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SLA7082MPR Folha de dados(PDF) 6 Page - Sanken electric |
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SLA7082MPR Folha de dados(HTML) 6 Page - Sanken electric |
6 / 18 page 6 SANKEN ELECTRIC CO., LTD. 28610.23, Rev. 1 Unipolar 2-Phase Stepping Motor Driver ICs SLA7080M Series Logic Block This circuit block is integrated on the Control IC (MIC). It oper- ates by the logic power supply, VDD , and propagates signals to each circuit block in accordance with the logic input signals. Regulator Circuit This circuit block is integrated on the Control IC (MIC). The integrated regulator circuit is used in driving the output MOSFET gates and in powering other internal linear circuits. Dual Phase Output Control The SLA7080M series allows dual phase operation based on external input to the INx pins. The phase-switching logic is shown in the following table: Phase A [B] INA [INB] I¯¯N¯¯A¯ [ I¯¯N¯¯B¯] OUTA [OUTB]* ¯O¯¯U¯¯T¯¯A¯ [¯O¯¯U¯¯T¯¯B¯ ]* Low Low OFF OFF High Low ON OFF Low High OFF ON High High OFF OFF *OUT indicates power MOSFET drain state (does not indicate PWM operation) PWM Control This circuit block is integrated on the Control IC (MIC). This is the main circuit block for pulse width modulated (PWM) control of self-excitation and external excitation for motor driving. An illustration of PWM behavior is shown in figure 1. PWM control mode is set by the SYNC pin. Set SYNC to logic high for synchronous PWM, and set it to logic low for asynchro- nous PWM. PWM Off-Time, toff, (for self-excitation), minimum off-time (for external excitation), and PWM Minimum On-Time (blanking time), ton(min), are clocked by means of the built-in oscillator. The length of toff is fixed internally. Like in the SLA7070M series, the SLA7080M series has a power-saving function that reduces power consumption during toff. This function recirculates electromotive force that is stored in the motor coil while the power MOSFETs are turned on. The time interval during which the output MOSFETs are on is ton. The minimum duration for the PWM Minimum On-time, ton(min), is effectively the blanking time selected, even if the application attempts to shorten ton in order to limit current. The minimum coil current is at ton(min), so when the coil current is limited at power- down or other events, it can be no shorter than the blanking time. Blanking Time The blanking time function is provided to limit current in order to suppress ringing immediately after PWM turns on, and to improve current control tracking. Blanking time in effect deter- mines PWM Minimum On-Time, ton(min). The length of the blank- ing time is selected by the B_SEL pin. Set B_SEL to logic high for 3.2 μs blanking time, and set it to logic low for 5.2 μs. Some ringing is generated for a few microseconds after PWM switching (see figure 2). Ringing can result from various causes, such as capacitance between motor cells, or inappropriate motor wiring. To suppress this behavior, the blanking time selection sets a minimum time interval during which current detection signals from the current sense comparators are ignored after a PWM switch-on. Current control (tracking) in the SLA7080M series is regulated by comparing the detection voltage on the sense resistor, VRS , with the reference voltage, VREF. If the ringing noise causes VRS to exceed VTRIP, the comparator is activated and PWM turns off. Current control performance at shorter PWM waveforms can be improved by shortening the blanking time, but this decreases the effectiveness of ringing suppression, resulting in the seek- ing behavior shown in figure 3.) To solve this problem, the SLA7080M series is designed to allow dynamic selection of blanking time duration. In the event that the seeking behavior Functional Description Figure 1. PWM waveform on SLA7080M sense resistor, RS; toff is fixed and the blanking time, toff(min), is dynamically selectable. 0 VOUT ton(min) ITRIP One PWM Cycle ton toff Phase A [B] A [ B ] A [ B ] |
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