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UC1620SP883C Scheda tecnica(PDF) 4 Page - Texas Instruments |
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UC1620SP883C Scheda tecnica(HTML) 4 Page - Texas Instruments |
4 / 8 page UC1620 UC3620 off. On time is determined by the amount of time required for motor current to increase to the value required to re- trip the monostable. A timing sequence of these events is shown in Figure 2. CURRENT LIMIT Since peak current is being controlled at all times by the internal comparator, a simple voltage clamp at its nega- tive (-) input will limit peak current to a maximum value. A fixed 0.5V internal clamp has been included on the UC3620, and any current spike in the output which gener- ates a sensed voltage greater than 0.5V will immediately shut down the outputs. Actual peak current values may be programmed by selecting the appropriate value of RS ac- cording to the formula: RS = 0.5 ICURRENTLIMIT Since peak current is being controlled at all times by the internal comparator, a simple voltage clamp at its nega- tive (-) input will limit peak current to a maximum value. A fixed 0.5V internal clamp has been included on the UC3620, and any current spike in the output which gen- erates a sensed voltage greater than 0.5V will immedi- ately shut down the outputs. Actual peak current values may be programmed by selecting the appropriate value of RS according to the formula: RS = 0.5 ICURRENTLIMIT ERROR AMPLIFIER LIMIT A high performance, on-board error amplifier is included to facilitate implementing closed loop motor control. Error voltage generation and loop compensation are easily ac- complished by appropriately configuring the gain and feedback of this amplifier. To provide a larger dynamic sig- nal range at the output of the error amplifier, a divide by 5 resistor network is used to reduce the error signal level before applying to the internal comparator. In addition, a one volt offset has been introduced at the output of the error amplifier to guarantee control down to zero current in the output stages. Since this offset is divided by the open loop gain of the feedback loop, it has virtually no ef- fect on closed loop performance. PROTECTION FUNCTIONS Protective functions including under-voltage lockout, peak current limiting, and thermal shutdown, provide an ex- tremely rugged device capable of surviving under many types of fault conditions. Under-voltage lockout guaran- tees the outputs will be off or tri-slated until VCC is suffi- cient for proper operation of the chip. Current limiting limits the peak current for a stalled or shorted motor, whereas thermal shutdown will tri-state the outputs if a temperature above 150°C is reached. Figure 2. Chopped Mode Timing Diagram CIRCUIT DESCRIPTION (cont.) 4 |
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Descrizione simile - UC1620SP883C |
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