tea5705 STMicroelectronics, tea5705 Datasheet - Page 2

• Manufacturer Part Number: tea5705
• Description: Advanced 4-head Play-back And Record Amplifier For Vcr
• Manufacturer: STMicroelectronics

TEA5705
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
output level of 200mV
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
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PP
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at 3.8MHz signal.
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Detector
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Detector
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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
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.
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3% transconductanceaccuracy is guar-
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TRIVADJ
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