AD5380_15 datasheet(39/40 Pages) AD

39 / 40 page

Data Sheet

AD5380

UTILIZING THE AD5380 FIFO

The AD5380 FIFO mode optimizes total system update rates

in applications where a large number of channels need to be

updated. FIFO mode is 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 status can only be changed by

resetting the device. In a telescope that provides for the cancella-

tion of atmospheric distortion, for example, a large number of

channels need to be updated in a short period of time.

In such systems, as many as 400 channels need to be updated

within 40 µs. Four-hundred channels requires the use of 10

AD5380s. With FIFO mode enabled, the data write cycle time

is 40 ns; therefore, each group consisting of 40 channels can be

fully loaded in 1.6 µs. In FIFO mode, a complete group of 40

channels 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 49 shows

the FIFO operation scheme.

Figure 49. Using FIFO Mode 400 Channels Updated in Under 30 µs

GROUP A

CHNLS 0–39

GROUP B

CHNLS 40–79

GROUP C

CHNLS

80–119

GROUP D

CHNLS

120–159

GROUP E

CHNLS

160–199

GROUP F

CHNLS

200–239

GROUP G

CHNLS

240–279

GROUP H

CHNLS

280–319

GROUP I

CHNLS

320–359

GROUP J

CHNLS

360–399

TIME TO UPDATE 400 CHANNELS = 28.8

µs

1.6

µs

14.4

µs

14.4

µs

1.6

µs

FIFO DATA LOAD

GROUP A

FIFO DATA LOAD

GROUP B

OUTPUT UPDATE

TIME FOR GROUP A

1.6

µs

14.4

µs

FIFO DATA LOAD

GROUP J

OUTPUT UPDATE

TIME FOR GROUP J

OUTPUT UPDATE

TIME FOR GROUP B

Rev. D | Page 39 of 40

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