U2514B Datasheet, PDF (6/15 Pages) TEMIC Semiconductors – AM/FM Receiver for Digital Tuning with FM-Stereo Decoder

U2514B
METER
VREF
FM
AM
CTRLB
VS
12425
30 k
23
1.2 V
CTRLB
17 METER
GND
Figure 14.
This pin is driven by a current corresponding to the level
W ^{of the FM or AM-IF-signal. The required external load}
consists of a resistor (100 to 150 k ) in parallel with an
m external capacitor (e.g., 10 F necessary to achieve a
good THD in AM mode and to supress AF influence in
FM mode). The voltage at this pin controls the high cut
and mono/ stereo blend function in the case of reception
mode. These functions can be affected by the designer by
choosing different values of the load resistor.
CTRLA
22
12447
Figure 16.
The signal at the output CTRLB (Pin 23) shows stereo or
mono reception. The stereo reception is indicated if the
voltage is higher than 1.2 V, otherwise it is mono.
Furthermore there is the possibility to force the receiver
circuit to mono by applying an external control voltage
<0.8 V at CTRLB. If the search mode is selected, the low
active stop signal appears at CTRLB. If the output
CTRLB is connected directly to the I/O-port of the micro-
controller, the high level of CTRLB has to be adapted by
connecting a resistor between CTRLB and GND.
VREF
A internal voltage regulator generates a stable reference
voltage of 2.4 V which is needed for all function blocks
of the IC. An external capacitor has to be connected to
GND in order to achieve stability and noise suppression.
AMFM
CTRLA
12448
GND
Figure 15.
The reception mode, search mode, as well as mute
function and search sensitivity can be selected by
applying a control voltage at CTRLA (Pin 22). If the
control voltage is higher than 0.8 V, the receiver circuit
is in the reception mode, otherwise it is in search mode.
When reducing the control voltage between 1.3 and 0.8 V,
the AF level output at OUTR, OUTL (Pin 18, 19) is
reduced (mute function). In the search mode (0.7 to 0 V),
the voltage size determines the degree of the search
sensitivity.
26
AMFM
12454
Figure 17.
By applying a low voltage (<1.1 V) at AMFM (Pin 26),
the receiver circuit is switched to AM mode. If Pin
AMFM is open, the FM mode is selected. This switching
function can easily be performed by a microcontroller
with “open drain” I/O-ports. A capacitor has to be
connected between AMFM and GND for FM mode
operation. It serves for smoothing the control voltage of
the pilot canceller.
6 (15)
TELEFUNKEN Semiconductors
Preliminary Information
Rev. A2, 04-Nov-96