Datasheet

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MAX5186/MAX5189

Dual, 8-Bit, 40MHz, Current/Voltage,

Simultaneous-Output DACs

12 ______________________________________________________________________________________

REN AGNDDGND

**MAX5186 ONLY

OUT1P

CREF2

CREF1

CLK

OUT1N

OUT2P

OUT2N

0.1µF

0.1µF0.1µF

SET

*400Ω RESISTORS INTERNAL TO MAX5189 ONLY.

MAX5186

MAX5189

10µF

0.1µF

REFR

REFO

D0–D7

10µF

400Ω

-5V

402Ω

OUTPUT 1

MAX4108

400Ω*

400Ω

-5V

402Ω

OUTPUT 2

MAX4108

Figure 5. Differential to Single-Ended Conversion Using a Low-Distortion Amplifier

Differential to Single-Ended Conversion

The MAX4108 low-distortion, high-input bandwidth

amplifier may be used to generate a voltage from the

array current output of the MAX5186. The differential

voltage across OUT1P (or OUT2P) and OUT1N (or

OUT2N) is converted into a single-ended voltage by

designing an appropriate operational amplifier configu-

ration (Figure 5).

I/Q Reconstruction in a QAM Application

The MAX5186/MAX5189’s low distortion supports ana-

log reconstruction of in-phase (I) and quadrature (Q)

carrier components typically used in quadrature ampli-

tude modulation (QAM) architectures where I and Q

data are interleaved on a common data bus. A QAM

signal is both amplitude and phase modulated, created

by summing two independently modulated carriers of

identical frequency but different phase (90° phase dif-

ference).

In a typical QAM application (Figure 6), the modulation

occurs in the digital domain and the MAX5186/

MAX5189’s dual DACs may be used to reconstruct the

analog I and Q components.

The I/Q reconstruction system is completed by a quad-

rature modulator that combines the reconstructed I and

Q components with in-phase and quadrature carrier

frequencies and then sums both outputs to provide the

QAM signal.