MC44829 Datasheet, PDF (8/10 Pages) Motorola, Inc – TV AND VCR I2C PLL TUNING CIRCUIT WITH 1.3 GHz PRESCALER AND MIX/OSC DECODER

MC44829
Since latches A receive the data asynchronously with the
programmable divider, this double latch scheme is needed to
assure correct data transfer to the counter.
The division ratio definition is given by:
N = 16384 x N14 + 8132 x N13 + … + 4 x N2 + 2 x N1 + N0
Maximum Ratio 32767
Minimum Ratio 256
Where N0 … N14 are the different bits for frequency
information.
The counter may be used for any ratio between 256 and
32767 and reloads correctly as long as its output frequency
does not exceed 1.0 MHz.
The data transfer between latches A and B (signal TDI) is
also initiated by any start condition on the I2C bus.
At power “on” the whole bus receiver is reset and the bit N8
of the programmable divider is set to N8 = 1. Thus the
programmable divider starts with a division ratio of 256 or
higher.
The first I2C message must be sent only when the
POWER ON RESET is completed. Division ratios of N < 256
are not allowed.
The Prescaler
The prescaler has a preamplifier which guarantees high
input sensitivity.
The Phase Comparator
The phase comparator is phase and frequency sensitive
and has very low output leakage current in the high
impedance state.
The Tuning Voltage Amplifier
The amplifier is designed for very low noise, low input bias
current and high power supply rejection. The positive input is
biased internally. The tuning voltage amplifier needs an
external pull–up resistor to generate the tuning voltage.
The amplifier can be switched “off” through bit T8. When bit
T8 is “One”, the amplifier is “Off”. The tuning voltage is then
pulled high by the external pull–up resistor.
Figure NO TAG shows a possible filter arrangement. The
component values depend very much on the application
(tuner characteristic, reference frequency, etc.).
The Oscillator
The oscillator uses a 3.2 or 4.0 MHz crystal tied to ground in
series with a capacitor. The crystal operates in its series
resonance mode.
The voltage at Pin 13, has low amplitude and low
harmonic distortion.
The negative impedance of the crystal input (Pin 13) is
about 3.0 kΩ.
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