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Detector

Detector

TRIVADJ

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BLOCK DIAGRAM

FUNCTIONAL DESCRIPTION

TEA5705 is intended for 4 heads VCR applications.

It includes all the electrical functions necessary to

achieve play-back and record processing for VHS

and S-VHS applications (10MHz bandwidth).

High performance technologyallows very low noise

levels (current and voltage), which are frequency

independant in all the frequency range. In play-

back mode a special feature suppresses the DC

offset when switching two channels. Optimized

play-back output stage gives to the TEA5705 large

capability to drive directly a coaxial cable in order

to reduce number of external components.

Two play-back outputs are availabe : one, dedi-

cated to Chroma processing, is a 60dB voltage

amplifier output, the other, dedicatedto Luma proc-

essing, is phase opposite signal with a constant AC

A tracking information for video signal (TRIV) is

Luma amplitude proportional and allows automatic

phase correction. The transfer function has a gain

of 2.5dB higher when a LP channel is selected.

Adding to this, a gain control bloc allows to modify

the gain (

± 6dB) of the TRIV function for all the

channels by applying a bias on pin TRIVADJ.

An automatic scanning of record supply voltage

permits TEA5705 automatically switching either in

play-back or in record mode. The switching thresh-

old voltage is fixed to a value which forbids high

current peaking through the heads.

During play-back mode, record output is grounded

via an internal transistor and during record mode

preamplifiers are turned off.

There is one output current for two recording

heads, the DC current and the AC characteristics

can be very precisely controlled with accurate ex-

ternal resistors. If recommended resistances are

used, a

± 3% transconductanceaccuracy is guar-

anteed. Feedback loop gains of SP channel and LP

channel can be different.

A particular feature is the SP/LP envelope compa-

rator and detector. This system can be used in

search mode, still mode, slow mode... The output

signal is an output current feeding a capacitor

(CSPLP) which is bufferised through a schmidt

trigger circuit to VSPLP. This output is high in record

mode. By varying the capacitance on CSPLP a

good compromise can be found between short

delay time and spike free signal.

TEA5705 is fully protected against ESD.

TEA5705

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