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LS8397 Datasheet(PDF) 2 Page - LSI Computer Systems |
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LS8397 Datasheet(HTML) 2 Page - LSI Computer Systems |
2 / 8 page SYNC As an output the sync can be used to drive sync pins of other LS8397s. This eliminates the need for RC components for any other LS8397 controllers used in the system. As an input the sync can be driven by the LS8397 that has the RC oscillator components or by any other system external clock. PHA/PHB/PHC/PHD Phase drive output signals for power stages. In a Bipolar motor PHA and PHB are used for one H-bridge while PHC and PHD are used for the other. INH1/INH2 Outputs These outputs are active low inhibit controls for motor drive outputs. INH1 controls driver stage using PHA and PHB sig- nals while INH2 control driver stage using PHC and PHD sig- nals. When the Control input is low, these outputs are chopped using the internal oscillator for current regulating. CONTROL Input When high, the phase outputs, PHA, PHB, PHC and PHD are chopped. When low, INH1 and INH2 are chopped. Normally, inhibit outputs are chopped. Phase chopping might be used with a Bipolar motor that does not store much energy to pre- vent fast current decay and a low useful torque. ENABLE Input When Enable input is low, INH1, INH2, PHA, PHB, PHC and PHD are brought low. HOME Output An open drain output that indicates when the LS8397 is in its initial state with PHA, PHB, PHC, PHD = logic states 0101 re- spectively. Refer to Figure 4. In the active state the open drain device is off. STEP Input An active low pulse on this input causes the motor to advance one step. The step occurs on the rising edge of the step signal. FRD/REV Input A logic 1 on this input causes the motor to advance through the stepping sequence of Fig. 4. A logic 0 on this input cause the motor to reverse the sequence. RESET Input An active low on this input cause the motor to be restored to the home position (0101). HALF/FULL Input When high, half-step operation is selected. When low, full-step operation is selected. The one-phase-on full step is selected by selecting full when the stepping sequence is at an even state. The two-phase-on full step operation is selected when the stepping sequence is at an odd state. Refer to Figure 4. SENSE1/ SENSE2 Inputs Inputs for load current sense voltages from power stages using PHA and PHB drive signals or PHC and PHD drive signals, respectively. When holding-torque mode is enabled, the motor torque is switched to stepping torque at a step command followed by holding torque after a programmable delay. The stepping torque is controlled by the reference voltage VREFs input and the hold- ing torque is controlled by the voltage at the VREFh input. The delay is controlled by a resistor-capacitor pair connected to the RC pin. When the holding-torque mode is disabled, the motor torque re- mains in the stepping torque mode all the time controlled by the VREFs voltage. RC Input/Output A resistor-capacitor pair connected to this pin starts a time-out delay at every step command. At the start of the delay, the ref- erence voltage at the VREFs pin is switched in for the SENSE comparators to produce higher stepping torque. At the end of the time-out, the reference voltage at the VREFh pin is switched in for the SENSE comparators to produce the lower holding torque, reducing power dissipation while the motor is stationary. The delay is given by Tds = 1.4RC If tied low, holding torque mode is disabled and stepping torque is produced in both dynamic and static states by using the VREFs reference voltage. VREFs Input Input for the SENSE comparator reference voltage for produc- ing stepping torque. VREFh Input Input for the SENSE comparator reference voltage for produc- ing holding torque. CT_EN Input Input for selecting/deselecting compensated torque-ripple mode. The step sequence in the half-step mode alternates be- tween one-phase-on and two-phase-on states resulting in torque ripple during the stepping sequence. In the compensat- ed-torque mode, the ripple is eliminated by equalizing the torques for the alternate states. This is done by alternately switching the SENSE reference voltages between 100% and 70.7% in alternate cycles. The CT_EN input is relevant only in the half-step mode, since the alternating one-step-on and two-step-on sequence does not exist in the full-step mode. This input has an internal pull-up. 8397-011409-2 |
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Similar Description - LS8397 |
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