MAX5854
Dual, 10-Bit, 165Msps, Current-Output DAC
16 ______________________________________________________________________________________
or spurious-free dynamic range. In addition, electromagnetic interference (EMI) can either couple into or
be generated by the MAX5854. Observe the grounding
and power-supply decoupling guidelines for highspeed, high-frequency applications. Follow the power
supply and filter configuration to realize optimum
dynamic performance.
Use of a multilayer printed circuit (PC) board with separate ground and power-supply planes is recommended. Run high-speed signals on lines directly above the
ground plane. The MAX5854 has separate analog and
digital ground buses (AGND, CGND, and DGND,
respectively). Provide separate analog, digital, and
clock ground sections on the PC board with only one
point connecting the three planes. The ground connection points should be located underneath the device
and connected to the exposed paddle. Run digital signals above the digital ground plane and analog/clock
signals above the analog/clock ground plane. Digital
signals should be kept away from sensitive analog,
clock, and reference inputs. Keep digital signal paths
short and metal trace lengths matched to avoid propagation delay and data skew mismatch.
The MAX5854 includes three separate power-supply
inputs: analog (AVDD), digital (DVDD), and clock
(CV
DD
). Use a single linear regulator power source to
branch out to three separate power-supply lines (AVDD,
DV
DD
, CVDD) and returns (AGND, DGND, CGND).
Filter each power-supply line to the respective return
line using LC filters comprising ferrite beads and 10µF
capacitors. Filter each supply input locally with 0.1µF
ceramic capacitors to the respective return lines.
Note: To maintain the dynamic performance of the
Electrical Characteristics, ensure the voltage difference between DV
DD
, AVDD, and CVDDdoes not
exceed 150mV.
Thermal Characteristics and Packaging
Thermal Resistance
40-lead thin QFN-EP:
θ
JA
= 38°C/W
The MAX5854 is packaged in a 40-pin thin QFN-EP
package, providing greater design flexibility, increased
thermal efficiency, and optimized AC performance of
the DAC. The EP enables the implementation of
grounding techniques, which are necessary to ensure
highest performance operation.
In this package, the data converter die is attached to
an EP leadframe with the back of this frame exposed at
the package bottom surface, facing the PC board side
of the package. This allows a solid attachment of the
package to the PC board with standard infrared (IR)
flow soldering techniques. A specially created land pattern on the PC board, matching the size of the EP
(4.1mm ✕ 4.1mm), ensures the proper attachment and
grounding of the DAC. Designing vias* into the land
area and implementing large ground planes in the PC
board design allows for highest performance operation
of the DAC. Use an array of 3
✕ 3 vias (≤0.3mm diame-
ter per via hole and 1.2mm pitch between via holes) for
this 40-pin thin QFN-EP package (package code:
T4066-1).
Dynamic Performance Parameter Definitions
Adjacent Channel Leakage Ratio (ACLR)
Commonly used in combination with wideband codedivision multiple-access (WCDMA), ACLR reflects the
leakage power ratio in dB between the measured
power within a channel relative to its adjacent channel.
ACLR provides a quantifiable method of determining
out-of-band spectral energy and its influence on an
adjacent channel when a bandwidth-limited RF signal
passes through a nonlinear device.
Total Harmonic Distortion (THD)
THD is the ratio of the RMS sum of all essential harmonics (within a Nyquist window) of the input signal to the
fundamental itself. This can be expressed as:
where V1is the fundamental amplitude, and V2through
VNare the amplitudes of the 2nd through Nth order harmonics. The MAX5854 uses the first seven harmonics
for this calculation.
Spurious-Free Dynamic Range (SFDR)
SFDR is the ratio of RMS amplitude of the carrier frequency (maximum signal component) to the RMS value
of their next-largest spectral component. SFDR is usually measured in dBc with respect to the carrier frequency amplitude or in dBFS with respect to the DAC’s
full-scale range. Depending on its test condition, SFDR
is observed within a predefined window or to Nyquist.