Power-supply and layout considerations – Rainbow Electronics MAX5295 User Manual

Page 29

MAX5290–MAX5295

Buffered, Fast-Settling, Dual, 12-/10-/8-Bit,

Voltage-Output DACs

______________________________________________________________________________________

Power-Supply and Layout Considerations

Bypass the analog and digital power supplies with a
10µF capacitor in parallel with a 0.1µF capacitor to ana-
log ground (AGND) and digital ground (DGND) (see
Figure 10). Minimize lead lengths to reduce lead induc-
tance. If noise is an issue, use shielding and/or ferrite
beads to increase isolation.

Digital and AC transient signals coupling to AGND cre-
ate noise at the output. Connect AGND to the highest
quality ground available. Use proper grounding tech-

niques, such as a multilayer board with a low-induc-
tance ground plane. Wire-wrapped boards and sockets
are not recommended. For optimum system perfor-
mance, use printed circuit (PC) boards with separate
analog and digital ground planes. Connect the two
ground planes together at the low-impedance power-
supply source.

Using separate power supplies for AV

and DV

improves noise immunity. Connect AGND and DGND at
the low-impedance power-supply source (see Figure 11).

MAX5290–MAX5295

REF

µF*

0.1

µF*

REF

SCLK

DIN

UPIO1

UPIO2

DSP

AGND**

DGND**

OUTA

FBA

FBB

OUTB

MAX5291/
MAX5293/

MAX5295

ONLY

µF

0.1

µF

0.1

µF

*REMOVE BYPASS CAPACITORS ON REF FOR AC-REFERENCE INPUTS.
**CONNECT ANALOG AND DIGITAL GROUND PLANES AT THE
LOW-IMPEDANCE POWER-SUPPLY SOURCE.

Figure 10. Bypassing Power Supplies and Reference

MAX5290–MAX5295

0.1

µF

AGND

0.1

µF

DGND

ANALOG SUPPLY

DIGITAL SUPPLY

DIGITAL

CIRCUITRY

Figure 11. Separate Analog and Digital Power Supplies