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SE567D Datasheet(PDF) 8 Page - NXP Semiconductors |
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SE567D Datasheet(HTML) 8 Page - NXP Semiconductors |
8 / 13 page Philips Semiconductors Linear Products Product specification NE/SE567 Tone decoder/phase-locked loop April 15, 1992 410 Figure 3. Sensitivity Adjust 567 567 567 DECREASE SENSITIVITY INCREASE SENSITIVITY V+ R R 1 1 1 SILICON DIODES FOR TEMPERATURE COMPENSATION (OPTIONAL) 2.5k 1.0k 50k C3 C3 C3 RB RC V+ DECREASE SENSITIVITY INCREASE SENSITIVITY RA connected to pin 6 without affecting the CCO duty cycle or temperature stability. OPERATING PRECAUTIONS A brief review of the following precautions will help the user achieve the high level of performance of which the 567 is capable. 1. Operation in the high input level mode (above 200mV) will free the user from bandwidth variations due to changes in the in-band signal amplitude. The input stage is now limiting, however, so that out-band signals or high noise levels can cause an apparent bandwidth reduction as the inband signal is suppressed. Also, the limiting action will create in-band components from sub-harmonic signals, so the 567 becomes sensitive to signals at fO/3, fO/5, etc. 2. The 567 will lock onto signals near (2n+1) fO, and will give an output for signals near (4n+1) fO where n=0, 1, 2, etc. Thus, signals at 5fO and 9fO can cause an unwanted output. If such signals are anticipated, they should be attenuated before reaching the 567 input. 3. Maximum immunity from noise and out-band signals is afforded in the low input level (below 200mVRMS) and reduced bandwidth operating mode. However, decreased loop damping causes the worst-case lock-up time to increase, as shown by the Greatest Number of Cycles Before Output vs Bandwidth graph. 4. Due to the high switching speeds (20ns) associated with 567 operation, care should be taken in lead routing. Lead lengths should be kept to a minimum. The power supply should be adequately bypassed close to the 567 with a 0.01 µF or greater capacitor; grounding paths should be carefully chosen to avoid ground loops and unwanted voltage variations. Another factor which must be considered is the effect of load energization on the power supply. For example, an incandescent lamp typically draws 10 times rated current at turn-on. This can be somewhat greater when the output stage is made less sensitive, rejection of third harmonics or in-band harmonics (of lower frequency signals) is also improved. cause supply voltage fluctuations which could, for example, shift the detection band of narrow-band systems sufficiently to cause momentary loss of lock. The result is a low-frequency oscillation into and out of lock. Such effects can be prevented by supplying heavy load currents from a separate supply or increasing the supply filter capacitor. SPEED OF OPERATION Minimum lock-up time is related to the natural frequency of the loop. The lower it is, the longer becomes the turn-on transient. Thus, maximum operating speed is obtained when C2 is at a minimum. When the signal is first applied, the phase may be such as to initially drive the controlled oscillator away from the incoming frequency rather than toward it. Under this condition, which is of course unpredictable, the lock-up transient is at its worst and the theoretical minimum lock-up time is not achievable. We must simply wait for the transient to die out. The following expressions give the values of C2 and C3 which allow highest operating speeds for various band center frequencies. The minimum rate at which digital information may be detected without information loss due to the turn-on transient or output chatter is about 10 cycles per bit, corresponding to an information transfer rate of fO/10 baud. Rf Figure 4. Chatter Prevention 567 V+ 8 Cf LOWER VALUE OF Cf RL Rf* 10k *OPTIONAL - PERMITS C3 567 V+ 8 200 TO RL RA C3 1 1k 10k 567 V+ 8 1 10k Rf RL V+ 200 TO 1k RA 1 Figure 5. Skew Adjust 567 567 567 V+ R R 2 2 1 SILICON DIODES FOR TEMPERATURE COMPENSATION (OPTIONAL) 2.5k 1.0k 50k C2 C2 C2 RB RC V+ RA RAISES fO LOWERS fO RAISES fO RAISES fO LOWERS fO |
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