AD5381BSTZ-5 datasheet(35/40 Pages) AD

35 / 40 page

Data Sheet

AD5381

Rev. D | Page 35 of 40

12-BIT DAC

DAC

INPUT

DATA

INPUT

DATA

A/B

VOUT

LDAC

CONTROL INPUT

Figure 42. Toggle Mode Function

OPTICAL ATTENUATORS

Based on its high channel count, high resolution, monotonic

behavior, and high level of integration,the AD5381 is ideally

targeted at optical attenuation applications used in dynamic

gain equalizers, variable optical attenuators (VOAs), and optical

add-drop multiplexers(OADMs). In these applications, each

wavelength is individually extracted using an arrayed wave

guide; its power is monitoredusing a photodiode, transimped-

ance amplifier and ADC in a closed-loop control system. The

AD5381 controls the optical attenuator for each wavelength,

ensuring that the power is equalized in all wavelengthsbefore

being multiplexed ontothe fiber. This preventsinformation loss

and saturation fromoccurring at amplification stages further

along the fiber.

UTILIZING FIFO

The AD5381 FIFO mode optimizes total systemupdate rates

in applications where a largenumber of channels needto be

updated. FIFO modeis only available when parallel interface

mode is selected. The FIFO EN pin is used to enable the FIFO.

The status of FIFO EN is sampled during the initialization

sequence. Therefore,the FIFO statuscan only be changed by

resetting the device.

In a telescope that provides for the cancel-lation of atmospheric

distortion, for example, a large numberof channels need to be

updated in a short period of time. In such systems, as manyas

400 channels need to be updated within 40 µs. Four-hundred

channels require the useof 10 AD5381s. With FIFO mode

enabled, the data writecycle time is 40 ns; therefore, each group

consisting of 40 channels can be fully loaded in 1.6 µs. In FIFO

mode, a completegroupof 40 chan-nels will update in 14.4 µs.

The time taken to update all 400 channels is

14.4 µs + 9 × 1.6 µs = 28.8 µs.

Figure 44 shows the FIFO operation scheme.

ATTENUATOR

AWG

FIBRE

DWDM

OUT

OPTICAL

SWITCH

1n–1

DWDM

AD5381,

40-CHANNEL,

12-BIT DAC

N:1 MULTIPLEXER

16-BIT ADC

CONTROLLER

TIA/LOG AMP

(AD8304/AD8305)

ADG731

(40:1 MUX)

AD7671

(0V TO 5V, 1MSPS)

PHOTODIODES

ADD

PORTS

DROP

PORTS

Figure 43. OADM Using the AD5381 as Part of an Optical Attenuator

AD5381BSTZ-5 Datasheet(PDF) 35 Page - Analog Devices

AD5381BSTZ-5 Datasheet(HTML) 35 Page - Analog Devices

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40

Datasheet Download

Link URL