TDA9614H datasheet(11/60 Pages) PHILIPS

11 / 60 page

1995 Mar 21

Philips Semiconductors

Preliminary speciﬁcation

Audio processor for VHS hi-ﬁ

and linear audio

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

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

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

SELECTION

DESCRIPTION

TUNER(1)

audio from input TUNER

EXT1(2)

audio from input EXT1

EXT3

audio from input EXT3

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’

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:

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

3.98

1200

(

)

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