Preliminary Development
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BARIX IP AUDIO MODULE 400
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V 02.20
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9.April.2018
Layout Guidelines
11
Layout Guidelines
General rules
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A low ESR Capacitor of 10uF to 47uF in parallel to a low loss ceramic
100nF capacitor is recommended as power supply bypass close to the
Barix Audio Module's power supply pins.
•
All available ground pins of the Barix Audio Module should be attached to
their respective ground domain.
•
Analog and digital ground domains must be connected outside of the
IPAM 400 ! To allow low noise designs, the analog ground domain on the
IPAM is kept unconnected from the digital (noisy) ground.
•
Avoid signal trace routing crossing domain borders (see graphic on next
page).
•
Restricted Area A must not contain any high current switching circuitry nor
any components creating magnetic flux (see graphic on next page).
•
Flood unused PCB areas with copper and connect those planes to it's
respective ground.
•
Designers should use good PCB layout techniques suited for high speed
bidirectional data bus design when the USB signal run is more than a few
cm in length
•
The USB signal lines should be of equal electrical length and track width
for their entire length
•
The USB signal lines include provision for termination resistors (to DGND).
The exact value of the terminations may need to be checked or confirmed
by a designer and are in the vicinity of 15 Kilo-Ohms (+/- 5%). These
termination resistors should be close to either the USB socket or the IPAM
connector.
•
A more complex (capacitive) termination may be needed under some
circumstances.
•
Any unused pins can be left open to save power consumption (no pull-up
or pull-down needed).
•
Any unused audio pins can be left open. Only exception is the need of a
1uF capacitor on MICI- (CON3 pin 1) to ground when using as unbalanced
Mic input or when using Line in.
•
When planning on variations of carrier PCBs consider a filter consisting of
a resistor/ inductivity and a capacitor (close to the target devices connector)
for audio inputs and outputs:
•
For audio inputs always place a filter capacitor (Ci, see schematic
below) to ground just after the above-mentioned resistor/
inductivity (towards the IPAM connector).
For unused audio connectors inputs simply do not populate the
resistor/inductivity. Calculate the values for this R-C filter
according to your use (desired cut-off frequency versus
impedance).
•
For audio outputs always place a filter capacitor (Co, see
schematic below) to ground just after the above-mentioned
resistor/ inductivity (towards the IPAM connector) and populate
the resistor/inductivity. Calculate the values for this R-C filter
according to your use (desired cut-off frequency versus
impedance).
