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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)