AL1201 データシートの表示（PDF） - Unspecified

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AL1201

Stereo DAC

Unspecified 

Differential Analog Outputs

The AL1201 outputs are self-biased to MID

potential. Maximum differential output

signal level is +/-4V. The outputs have been

internally filtered to reduce out-of-band

noise, and further filtering is suggested

where this is considered critical. The

differential-to-single-ended filter shown

8.2k

is a two-pole 48kHz lowpass filter whose

frequency response is flat from dc to 20kHz

+/-.03dB. Its group delay deviation from flat

is 1.3µs at 20kHz. High quality ceramic or

film capacitors suggested.

MID

4Vpp

390p

1+0µ 8.2k

IN-

1000p

10+µ 8.2k

IN+

1.8k

1.8k

-

Out

+

GND

8Vpp

MID

4Vpp

8.2k

GND

390p

GND

Differential to Single-ended Converter and 2-pole 48kHz lowpass filter

Reference and Mid

Power Supplies and Ground

The differential potential between the REF+

and REF- pins (connected to VA and GND

respectively) determines the amount of

charge that is added to or removed from the

switched-capacitor filter input for each ∆-Σ

modulator output (128Fs). It is very

important that REF+ is well bypassed to

REF- (.1µF ceramic as close as possible to

pins) to remove the unwanted effects of high

frequency noise.

The MID potential is developed on chip

(VA/2 volts) and is used to bias the internal

amplifiers in the switched-capacitor and

continuous-time filters. It requires a .1µF

bypass to GND at the pin. No load current

should be taken from the MID pin.

A single low-impedance 5V supply is all that

is required to achieve specified performance.

A 5V supply plane is recommended if

possible. VA and VD can be directly

connected to 5V, and REF+ should be

isolated with a 220-ohm resistor to 5V.

A single low impedance ground plane can be

used for all GND connections, simplifying

PCB layout. Each supply pin should be

bypassed to GND with a .1µF ceramic cap

positioned as close to the pin as possible.

Alesis Semiconductor

DS1201-0702

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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