cx20493-35/app Conexant Systems, Inc., cx20493-35/app Datasheet - Page 57

• Manufacturer Part Number: cx20493-35/app
• Description: With Cx20493 Smartdaa?
• Manufacturer: Conexant Systems, Inc.

Table 3-8. CX20493 LSD Pin Signal Definitions
102247B
AVdd
AGnd
VRef
Vc
PWR+
DVdd
DGnd
CLK
DIB_P
DIB_N
Label
CX81801-7x/8x SmartV.XX Modem in 128-Pin LQFP with CX20493 in 32-Pin LQFP Data Sheet
2, 3
7
5
4
8
28
26, 27
29
30
31
Pin
AGND_LSD
DGND_LSD
PWR
PWR
PWR
REF
REF
I/O
I/O
I/O
I
AGND_LSD
DGND_LSD
I/O Type
PWR
PWR
PWR
REF
REF
I/O
I/O
I
DIB Interface Signals
Regulated Power Output. Provides external power for LSD digital
circuits and a connection point for external decoupling. (AVdd is routed
internally to LSD analog circuits.) See PWR+ pin description. Connect to
LSD DVdd pin and connect to AGND_LSD through C928 and C930 in
parallel. C928 and C930 must be placed close to pin 3 (AVdd) and pin 7
(AGnd). C930 must have ESR < 2 Ω.
Analog Ground. Connect to minus (-) terminal of full wave rectifier
(FWR). Connect FWR BR980 terminal to DIB transformer secondary
winding undotted terminal through R922.
Output Reference Voltage. Connect to AGND_LSD through C940 and
C976, which must be placed close to pin 5 (VRef). Ensure a very close
proximity between C940 and pin 5. C940 must have a maximum ESR of
2 Ω.
Output Middle Reference Voltage. Connect to AGND_LSD through
C944 and C974, which must be placed close to pin 4 (Vc). Ensure a very
close proximity between C944 and pin 4. Use a short path and a wide
trace to AGND_LSD pin.
Unregulated Power Input. Provides unregulated input power to the
LSD. PWR+ pin is an input which takes unregulated +3.2V to +4.5V from
the DIB power supply made up of the transformer, full-wave rectifier, and
filter capacitors. The PWR+ input is regulated by an internal linear
regulator to +3.3V ± 5% which is routed to the AVdd pin. If PWR+ is less
than +3.4V, then AVdd is equal to the unregulated PWR+ input value
minus 150 mV (Table 3-10).
Connect to plus (+) terminal of FWR. Connect terminal BR908 AC1 to
DIB transformer secondary winding dotted terminal through R990.
Connect transformer side of FB906 to AGND_LSD though C970. Place
FB906 and C970 close to pin 8 (PWR+) and pin 7 (AGnd).
Digital Power Input. Input power for LSD digital circuits. Connect to LSD
AVdd pin and connect to DGND_LSD through C978. Place C978 near
pin 27 (DVdd).
LSD Digital Ground. Connect to DGND_LSD, and to AGND_LSD at the
DGND_LSD/AGND_LSD tie point (U908).
Clock. Provides input clock, AC coupled to the LSD. Connect to DIB
transformer secondary winding undotted terminal through C926 (closest
to the CX20493), R932, then R922 in series. Connect the R932 and
R922 node to LSD AGND pin through full-wave rectifier BR908. Place
C926 near pin 29 (CLK) and place R932 near C926.
Data and Control Positive. Connect to DIBDAT_P through R924 in
series with C922. DIB_P and DIB_N signals are differential and half-
duplex bidirectional.
Data and Control Negative. Connect to DIBDAT_N through R926 in
series with C924. DIB_P and DIB_N signals are differential and half-
duplex bidirectional.
System Signals
Conexant
Signal Name/Description
3-25