ETC5054D/H013TR 查看數據表（PDF） - STMicroelectronics
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ETC5054D/H013TR Datasheet PDF : 18 Pages
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APPLICATION INFORMATION
POWER SUPPLIES
While the pins at the ETC505X family are well
protected against electrical misuse, it is recom-
mended that the standard CMOS practice be fol-
lowed, 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. 0.1µF supply decoupling capaci-
tors should be connected from this common
ground point to VCC and VBB as close to the de-
vice as 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. This common ground point
should be decoupled to VCC and VBB with 10µF
capacitors.
Figure 4: T-PAD Attenuator
ETC5054 - ETC5057
R3
=
√Z1.Z 2
2
N2 −
N
1
R3
=
Z1
N2
N2 − 1
− 2NS
+
1
RECEIVE GAIN ADJUSTMENT
For applications where a ETC505X family
CODEC/filter receive output must drive a 600Ω
load, but a peak swing lower then ± 2.5V is re-
quired, the receive gain can be easily adjusted by
inserting a matched T-pad or π –pad at the out-
put. Table II lists the required resistor values for
600Ω terminations. As these are generally non-
standard values, the equations can be used to
compute the attenuation of the closest pratical 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 tol-
erable to allow a small deviation of the input im-
pedance from nominal while still maintaining a
good return loss. For example a 30dB return loss
against 600Ω is obtained if the output impedance
of the attenuator is in the range 282Ω to 319Ω
(assuming a perfect transformer).
R1
=
Z1
N2
N2
+
−
1
1
−2
√Z1. Z2
N
N2
−
1
R2
=
2
√Z1.Z2
N
N2
−
1
Where: N = √PPOOWWEERROIUNT
an
d:
S
=
√Z1
Z2
Also : Z = √ZSC.ZOC
Where ZSC = impedance with short circuit termi-
nation and ZOC = impedance with open circuit ter-
mination.
Figure 5: Π-PAD Attenuator
Table 2 : Attenuator Tables For
Z1 = Z2 = 300 Ω (all values in Ω).
dB
R1
R2
R3
0.1
1.7
26k
3.5
0.2
3.5
13k
6.9
0.3
5.2
8.7k
10.4
0.4
6.9
6.5k
13.8
0.5
8.5
5.2k
17.3
0.6
10.4
4.4k
21.3
0.7
12.1
3.7k
24.2
0.8
13.8
3.3k
27.7
0.9
15.5
2.9k
31.1
1.0
17.3
2.6k
34.6
2
34.4
1.3k
70
3
51.3
850
107
4
68
650
144
5
84
494
183
6
100
402
224
7
115
380
269
8
129
284
317
9
143
244
370
10
156
211
427
11
168
184
490
12
180
161
550
13
190
142
635
14
200
125
720
15
210
110
816
16
218
98
924
18
233
77
1.17k
20
246
61
1.5k
R4
52k
26k
17.4k
13k
10.5k
8.7k
7.5k
6.5k
5.8k
5.2k
2.6k
1.8k
1.3k
1.1k
900
785
698
630
527
535
500
473
450
430
413
386
366
13/18
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