AD7225 Просмотр технического описания (PDF) - Analog Devices

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AD7225

LC2MOS Quad 8-Bit DAC with Separate Reference Inputs

Analog Devices 

GROUND MANAGEMENT AND LAYOUT

Because the AD7225 contains four reference inputs that can be

driven from ac sources (see the AC Reference Signal section),

careful layout and grounding is important to minimize analog

crosstalk between the four channels. The dynamic performance

of the four DACs depends on the optimum choice of board

layout. Figure 14 shows the relationship between input fre-

quency and channel-to-channel isolation. Figure 15 shows a

printed circuit board layout that minimizes crosstalk and

feedthrough. The four input signals are screened by AGND.

VREF was limited to between 2 V and 3.24 V to avoid slew rate

limiting effects from the output amplifier during measurements.

VDD = +15V

–80

VSS = –5V

TA = 25°C

–70

–60

–50

–40

VREF = 1.24V p-p

–30

20k

50k

100k 200k

500k

1M

INPUT FREQUENCY (Hz)

Figure 14. Channel-to-Channel Isolation

AD7225

VOUTB

VOUTA

VSS

VREFB

VREFA

AGND

DGND

PIN 1

MSB

SYSTEM

GND

VOUTC

VOUTD

VDD

VREFC

VREFD

LSB

Figure 15. Suggested PCB Layout for AD7225, Component Side (Top View)

Rev. C | Page 11 of 24

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