TDA9614H Ver la hoja de datos (PDF) - Philips Electronics
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TDA9614H Datasheet PDF : 60 Pages
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Philips Semiconductors
Audio processor for VHS hi-fi
and linear audio
Preliminary specification
TDA9614H
6.1.8 DECODER SELECT (DECODESEL)
The line 2 output is normally connected to a decoder box
or e.g. a second VCR (SCART2). Normally the audio
signal from the output select will be available at this output,
but three extra selections are shown in Table 3.
Table 3 Extra decoder select possibilities
SELECTION
DESCRIPTION
TUNER(1) audio from input TUNER
EXT1(2)
audio from input EXT1
EXT3
audio from input EXT3
Notes
1. Enables the use of a decoder box (connected to line 2
[EXT2]) by the VCR.
2. Decoder box connection to television set
(See Section 6.1.7).
6.1.9 HEADPHONE SELECT (HPSEL)
The headphone output will normally carry the output select
signal, however three more selections are possible and
shown in Table 4.
Table 4 Extra headphone select possibilities
SELECTION
DESCRIPTION
LEFT(1)
left hi-fi channel
RIGHT(1)
right hi-fi channel
NORMAL
linear audio, useful for monitoring the
recording by ‘audio dubbing’
Note
1. The selections LEFT and RIGHT make it possible to
select a different language for the headphone as for
the line outputs. A possible implementation is to invert
always a language selection made at the output select.
6.1.10 HEADPHONE VOLUME
The headphone volume control has a control range of
+16 dB to −47 dB in 1 dB steps and a full mute.
6.1.11 DC SELECT (DCSEL)
The VU meter output is normally connected to the
headphone select, but can also be switched to STEREO
(hi-fi stereo, before the output select). When using the
VU meter output signal to implement a ‘digital AGC’ (read
the level at the DC output, and adjust the VOLUME L/R
controls accordingly) it is necessary to have information of
both hi-fi audio channels, independent from the setting of
output or headphone select. For this mode the selection
STEREO can be made.
6.2 Linear audio circuits
6.2.1 RECORD/LOOP-THROUGH
The signal selected with the normal select can be level
controlled in the AGC block. If wanted this AGC can be
switched off using bit AGCN. The audio signal is thereafter
DC decoupled using a capacitor between pin 29 (LINOUT)
and pin 28 (LININ).
From here on the signal goes to the output select and (in
the event of record mode) to the record equalizer. The
record equalizer is a non-inverting amplifier with a gain of
+12 dB, consisting of an opamp with feedback resistors,
and acts as a pre-correction filter for the tape and head
characteristics. The inverting input of the opamp is
connected to pin 31 (RECEQ), its output to pin 33
(RECOUT). The circuit externally connected between
pin 31 and ground defines the transfer of the record
equalizer with equation: A = 3.98 × -(---1---2----0---Z0-----+-----Z----)-
Where: Z is the complex impedance of the external circuit.
Two equalizings can be used, switching additional circuitry
to ground with pin 30 (EQSW) in long play or extended
play (I2C-bus: LP = 1).
Instead of the hi-fi circuit, linear audio has two
loop-through modes:
• Loop-through playback
• Loop-through record.
The only difference between Loop-through record and
record is the RECOUT output, which is muted.
The LINREC output (pin 32) is used to drive the external
high-voltage switch and possibly the bias oscillator. The
LINREC voltage has a small internal delay to be
non-overlapping with the internal switching to playback
mode. This ensures that no bias voltage will appear at the
PBIN input while the IC is in playback mode.
6.2.2 PLAYBACK
The signal coming from the head is amplified and can be
level controlled in 16 steps of 1 dB. This setting can be
used to adjust for spread or nominal difference in head
output level. Afterwards, the signal is frequency corrected
in the playback equalizer. This equalizer includes the two
standard VHS equalizing settings of 3180 and 120 µs
1995 Mar 21
11
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