MC13055 Datasheet, PDF (7/8 Pages) Motorola, Inc – WIDEBAND FSK RECEIVER

MC13055
GENERAL DESCRIPTION
The MC13055 is an extended frequency range FM IF,
quadrature detector, signal strength detector and data
shaper. It is intended primarily for FSK data systems. The
design is very similar to MC3356 except that the
oscillator/mixer has been removed, and the frequency
capability of the IF has been raised about 2:1. The detector
output configuration has been changed to a balanced,
open–collector type to permit symmetrical drive of the data
shaper (comparator). Meter drive and squelch features have
been retained.
The limiting IF is a high frequency type, capable of being
operated up to 100 MHz. It is expected to be used at 40 MHz
in most cases. The quadrature detector is internally coupled
to the IF, and a 2.0 pF quadrature capacitor is internally
provided. The 20 dB quieting sensitivity is approximately
20 µV, tuned input, and the IF can accept signals up to
220 mVrms without distortion or change of detector
quiescent DC level.
The IF is unusual in that each of the last 5 stages of the
6 stage limiter contains a signal strength sensitive, current
sinking device. These are parallel connected and buffered
to produce a signal strength meter drive which is fairly linear
for IF input signals of 20 µV to 20 mVrms (see Figure 4).
A simple squelch arrangement is provided whereby the
meter current flowing through the meter load resistance flips
a comparator at about 0.8 Vdc above ground. The signal
strength at which this occurs can be adjusted by changing
the meter load resistor. The comparator (+) input and output
are available to permit control of hysteresis. Good positive
action can be obtained for IF input signals of above
20 µVrms. A resistor (R) from Pin 13 to Pin 12 will provide
VCC/R of feedback current. This current can be correlated to
an amount of signal strength hysteresis by using Figure 4.
The squelch is internally connected to the data shaper.
Squelch causes the data shaper to produce a high (VCC)
output.
The data shaper is a complete “ floating” comparator, with
diodes across its inputs. The outputs of the quadrature
detector can be fed directly to either or preferably both inputs
of the comparator to produce a squared output swinging from
VCC to ground in inverted or noninverted form.
MOTOROLA ANALOG IC DEVICE DATA
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