happens the current must first decay to zero before it can reverse. The cur- rent path then provided is through the two diodes and the power-supply. Refer to Figure 7. It should be noted at this time that the slope of the current decay is steeper, and this is due to the higher voltage build up across the winding. For better speed performance of the stepping motor at half step mode, the phase logic level should be changed at the same time the current inhibit is applied. A typical current wave form is shown in Figure 8. APPLICATIONS A typical chopper drive for a two phase bipolar perma- nent magnet or hybrid stepping motor is shown in Figure 9. The input can be controlled by a microprocessor, TTL, LS or CMOS logic. The timing diagram in Figure 10 shows the required sig- nal input for a two phase, full step, stepping sequence. Figure 11 shows a one phase, full step, stepping se- quence, commonly referred to as wave drive. Figure 12 shows the required input signal for a one phase-two phase stepping sequence called half-stepping. The circuit of Figure 13 provides the signal shown in Fig- ure 10, and in conjunction with the circuit shown in Fig- ure 9, will implement a pulse-to-step two phase, full step, bidirectional motor drive. The schematic of Figure 14 shows a pulse to half step circuit generating the signal shown in Figure 12. Care has been taken to change the phase signal the same time the current inhibit is applied. This will allow the cur- rent to decay faster and therefore enhance the motor performance at higher step rates. Using the UC3717 to drive the L298 provides a uniquely packaged state-of-the-art high power stepper motor con- trol and drive. See Figure 15. Figure 8 FUNCTIONAL DESCRIPTION (cont.) Figure 9 UC1717 UC2717 UC3717 5 |
Аналогичный номер детали - UC3717 |
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Аналогичное описание - UC3717 |
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