adc16061ccvt National Semiconductor Corporation, adc16061ccvt Datasheet - Page 17

• Manufacturer Part Number: adc16061ccvt
• Description: Self-calibrating 16-bit, 2.5 Msps, 390 Mw A/d Converter
• Manufacturer: National Semiconductor Corporation

Applications Information
5.0 LAYOUT AND GROUNDING
Proper routing of all signals and proper ground techniques
are essential to ensure accurate conversion. Separate ana-
log and digital ground planes may be used if adequate care
is taken with signal routing, but may result in EMI/RFI. A
single ground plane with proper component placement with
yield good results while minimizing EMI/RFI.
Analog and digital ground current paths should not coincide
with each other as the common impedance will cause digital
noise to be added to analog signals. Accordingly, traces
carrying digital signals should be kept as far away from
traces carrying analog signals as possible. Power should be
routed with traces rather than the use of a power plane. The
analog and digital power traces should be kept well away
FIGURE 7. Differential drive circuit of Figure 6. Lower offset can be realized by using 0.1% resistors in place of the
FIGURE 8. Driving the signal inputs with a transformer.
(Continued)
1% resistors.
17
from each other. All power to the ADC16061 should be
considered analog. The DGND I/O pin should be considered
a digital ground and not be connected to the ground plane in
close proximity with the other ground pins of the ADC16061
The ground return for the digital supply (DGND I/O ) carries
the ground current for the output drivers and is isolated on
the die from the other ground pins. The DGND I/O current
can exhibit high transients that could add noise to the con-
version process. To prevent this from happening, the DGND
I/O pin should NOT be connected in close proximity to any of
the ADC16061’s other ground pins.
Capacitive coupling between the typically noisy digital
ground plane and the sensitive analog circuitry can lead to
poor performance that may seem impossible to isolate and
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