max5889 Maxim Integrated Products, Inc., max5889 Datasheet - Page 12

• Manufacturer Part Number: max5889
• Description: Max5889 12-bit, 600msps, High-dynamic-performance Dac With Lvds Inputs
• Manufacturer: Maxim Integrated Products, Inc.

Grounding and power-supply decoupling strongly influ-
ence the MAX5889 performance. Unwanted digital
crosstalk coupling through the input, reference, power
supply, and ground connections affects dynamic per-
formance. High-speed, high-frequency applications
require closely followed proper grounding and power-
supply decoupling. These techniques reduce EMI and
internal crosstalk that can significantly affect the
MAX5889 dynamic performance.
Use a multilayer printed circuit (PC) board with sepa-
rate ground and power-supply planes. Run high-speed
signals on lines directly above the ground plane. Keep
digital signals as far away from sensitive analog inputs
and outputs, reference input sense lines, common-
mode inputs, and clock inputs as practical. Use a sym-
metric design of clock input and the analog output lines
to minimize 2nd-order harmonic distortion components,
thus optimizing the DAC’s dynamic performance. Keep
digital signal paths short and run lengths matched to
avoid propagation delay and data skew mismatches.
The MAX5889 requires five separate power-supply
inputs for analog (AV
(DV
Decouple each AV
DV
to the device as possible with the shortest possible con-
nection to the respective ground plane (Figure 7).
Connect all the 3.3V supplies together at one point with
ferrite beads to minimize supply noise coupling.
Decouple all five power-supply voltages at the point they
enter the PC board with tantalum or electrolytic capaci-
tors. Ferrite beads with additional decoupling capacitors
forming a pi network can also improve performance.
Similarly, connect all 1.8V supplies together at one point
with ferrite beads.
12-Bit, 600Msps, High-Dynamic-Performance
DAC with LVDS Inputs
Figure 6. Differential Output Configuration
12
Grounding, Bypassing, and Power-Supply
DD1.8
DATA INPUTS
DD1.8
______________________________________________________________________________________
D0–D11
LVDS
input with a separate 0.1µF capacitor as close
and DV
DD3.3
DD3.3
MAX5889
AGND
, AV
), and clock (AV
DD1.8
DD1.8
and AV
OUTP
OUTN
, AV
Considerations
CLK
DD3.3
, DV
25Ω
50Ω
25Ω
CLK
) circuitry.
DD3.3
), digital
OUTP
OUTN
, and
The analog and digital power-supply inputs AV
AV
voltage range. The analog and digital power-supply
inputs AV
supply voltage range.
The MAX5889 is packaged in a 68-pin QFN-EP pack-
age with exposed paddle, providing optimized DAC AC
performance. The exposed pad must be soldered to
the ground plane of the PC board. Thermal efficiency is
not the key factor, since the MAX5889 features low-
power operation. The exposed pad ensures a solid
ground connection between the DAC and the PC
board’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 PC board side of the pack-
age. This allows for a solid attachment of the package
to the PC board with standard infrared (IR) reflow sol-
dering techniques. A specially created land pattern on
the PC board, matching the size of the EP (6mm x
6mm), ensures the proper attachment and grounding of
the DAC. Place vias into the land area and implement
Figure 7. Recommended Power-Supply Decoupling and
Bypassing Circuitry
CLK
BYPASSING—DAC LEVEL
DATA INPUTS
*FERRITE BEADS
, and DV
D0–D11
DD1.8
LVDS
DD3.3
and DV
1.8V VOLTAGE SUPPLY
*
*
allow a 3.135V to 3.465V supply
AV
AV
3.3V VOLTAGE SUPPLY
DD3.3
DD1.8
DD1.8
0.1µF
0.1µF
MAX5889
*
*
DV
DV
DD3.3
DD1.8
allow a 1.71V to 1.89V
0.1µF
0.1µF
AV
*
CLK
OUTP
OUTN
0.1µF
DD3.3
,