Datenblatt-Suchmaschine für elektronische Bauteile |
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CA3524 Datenblatt(PDF) 7 Page - Intersil Corporation |
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CA3524 Datenblatt(HTML) 7 Page - Intersil Corporation |
7 / 16 page 7 CA1524, CA2524, CA3524 Circuit Description Voltage Reference Section The CAl524 series contains an internal series voltage regu- lator employing a zener reference to provide a nominal 5-volt output, which is used to bias all internal timing and control circuitry. The output of this regulator is available at terminal l6 and is capable of supplying up to 50mA output current. Figure 1 shows the temperature variation of the reference voltage with supply voltages of 8V to 40V and load currents up to 20mA. Load regulation and line regulation curves are shown in Figures 2 and 3, respectively. FIGURE 1. TYPICAL REFERENCE VOLTAGE AS A FUNCTION OF AMBIENT TEMPERATURE FIGURE 2. TYPICAL REFERENCE VOLTAGE AS A FUNCTION OF REFERENCE OUTPUT CURRENT FIGURE 3. TYPICAL REFERENCE VOLTAGE AS A FUNCTION OF SUPPLY VOLTAGE 5.02 5.00 4.98 4.96 -60 -40 -20 0 20 40 60 80 100 120 140 AMBIENT TEMPERATURE (oC) V+ = 40V, IL = 0mA V+ = 20V, IL = 0mA V+ = 40V, IL = 20mA V+ = 8V, IL = 0mA V+ = 20V, IL = 20mA V+ = 8V, IL = 20mA 5.1 4.9 4.7 4.5 4.3 4.1 3.9 3.7 3.5 0 8 16 24 32 40 48 56 64 72 80 REFERENCE OUTPUT CURRENT (mA) TA = +25oC V+ = 20V V+ = 40V V+ = 20V V+ = 8V 6 5 4 3 2 1 0 0 7 8 10 20 30 40 SUPPLY VOLTAGE, V+ (V) TA = +25oC Osclllator Section Transistors Q42, Q43 and Q44, in conjunction with an external resistor RT, establishes a constant charging current into an external capacitor CT to provide a linear ramp voltage at terminal 7. The ramp voltage has a value that ranges from 0.6V to 3.5V and is used as the reference for the comparator in the device. The charging current is equal to (5-2VBE)/RT or approximately 3.6/RT and should be kept within the range of 30pA to 2mA by varying RT. The discharge time of CT deter- mines the pulse width of the oscillator output pulse at termi- nal 3. This pulse has a practical range of 0.5 µsto5µs for a capacitor range of 0.001 to 0.1 µF. The pulse has two internal uses: as a dead-time control of blanking pulse to the output stages to assure that both outputs cannot be on simulta- neously and as a trigger pulse to the internal flip-flop which controls the switching of the output between the two output channels. The output dead-time relationship is shown in Fig- ure 4. Pulse widths less than 0.5 µs may allow false trigger- ing of one output by removing the blanking pulse prior to a stable state in the flip-flop. FIGURE 4. TYPICAL OUTPUT STAGE DEAD TIME AS A FUNCTION OF TIMING CAPACITOR VALUE If a small value of CT must be used, the pulse width can be further expanded by the addition of a shunt capacitor in the order of 100pF but no greater than 1000pF, from terminal 3 to ground. When the oscillator output pulse is used as a sync input to an oscilloscope, the cable and input capacitances may increase the pulse width slightly. A 2-K Ω resistor at terminal 3 will usually provide sufficient decoupling of the cable. The upper limit of the pulse width is determined by the maximum duty cycle acceptable. The oscillator period is determined by RT and CT, with an approximate value of t = RTCT, where RT is in ohms, CT is in µF, and t is in µs. Excess lead lengths, which produce stray capacitances, should be avoided in connecting RT and CT to their respective terminals. Figure 5 provides curves for selecting these values for a wide range of oscillator periods. For series regulator applications, the two outputs can be connected in parallel for an effective 0-90% duty cycle with the output stage frequency the same as the oscillator frequency. Since the outputs are separate, push-pull and flyback applications are possible. The flip-flop divides the frequency such that the duty cycle of each output is 0-45% and the overall frequency is half that of the oscillator. Curves 100 10 1.0 0.1 0.0001 0.001 0.01 0.1 1.0 TIMING CAPACITOR, CT (µF) TA = +25 oC V+ = 8V - 40V |
Ähnliche Teilenummer - CA3524 |
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Ähnliche Beschreibung - CA3524 |
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