U2514B Datasheet, PDF (8/15 Pages) TEMIC Semiconductors – AM/FM Receiver for Digital Tuning with FM-Stereo Decoder

U2514B
Functional Description
FM
The antenna signal is fed via a tuned RF-circuit to the
integrated pre-stage which consists of a transistor
grounded base circuit. To protect the prestage against
overload, an automatic gain control (AGC) is included on
the chip. Additional there is the possibility to extend the
AGC control range by use of an external pin diode. For
economic applications a hybrid-band pass filter can be
used instead of a tuned RF-circuit.
A tuned RF circuit on the collector is necessary for
amplifying and filtering of the FM signal which is fed
internally to the mixer. It consists of a double balanced
Gilbert Cell.
The LO signal is generated by an integrated oscillator.
The buffered LO signal is used to drive a PLL. The
IF-signal (10.7 MHz) is coupled out at the mixers output
and fed via a ceramic filter to the demodulator. The
demodulated AF signal is available at MPXOUT.
AM
The antenna signal is fed directly to the mixer. In order to
ensure the level control which is necessary in the case of
W ^{large signals, the generator resistance has to be higher}
than 25 k . The LO signal is generated by an integrated
oscillator. The buffered LO signal is used to drive the
PLL. If the AM-search mode is required, the IF must be
455 kHz. The IF output signal is fed via a ceramic filter
to the demodulator. The demodulated AF signal is
available at MPXOUT.
CTRLA
By applying a control voltage at pin CTRLA the mode of
the receiver can be selected.
Search Mode
The search-mode is selected by applying a control voltage
less than 0.7 V at pin CTRLA.
50
40
30
20
10
0
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8
12591
V_CTRLA ( V )
Figure 24.
The search sensitivity can be chosen by varying of the
control voltage in the range of 0 to 0.7 V. If the control
voltage is 0 V, the highest sensitivity is achieved.
Reception Mode
In the reception-mode there is a possibility for muting by
varying the control voltage in the range of 1.3 to 0.8 V. If
the control voltage is 0.8 V, the highest mute depth is
achieved.
10
Mode
12593
0
–10
–20
Reception
–30
Mute
–40
Search
0.8 V
1.3 V
Figure 23.
V_CTRLA
V_Ref
–50
0
12690
0.4 0.8 1.2 1.6 2.0
V_CTRLA ( V )
Figure 25.
8 (15)
TELEFUNKEN Semiconductors
Preliminary Information
Rev. A2, 04-Nov-96