SWITCH-MODE DRIVER FOR DC MOTORS
*DRIVING CAPABILITY : 2 A, 36 V, 30 KHz 2
*LOGIC CHIP ENABLE
*EXTERNAL LOOP GAIN ADJUSTEMENT
*SINGLE POWER SUPPLY (18 TO 36 V)
*INPUT SIGNAL SYMMETRIC TO GROUND
*THERMAL PROTECTION
DESCRIPTION
The L292 is a monolithic LSI circuit in 15-lead Multiwatt ® package. It is intended for use, together with L290 and L291, as a complete 3-chip motor positioning system for applications such as carriage/daisy-wheel position control in type-writes. The L290/1/2 system can be directly controlled by
SYSTEM DESCRIPTION
The L290, L291 and L292 are intended to be used as a 3-chip microprocessor controlled positioning system. The device may be used separately - particularly the L292 motor driver - but since they will usually be used together, a description of a typical L290/1/2 system follows. Figure 1. System Block Diagram The system operates in two modes to achieve high speed, high-accurancy positioning. Speed commands for the system originate in the microprocessor. It is continuosly updated on the motor position by means of pulses from the L290 tachometer chip, whitch in tur gets its information from the optical encoder. From this basic input, the microprocessor computes a 5-bit control word that sets the system speed dependent on the distance to travel. When the motor is stopped and the microprocessor orders it to a new positio, the system operates initially in an open-loop configuration as there is no feedback from the tachometer generator. A maximum speed is reached, the tachometer chip output backs off the processor signal thus reducing accelering torque. The motor continues to run at rop speed but under closed-loop control. As the target position is approached, the microprocessor lowers the value of the speed-demand word; this reduces the voltage at the main summing point, in effect braking the motor. The braking is applied progressively until the motor is running at minimum speed. At the time, the microprocessor orders a switch to the position mode, (strobe signal at pin 8 of L291) and within 3 to 4 ms the L292 drives the motor to a null position, where it is held by electronic "detenting". The mechanical/electrical interface consists of an
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Telp : 082177773323
Email : odang@magentaelectronics.com
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