MAX525BCAP 데이터 시트보기 (PDF) - Maxim Integrated

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MAX525BCAP

Low-Power, Quad, 12-Bit Voltage-Output DAC with Serial Interface

Maxim Integrated 

Low-Power, Quad, 12-Bit Voltage-Output DAC

with Serial Interface

MAX525

REFERENCE INPUTS

REFAB

REFCD

+5V

VDD

DAC A

DAC B

DAC C

DAC D

AGND

DGND

FBA 10k

10k

OUTA

FBB 10k

10k

OUTB

FBC 10k

10k

OUTC

FBD 10k

10k

OUTD

VREFAB = VREFCD = 2.5V

Figure 10. Unipolar Rail-to-Rail Output Circuit

Using an AC Reference

In applications where the reference has AC signal com-

ponents, the MAX525 has multiplying capability within

the reference input range specifications. Figure 12

shows a technique for applying a sine-wave signal to

the reference input where the AC signal is offset before

being applied to REFAB/REFCD. The reference voltage

must never be more negative than DGND.

The MAX525’s total harmonic distortion plus noise (THD

+ N) is typically less than -72dB, given a 1Vp-p signal

swing and input frequencies up to 25kHz. The typical

-3dB frequency is 650kHz, as shown in the Typical

Operating Characteristics graphs.

Digitally Programmable Current Source

The circuit of Figure 13 places an NPN transistor

(2N3904 or similar) within the op-amp feedback loop to

implement a digitally programmable, unidirectional cur-

rent source. This circuit can be used to drive 4mA to

20mA current loops, which are commonly used in

industrial-control applications. The output current is cal-

culated with the following equation:

IOUT = (VREF / R) x (NB / 4096)

where NB is the numeric value of the DAC’s binary

input code and R is the sense resistor shown in

Figure 13.

R1

R2

REF_

+5V

FB_

DAC

MAX525

OUT_

-5V

R1 = R2 = 10kΩ ± 0.1%

+5V

AC

26k

REFERENCE

INPUT

500mVp-p

10k

VOUT

1/2 MAX492

REF_

VDD

DAC_

OUT_

MAX525

AGND

DGND

Figure 11. Bipolar Output Circuit

Figure 12. AC Reference Input Circuit

14 ______________________________________________________________________________________

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