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BOARD DESIGN CONSIDERATIONS
ADS6445, ADS6444
ADS6443, ADS6442
SLAS531 – MAY 2007
Grounding
A single ground plane is sufficient to give optimum performance, provided the analog, digital and clock sections
of the board are cleanly partitioned. Refer to the EVM User Guide (SLAU196) for board layout schemes.
Supply Decoupling
As the ADS644X already includes internal decoupling, minimal external decoupling can be used without loss in
performance. Note that the decoupling capacitors can help to filter external power supply noise, so the optimum
number of decoupling capacitors would depend on actual application.
It is recommended to use separate supplies for the analog and digital supply pins to isolate digital switching
noise from sensitive analog circuitry. In case only a single 3.3-V supply is available, it should be routed first to
AVDD. It can then be tapped and isolated with a ferrite bead (or inductor) with decoupling capacitor, before
being routed to LVDD.
Exposed Thermal Pad
It is necessary to solder the exposed pad at the bottom of the package to a ground plane for best thermal
performance. For detailed information, see application notes QFN Layout Guidelines (SLOA122A) and
QFN/SON PCB Attachment (SLUA271A).
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