MAX5876
12-Bit, 250Msps, High-Dynamic-Performance,
Dual DAC with LVDS Inputs
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tantalum or electrolytic capacitors. Ferrite beads with
additional decoupling capacitors forming a pi-network
could also improve performance.
The analog and digital power-supply inputs AV
DD3.3
,
AV
CLK
, and DV
DD3.3
allow a +3.135V to +3.465V sup-
ply voltage range. The analog and digital power-supply
inputs AV
DD1.8
and DV
DD1.8
allow a +1.71V to +1.89V
supply voltage range.
The MAX5876 is packaged in a 68-pin QFN-EP pack-
age, providing greater design flexibility, and optimized
DAC AC performance. The EP enables the use of nec-
essary grounding techniques to ensure highest perfor-
mance operation. Thermal efficiency is not the key
factor, since the MAX5876 features low-power opera-
tion. The exposed pad ensures a minimum inductance
ground connection between the DAC and the PCB’s
ground layer.
The data converter die attaches to an EP lead frame with
the back of this frame exposed at the package bottom
surface, facing the PCB side of the package. This allows
for a solid attachment of the package to the PCB with
standard infrared reflow (IR) soldering techniques. A spe-
cially created land pattern on the PCB, matching the size
of the EP (6mm x 6mm), ensures the proper attachment
and grounding of the DAC (refer to the MAX5878 EV kit).
Designing vias into the land area and implementing large
ground planes in the PCB design allow for the highest
performance operation of the DAC. Use an array of at
least 4 x 4 vias (≤ 0.3mm diameter per via hole and
1.2mm pitch between via holes) for this 68-pin QFN-EP
package. Connect the MAX5876 exposed paddle to
GND. Vias connect the land pattern to internal or external
copper planes to spread heat. Use as many vias as pos-
sible to the ground plane to minimize inductance.
Static Performance Parameter Definitions
Integral Nonlinearity (INL)
Integral nonlinearity is the deviation of the values on an
actual transfer function from either a best straight-line fit
(closest approximation to the actual transfer curve) or a
line drawn between the end points of the transfer func-
tion, once offset and gain errors have been nullified.
For a DAC, the deviations are measured at every indi-
vidual step.
Differential Nonlinearity (DNL)
Differential nonlinearity is the difference between an
actual step height and the ideal value of 1 LSB. A DNL
error specification of less than 1 LSB guarantees a
monotonic transfer function.
Offset Error
The offset error is the difference between the ideal and
the actual offset current. For a DAC, the offset point is
the average value at the output for the two midscale
digital input codes with respect to the full scale of the
DAC. This error affects all codes by the same amount.
Gain Error
A gain error is the difference between the ideal and the
actual full-scale output voltage on the transfer curve,
after nullifying the offset error. This error alters the slope
of the transfer function and corresponds to the same
percentage error in each step.
