CS4297A
CS4297A
6.3
Miscellaneous Analog Signals
6.4
Power Supplies
The power supplies providing analog power should
be as clean as possible to minimize coupling into
the analog section which could degrade analog per-
formance. The analog power pins, AVdd1 and
AVdd2, supply power to all the analog circuitry on
the CS4297A. The +5 V analog supply should be
generated from a linear voltage regulator (7805
type) connected to a +12 V supply. This helps iso-
late the analog circuitry from noise typically found
on +5 V digital supplies. A typical voltage regula-
The AFLT1 and AFLT2 pins must have a 1000 pF
NPO capacitor to analog ground. These capacitors
provide a single-pole low-pass filter at the inputs to
the ADCs. This makes low-pass filters at each ana-
log input pin unnecessary.
The REFFLT pin must have a 1 µF and a 0.1 µF ca-
pacitor connected to analog ground with a short,
wide trace to this pin (see Figure 21 in Section 8,
Grounding and Layout, for an example). The 1 µF
capacitor must not be replaced with any value high-
er than 1 µF. No other connection should be made,
as any coupling onto this pin will degrade the ana-
log performance of the CS4297A. Likewise, digital
signals should be kept away from REFFLT for sim-
ilar reasons.
tor circuit for analog power using
a
MC78M05CDT +5 V regulator is shown in
Figure 19. The digital power pins, DVdd1 and
DVdd2, should be connected to the same digital
supply as the controller AC-link interface. The dig-
ital interface on the CS4297A may operate at either
+3.3 V or +5 V and proper connection of these pins
will depend on the digital power supply of the con-
troller.
The Vrefout pin is typically 2.3 V and provides a
common mode signal for single-supply external
circuits. Vrefout only supports light DC loads and
should be buffered if AC loading is needed. For
typical use the Vrefout pin should have a 1 µF and
a 0.1 µF capacitor connected to analog ground.
6.5
Reference Design
See Section 11 for a CS4297A reference design.
+12VD
+5VA
MC78M05CDT
1
3
IN
OUT
+
GND
ELEC
10µF
+
ELEC
10µF
Y5V
0.1µF
Y5V
0.1µF
2
DGND
AGND
Figure 19. Voltage Regulator
38
38
DS318PP6
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