Microprocessor-Compatible,

14-Bit DACs

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7

Zero-Offset Adjustment

(Figures 4a and 4b)

1) Load the DAC register with all 0s.

ure) is at a minimum (i.e.,

≤ 30µV).

Gain Adjustment

(Figures 4a and 4b)

1) Load the DAC register with all 1s.

(

16384

In fixed-reference applications, adjust full scale by

omitting R1 and R2 and trimming the reference voltage

magnitude. In many applications, the excellent Gain

Tempco and Gain Error specifications eliminate the

need for gain adjustment. However, if trims are

required and the DAC is to operate over a wide temper-

ature range, use low-tempco (>300ppm/°C) resistors.

Bipolar Operation

(4-Quadrant Multiplication)

Bipolar or 4-quadrant operation is shown in Figures 5a

and 5b. This configuration provides for offset binary

coding. Table 4 shows DAC codes and the corre-

sponding analog outputs for Figures 5a and 5b. With

the DAC loaded to 10 0000 0000 0000, either adjust R1

or vary the value of R7 for full-scale trimming.

Resistors R5, R6, and R7 must be matched to 0.003%.

Mismatch of R5 and R6 causes both offset and full-

scale errors. For wide temperature range operation,

use resistors of the same material so that their tempera-

ture coefficients match and track.

2R

2R

G

F

E

D

C

B

A

S10

S9

S0

2R

2R

2R

2R

2R

2R

2R

R

R

R

2R

2R

R/4

RFB

IOUT

AGNDS

AGNDF

*NOTE: VALID FOR MX7535. IN MX7534, 0REFS AND 0REFF ARE REPLACED BY ONE PIN: REF.

REFS*

REFF*

R/4

+

–

AGNDS

AGNDF

IOUT

RFB

Figure 2. Simplified Circuit Diagram

Figure 3. Equivalent Analog Output Circuit

Table 1. MX7534 Logic States

WR

CS

A1

A2

FUNCTION

X

1

X

X

Device not selected (Note 1)

1

X

X

X

No data transfer

0000

DAC loaded directly from

Data Bus (Note 2)

0001

MS Input Register loaded

from Data Bus

0010

LS Input Register loaded

from Data Bus

0011

DAC Register loaded from

Input Registers

Note 1: X = Don’t Care.

Note 2: When A1 = 0 and A0 = 0, all DAC registers are trans-

parent. By placing all 0s or all 1s on the data inputs, the

user can load the DAC to zero or full-scale output in

one write operation. This simplifies system calibration.