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U2514B
AM/FM Receiver for Digital Tuning with FM-Stereo Decoder
Description
The U2514B is an integrated bipolar radio suitable for
digital tuning systems. It contains a FM front end with
pre-amplifier and FM-stereo decoder as well as a
complete AM receiver and demodulator. Stop-signal
generation is implemented for FM and AM mode. This
circuit is designed for use in small radios, power packs
and multimedia applications
Features
D FM wideband AGC
D LO-buffer for digital tuning
D Integrated stop signal generation with true
AM/ FM discriminators
D Adjustable stop signal sensitivity
D Automatic stereo-mono-blend
D High cut
D Mute function
D Pilot canceller
D Supply voltage range 3 to 12 V
D Package: SSO28
Block Diagram
FMOSCE
FMOSCB
FMRF
653
FMIN
FMAGC
28
2
FM front end
OSCOUT
GNDRF
8
4
AFSM
FMDET
MPXOUT
15 11 25
FM IF +
demodulator
AM FM stop
signal detect
MPXIN
24
Matrix
decoder
+ HCC
Pilot PLL
18
OUTR
19
OUTL
21
LPF
20
CERES
23
CTRLB
1
AMIN
AM front end
AM IF +
demodulator
Control
unit
7 10 12 13
AMOSC
FMIFIN
IFOUT
AMIFIN
17
9 22
26
METER
CTRLA AMFM
AMSADJ
Figure 1.
V Ref
14
VREF
27
VS
GND
16
12305
TELEFUNKEN Semiconductors
Rev. A2, 04-Nov-96
Preliminary Information
1 (15)

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U2514B
Pin Description
AMIN 1
FMAGC 2
FMRF 3
GNDRF 4
FMOSCE 5
FMOSCB 6
AMOSC 7
OSCOUT 8
AMSADJ 9
IFOUT 10
AFSM 11
FMIFIN 12
AMIFIN 13
VREF 14
28 FMIN
27 VS
26 AMFM
25 MPXOUT
24 MPXIN
23 CTRLB
22 CTRLA
21 LPF
20 CERES
19 OUTL
18 OUTR
17 METER
16 GND
15 FMDET
10547
Figure 2. Pinning
Pin Symbol
Function
1 AMIN AM antenna input
2 FMAGC FM-AGC time constant
3 FMRF FM RF tank
4 GNDRF Ground RF
5 FMOSCE FM oscillator emitter
6 FMOSCB FM oscillator basis
7 AMOSC AM oscillator
8 OSCOUT Buffered AM/FM oscillator
output
9 AMSADJ Current-input for AM stop signal
adjust
10 IFOUT AM/FM IF output
11 AFSM AF smoothing voltage
12 FMIFIN FM IF amplifier input
13 AMIFIN AM IF amplifier input
14 VREF Reference voltage
15 FMDET FM discriminator output
16 GND Ground
17 METER Fieldstrength voltage output
18 OUTR AF output right
19 OUTL AF output left
20 CERES Resonator 456 kHz
21 LPF Low pass filter for Pilot-PLL
22 CTRLA Control input for mute, search
mode and search sensitivity
23 CTRLB Control input for forced mono,
control output for stop function
and stereo information
24 MPXIN Stereo decoder MPX input
25 MPXOUT AM/FM MPX output
26 AMFM AM/FM switch and pilot
canceller time constant
27 VS Supply voltage
28 FMIN FM antenna input
Ordering and Package Information
Extended Type Number
U2514B-AFN
U2514B-AFNG3
Package
SSO28
SSO28
Remarks
Taping according to ICE-286-3
2 (15)
TELEFUNKEN Semiconductors
Preliminary Information
Rev. A2, 04-Nov-96

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Pin Description
FMIN, FMAGC, FMRF
U2514B
FMOSCE, FMOSCB
VREF
3 FMRF
MIXER
T1 T2
FMAGC
2
FMOSCB
6
FMOSCE
5
1.2 k
GNDRF
Figure 4.
FMON
12415
FMIN
28
1.5 k
GNDRF
I
AGC
FMON
12414
Figure 3.
The FM local oscillator consists of a transistor in
grounded collector configuration. The negative
resistance at the base of the transistor is generated by an
external capacitor connected between emitter FMOSCE
(Pin 5) and GNDRF (Pin 4) An other external capacitor
is connected between base FMOSCB (Pin 6) and emitter
FMOSCE (Pin 5) which increases the resistance at the
emitter and leads to a higher oscillator swing. The
Wnegative resistance at FMOSCB is approximately 250 .
WTherefore, the resonant LO tank resistance of
approximately 5 k (depends on Q-factor of the coil) is
transformed to this magnitude via a capacitor.
OSCOUT
8 OSCOUT
The FM pre-amplifier input FMIN (Pin 28) consists of a
transistor grounded base circuit (T2) which provides
excellent noise performance and large signal behavior. It
Wis recommended to connect a source impedance of 100
in order to achieve optimal performance. The dc current
through the amplifying transitor is reduced by the internal
AGC. This means in the case of large input signals, the
input ac current is bypassed via the wideband AGC
transistor T1. A capacitor is connected between FMAGC
(Pin 2) and GNDRF (Pin 4). It shortens the transistor base
to GNDRF and it also serves for smoothing of the AGC
voltage. A tuned RF circuit is connected between FMRF
(Pin 3) and VS (Pin 27). The amplified RF signal is fed
internally to the mixer input.
FM AM
Figure 5.
12416
A resistor is connected between OSCOUT (Pin 8) and
VREF (Pin 14). It determines the amplitude of oscillator
voltage which is fed to the PLL circuit. The TEMIC PLL
familiy U428xBM is recommended because it offers high
signal to noise ratio and low current consumption.
TELEFUNKEN Semiconductors
Rev. A2, 04-Nov-96
Preliminary Information
3 (15)

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U2514B
AMIN
AMIN
1
VREF
AMSADJ
12418
9 AMSADJ
GNDRF
I AGC
12417
Figure 8.
GND
Figure 6.
The AM antenna coil is connected between AMIN (Pin 1)
and VREF (Pin 14). In order to ensure that the AGC
Woperates correctly, a coil impedance of approximately 25
k is necessary.
AMOSC
7 AMOSC
The ceramic resonator of the stereo decoder PLL circuit
is used as a stop signal detector for AM signals. For this
purpose, the parallel resonance frequency of the
resonator, which is unloaded about 456 kHz, is reduced
by an internal load capacitor down to 455 kHz. Therefore,
the AM IF must be 455 kHz. The internal loading
capacitor is defined by the current through AMSADJ
(Pin 9) to GND. An external resistor is connected
between AMSADJ (Pin 9) and GND. It allows the
alignment of the stop signal center frequency. The width
of the stop window is typicaly 800 Hz. If AM search-
mode is not activated, the pin is internally pulled to
ground.
VREF
6k
IFOUT
10 IFOUT
AMON
FM AM
12419
Figure 7.
GNDRF
Figure 9.
12420
The AM oscillator has to be loaded by an external tank
referred to VREF (Pin 14). If reduction of the oscillator
voltage is necessary, this may be achieved by a parallel
resistor.
The IF output (IFOUT Pin 10) of both the FM and the AM
mixer has to be loaded into external IF-tank circuits
refered to VREF (Pin 14). Q-factor of IF coils must not be
lower than 50.
4 (15)
TELEFUNKEN Semiconductors
Preliminary Information
Rev. A2, 04-Nov-96

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AMIFIN
3.3 k
13
AMIFIN
VREF
12421
Figure 10.
FMDET
U2514B
VREF
150 mA
Figure 12.
15
FMDET
12422
WThe input impedance of the AM IF amplifier is 3.3 k
according to the required impedance of most ceramic
filters. The input refers to VREF (Pin 14).
The discriminator allows the connection of a ceramic
resonator or LC tank. A minimization of THD and
adjustment of center frequency versus temperature can
only be achieved by using a LC tank. This performs a
temperature independent stop signal.
FMIFIN
AFSM
25 MPXOUT
11 AFSM
40 mA
12
FMIFIN
100 k
12423
GND
Figure 13.
12424
Figure 11.
WThe input impedance of the FM IF amplifier is 330
according to the required impedance of most FM ceramic
filters. The input referes to GND (Pin 16).
A capacitor is connected between AFSM (Pin 11) and
GND for smoothing of the FM-AF. This is necessary to
generate a modulation independent stop signal. (Because
the deviation of the FM signal (75 kHz) can be greater
than the stop signal window (25 kHz)). In the
AM-search-mode, the external capacitor smoothes the
demodulated AM-IF-signal.
TELEFUNKEN Semiconductors
Rev. A2, 04-Nov-96
Preliminary Information
5 (15)