MC44826D Просмотр технического описания (PDF) - Motorola => Freescale
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MC44826D Datasheet PDF : 8 Pages
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MC44826
Bits B1, B3, B5: Control the Band Buffers
B1, B3, B5 = 0
B0, B1, B3 = 1
Buffer “Off”
Buffer “On”
Bit T8: Controls the Output of the Operational Amplifier
T8 = 0
Normal Operation
Operational Amplifier Active
T8 = 1
Output State of Operational Amplifier Switched “Off”,
Output Pulls High Through the External Pull–Up
Resistor RL
Bits T9, T12: Control the Phase Comparator
T9
T12
Function
1
0
Normal Operation
1
1
High Impedance
0
0
Upper Source “On” Only
0
1
Lower Source “On” Only
Bits T10, T11: Control the Reference Divider
T10
T11
Division Ratio
0
0
512
0
1
1024
1
0
1024
1
1
512
Bit T13: Switches the Internal Signals Fref and FBY2 to
Bit T13: the Band Buffer Outputs (Test)
T13 = 0
T13 = 1
Normal Operation
Test Mode
Fref Output at B3 (Pin 7)
FBY2 Output at B5 (Pin 8)
Bits B3 and B5 have to be “On”, B3 = B5 = 1 in the test mode.
Fref is the reference frequency.
FBY2 is the output frequency of the programmable divider, divided by two.
Bit T14: Controls the Charge Pump Current of the
Bit T14: Phase Comparator
T14 = 0
T13 = 1
Pump Current 40 µA Typical
Normal Operation. Pump Current 125 µA Typical
Bits T6, T7: Mixer/Oscillator Band Decoder
The band decoder provides the band switching signal for
the mixer/oscillator circuit. The buffer bits control the decoder
output. The decoder can be controlled by the buffer bits or
independently by the control bits T6 and T7 as per the tables
below.
T7
T6
Decoder Output DEC
0
0
Decoder Output Controlled by Buffer Bits
B1, B3, B5
0
1
0 to 0.8 V
1
0
1.8 to 2.1 V
1
1
3.4 V to VCC1 (VCC1 = 4.5 to 5.5 V)
B5
B3
B1
0
X
0
0
X
1
1
X
0
1
X
1
BA_Band Information
T7 T6 B5 X
Decoder Output DEC
1.8 to 2.1 V
0 to 0.8 V
3.4 V to VCC1
(VCC1 = 4.5 to 5.5 V)
Undefined
B3 X B1 X ACK
The band buffers are open collector buffers and are active
“low” at Bn = 1. They are designed for 15 mA with a typical
“On” voltage of 200 mV. These buffers are designed to
withstand relative high output voltage in the “Off” state.
B3 and B5 buffers may also be used to output internal IC
signals (reference frequency and programmable divider
output frequency divided by 2) for test purposes.
The bit B3 and/or B5 have to be one if the buffers are used
for these additional functions.
The Programmable Divider
The programmable divider is a presettable down counter.
When it has counted to zero it takes its required division ratio
out of the latches B. Latches B are loaded from latches A by
means of signal TDI which is synchronous to the
programmable divider output signal.
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 + 8192 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 6 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.
MOTOROLA ANALOG IC DEVICE DATA
7
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