AD7225 Просмотр технического описания (PDF) - Analog Devices

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AD7225

LC2MOS Quad 8-Bit DAC with Separate Reference Inputs

Analog Devices 

UNIPOLAR OUTPUT OPERATION

This is the basic mode of operation for each channel of the

AD7225, with the output voltage having the same positive

polarity as VREFx. The AD7225 can be operated single supply

(VSS = AGND) or with positive/negative supplies (see the Op

Amp Section, which outlines the advantages of having negative

VSS). Connections for the unipolar output operation are shown

in Figure 16. The voltage at any of the reference inputs must

never be negative with respect to DGND. Failure to observe this

precaution may cause parasitic transistor action and possible

device destruction. The code table for unipolar output

operation is shown in Table 7.

Note,

( ) ( ) 1 LSB = VREF

2 −8

=

VREF





1

256





AD7225

VREFA VREFB VREFC VREFD

VDD

DB7

(MSB)

DB0

(LSB)

DAC A

DAC B

VOUTA

VOUTB

WR

A1

A2

LDAC

DAC C

DAC D

AD7225

VSS

AGND

VOUTC

VOUTD

DGND

Figure 16. Unipolar Output Circuit

Table 7. Unipolar Code Table

DAC Latch Contents

MSB

LSB

1111

1111

1000

0001

1000

0000

0111

0000

0000

1111

0001

0000

Analog Output

( ) + VREF

255

256

( ) + VREF

129

256

( ) + VREF

128

256

= + VREF

2

( ) + VREF

127

256

( ) + VREF

1

256

0V

Rev. C | Page 13 of 24

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