DAC5675

SLAS352C − DECEMBER 2001 − REVISED AUGUST 2004

10

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detailed description (continued)

supply inputs

inputs can be set independently from 3.6 V down to 3.15 V.

DAC transfer function

The DAC5675 delivers complementary output currents IOUT1 and IOUT2. The DAC supports straight binary

coding, with D13 being the MSB and D0 the LSB (For ease of notation we denote D13..D10 as the logical bit

equivalent of the complementary LVDS inputs D[13..0]A and D[13..0]B). Output current IOUT1 equals the

approximate full-scale output current when all input bits are set high, i.e., the binary input word has the decimal

representation 16383. Full-scale output current flows through terminal IOUT2 when all input bits are set low

(mode 0, straight binary input). The relation between IOUT1 and IOUT2 can thus be expressed as:

IOUT1

+

I

O(FS)

CODE

16384

IOUT2

+

I

O(FS)

(16383–CODE)

16384

where CODE is the decimal representation of the DAC data input word. Output currents IOUT1 and IOUT2 drive

IOUT1 and IOUT2, respectively, of:

VOUT1

+ IOUT1

R

L +

CODE

I

O(FS)

R

L

16384

VOUT2

+ IOUT2

R

L +

(16383

* CODE)

I

O(FS)

R

L

16384

VOUT

(DIFF) +

VOUT1

* VOUT2 +

(2CODE

* 16383)

I

O(FS)

R

L

16384

The latter equation shows that applying the differential output results in doubling of the signal power delivered

to the load. Since the output currents IOUT1 and IOUT2 are complementary, they become additive when

processed differentially. Note that care should be taken not to exceed the compliance voltages at node IOUT1

and IOUT2, which leads to increased signal distortion.