Philips TDA1572 Datasheet

DATA SH EET

Product specification
File under Integrated Circuits, IC01

December 1987

INTEGRATED CIRCUITS

TDA1572

AM receiver circuit

December 1987 2

Philips Semiconductors Product specification

AM receiver circuit TDA1572

GENERAL DESCRIPTION

The TDA1572 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.

Features

• 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

PACKAGE OUTLINE

18-lead DIL; plastic (SOT102); SOT102-1; 1996 August 12.

PARAMETER SYMBOL MIN. TYP. MAX. UNIT

Supply voltage range V

P

7,5 − 18,0 V

Supply current range I

P

15 − 30 mA

RF input voltage

for (S+N)/N = 6 dB at m = 30% V

i(RF)

− 1,5 −µV

RF input voltage for 3% total

harmonic distortion (THD) at m = 80% V

i(RF)

− 500 − mV

IF output voltage with V

i

= 2 mV V

o(IF)

− 230 − mV

AF output voltage with V

i

= 2 mV;

f

i

= 1 MHz; m = 30%; fm = 400 Hz V

o(AF)

− 310 − mV

AGC range: change of V

i

for

1 dB change of V

o(AF)

− 86 − dB

Field strength indicator voltage at V

i

= 500 mV;

R

L(11)

= 2,7 kΩ V

IND

− 2,8 − V

December 1987 3

Philips Semiconductors Product specification

AM receiver circuit TDA1572

Fig.1 Block diagram and test circuit (connections shown in broken lines are not part of the test circuit).

(1) Coil data: TOKO sample no. 7XNS-A7523DY; L1 : N1/N2 = 12/32; Q

o

= 65; Q

B

= 57.

Filter data: Z

F

= 700 Ω at R

3-4

= 3 kΩ; Z

I

= 4,8 kΩ.

(2) AF output is pin 6 is not used.

December 1987 4

Philips Semiconductors Product specification

AM receiver circuit TDA1572

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

13-18

. An extra

buffered oscillator output (pin 12) is available for driving a synthesizer. If this is not needed, resistor R

L(12)

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 10.

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(11)

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.

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Philips Semiconductors Product specification

AM receiver circuit TDA1572

RATINGS

Limiting values in accordance with the Absolute Maximum Rating System (IEC 134)

THERMAL RESISTANCE

PARAMETER SYMBOL MIN. MAX. UNIT

Supply voltage V

P

= V

15-18

− 20 V

Total power dissipation P

tot

− 875 mW

Input voltage V

16-17

−12 V

−V

16-18,−V17-18

− 0,6 V

V

16-18

, V

17-18

− V

P

V

Input current I

16

, I18−200 mA

Operating ambient temperature range T

amb

−40 + 85 °C

Storage temperature range T

stg

−55 + 150 °C

Junction temperature T

j

−+ 125 °C

From junction to ambient R

th j-a

80 K/W

December 1987 6

Philips Semiconductors Product specification

AM receiver circuit TDA1572

CHARACTERISTICS

V

P

= V

15-18

= 8,5 V; T

amb

= 25 °C; fi = 1 MHz; fm = 400 Hz; m = 30%; fIF = 460 kHz; measured in test circuit of Fig.1; all

voltages referenced to ground; unless otherwise specified.

PARAMETER SYMBOL MIN. TYP. MAX. UNIT

Supply

Supply voltage (pin 15) V

P

7,5 8,5 18,0 V

Supply current (pin 15) I

P

15 23 30 mA
RF stage and mixer (pins 16 and 17)
DC input voltage V

I

− VP/2 − V

RF input impedance at V < 300 µVZ

i

−5,5 − kΩ

RF input capacitance C

i

− 25 − pF

RF input impedance at V

I

> 10 mV Z

i

− 8 − kΩ

RF input capacitance C

i

− 22 − pF

IF output impedance (pin 1) Z

o

200 −−kΩ
IF output capacitance C

o

− 6 − pF

Conversion transconductance

before start of AGC I

1/Vi

− 6,5 − mA/V

Maximum IF output voltage, inductive

coupling to pin 1 (peak-to-peak value) V

1-15(p-p)

− 5 − V

DC value of output current;

at V

I

= 0 V (pin 1) I

O

− 1,2 − mA
AGC range of input stage − 30 − dB
RF signal handling capability:

(r.m.s. value): input voltage
for THD = 3% at m = 80% V

i(rms)

− 500 − mV

Oscillator

Frequency range f

osc

0,1 − 60 MHz
Oscillator amplitude (pins 13 to 14) V − 130 150 mV
External load impedance (pins 14 to 13) R

(ext)

0,5 − 200 kΩ
External load impedance for no

oscillation (pins 14 to 13) R

(ext)

−−60 Ω

Ripple rejection at V

P(rms)

= 100 mV;

f

p

= 100 Hz

(SVRR = 20 log [V

15/V13

]) RR − 55 − dB

Source voltage for switching diodes

(6 × V

BE

) (pin 13) V − 4,2 − V

DC output current (for switching

diodes) (pin 13) −I

O

0 − 20 mA
Change of output voltage at

∆l13 = 20 mA (switch to maximum load)
(pin 13) ∆V

I

− 0,3 − V