AD7294 Datasheet, PDF (40/45 Pages) Analog Devices – 12-Bit, Multichannel, DAC/ADC Temperature Sensor and Current Sense for Monitor and Control Applications

AD7294
LAYOUT AND CONFIGURATION
POWER SUPPLY BYPASSING AND GROUNDING
When accuracy is important in a circuit, carefully consider the
power supply and ground return layout on the board. The
printed circuit board containing the AD7294 should have
separate analog and digital sections, each having its own area
of the board. If the AD7294 is in a system where other devices
require an AGND-to-DGND connection, the connection
should be made at one point only. This ground point should be
as close as possible to the AD7294.
The power supply to the AD7294 should be bypassed with
10 µF and 0.1 µF capacitors. The capacitors should physically be
as close as possible to the device, with the 0.1 µF capacitor
ideally right up against the device. The 10 µF capacitors are the
tantalum bead type. It is important that the 0.1 µF capacitor has
low effective series resistance (ESR) and low effective series
inductance (ESI); common ceramic types of capacitors are
suitable. The 0.1 µF capacitor provides a low impedance path to
ground for high frequencies caused by transient currents due to
internal logic switching.
Preliminary Technical Data
The power supply line should have as large a trace as possible to
provide a low impedance path and reduce glitch effects on the
supply line. Clocks and other components with fast switching
digital signals should be shielded from other parts of the board
by a digital ground. Avoid crossover of digital and analog
signals if possible. When traces cross on opposite sides of the
board, ensure that they run at right angles to each other to
reduce feedthrough effects on the board. The best board layout
technique is the microstrip technique where the component
side of the board is dedicated to the ground plane only and the
signal traces are placed on the solder side; however, this is not
always possible with a 2-layer board.
Rev. PrB | Page 40 of 45