TP3054-X NSC [National Semiconductor], TP3054-X Datasheet - Page 12

• Manufacturer Part Number: TP3054-X
• Description: Extended Temperature Serial Interface CODEC/Filter COMBO Family
• Manufacturer: NSC [National Semiconductor]

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Applications Information
POWER SUPPLIES
While the pins of the TP3050 family are well protected
against electrical misuse, it is recommended that the stan-
dard CMOS practice be followed, ensuring that ground is
connected to the device before any other connections are
made. In applications where the printed circuit board may be
plugged into a “hot” socket with power and clocks already
present, an extra long ground pin in the connector should be
used.
All ground connections to each device should meet at a
common point as close as possible to the GNDA pin. This
minimizes the interaction of ground return currents flowing
through a common bus impedance. 0.1 µF supply decou-
pling capacitors should be connected from this common
ground point to V
possible.
For best performance, the ground point of each CODEC/
FILTER on a card should be connected to a common card
ground in star formation, rather than via a ground bus.
T-Pad Attenuator
CC
and V
BB
, as close to device pins as
12
This common ground point should be decoupled to V
V
RECEIVE GAIN ADJUSTMENT
For applications where a TP3050 family CODEC/filter re-
ceive output must drive a 600Ω load, but a peak swing lower
than
justed by inserting a matched T-pad or π-pad at the output.
Table 2 lists the required resistor values for 600Ω termina-
tions. As these are generally non-standard values, the equa-
tions can be used to compute the attenuation of the closest
practical set of resistors. It may be necessary to use unequal
values for the R1 or R4 arms of the attenuators to achieve a
precise attenuation. Generally it is tolerable to allow a small
deviation of the input impedance from nominal while still
maintaining a good return loss. For example a 30 dB return
loss against 600Ω is obtained if the output impedance of the
attenuator is in the range 282Ω to 319Ω (assuming a perfect
transformer).
BB
with 10 µF capacitors.
±
2.5V is required, the receive gain can be easily ad-
00867411
CC
and