AD5040 datasheet(16/24 Pages) AD

16 / 24 page

AD5512A/AD5542A

Rev. A | Page 16 of 24

Assuming a perfect reference, the unipolar worst-case output

voltage can be calculated from the following equation:

(

)

INL

ZSE

REF

UNI

OUT

−

where:

VOUT−UNI is the unipolar mode worst-case output.

D is the code loaded to DAC.

N is the resolution of the DAC.

VREF is the reference voltage applied to the part.

VGE is the gain error in volts.

VZSE is the zero-scale error in volts.

INL is the integral nonlinearity in volts.

BIPOLAR OUTPUT OPERATION

With the aid of an external op amp, the AD5512A/AD5542A

can be configured to provide a bipolar voltage output. A typical

circuit is shown in Figure 32. The matched bipolar offset resistors,

RFB and RINV, are connected to an external op amp to achieve

this bipolar output swing, typically RFB = RINV = 28 kΩ. Table 10

shows the transfer function for this output operating mode.

Also provided on the AD5542A are a set of Kelvin connections

to the analog ground inputs. The example includes the ADR421

2.5 V reference and the AD8628 low offset and zero-drift

reference buffer.

Table 10. AD5542A Bipolar Code Table

DAC Latch Contents

MSB

LSB

Analog Output

1111 1111 1111 1111

REF × (32,767/32,768)

1000 0000 0000 0001

REF × (1/32,768)

1000 0000 0000 0000

0 V

0111 1111 1111 1111

−V

REF × (1/32,768)

0000 0000 0000 0000

−V

REF × (32,768/32,768) = −VREF

Assuming a perfect reference, the worst-case bipolar output

voltage can be calculated from the following equation:

REF

UNI

OUT

BIP

OUT

)

(

)]

(

)

)(

[(

−

where:

VOUT−BIP is the bipolar mode worst-case output

VOUT−UNI is the unipolar mode worst-case output.

VOS is the external op amp input offset voltage.

RD is the RFB and RINV resistor matching error.

A is the op amp open-loop gain.

VOUT

REFS

REFF

INV

RFB

RINV

DGND AGNDF

VDD

DIN

SCLK

LDAC

AD5512A/

AD5542A

AGNDS

0.1µF

10µF

BIPOLAR

OUTPUT

EXTERNAL

OP AMP

+2.5V

+5V

–5V

SERIAL

INTERFACE

RFB

Figure 32. Bipolar Output

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