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MC33094 数据表(PDF) 9 Page - Motorola, Inc |
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MC33094 数据表(HTML) 9 Page - Motorola, Inc |
9 / 16 page MC33094 9 MOTOROLA ANALOG IC DEVICE DATA represents an effort to reduce excess dwell and therefore power dissipation during high voltage operation. The 5.88 µA discharge rate is used under normal VCC operating conditions. Under a start mode, this block will discharge the adaptive capacitor forcing an enhanced start mode dwell. The start/run modes are set internally by detecting the engine frequency, which corresponds to the ramp capacitor voltage. The Stall Capacitor Charging and Sensing block controls the charging and discharging rates of the stall capacitor. The charging rate is 31.5 µA, and the two discharging rates are 1.0 µA and 7.0 µA. The stall capacitor potential commands the IC to maintain or reduce the coil current. When the engine is turning very slowly (or stalled), the stall capacitor will have enough time to discharge below threshold and thereby reduce coil current. The output current limiter (see Output Current Driver and Limiter block description below) forces the coil current to be proportional to the stall capacitor voltage when the stall capacitor voltage is less than 2.0 V. The Ramp Capacitor Charging and Sensing block charges the ramp capacitor at approximately 8.4 µA and discharges it at about 33.6 µA. The charging circuit is always on and sources current during the “not 25%” part of the engine cycle. The discharging circuit is only on and sinking current during the “25%” part of the engine cycle. The positive edge of the distributor input signal sets the 25% mode, and the ramp comparator output clears this mode. The CR > CA Adaptive Comparator block signals the point where the ramp capacitor voltage is greater than the adaptive capacitor voltage. The point at which the two capacitor voltages are equal is the point where charging of the coil is begun. The adaptive algorithm used in the IC maintains the required excess dwell throughout all reasonable accelerations and decelerations without causing excess coil power dissipation, in addition, it insures that more than adequate spark energy is available for very high engine speeds, when excess dwell is impossible. The Output Current Driver and Limiter block sources a limited supply current of about 50 mA to the base of the Darlington power transistor. The Darlington will cause the coil to conduct to about 6.5 amps and the voltage drop on the IS pin of the IC will rise to the threshold of the current limiter. The current limiter will then hold the coil current at that level until either a spark is commanded by the logic block, or the engine begins to stall (causing the coil to slowly discharge). The Internal Logic block performs the required memory and gating functions on the IC to implement the adaptive ignition control algorithm. Band Gap Reference Input Voltage Comparator Negative Edge Filter Ramp Capacitor Charging and Sensing Adaptive Capacitor Charging and Sensing CR > CA Adaptive Comparator VCC Comparator and Clamp CS Out DS CL S VCC MB Vr Gnd Vr BG Master Bias Vin(-) CA CR CR CA Vr Master Bias 25% Reset BG 25% Vr Master Bias BG VCC Vr 25% 25% Reset ZC Stall CR > CA Stall ST T Hi-Bat. Stall Limit Dump Master Bias Current Reference Vr Zener Reference Output Current Driver and Limiter Internal Logic Stall Capacitor Charging and Sensing Figure 10. Block Diagram 9 26 12 10 11 14 15 7 3 4 8 13 Freescale Semiconductor, Inc. For More Information On This Product, Go to: www.freescale.com |
类似零件编号 - MC33094 |
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类似说明 - MC33094 |
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