Philips Semiconductors Linear Products Product specification
NE/SE567Tone 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
C
3
C
3
C
3
R
B
R
C
V+
DECREASE 
SENSITIVITY
INCREASE 
SENSITIVITY
R
A
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 f
O
/3, fO/5, etc.
2. The 567 will lock onto signals near (2n+1) f
O
, and will give an
output for signals near (4n+1) f
O
 where n=0, 1, 2, etc. Thus,
signals at 5f
O
 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 200mV
RMS
) 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 0.01µF 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 C
2
 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 C
2
 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 f
O
/10 baud.
R
f
Figure 4. Chatter Prevention
567
V+
8
C
f
LOWER VALUE OF C
f
R
L
Rf*
10k
*OPTIONAL - PERMITS
C
3
567
V+
8
200 TO
R
L
R
A
C
3
1
1k
10k
567
V+
8
1
10k
R
fRL
V+
200 TO 1k
R
A
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
C
2
C
2
C
2
R
B
R
C
V+
R
A
RAISES f
O
LOWERS f
O
RAISES f
O
RAISES f
O
LOWERS f
O