STV0056AF datasheet(5/27 Pages) STMICROELECTRONICS

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PIN DESCRIPTION (continued)

2 - Baseband Audio Processing

PK OUT L, PK OUT R, PK OUT

The noise reduction control loop peak detector

output requires a capacitor to ground from this pin,

and a resistor to VREF pin to give some accurate

decaytime constant.An on chip5k

Ω ±25 % resistor

and external capacitor give the attack time.

PK IN L, PK IN R or PK IN

Each of thesepins is an input to a control loop peak

detector and is connected to the output of the

offchip control loop band pass filter.

LEVEL L, LEVEL R

Respectively the audio left and right signals of the

FM demodulators are output to level L and level R

pins through an input follower buffer. The off-chip

filters driven by these pins must include AC cou-

pling to the next stage (PK IN L and PK IN R pins

respectively).

FC L, FC R

The variable bandwidth transconductance ampli-

fier has a current output which is variable depend-

ing on the input signal amplitude as defined by the

control loop of the noise reduction. The output

current is then dumped into an off-chip capacitor

which together with the accurate current reference

define the min/max rolloff frequencies.A resistor in

series with a capacitor is connectedto ground from

these two pins.

J17 L, J17 R

The external J17 de-emphasis networks for chan-

nels left and right. The amplifier for this filter is

voltage input, current output. Output with

±500mV

input will be

±55µA.

To perform J17 de-emphasis with the STV0042,an

external circuit is required.

U75 L, U75 R

External deemphasis networks for channels left

and right. For each channela capacitorand resistor

in parallel of 75

µs time constant are connected

between here and VREF to provide 75

µs de-empha-

sis. Internally selectable is an internal resistor that

can be programmed to be added in parallel thereby

converting the network to approx 50

µs de-empha-

sis (see control block map). The value of the inter-

nal resistors is 54k

Ω ±30 %. The amplifier for this

filter is voltage input, current output ; with

±500mV

input the output will be

±55µA.

VOL L, VOL R

The main audio output from the volume control

amplifier the signal to get output signals as high as

2VRMS (+12dB) on a DC bias of 4.8V. Control is

from +12dB to -26.75dB plus Mute with 1.25dB

steps. This amplifier has short circuit protection and

is intendedto drive a SCART connectordirectly via

AC coupling and meets the standard SCART drive

requirements. These outputs feature high imped-

ance mode for parallel connection.

S2 OUT L, S2 OUT R, S3 OUT L, S3 OUT R

These audio outputs are sourced directly from the

audio MUX, and as a result do not include any

volume control function. They will output a 1VRMS

signal biased at 4.8V. They are short circuit pro-

tected. These outputs feature high impedance

mode for parallel connection and meet SCART

drive requirement.

S2 RTN L, S2 RTN R, S3 RTN L, S3 RTN R

These pins allow auxiliary audio signals to be con-

nected to the audio processor and hence makes

use of the on-chip volume control. For additional

details please refer to the audio switching table.

STV0056AF

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