U4313B Datasheet, PDF (5/14 Pages) TEMIC Semiconductors – Low-Current Superhet Remote Control Receiver

TELEFUNKEN Semiconductors
U4313B
Circuit Description
General functions
The integrated circuit U4313B includes the following
functions: IF-amplifier, FM-demodulator, wake-up
circuit with monoflop, operational-amplifier, inverting
data comparator and voltage-regulator.
The 10.7 MHz IF-signal from the front end passes the
integrated IF-amplifier which operates for amplitude- or
frequency-modulated signals to either a logarithmic AM-
demodulator which was implemented to avoid settling
time problems effected by use of an automatic gain
control system or a quadrature detector for FM. A data
* shaping filter advantageously realized with the inter-
* nal high performance operational-amplifier reduces
system bandwidth to an optimized compromise regarding
transmission distance and data recognition. Thus an opti-
mal bit error rate can be achieved without any further
active component.
The comparator connected to the output of the filter has
a level-dependent hysteresis and clamps its reference
voltage to the signal minimum and maximum peaks as
described later.
* Without IF-input signal in the normal mode only the
IF-amplifier and the AM demodulator which operates as
a level strength indicator are activated. If the level of the
IF signal increases, the whole circuitry is turned on by the
wake-up circuit. This signal is externally available at
pin 10 and can be used to wake up a microcontroller.
After an adjustable reset time, determined by the mono-
flop time constant, the integrated circuit rests down to the
sleep mode. In this case typically 1 mA supply current is
required. An external resistor matched at pin 3 to ground
blocks the wake-up circuit and gives fully function at
lower IF-level as to recognize in figures 24 and 27, but
supply current increases up to typically 2.8 mA.
Function of the clamping comparator
The output signal of the operational amplifier is fed to the
input of the inverting comparator and two peak detectors
(Q1 and Q2, figure 3). Their time constants are distin-
guished by RC+ and RC–. The components value must be
adapted to the transmission code. The time constant
should be large compared to the bit-rate for optimized
noise and hum suppression. To compensate the input tran-
sistors base-emitter-voltage differences these two signals
are buffered by Q3 and Q4. The mean value is used as
comparator threshold, the difference of the peak values
controls the hysteresis. This clamping comparator works
as a data regenerator.
Another version of the IC, with a non-inverting clamping
comparator, is also available (U4311B). Therefore the op-
erational amplifier can be used either as a non-inverting
or an inverting filter without the need of any additional
components.
V_Ref
1
2
3
4
5
6
7
8
95 10214
ÎÎÎÎÎÎ _Inverter
Op. amp.
+–
to pin 16
Comparator
Q1
Q3
Hysteresis
Comp. threshold
Q4
Q2
Rev. A1: 23.06.1995
Figure 3. Principle function of the clamping comparator
5 (14)