With this in mind, power to the ADS7834 should be clean
and well bypassed. A 0.1µF ceramic bypass capacitor should
be placed as close to the device as possible. In addition, a
1µF to 10µF capacitor is recommended. If needed, an even
larger capacitor and a 5Ω or 10Ω series resistor my be used
to lowpass filter a noisy supply.
capacitor. An additional larger capacitor may also be used,
if desired. If the reference voltage is external and originates
from an op-amp, make sure that it can drive the bypass
capacitor or capacitors without oscillation.
The GND pin should be connected to a clean ground point.
In many cases, this will be the “analog” ground. Avoid
connections which are too near the grounding point of a
microcontroller or digital signal processor. If needed, run a
ground trace directly from the converter to the power supply
entry point. The ideal layout will include an analog ground
plane dedicated to the converter and associated analog
circuitry.
The ADS7834 draws very little current from an external
reference on average as the reference voltage is internally
buffered. However, glitches from the conversion process
appear at the VREF input and the reference source must be
able to handle this. Whether the reference is internal or
external, the VREF pin should be bypassed with a 0.1µF
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ADS7834
BB [ BURR-BROWN CORPORATION ]
