N681622YG Nuvoton Technology Corporation of America, N681622YG Datasheet - Page 55

• Manufacturer Part Number: N681622YG
• Manufacturer: Nuvoton Technology Corporation of America

Specifications of N681622YG

• Lead Free Status / RoHS Status: Supplier Unconfirmed

Conversely, to calculate the dB value of the gain based on known gain step values, the equation is:
The table below contains a sample of possible gain settings.
The device exceeds the maximum ITU requirements for frequency response, group delay distortion and signal to
distortion as can be verified from the diagrams in Section 11. Audio signals larger than 0dBm0 can be processed
without clipping in either compression scheme. The maximum PCM code generated for a sine wave is 3.17 dBm0 (μ-
law) or 3.14 dBm0 (A-law).
The N681386/87 overload clipping limits are driven by the PCM encoding process. The presence of a high-pass filter
transfer function ensures at least 30 dB of attenuation for signals below 65 Hz. The Low Pass Filter transfer function
which attenuates signals above 3.6 kHz has to exceed the requirements specified by ITU G.714 and it is
implemented as part of the A/D. The receive path transfer function requirement is very similar to the transmit path
transfer function. We have added the high-pass filter portion as a user controlled option. Pass-band has been defined
between 300 Hz to 3600 Hz. As the PCM data rate is 8 kHz, no frequencies greater than 4 kHz can be digitally
encoded in the data stream.
The N681386/87 provides fully programmable hybrid balancing to cancel transmit and receive signal echo on the full-
duplex 2-wire pair. The hybrid balancing is performed at the internal 4-wire port. It is measured as the ratio of the
un-cancelled return signal to the reference signal (digital-to-digital gain). Although the ITU standard recommends a
hybrid balance below –18 dB within the voice band, care has been taken to reduce this further to –30 dB in order to
avoid unacceptable voice quality for packet based networks.
The Tran hybrid Balance is internally set to subtract a –6 dB level from the transmit path signal, corresponding to the
ideal case when the impedance matching perfectly matches the subscriber loop. This level can be adjusted from -
Preliminary Datasheet Rev1.0
12.1.6.1.3.
Table 23: Digital Gain Adjust Coefficients and Attenuation weightings
ANALOG TRANSHYBRID BALANCING
-24
-12
dB
-∞
-6
0
6
X
dB
Page 55 of 164
=
20
Gain
1 / 8
1 / 4
1 / 2
Off
1
2
×
log
Single Programmable Extended Codec/SLCC
10
(
Y
1024
Gain Setting (Y)
)
0x7FF
0x000
0x040
0x100
0x200
0x400
N681386/87
January 2010