TCM38C17IDL Datasheet, PDF (17/22 Pages) Texas Instruments – QComboE FOUR-CHANNEL QUAD PCM COMBO

TCM38C17IDL
QCombo™ FOUR-CHANNEL (QUAD) PCM COMBO
SLWS040C – JUNE 1996 – REVISED OCTOBER 1999
PRINCIPLES OF OPERATION
receive operation
The TCM38C17IDL receive operation is described in the following paragraphs.
receive filter
The receive filters provide pass-band flatness and stopband rejection that fulfills both the AT&T D3/D4
specification and CCITT recommendation G.712. The filter contains the required compensation for the (sin x)/x
response of such decoders.
output amplifier
The QCombo incorporates a versatile analog output power amplifier than can drive transformer hybrids or
low-impedance loads directly in either a single-ended or differential configuration. The QCombo output stage
allows for volume control (in the differential mode) by connection of a resistor divider chain to the output
terminals of the device. The inverting operational amplifier can drive a 600 Ω load in parallel with 100 pF. Figure 8
is a representation of the internal structure of the output amplifier.
RF
DAC
R1
R2
_
PWRO +
+
AREF
RINV
+
_
GSR
RINV
_
RGSR1
RGSR2
Unity Gain
+
Inverter
AREF
PWRO –
Internal External
Figure 8. Output Amplifier Architecture
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