ne564d NXP Semiconductors, ne564d Datasheet - Page 7

• Manufacturer Part Number: ne564d
• Description: Ne564 Phase-locked Loop
• Manufacturer: NXP Semiconductors

Philips Semiconductors
APPLICATIONS
FM Demodulator
The NE564 can be used as an FM demodulator. The connections
for operation at 5V and 12V are shown in Figures 7 and 8,
respectively. The input signal is AC coupled with the output signal
being extracted at Pin 14. Loop filtering is provided by the
capacitors at Pins 4 and 5 with additional filtering being provided by
the capacitor at Pin 14. Since the conversion gain of the VCO is not
very high, to obtain sufficient demodulated output signal the
frequency deviation in the input signal should be 1% or higher.
Modulation Techniques
The NE564 phase-locked loop can be modulated at either the loop
filter ports (Pins 4 and 5) or the input port (Pin 6) as shown in Figure
9. The approximate modulation frequency can be determined from
the frequency conversion gain curve shown in Figure 10. This curve
will be appropriate for signals injected into Pins 4 and 5 as shown in
Figure 9.
FSK Demodulation
The 564 PLL is particularly attractive for FSK demodulation since it
contains an internal voltage comparator and VCO which have TTL
compatible inputs and outputs, and it can operate from a single 5V
power supply. Demodulated DC voltages associated with the mark
and space frequencies are recovered with a single external
capacitor in a DC retriever without utilizing extensive filtering
networks. An internal comparator, acting as a Schmitt trigger with
an adjustable hysteresis, shapes the demodulated voltages into
compatible TTL output levels. The high-frequency design of the 564
enables it to demodulate FSK at high data rates in excess of 1.0M
baud.
Figure 10 shows a high-frequency FSK decoder designed for input
frequency deviations of +1.0MHz centered around a free-running
frequency of 10.8MHz. the value of the timing capacitance required
was estimated from Figure 8 to be approximately 40pF. A trimmer
capacitor was added to fine tune f
1994 Aug 31
FM INPUT
f
f
O
M
Phase-locked loop
.01 F
= 5MHz
= 1kHz
BIAS
FILTER
0.47 F
.01 F
Figure 8. FM Demodulator at 12V
12V
1k
6
7
3
1
16
8
200
10
2
564
O
11
’ 10.8MHz.
9
I
1k
2
LOCK RANGE ADJUSTMENT
4
12
0.01 F
15
14
13
f
FREQUENCY SET CAP
O
5
80pF
= 5MHz
LOOP FILTER
0.01 F
0.1 F
1kHz
ANALOG OUT
POST
DETECTION
FILTER
SR01032
7
The lock range graph indicates that the +1.0MHz frequency
deviations will be within the lock range for input signal levels greater
than approximately 50mV with zero Pin 2 bias current. (While
strictly this figure is appropriate only for 50MHz, it can be used as a
guide for lock range estimates at other f
The hysteresis was adjusted experimentally via the 10k
potentiometer and 2k bias arrangement to give the waveshape
shown in Figure 12 for 20k, 500k, 2M baud rates with square wave
FSK modulation. Note the magnitude and phase relationships of the
phase comparators’ output voltages with respect to each other and
to the FSK output. The high-frequency sum components of the input
and VCO frequency also are viable as noise on the phase
comparator’s outputs.
OUTLINE OF SETUP PROCEDURE
1. Determine operating frequency of the VCO: IF N in feedback
2. Calculate value of the VCO frequency set capacitor:
3. Set I
4. Check VCO output frequency with digital counter at Pin 9 of
5. Close loop and inject input signal to Pin 6. Monitor Pins 3 and 6
1kHz
MODULATING
INPUT
1kHz
loop, then
f
obtained, this value may be adjusted for best dynamic behavior,
and replace with fixed resistor value of R
device (loop open, VCO to
adj. Pins 4 - 5 for exact center frequency, if needed.
with two-channel scope. Lock should occur with
90
O
C
O
o
= N x f
2
0.47 F
(phase error).
.01 F
(current sinking into Pin 2) for
5V
IN
2200 f
1k
.
1
6
7
3
1
O
16
8
Figure 9. Modulator
10
2
564
1k
2k
11
5V
9
I
2
det.). Adjust C
4
12
MODULATED OUTPUT
15
14
13
f
FREQUENCY SET CAP
O
5
80pF
= 5MHz
O
100 A. After operation is
’ frequencies).
(TTL)
2
=
NE/SE564
O
Product specification
V
trim or frequency
CC
5V
FINE FREQUENCY
ADJUSTMENT
I
B 2
3 - 6
1.3V
equal to
SR01033
.