FX806A 데이터 시트보기 (PDF) - CML Microcircuits

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FX806A

AUDIO PROCESSOR

CML Microcircuits 

Analogue Application Information ......

The Gain Control System

EXTERNAL INTEGRATION COMPONENTS

R5

C8

VOGAD

IN

MIC. OUT

MIC. IN

MIC. IN

VOLTAGE

CONTROLLED (VOGAD)

AMPLIFIER

Tx INPUT PROCESS

R6

VDD

R12

VSS

VOGAD

OUT

HI

PEAK

DETECTOR

HI/LO

Tx

PEAK DETECTOR

MAIN PROCESS

To EXTERNAL AUDIO PROCESSES

PROCESSED AUDIO IN

Fig.3 “VOGAD” Sensors and Timing Components – (part of Fig.4)

CAL INPUT

Tx

DRIVES

Rx

DRIVE

Tx gain control of the FX806A is by 1 of 2 selectable signal

peak detectors whose output is fed via external integrating

components to the Voltage Controlled Amplifier positioned

in the Tx Input Process Path.

The integrated level to the VOGAD In pin causes the Voltage

Controlled Amplifier gain to be reduced. VOGAD attack

and decay calculations are described at the foot of the

proceeding page.

The FX806A automatically chooses the appropriate peak

detector when the signal path is set by a Mode Command.

The Hi/Lo Peak Detector is employed when external audio

processes are used.

The Hi Peak Detector is employed when external audio

processes are not used.

25

Limiter Only

20

Internal Path with Pre-emphasis

Circuit Elements set to 0dB

Input Level for 0dB = 71.0mV p-p

15

Input Frequency

= 1.0kHz

Output Deviation

= 60% = 0dB

10

60%

Output Deviation

308mVrms

5

“Hi-Peak” VOGAD & Limiter

0.0

+10.0

0

0.071

0.0

0.2

0.4

Fig.4 Distortion vs Mic. Input Level

+20.0

0.6

Input Level (dB)

Mic. Input Level (Vp-p)

Suggested Calibration Methods

To effectively null all internal microcircuit tolerances, the following initial calibration routine is suggested:

Tx Calibration : From Mic. In to Modulator Drives Out

Rx Calibration: From Rx Audio In to Audio Output

Disable Peak Detectors (Mode Command).

Set Transmitter Drives to 0dB (Mod Levels Set).

Pre-emphasis may be employed as required (Control

Command).

Set Input Level Amp to 0dB (Control Command).

Set Audio Output Drive to 0dB (Volume Set).

Leave Process Gain Amp set as In (1) (above).

(3) With Rx Audio In level of between 154mVrms and

308mVrms (see Specification page), at 1kHz, set the

Input Level Amp for an output level of 308mVrms.

(1) Mic. In = 250mVrms at 1kHz; Set Process Gain Amp for

output of 1440mV p - p (100% deviation).

(2) With Process Gain Amp set as (1); Mic In = 25mVrms at

1kHz, set Input Level Amp for output level of 308 mVrms

(60% deviation).

5

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