TDA1572T CNV, ELEKTRONIKA, ELEKTRONIKA MIESZANA
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INTEGRATED CIRCUITS
DATA SHEET
TDA1572T
AM receiver
May 1992
Product specification
File under Integrated Circuits, IC01
Philips Semiconductors
Product specification
AM receiver
TDA1572T
GENERAL DESCRIPTION
Features
The TDA1572T integrated AM receiver circuit performs all
the active functions and part of the filtering required of an
AM radio receiver. It is intended for use in mains-fed home
receivers and car radios. The circuit can be used for
oscillator frequencies up to 50 MHz and can handle RF
signals up to 500 mV.
RF radiation and sensitivity to interference are minimized
by an almost symmetrical design. The controlled-voltage
oscillator provides signals with extremely low distortion
and high spectral purity over the whole frequency range,
even when tuning with variable capacitance diodes. If
required, band switching diodes can easily be applied.
Selectivity is obtained using a block filter before the IF
amplifier.
·
Inputs protected against damage by static discharge
·
Gain-controlled RF stage
Double balanced mixer
·
·
Separately buffered, voltage-controlled and
temperature-compensated oscillator, designed for
simple coils
·
Gain-controlled IF stage with wide AGC range
·
Full-wave, balanced envelope detector
·
Internal generation of AGC voltage with possibility of
second-order filtering
·
Buffered field strength indicator driver with short-circuit
protection
·
AF preamplifier with possibilities for simple AF filtering
·
Electronic standby switch
·
IF output for stereo demodulator and search tuning.
QUICK REFERENCE DATA
SYMBOL
PARAMETER
CONDITIONS
MIN.
TYP.
MAX.
UNIT
V
P
Supply voltage range
7.5
8.5
14.0
V
I
P
Supply current range
V
P
= 8.5 V
15
25
28
mA
RF input voltage (RMS value)
V
iFR(rms)
for (S
+
N)/N = 6 dB
m = 30%
-
1.5
-
m
V
V
iRF(rms)
for THD = 3%
m = 80%
-
500
-
mV
V
oIF(rms)
IF output voltage (RMS value)
V
i
= 2 mV(rms)
180
230
290
mV
AF output voltage (RMS value)
V
i
= 2 mV(rms);
f
i
= 1 MHz; m = 30%;
V
oAF(rms)
f
m
= 400 Hz
240
310
390
mV
AGC range
Change of V
i
for 1 dB
D
V
i
change of V
oAF
-
86
-
dB
Indicator driver (pin 13)
Output voltage
V
i
= 500 mV(rms);
V
o
R
L
= 2.7 k
W
2.5
2.8
3.1
V
PACKAGE OUTLINE
20-lead mini-pack; plastic (SO20; SOT163A); SOT163-1; 1996 August 13.
May 1992
2
(1)
Coil data: TOKO sample no. 7XNS-A7523DY; L1 : N1/N2 = 12/32; Q
o
= 65; Q
B
= 57.
Filter data: Z
F
= 700
W
at R
3-4
= 3 k
W
; Z
I
= 4.8 k
W
.
Fig.1 Block diagram and test circuits (connections shown in broken lines are not part of the test circuits).
Philips Semiconductors
Product specification
AM receiver
TDA1572T
PINNING
1
MXO
mixer output
2
STB
standby switch
3
IFI1
IF input 1
4
IFI2
IF input 2
5
DET
detector
6
AFO1
AF output 1
7
AGC1
AGC stage 1
8
ACG2
AGC stage 2
9
AFO2
AF output 2
10
n.c.
not connected
11
n.c.
not connected
12
IFO
IF output
13
IND
indicator output
14
OSO
buffered oscillator output
15
OSC1
oscillator 1
16
OSC2
oscillator 2
17
V
P
supply voltage
18
RFI1
RF input 1
19
RFI2
RF input 2
Fig.2 Pinning diagram.
20
GND
ground
May 1992
4
Philips Semiconductors
Product specification
AM receiver
TDA1572T
FUNCTIONAL DESCRIPTION
Gain-controlled RF stage and mixer
The differential amplifier in the RF stage employs an AGC negative feedback network to provide a wide dynamic range.
Very good cross-modulation behaviour is achieved by AGC delays at the various signal stages. Large signals are
handled with low distortion and the (S + N)/N ratio of small signals is improved. Low noise working is achieved in the
differential amplifier by using transistors with low base resistance.
A double balanced mixer provides the IF output signal to pin 1.
Oscillator
The differential amplifier oscillator is temperature compensated and is suitable for simple coil connection. The oscillator
is voltage-controlled and has little distortion or spurious radiation. It is specially suitable for electronic tuning using
variable capacitance diodes. Band switching diodes can easily be applied using the stabilized voltage V
15-20
. An extra
buffered oscillator output (pin 14) is available for driving a synthesizer. If this is not needed, resistor R
L(14)
can be omitted.
Gain-controlled IF amplifier
This amplifier comprises two cascaded, variable-gain differential amplifier stages coupled by a band-pass filter.
Both stages are gain-controlled by the AGC negative feedback network. The IF output is available at pin 12.
Detector
The full-wave, balanced envelope detector has very low distortion over a wide dynamic range. Residual IF carrier is
blocked from the signal path by an internal low-pass filter.
AF preamplifier
This stage preamplifies the audio frequency output signal. The amplifier output has an emitter follower with a series
resistor which, together with an external capacitor, yields the required low-pass for AF filtering.
AGC amplifier
The AGC amplifier provides a control voltage which is proportional to the carrier amplitude. Second-order filtering of the
AGC voltage achieves signals with very little distortion, even at low audio frequencies. This method of filtering also gives
fast AGC settling time which is advantageous for electronic search tuning. The AGC settling time can be further reduced
by using capacitors of smaller value in the external filter (C16 and C17). The AGC voltage is fed to the RF and IF stages
via suitable AGC delays. The capacitor at pin 7 can be omitted for low-cost applications.
Field strength indicator output
A buffered voltage source provides a high-level field strength output signal which has good linearity for logarithmic input
signals over the whole dynamic range. If the field strength information is not needed, R
L(13)
can be omitted.
Standby switch
This switch is primarily intended for AM/FM band switching. During standby mode the oscillator, mixer and AF
preamplifier are switched off.
Short-circuit protection
All pins have short-circuit protection to ground.
May 1992
5
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