MAX5854 Datasheet, PDF (15/18 Pages) Maxim Integrated Products – Dual, 10-Bit, 165Msps, Current-Output DAC

Dual, 10-Bit, 165Msps, Current-Output DAC
AV_DD DV_DD CV_DD
DA0–DA9
10
1/2
MAX5854
50Ω
OUTPA
100Ω
OUTNA
50Ω
V_OUTA,
SINGLE ENDED
AV_DD DV_DD CV_DD
DA0–DA9
10
1/2
MAX5854
50Ω
OUTPA
OUTNA
50Ω
DB0–DB9
10
1/2
MAX5854
AGND DGND CGND
50Ω
OUTPB
100Ω
OUTNB
50Ω
V_OUTB,
SINGLE ENDED
DB0–DB9
10
1/2
MAX5854
AGND DGND CGND
50Ω
OUTPB
OUTNB
50Ω
Figure 7. Application with Output Transformer Performing
Differential-to-Single-Ended Conversion
Figure 8. Application with DC-Coupled Differential Outputs
Applications Information
Differential-to-Single-Ended Conversion
The MAX5854 exhibits excellent dynamic performance
to synthesize a wide variety of modulation schemes,
including high-order QAM modulation with OFDM.
Figure 7 shows a typical application circuit with output
transformers performing the required differential-to-sin-
gle-ended signal conversion. In this configuration, the
MAX5854 operates in differential mode, which reduces
even-order harmonics, and increases the available out-
put power.
Differential DC-Coupled Configuration
Figure 8 shows the MAX5854 output operating in differ-
ential, DC-coupled mode. This configuration can be
used in communications systems employing analog
quadrature upconverters and requiring a baseband
sampling, dual-channel, high-speed DAC for I/Q synthe-
sis. In these applications, information bandwidth can
extend from 10MHz down to several hundred kilohertz.
DC-coupling is desirable to eliminate long discharge
time constants that are problematic with large, expensive
coupling capacitors. Analog quadrature upconverters
have a DC common-mode input requirement of typically
0.7V to 1.0V. The MAX5854 differential I/Q outputs can
maintain the desired full-scale level at the required 0.7V
to 1.0V DC common-mode level when powered from a
single 2.85V (±5%) supply. The MAX5854 meets this
low-power requirement with minimal reduction in dynam-
ic range while eliminating the need for level-shifting
resistor networks.
Power Supplies, Bypassing,
Decoupling, and Layout
Grounding and power-supply decoupling strongly influ-
ence the MAX5854 performance. Unwanted digital
crosstalk can couple through the input, reference,
power-supply, and ground connections, which can
affect dynamic specifications, like signal-to-noise ratio
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