Cirrus Logic CS5373A - Manual (Page 33)

CS5373A
DS703F2 33
9. POWER SUPPLIES
The CS5373A has a positive analog power
supply pin (VA+), a negative analog power
supply pin (VA-), a digital power supply pin
(VD), and a ground pin (GND).
For proper operation, power must be supplied
to all power supply pins, and the ground pin
must be connected to system ground. The
CS5373A digital power supply (VD) and the
CS5378 digital power supply (VDDPAD) must
share a common power supply voltage.
9.1 Power Supply Bypassing
The VA+, VA-, and VD power supplies should
be bypassed to system ground with 0.1
μF ca-
pacitors placed as close as possible to the
power pins of the device. In addition to the
0.1
μF local bypass capacitors, at least 100 μF
bulk capacitance to system ground should be
placed on each power supply near the voltage
regulator output, with additional power supply
bulk capacitance placed among the analog
component route if space permits. Bypass ca-
pacitors should be X7R, C0G, tantalum, or
other high-quality dielectric type.
9.2 PCB Layers and Routing
The CS5373A is a high-performance device,
and special care must be taken to ensure pow-
er and ground routing is correct. Power can be
supplied either through dedicated power
planes or routed traces. When routing power
traces, it is recommended to use a “star” rout-
ing scheme with the star point either at the
voltage regulator output or at a local power
supply bulk capacitor.
It is also recommended to dedicate a full PCB
layer to a solid ground plane, without splits or
routing. All bypass capacitors should connect
between the power supply circuit and the solid
ground plane as near as possible to the device
power supply pins.
The CS5373A analog signals are differentially
routed and do not normally require connection
to a separate analog ground. However, if a
separate analog ground is required, it should
be routed using a “star” routing scheme on a
separate layer from the solid ground plane and
connected to the ground plane only at the star
point. Be sure all active devices and passive
components connected to the analog ground
are included in the “star” route to ensure sen-
sitive analog currents do not return through the
ground plane.
9.3 Power Supply Rejection
Power supply rejection of the CS5373A is fre-
quency dependent. The CS5378 digital filter
rejects power supply noise for frequencies
above the selected digital filter corner frequen-
cy. Power supply noise frequencies between
DC and the digital filter corner frequency are
rejected as specified in the
Power Supply Characteristics table.
CS5373A
VA+ VD
VA- GND
0.1 uF 100 uF 0.1 uF 100 uF
100 uF 0.1 uF
To VA+
Regulator
To VA-
Regulator
To VD
Regulator
Figure 17. Power Supply Diagram