Philips tda3842 DATASHEETS

INTEGRATED CIRCUITS

DATA SH EET

TDA3842

Multistandard TV IF amplifier and demodulator with TV signal identification

Preliminary speciﬁcation File under Integrated Circuits, IC02

April 1991

Philips Semiconductors Preliminary speciﬁcation

Multistandard TV IF ampliﬁer and

TDA3842

demodulator with TV signal identiﬁcation

FEATURES

• Low supply voltage range, from 5.0 V to 8.0 V

• Low power dissipation, 200 mW at 5 V

• High supply ripple rejection

• Wide IF bandwidth of 80 MHz

• Synchronous demodulator with low differential phase

and gain

• Additional video buffer with a wide bandwidth of 10 MHz

• Video off switch

• Peak sync AGC for negative modulation, e.g. B/G

• Peak white AGC for positive modulation, e.g. L

QUICK REFERENCE DATA

SYMBOL PARAMETER CONDITIONS MIN. TYP. MAX. UNIT

1-20(rms)

supply voltage range (pin 15) 4.75 5.0 8.8 V supply current (pin 15) VP= 5.0 V − 42 − mA IF input signal for nominal video output

voltage at pin 14 (RMS value) minimum IF input signal for TV signal

identiﬁcation at pin 6 (RMS value)

video output signal (pin 12) buffered − 2.0 − V

IF voltage gain control range − 66 − dB S/N signal-to-noise ratio V V S

8 AFC

AFC output voltage swing − 4.0 − V

AFC steepness (pin 8) − 2 −µA/kHz RR supply voltage ripple rejection (pin 12) 30 35 − dB

• Adjustable take-over point (TOP); positive AGC slope

• Switching to fast AGC dependent on TV identification

• Alignment free AFC detector with integrated phase shift

• ESD protection

• TV signal identification

• Options: tracking of reference circuit, suitable for

MAC-on-cable

GENERAL DESCRIPTION

The TDA3842 is a bipolar integrated circuit for vision IF-signal processing in multistandard TV and VTRs, designed for a supply voltage range from 5.0 V to 8.0 V.

f = 38.9 MHz − 70 −µV

maximum G

=10mV 55 60 − dB

1-20

− 20 40 µV

ORDERING INFORMATION

EXTENDED

TYPE NUMBER

TDA3842 20 DIL plastic SOT146 TDA3842T 20 mini-pack plastic SO20L; SOT163A

Notes

1. SOT146-1; 1997 January 08.

2. SOT163-1; 1997 January 08

April 1991 2

PACKAGE

PINS PIN POSITION MATERIAL CODE

(1)

(2)

Philips Semiconductors Preliminary speciﬁcation

Multistandard TV IF ampliﬁer and demodulator with TV signal identiﬁcation

TDA3842

PIN CONFIGURATION

Fig.2 Pin configuration.

Fig.1 Block diagram.

PINNING

SYMBOL PIN DESCRIPTION

I IF

TOP v

SYNC

IDENT

TV C

AFC

TV L

REF

O BUF

STAB

ADJ

IDENT

SEL

1 IF input (balanced) 2 tuner AGC take-over point adjustment 3 black level voltage 4 sync pulse amplitude voltage 5 identiﬁcation capacitor 6 video identiﬁcation output 7 AFC capacitor 8 AFC output signal 9 video standard selection switch 10 LC reference tuned circuit 11 LC reference tuned circuit 12 buffered video output signal 13 video input signal for buffer 14 video output signal with intercarrier signal 15 supply voltage

16 supply voltage stabilization GND 17 ground C

AGC

O AGC

I IF

18 AGC capacitor

19 tuner AGC output signal

20 IF input (balanced)

April 1991 3

Philips Semiconductors Preliminary speciﬁcation

Multistandard TV IF ampliﬁer and demodulator with TV signal identiﬁcation

FUNCTIONAL DESCRIPTION

The complete circuit consists of the following functional blocks as shown in Fig.1:

1. 3-stage gain controlled IF ampliﬁer

2. Overload detector

3. Reference ampliﬁer

4. Carrier signal reference limiter

5. Video demodulator

6. Video ampliﬁer

7. Video buffer ampliﬁer

8. AGC detector

9. IF and tuner AGC (with adjustable TOP)

10. Sync pulse separator

11. Video identiﬁcation

12. 90°phase shift and AFC demodulator

13. AFC gating, AFC ampliﬁer and AFC switch

14. Voltage stabilizer

15. Standard switch

1. 3-stage gain controlled IF ampliﬁer (pins 1 and 20)

The vision IF amplifier consists of three AC-coupled differential amplifier stages. Gain control is achieved by current divider stages. The emitter feedback resistors are optimized for low noise and signal handling capability.

2. Overload detector

The overload detector is fed from the output of the third IF amplifier. As soon as the IF voltage exceeds the overload threshold in the detector, its output current reduces the IF amplification by discharging the AGC capacitor.

3. Reference ampliﬁer

For passive video carrier regeneration an integrated differential amplifier with resistive load allows

capacitive coupling of the resonant circuit for notch and tracking functions.

4. Carrier signal reference limiter

A limiter stage after the reference amplifier eliminates amplitude modulation. Its output is fed to the video demodulator.

5. Video demodulator

The video demodulator receives both the limited reference carrier signal and the IF signal. The video signal polarity is switched according to the TV standard selected. The video signal can also be switched off.

6. Video ampliﬁer

The video amplifier is an operational amplifier with internal feedback and wide bandwidth. The DC level is shifted according to the TV standard to provide the same sync level for positive and negative IF modulation.

7. Video buffer ampliﬁer

The video buffer amplifier is an operational amplifier with internal feedback, wide bandwidth and frequency compensation; gain and input impedance are adapted to operate with a ceramic sound trap. The load for the sound trap is an integrated resistive divider.

8. AGC detector

With negative modulation

peak sync AGC detector generates a fast current pulse to discharge the AGC capacitor (gain reduction). This minimizes the video signal distortion.

Positive modulation

white AGC detector. To filter out the sound carrier the

video signal is fed through low pass filters. After the low pass filters the video signal with attenuated sound carrier, is fed to the AGC detector.

(B/G) a

(L) uses a peak

TDA3842

The charging current of the AGC capacitor is optimized for minimum distortion of the video signal. With positive modulation the charging current is very low and consequently the AGC time constant is large. When the video identification circuit does not detect a video signal, the charging current is increased.

9. IF and tuner AGC

The voltage on the AGC capacitor is used to control the gain of the three IF amplifier stages and to supply the tuner AGC current (open-collector). The tuner AGC TOP potentiometer at pin 2 adjusts the IF signal level from the tuner. To stabilize the IF output voltage of the tuner, IF slip (= variation of IF gain over the total tuner range) is kept at a minimum.

10. Sync pulse separator

The sync pulse separator supplies two internally-used pulses using the bandwidth limited video signal. These are the composite sync for the AFC detector and the vertical sync for the video identification output. The bandwidth is limited to reduce the noise and increase the ident sensitivity.

11. Video identiﬁcation

An analog integrator monitors the duty cycle of the vertical sync pulses to identify the video signal. The integrator output is fed to a window comparator which has an open collector output stage to provide the video ident signal. The complete circuit operates in combination with the sync separator and is optimized for high sensitivity.

12. 90° phase shift and AFC demodulator

The AFC demodulator needs a 90° phase-shifted carrier. The output of the carrier signal reference limiter is

April 1991 4

Philips Semiconductors Preliminary speciﬁcation

Multistandard TV IF ampliﬁer and demodulator with TV signal identiﬁcation

fed to an active 90° phase-shift circuit. The 90° (lead) phase-shifted carrier and the IF signal are fed to the AFC demodulator. The demodulated signal is fed to the AFC gating stage.

13. AFC gating, AFC ampliﬁer and AFC switch

With negative modulated video IF signals the output of the AFC detector is gated by composite sync pulses to prevent video modulation on the AFC

output. The gated signal is integrated by an AFC capacitor. The AFC amplifier converts the capacitor voltage to an AFC current (open collector sink/source output). At positive modulation the AFC operates continuously. AFC function can be externally switched off for test purposes. For high-performance signal handling the AFC signal can be used to track the resonant circuit as shown in Fig.11.

TDA3842

14. Voltage stabilizer

An integrated bandgap voltage stabilizer generates an internal supply voltage of 4 V. A decoupling capacitor reduces noise and supply voltage ripple.

15. Standard switch

The operating mode of the AGC detector and video IF demodulator for positive and negative IF modulation is selected by the logic level on pin 9.

April 1991 5

Fig.3 Internal circuits.

Philips Semiconductors Preliminary speciﬁcation

Multistandard TV IF ampliﬁer and

TDA3842

demodulator with TV signal identiﬁcation

LIMITING VALUES

In accordance with the Absolute Maximum System (IEC 134)

SYMBOL PARAMETER MIN. MAX. UNIT

stg

amb

ESD

CHARACTERISTICS

= 5 V and T

Fig.4.; unless otherwise speciﬁed.

SYMBOL PARAMETER CONDITIONS MIN. TYP. MAX. UNIT

RR ripple rejection (pin 12) 30 35 − dB

supply voltage at pin 15: SOT146 − 8.8 V

SOT163A − 6.0 V tuner AGC voltage − 13.2 V permissible voltage at AFC output − V

V supply current − 55 mA storage temperature range −25 + 150 °C operating ambient temperature range 0 + 70 °C ESD sensitivity −±300 V

=25°C; fVC= 38.9 MHz; all voltages are measured to GND (pin 17); measured in test circuit of

amb

supply voltage range (pin 15) DIL-package 4.75 5.0 8.8 V

SO-package 4.75 5.0 6.0 V

supply current (pin 15) VP= 5.0 V − 42 − mA

IF ampliﬁer

B bandwidth −3dB − 80 − MHz R

1-20(rms)

input resistance (pins 1 and 20) − 2 − kΩ input capacitance (pins 1 and 20) − 1.5 − pF IF input signal (RMS value) video output −1dB − 70 −µV maximum IF input signal minimum G

; note 1 100 −−mV

gain control range 63 66 − dB

IF AGC: negative modulation

leakage current AGC capacitor −−1µA charging current AGC capacitor with video identiﬁcation − 13 −µA charging current AGC capacitor without video identiﬁcation − 35 −µA

18M

discharging peak current capacitor − 2 − mA response time of IF input signal

change

50 dB increasing step − 1 − ms

50 dB decreasing step − 150 − ms IF AGC: standard L (note 2) I

leakage current AGC capacitor −−20 nA charging current AGC capacitor with video identiﬁcation − 280 − nA

without video identiﬁcation − 22 −µA I

18M

discharging peak current capacitor − 2 − mA response time of IF input signal

change

50 dB increasing step − 1 − ms

50 dB decreasing step − 300 − ms

April 1991 6

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