AD7225 Просмотр технического описания (PDF) - Analog Devices

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AD7225

LC2MOS Quad 8-Bit DAC with Separate Reference Inputs

Analog Devices 

AD7225

less, there exists a good correlation with the actual performance

of the transversal filter (see Figure 23).

DIGITAL WORD MULTIPLICATION

Because each DAC of the AD7225 has a separate reference input,

the output of one DAC can be used as the reference input for

another. This means that multiplication of digital words can be

performed (with the result given in analog form). For example,

if the output from DAC A is applied to VREFB, then the output

from DAC B, VOUTB, can be expressed as:

VOUTB = DA × DB × VREFA

where DA and DB are the fractional representations of the digital

words in DAC Latch A and DAC Latch B, respectively.

If DA = DB = D, the result is D2 × VREFA.

In this manner, the four DACs can be used on their own or in

conjunction with an external summing amplifier to generate

complex waveforms. Figure 24 shows one such application.

In this case, the output waveform, Y, is represented by

Y = −(x4 + 2x3 + 3x2 + 2x + 4) × VIN

where x is the digital code that is applied to all four DAC

latches.

15V

VDD

25kΩ

100kΩ

AD7225*

50kΩ

VIN

VREFA

VOUTA

33kΩ

Y

VREFB

VOUTB

VREFC

VOUTC

50kΩ

VREFD

VOUTD

100kΩ

AGND DGND VSS

*DIGITAL INPUTS OMITTED FOR CLARITY.

Figure 24. Complex Waveform Generation

Rev. C | Page 18 of 24

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