MC44829

8

MOTOROLA ANALOG IC DEVICE DATA

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 k

Ω.