Datasheet
LAYOUT
GROUNDING
ADS8365
SBAS362C – AUGUST 2006 – REVISED MARCH 2008 ....................................................................................................................................................
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capacitor and a 5 Ω or 10 Ω series resistor may be
used to low-pass filter a noisy supply. On average,
For optimum performance, care should be taken with
the ADS8365 draws very little current from an
the physical layout of the ADS8365 circuitry. This
external reference because the reference voltage is
recommendation is particularly true if the CLK input is
internally buffered. A bypass capacitor of 0.1 µ F and
approaching the maximum throughput rate.
10 µ F are suggested when using the internal
reference (tie pin 61 directly to pin 62).
The basic SAR architecture is sensitive to glitches or
sudden changes on the power supply, reference,
ground connections, and digital inputs that occur just
prior to latching the output of the analog comparator.
The AGND pins should be connected to a clean
Thus, driving any single conversion for an n-bit SAR
ground point. In all cases, this point should be the
converter, there are n windows in which large
analog ground. Avoid connections that are too close
external transient voltages can affect the conversion
to the grounding point of a microcontroller or digital
result. Such glitches might originate from switching
signal processor. If required, run a ground trace
power supplies, nearby digital logic, or high-power
directly from the converter to the power-supply entry
devices. The degree of error in the digital output
point. The ideal layout includes an analog ground
depends on the reference voltage, layout, and the
plane dedicated to the converter and associated
exact timing of the external event. Their error can
analog circuitry. Three signal ground pins (SGND) are
change if the external event changes in time with
the input signal grounds that are on the same
respect to the CLK input.
potential as analog ground.
With this information in mind, power to the ADS8365
should be clean and well-bypassed. A 0.1 µ F ceramic
bypass capacitor should be placed as close to the
device as possible. In addition, a 1 µ F to 10 µ F
capacitor is recommended. If needed, an even larger
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