AD7225KN データシートの表示（PDF） - Analog Devices

部品番号

コンポーネント説明

メーカー

AD7225KN

LC2MOS Quad 8-Bit DAC with Separate Reference Inputs

Analog Devices 

AD7225

BIPOLAR OUTPUT OPERATION

Each of the DACs of the AD7225 can be individually confi-

gured to provide bipolar output operation. This is possible

using one external amplifier and two resistors per channel.

Figure 17 shows a circuit used to implement offset binary

coding (bipolar operation) with DAC A (DAC Channel A)

of the AD7225. In this case,

VOUT

= 1+



R2

R1





×

(D

AVREF

)

−





R2

R1





×

(VREF

)

With R1 = R2

( ) ( ) VOUT = 2DA − 1 × VREF

where DA is a fractional representation of the digital word in

Latch A (0 ≤ DA ≤ 255/256).

Mismatch between R1 and R2 causes gain and offset errors and,

therefore, these resistors must match and track over tempera-

ture. The AD7225 can be operated in single supply or from

positive/negative supplies. Table 8 shows the digital code vs.

output voltage relationship for the circuit of Figure 17 with

R1 = R2.

VREF

VREFA

AD7225*

DAC A

R1

R2

VDD

+15V

VOUTA

–15V

VOUT

VSS

AGND

DGND

R1, R2 = 10kΩ ± 0.1%.

*DIGITAL INPUTS OMITTED

FOR CLARITY.

Figure 17. Bipolar Output Circuit

Table 8. Bipolar (Offset Binary) Code Table

DAC Latch Contents

MSB

LSB

Analog Output

1111

1000

1111

0001

( ) + VREF

127

128

( ) + VREF

1

128

1000

0000

0V

0111

0000

0000

1111

0001

0000

( ) −VREF

1

128

( ) −VREF

127

128

( ) − VREF

128

128

= 1 − VREF

Rev. C | Page 14 of 24

Share Link: