Philips TDA8340 Service Manual

INTEGRATED CIRCUITS

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TDA8340 TDA8341

Television IF amplifier and demodulator

Product speciﬁcation File under Integrated Circuits, IC02

November 1987

Philips Semiconductors Product speciﬁcation

Television IF ampliﬁer and demodulator

DESCRIPTION

The TDA8340;Q and TDA8341;Q are integrated IF amplifier and demodulator circuits for colour or black/white television receivers, the TDA8340;Q is for application with n-p-n tuners and the TDA8341;Q for p-n-p tuners.

The TDA8340;Q and TDA8341;Q are pin-compatible successors with improved performance to types TDA2540/2541;Q and TDA3540/3541;Q.

TDA8340 TDA8341

Features

• Full range gain-controlled wide-band IF amplifier

• Linear synchronous demodulator with excellent

intermodulation performance

• White spot inverter

• Wide-band video amplifier with noise protection

• AFC circuit with AFC on/off switching and

sample-and-hold function

• Low impedance AFC output

• AGC circuit with noise gating

• Tuner AGC output for n-p-n tuners (TDA8340) or p-n-p

tuners (TDA8341)

• External video switch for switching-off the video output

• Reduced sensitivity for high sound carriers

• Integrated filter to limit second harmonic IF signals

• Wide supply voltage range

• Requires few external components

QUICK REFERENCE DATA

PARAMETER CONDITIONS SYMBOL MIN. TYP. MAX. UNIT

Supply voltage (pin 11) V Supply current (pin 11) I

CC=V11-13

9,4 12 13,2 V 30 42 55 mA

IF input sensitivity

(r.m.s. value) V

IF gain control range G

1-16(rms)

20 40 80 µV

− 67 − dB

Video output voltage white signal;

(peak-to-peak value) 10% top sync V

Signal-to-noise ratio V

= 10 mV S/(S+N) 50 58 − dB

12−13(p−p)

2,4 2,7 3,0 V

AFC output voltage swing

(peak-to-peak value) V

5-13(p-p)

− 10 − V

PACKAGE OUTLINES

TDA8340; TDA8341: 16-lead DIL; plastic (SOT38); SOT38-1; 1996 november 29.

November 1987 2

Philips Semiconductors Product speciﬁcation

Television IF ampliﬁer and demodulator

TDA8340 TDA8341

November 1987 3

Fig.1 Block diagram.

Philips Semiconductors Product speciﬁcation

Television IF ampliﬁer and demodulator

PINNING

1 and 16 Balanced IF inputs 2 and 15 IF ampliﬁer decoupling 3 Tuner AGC starting point adjustment 4 Tuner AGC output 5 AFC output 6 AFC on/off switch and sample-and-hold capacitor 7 and 10 Reference carrier π/2 rad. phase shift 8 and 9 IF picture carrier passive regeneration 11 Positive supply voltage (V 12 Video output 13 Ground (V 14 IF AGC capacitor and VCR switch

FUNCTIONAL DESCRIPTION IF ampliﬁer

)

TDA8340 TDA8341

This is a 3-stage, gain-controlled IF amplifier with a wide dynamic range. On-chip capacitors in the d.c. feedback loop of the amplifier maintain stability at maximum gain. Internal stabilization of the supply voltage ensures the desired sensitivity and gain control range over the whole supply voltage range and also gives very good power supply ripple rejection in this part of the circuit.

Demodulator

The redesigned IF demodulator is a quasi-synchronous circuit that employs passive carrier regeneration and logarithmic clamping to give improved signal handling. The demodulator input is a.c. coupled to the IF amplifier to reduce d.c. offsets and thus minimize residual IF carrier in the output signal.

Video ampliﬁer

The linearity and bandwidth of the video amplifier are sufficient to meet all wide band requirements, e.g. for teletext transmissions. Second harmonics of the IF carrier are effectively reduced by a Sallen-Key low pass interstage filter between the demodulator output and the video amplifier input. An integrated filter in the noise inverter reduces the sensitivity of the video amplifier for high sound carriers.

White spot protection comprises a white spot clamp system combined with a delayed-action inverter which is also highly resistant to high sound carriers.

Note. To prevent radiated video output at the input pins, connect a 6,8 µH inductor in series with pin 12 and fit as close as possible to the IC body. Use short leads.

AGC detector

A Bessel low-pass filter between the video output and the AGC detector improves the detector function in the presence of high sound carriers. No ‘hang-up’ occurs in the detector after pin 14 has been short-circuited to ground (VCR switch operated). The detector also generates the sample-and-hold pulse for the AFC system.

November 1987 4

Philips Semiconductors Product speciﬁcation

Television IF ampliﬁer and demodulator

TDA8340 TDA8341

AGC control circuit

This converts the AGC detector voltage (pin 14) into a current signal which controls the gain of the IF amplifier. It also provides a tuner AGC control output from pin 4, current limiting is incorporated to prevent internal damage. The AGC starting point is adjusted via pin 3.

AFC circuit

The AFC circuit provides a voltage output which controls the IF frequency of the tuner. Video information on the AFC output (pin 5) is eliminated by a sample-and-hold circuit (external capacitor at pin 6). Coupling between the AFC and reference tuned circuits is via two small capacitors (or parasitic capacitance) between the respective tracks of the printed circuit board. If the capacitance is less than 1 pF, the steepness of the AFC characteristic is reduced.

RATINGS

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

PARAMETER SYMBOL MIN. MAX. UNIT

Supply voltage (pin 11) V IF AGC voltage/VCR switch V Tuner AGC voltage V AFC switch voltage V Maximum voltage level with

VCR switch active V DC current at video output I DC current at AFC output I Total power dissipation P Storage temperature range T Operating ambient temperature T

CC=V11−13 14-13 4-13 6-13

12-13 12 5

tot

stg

amb

9,4 13,2 V

− 13,2 V

− 12 V

− 13,2 V

− 5,0 V

− 10 mA

− 1,2 W

−55 +150 °C

−25 +70 °C

November 1987 5

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