1993_Motorola_Linear_Interface_ICs_Vol_2.pdf
1993_Motorola_Linear_Interface_ICs_Vol_2.pdf
1993_Motorola_Linear_Interface_ICs_Vol_2.pdf
Create successful ePaper yourself
Turn your PDF publications into a flip-book with our unique Google optimized e-Paper software.
The control and band information bits have the following<br />
functions:<br />
Bit RO and R1 (See Table 1) Define the reference divider<br />
division ratio. Four ratios are available.<br />
Bit R2 and R3 (See Table 2) Are used to switch internal<br />
signals to the buffer outputs. Pin 11 and 12.<br />
Bit R2, R6 and T (See Table 3) Are used to control the<br />
phase comparator output stage.<br />
Bit P (See Table 6) Switches the prescaler in and out. At<br />
Logic "1' the prescaler is bypassed and the power supply<br />
of the prescaler is switched off.<br />
Bits BO to B7 (See Table 7) Controls the buffers. At logic<br />
"1" the buffers are active (low).<br />
The circuit has two PLL chip addresses. The PLL chip<br />
address is programmable by Pin 8. When Pin 8 is open or<br />
normally used as a buffer the first PLL address is selected<br />
as follows:<br />
MSB LSB<br />
PLL Address 1: 1 1 a a a a 1 0= C2 (octal)<br />
When Pin 8 is at ground the 2nd address is selected.<br />
PLL Address 2: 1 1 a a a 1 1 a = C6 (octal)<br />
Bit B4 must be "zero" when Pin 11 is used to output<br />
62.5 kHz. Bits B4 and B5 have to be "zero" to output Fref<br />
and FBY2. FBY2 is the programmable divider output<br />
frequency divided by two.<br />
The data transfer to the latches (signals OTF and OTB)<br />
is initiated after the 2nd and 4th data bytes. The bus receiver<br />
fulfills the standard 12C bus specifications.<br />
The switching levels of Clock and Data (Pins 15 and 16)<br />
are 0.5 x VCC1.<br />
Table 1<br />
Input Data Reference Divider<br />
RO R1 Division Ratio<br />
0 0 2048<br />
1 0 1024<br />
0 1 512<br />
1 1 256<br />
Table 2<br />
Input Data Test Outputs on Buffers<br />
R2 R3 Pin 11 Pln12<br />
0 0 62.5 kHz -<br />
0 1 FRet FBY2<br />
1 0 - -<br />
1 1 - -<br />
Table 3<br />
Input Data Output Slate<br />
R2 R6 T of the Phase Comparator<br />
0 0 0 Normal Operation<br />
0 0 1 Off (High Impedance)<br />
0 1 0 High<br />
0 1 1 Low<br />
1 0 0 Normal Operation<br />
1 0 1 Off<br />
1 1 0 Normal Operation<br />
1 1 1 Off<br />
MC44810<br />
MOTOROLA LINEAR/INTERFACE <strong>ICs</strong> DEVICE DATA<br />
9-294<br />
Band Buffers - The band buffers are open collector<br />
transistors and are active "low" at Bn = 1. They are designed<br />
for 10 mA with a typical on-resistance of 70 Q. These buffers<br />
are designed to withstand relative high output voltage in the<br />
off-state. (16 V)<br />
B2 and B3 buffers (Pins 11 and 12) may also be used<br />
to output internal IC signals (reference frequency and<br />
programmable divider output frequency + 2) for test purposes.<br />
Buffer B2 may also be used to output a 62.5 kHz frequency<br />
from an intermediate stage of the reference divider. The bit<br />
B2 and/or B3 has to be zero if the buffers are used for these<br />
additional functions.<br />
Buffer BO, Pin 8, is also used to select the chip address.<br />
This buffer has a higher on-voltage than the other buffers.<br />
Programmable Divider - The programmable divider is<br />
a presettable down counter. When it has counted to zero it<br />
takes its required division ratio out of the Latches B. Latches<br />
B are loaded from Latches A by means of signal TDI which<br />
is synchronous to the programmable divider output signal.<br />
Since Latches A receive the data asynchronously with the<br />
programmable divider, this double latch scheme is needed<br />
to assure correct data transfer to the counter.<br />
The division ratio definition is given by:<br />
N = 16384 x N14+8132 x N13 + ... + 4 x N2+2 x N1 + NO<br />
Maximum ratio 32767, minimum ratio 1'7, where NO ... N14 are<br />
the different bits for frequency information.<br />
The counter may be used for any ratio between 17 and<br />
32767 and reloads correctly as long as its output frequency<br />
does not exceed 1.0 MHz.<br />
The data transfer between Latches A and B (signal TOI)<br />
is also initiated by any start condition on the 12C Bus.<br />
At power-on the whole bus receiver is reset and the<br />
programmable divider is set to a counting ratio of N=256<br />
or higher.<br />
Prescaler - The prescaler has a preamp and may be<br />
bypassed (Bit Pl. The signal then passes through preamp<br />
2. Table 6 shows the frequency ranges which may be<br />
synthesized with and without prescaler.<br />
Phase Comparator - The phase comparator is phase<br />
and frequency sensitive and has very low output leakage<br />
current in the high impedance state.<br />
Operational Amplifier - The operational amplifier for the<br />
tuning voltage is designed for very low nOise, low input bias<br />
current and high power supply rejection. The positive input<br />
is biased internally. The op amp needs 32 V supply (VCC2)<br />
as minimum voltage for a guaranteed maximum tuning voltage<br />
of 28 V.<br />
Figure 4 shows a possible filter arrangement. The<br />
component values depend very much on the application<br />
(tuner characteristic, reference frequency, etc.).<br />
As a starting point for optimization, the component values<br />
in Figure 4 may be used for 7.8125 kHz reference frequency<br />
in a multiband TV tuner.<br />
Oscillator - The oscillator uses a 4.0 MHz crystal tied<br />
to ground through a capacitor, used in the series resonance<br />
mode. The voltage at Pin 17 "crystal" has low amplitude and<br />
low harmonic distortion.