AD5546 datasheet(13/16 Pages) AD

13 / 16 page

AD5546/AD5556

Rev. 0 | Page 13 of 16

APPLICATIONS

UNIPOLAR MODE

2-Quadrant Multiplying Mode, VOUT = 0 V to –VREF

The AD5546/AD5556 DAC architecture uses a current-steering

R-2R ladder design that requires an external reference and op

amp to convert the unipolar mode of output voltage to

VOUT = –VREF × D/65,536

(AD5546)

(1)

VOUT = –VREF × D/16,384

(AD5556)

(2)

where D is the decimal equivalent of the input code.

The output voltage polarity is opposite to the VREF polarity in

this case (see Figure 21). Table 8 shows the negative output

versus code for the AD5546.

Table 8. AD5546 Unipolar Mode Negative Output vs. Code

D in Binary

VOUT (V)

1111 1111 1111 1111

–VREF(65,535/65,536)

1000 0000 0000 0000

–VREF/2

0000 0000 0000 0001

–VREF(1/65,536)

0000 0000 0000 0000

2-Quadrant Multiplying Mode, VOUT = 0 V to +VREF

The AD5546/AD5556 are designed to operate with either

positive or negative reference voltages. As a result, positive

output can be achieved with an additional op amp, (see

Figure 22), and the output becomes

VOUT = +VREF × D/65,536

(AD5546)

(3)

VOUT = +VREF × D/16,384

(AD5556)

(4)

Table 9 shows the positive output versus code for the AD5546.

Table 9. AD5546 Unipolar Mode Positive Output vs. Code

D in Binary

VOUT (V)

1111 1111 1111 1111

+VREF(65,535/65,536)

1000 0000 0000 0000

+VREF/2

0000 0000 0000 0001

+VREF(1/65,536)

0000 0000 0000 0000

16/14-BIT

+5V

GND

VIN

TRIM

ADR03

VOUT

VDD

ROFS

VOUT

–2.5V TO 0V

RFB

2.2pF

GND

AD5546/AD5556

IOUT

0.1

µF

RCOM

16/14 DATA

REF

AD8628

–

–5V

LDAC

MSB

0.1

µF

0.1

µF

V+

V–

Figure 21. Unipolar 2-Quadrant Multiplying Mode, VOUT = 0 to –VREF

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