WM5615IP datasheet(10/12 Pages) WOLFSON

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Wolfson Microelectronics

WM5615

Detailed Description (Continued)

Power-Supply Bypassing and Ground Management

Best system performance is obtained with printed-circuit

boards that use separate analog and digital ground planes.

Wire-wrap boards are not recommended. The two ground

planes should be connected together at the low-

impedance power-supply source. The best ground con-

nection may be achieved by connecting the DAC AGND

terminal to the system analogue ground plane.

VDD should be bypassed with a 0.1

µF ceramic capacitor

connected between VDD and AGND. It should be mounted

with short leads close to the device. Ferrite beads may be

used to further isolate the system analogue and digital

power supplies.

Figure 5 illustrates the grounding and bypassing scheme

described.

Figure 5 - Power-Supply Bypassing

Saving Power

When the DAC is not being used by the system, minimize

power consumption by setting the appropriate code to

minimize load. For example, with a resistive load to ground,

set the DAC code to 0 (see Table 1). In addition, the

REFIN buffer has to drive current into the DAC resistor

string and so setting REFIN to 0 further reduces power

consumption.

Analogue Feedthrough

Because of internal stray capacitance, higher frequency

analog input signals may couple to the output. this is

tested by holding CS high, setting the DAC code to all 0s

and sweeping REFIN.

Digital Feedthrough

High-speed serial data at any of the digital input or output

pins may couple through the DAC package internal stray

capacitance to appear at the DAC output as noise, even

though CS is held high. This digital feedthrough is tested

by holding CS high while transmitting 1010... from DIN to

DOUT.

0.1 µF

Analogue Ground Plane

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