AL1402 Просмотр технического описания (PDF) - Unspecified

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AL1402

OPTOREC CONVERTER

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Application Notes

The clock and data outputs of the AL1402

are undefined after power-up until a proper

data stream is well established at OPDIGIN

(pin 6). The clock outputs may be running

at an uncontrolled frequency. In this case,

the ERROR pin will be high, indicating that

the outputs are invalid. This may be

prevented by applying logic one to FORMAT1

(pin 4) and logic zero to FORMAT0 (pin 3) on

power-up. This resets the AL1402, stopping

the VCO clocks and muting the data output.

The FORMAT pins may then be set to the

value required in your system. Nevertheless

the AL1402 will synchronize and produce

proper outputs when proper and valid

inputs are provided, whether this reset

procedure is used or not.

The AL1402 in Master Mode can also

produce clock outputs running at

uncontrolled frequencies if the digital input

becomes unstable after stable use, due

mostly to poor connection of the optical

cable to the optical connector. If this is

unwanted in the system an external AND

implementation can be used to correct this.

The inverted error pin and the desired

AL1402 output clock are inputs to the AND

and the desired mutable clock is output.

This AND function will mute the selected

AL1402 clock when the error pin is high (i.e.

when unstable input is present at OpDigIn).

Care should be taken when running the

AL1402 with the AL1201 DAC as the

AL1201 DAC will output noise if the AL1402

WDCLK is at an uncontrolled VCO frequency

that is beyond the AL1201 maximum

frequency. The aforementioned AND

function can be used to select the AL1402

WDCLK to be muted when invalid

OpDigInput is present before proceeding as

the AL1201 WDCLK. See Figure F. with the

AND function implemented with NAND

gates. In place of this circuit the ERROR pin

can be used as a mute select for any audio

output stage muting circuitry that may be

present in the system.

Figure F. AL1402 –AL1201 CLK MUTE CIRCUIT.

Alesis Semiconductor

DS1402-0702

12555 Jefferson Blvd., Suite 285

Los Angeles, CA 90066

Phone (310) 301-0780 Fax (310) 306-1551 www.alesis-semi.com

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