參數(shù)資料
型號: MC145202F
廠商: MOTOROLA INC
元件分類: XO, clock
英文描述: Low-Voltage 2.0 GHz PLL Frequency Synthesizer
中文描述: PLL FREQUENCY SYNTHESIZER, 2000 MHz, PDSO20
封裝: SOG-20
文件頁數(shù): 10/24頁
文件大?。?/td> 343K
代理商: MC145202F
MC145202
10
MOTOROLA
OUTPUT A
Configurable Digital Output (Pin 16)
OUTPUT A is selectable as fR, fV, Data Out, or Port. Bits
A22 and A23 in the A register control the selection; see
Figure 15.
If A23 = A22 = high, OUTPUT A is configured as fR. This
signal is the buffered output of the 13–stage R counter. The
fR signal appears as normally low and pulses high. The fR
signal can be used to verify the divide ratio of the R counter.
This ratio extends from 5 to 8191 and is determined by the
binary value loaded into bits R0–R12 in the R register. Also,
direct access to the phase detectors via the REFin pin is al-
lowed by choosing a divide value of 1 (see Figure 16). The
maximum frequency at which the phase detectors operate is
2 MHz. Therefore, the frequency of fR should not exceed
2 MHz.
If A23 = high and A22 = low, OUTPUT A is configured as
fV. This signal is the buffered output of the 12–stage N
counter. The fV signal appears as normally low and pulses
high. The fV signal can be used to verify the operation of the
prescaler, A counter, and N counter. The divide ratio between
the fin input and the fV signal is N
×
64 + A. N is the divide
ratio of the N counter and A is the divide ratio of the A
counter. These ratios are determined by bits loaded into the
A register. See Figure 15. The maximum frequency at which
the phase detectors operate is 2 MHz. Therefore, the fre-
quency of fV should not exceed 2 MHz.
If A23 = low and A22 = high, OUTPUT A is configured as
Data Out. This signal is the serial output of the 24–1/2–stage
shift register. The bit stream is shifted out on the high–to–low
transition of the CLK input. Upon power up, OUTPUT A is
automatically configured as Data Out to facilitate cascading
devices.
If A23 = A22 = low, OUTPUT A is configured as Port. This
signal is a general–purpose digital output which may be used
as an MCU port expander. This signal is low when the Port
bit (C1) of the C register is low, and high when the Port bit is
high.
OUTPUT B
Open–Drain Digital Output (Pin 15)
This signal is a general–purpose digital output which may
be used as an MCU port expander. This signal is low when
the Out B bit (C0) of the C register is low. When the Out B bit
is high, OUTPUT B assumes the high–impedance state.
OUTPUT B may be pulled up through an external resistor or
active circuitry to any voltage less than or equal to the poten-
tial of the VPD pin.
Note
: the maximum voltage allowed on
the VPD pin is 5.5 V.
Upon power–up, power–on reset circuitry forces OUTPUT
B to a low level.
REFERENCE PINS
REFin and REFout
Reference Input and Reference Output (Pins 20 and 1)
Configurable pins for a Crystal or an External Reference.
This pair of pins can be configured in one of two modes: the
crystal mode or the reference mode. Bits R13, R14, and R15
in the R register control the modes as shown in Figure 16.
In crystal mode, these pins form a reference oscillator
when connected to terminals of an external parallel–reso-
nant crystal. Frequency–setting capacitors of appropriate
values, as recommended by the crystal supplier, are con-
nected from each of the two pins to ground (up to a maximum
of 30 pF each, including stray capacitance). An external re-
sistor of 1 M
to 15 M
is connected directly across the pins
to ensure linear operation of the amplifier. The required con-
nections for the components are shown in Figure 9.
To turn on the oscillator, bits R15, R14, and R13 must have
an octal value of one (001 in binary, respectively). This is the
active–crystal mode shown in Figure 16. In this mode, the
crystal oscillator runs and the R Counter divides the crystal
frequency, unless the part is in standby. If the part is placed in
standby via the C register, the oscillator runs, but the R
counter is stopped. However, if bits R15 to R13 have a value
of 0, the oscillator is stopped, which saves additional power.
This is the shut–down crystal mode (shown in Figure 16) and
can be engaged whether in standby or not.
In the reference mode, REFin (Pin 20) accepts a signal
from an external reference oscillator, such as a TCXO. A sig-
nal swinging from at least the VIL to VIH levels listed in the
Electrical Characteristics table may be directly coupled to the
pin. If the signal is less than this level, ac coupling must be
used as shown in Figure 8. Due to an on–board resistor
which is engaged in the reference modes, an external bias-
ing resistor tied between REFin and REFout is not required.
With the reference mode, the REFout pin is configured as
the output of a divider. As an example, if bits R15, R14, and
R13 have an octal value of seven, the frequency at REFout is
the REFin frequency divided by 16. In addition, Figure 16
shows how to obtain ratios of eight, four, and two. A ratio of
one–to–one can be obtained with an octal value of three.
Upon power up, a ratio of eight is automatically initialized.
The maximum frequency capability of the REFout pin is listed
in the Loop Specifications table for an output swing of
1 V p–p and 20 pF loads. Therefore, for higher REFin fre-
quencies, the one–to–one ratio may not be used for this
magnitude of signal swing and loading requirements. Like-
wise, for REFin frequencies above two times the highest
rated frequency, the ratio must be more than two.
The output has a special on–board driver that has slew–
rate control. This feature minimizes interference in the ap-
plication.
If REFout is unused, an octal value of two should be used
for R15, R14, and R13 and the REFout pin should be floated.
A value of two allows REFin to be functional while disabling
REFout, which minimizes dynamic power consumption.
LOOP PINS
fin and fin
Frequency Inputs (Pins 11 and 10)
These pins are frequency inputs from the VCO. These pins
feed the on–board RF amplifier which drives the 64/65 pre-
scaler. These inputs may be fed differentially. However, they
are usually used in a single–ended configuration (shown in
Figure 7). Note that fin is driven while fin must be tied to
ground via a capacitor.
Motorola does not recommend driving fin while terminating
fin because this configuration is not tested for sensitivity. The
sensitivity is dependent on the frequency as shown in the
Loop Specifications table.
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