Philips TDA1572T Datasheet

INTEGRATED CIRCUITS

DATA SH EET

TDA1572T

AM receiver

Product speciﬁcation File under Integrated Circuits, IC01

May 1992

Philips Semiconductors Product speciﬁcation

AM receiver TDA1572T

GENERAL DESCRIPTION

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.

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

SYMBOL PARAMETER CONDITIONS MIN. TYP. MAX. UNIT

Supply voltage range 7.5 8.5 14.0 V Supply current range VP = 8.5 V 15 25 28 mA RF input voltage (RMS value)

iFR(rms)

iRF(rms)

oIF(rms)

oAF(rms)

for (S + N)/N = 6 dB m = 30% − 1.5 −µV

for THD = 3% m = 80% − 500 − mV IF output voltage (RMS value) Vi = 2 mV(rms) 180 230 290 mV AF output voltage (RMS value) V

= 2 mV(rms);

= 1 MHz; m = 30%;

fm = 400 Hz 240 310 390 mV

AGC range

for 1 dB

oAF

− 86 − dB

∆V

Change of V

change of V

Indicator driver (pin 13)

Output voltage Vi = 500 mV(rms);

RL= 2.7 kΩ 2.5 2.8 3.1 V

PACKAGE OUTLINE

20-lead mini-pack; plastic (SO20; SOT163A); SOT163-1; 1996 August 13.

May 1992 2

Philips Semiconductors Product speciﬁcation

AM receiver TDA1572T

= 57.

= 65; Q

= 4.8 kΩ.

= 3 kΩ; Z

3-4

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

= 700 Ωat R

Filter data: Z

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

May 1992 3

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

18 RFI1 RF input 1 19 RFI2 RF input 2 20 GND ground

supply voltage

Fig.2 Pinning diagram.

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 buffered oscillator output (pin 14) is available for driving a synthesizer. If this is not needed, resistor R

L(14)

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.

. An extra

15-20

can be omitted.

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

can be omitted.

L(13)

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

Philips Semiconductors Product speciﬁcation

AM receiver TDA1572T

RATINGS

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

SYMBOL PARAMETER MIN. MAX. UNIT

= V

17-20

| Input voltage − 12 V

18-19

; −V

−V

18-19

I

; I20 Input current (pins 18 and 20) − 200 mA

tot

stg

amb

; V

19-20

Supply voltage (pin 17) − 16 V

− 0.6 V

− V

Total power dissipation − 500 mW Storage temperature range −55 +150 °C Operating ambient temperature range −40 +85 °C Junction temperature − +125 °C Electrostatic handling

(1)

all pins except pins 3, 6, 9, 14 −2000 +2000 V pins 3, 6, 14 −1500 +2000 V pin 9 −1000 +2000 V

Note

1. Equivalent to discharging a 100 pF capacitor through a 1.5 kΩ series resistor; (5 pulses, both polarities).

THERMAL RESISTANCE

From junction to ambient (in free air) R

th j-a (max.)

= 95 K/W

May 1992 6

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