
AD5930 
APPLICATIONS
GROUNDING AND LAYOUT 
The printed circuit board that houses the AD5930 should be 
designed so that the analog and digital sections are separated 
and confined to certain areas of the board. This facilitates the 
use of ground planes that can be easily separated. A minimum 
etch technique is generally best for ground planes because it 
gives the best shielding. Digital and analog ground planes 
should only be joined in one place. If the AD5930 is the only 
device requiring an AGND to DGND connection, then the 
ground planes should be connected at the AGND and DGND 
pins of the AD5930. If the AD5930 is in a system where 
multiple devices require AGND to DGND connections, the 
connection should be made at one point only, a star ground 
point that should be established as close as possible to the 
AD5930. 
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Avoid running digital lines under the device as these couple 
noise onto the die. The analog ground plane should be allowed 
to run under the AD5930 to avoid noise coupling. The power 
supply lines to the AD5930 should use as large a track as 
possible to provide low impedance paths and reduce the effects 
of glitches on the power supply line. Fast switching signals, such 
as clocks, should be shielded with digital ground to avoid 
radiating noise to other sections of the board. Avoid crossover 
of digital and analog signals. Traces on opposite sides of the 
board should run at right angles to each other. This reduces the 
effects of feedthrough through the board. A microstrip 
technique is by far the best, but is not always possible with a 
double-sided board. In this technique, the component side of 
the board is dedicated to ground planes, while signals are placed 
on the other side. 
Good decoupling is important. The analog and digital supplies 
to the AD5930 are independent and separately pinned out to 
minimize coupling between analog and digital sections of the 
device. All analog and digital supplies should be decoupled to 
AGND and DGND, respectively, with 0.1 μF ceramic capacitors 
in parallel with 10 μF tantalum capacitors. To achieve the best 
from the decoupling capacitors, they should be placed as close 
as possible to the device, ideally right up against the device. In 
systems where a common supply is used to drive both the 
AVDD and DVDD of the AD5930, it is recommended that the 
system’s AVDD supply be used. This supply should have the 
recommended analog supply decoupling between the AVDD 
pins of the AD5930 and AGND, and the recommended digital 
supply decoupling capacitors between the DVDD pins and 
DGND. 
Proper operation of the comparator requires good layout 
strategy. The strategy must minimize the parasitic capacitance 
between V
IN
 and the SIGN BIT OUT pin by adding isolation 
using a ground plane. For example, in a multilayered board, the 
V
IN
 signal could be connected to the top layer and the SIGN 
BIT OUT connected to the bottom layer, so that isolation is 
provided between the power and ground planes. 
Interfacing to Microprocessors 
The AD5930 has a standard serial interface that allows the part 
to interface directly with several microprocessors. The device 
uses an external serial clock to write the data/control 
information into the device. The serial clock can have a 
frequency of 40 MHz maximum. The serial clock can be 
continuous, or it can idle high or low between write operations. 
When data/control information is being written to the AD5930, 
FSYNC is taken low and is held low while the 16 bits of data are 
being written into the AD5930. The FSYNC signal frames the 
16 bits of information being loaded into the AD5930. 
AD5930 TO ADSP-21xx INTERFACE 
Figure 36 shows the serial interface between the AD5930 and 
the ADSP-21xx. The ADSP-21xx should be set up to operate in 
the SPORT transmit alternate framing mode (TFSW = 1). The 
ADSP-21xx are programmed through the SPORT control 
register and should be configured as follows:  
1.
Internal clock operation (ISCLK = 1) 
2.
Active low framing (INVTFS = 1) 
3.
16-bit word length (SLEN = 15) 
4.
Internal frame sync signal (ITFS = 1) 
5.
Generate a frame sync for each write (TFSR = 1) 
Transmission is initiated by writing a word to the Tx register 
after the SPORT has been enabled. The data is clocked out on 
each rising edge of the serial clock and clocked into the AD5930 
on the SCLK falling edge. 
AD5930
1
ADSP-2101/
ADSP-2103
1
1
ADDITIONAL PINS OMITTED FOR CLARITY.
TFS
DT
SCLK
FSYNC
0
SDATA
SCLK
Figure 36. ADSP-2101/ADSP-2103 to AD5930 Interface