AM79Q4457 Datasheet, PDF (29/44 Pages) List of Unclassifed Manufacturers – Quad Subscriber Line Audio Processing Circuit-Non-Programmable (QSLAC-NP) Devices

Table 3. Receive Gain Select
(Am79Q4457 Device Only)
Receive Gain Select 1 (RGS1) and
Receive Gain Select 2 (RGS2)
RGS2 RGS1
D-to-A Voltage Reference
0
0
Gr = Gr1 = 1
0
1
1
0
1
1
Note:
0.4 ≤ Gr ≤ 1
Gr = Gr2 = ------1---.-4-----^•-----R----^R---^E---^F---²--^A-------
R_REF2A + R_REF2B
Gr = Gr3 = ------1---.-4-----^•-----R----^R---^E---^F---³--^A-------
R_REF3A + R_REF3B
Do Not Use
Gain Settings for the Am79Q5457 Device
The transmit and receive gains for each of the four
channels are set for the Am79Q5457 device similarly
to those of the Am79Q4457 device. The Am79Q5457
device has only one I_REF output and one V_REF input as
shown in Figure 9b, and only one gain setting is avail-
able. The transmit gain is a function of the reference
current set up by the R_REF1 resistor and by the R_TX1
input resistor, and is set by the following equation:
Gt = -3----^•----R-----^R---^E---^F--¹-
R1_TX1
The receive gain Gr through the QSLAC-NP device is
equal to 1 and is not adjustable. However, this gain typ-
ically is set by choice of component values in the SLIC
portion of the circuit.
to
SLIC
VTX
R1_TX1 C1_TX1 l1_IN1
Am79Q4457JC
R2_TX1
l2_IN1
C2_TX1
BNS1
to
SLIC
RSN
R_RX1
Bal Bal
Net Net
1
2
*
*
Bal Bal
Net Net
1
2
C_RX1
V_OUT1
A/D 1 ^{2 3 4}
I_REF
IO
3 to 1
Multiplexer
I1 I2 I3
I_REF1
I_REF2
I_REF3
TGS1
TGS2
V_REF
to
I_REF
I_REF1 R_REF1
I_REF2 R_REF2A
I_{REF3 RREF3A}
R_REF2B
R_REF3B
V_REF1
V1
V2
3 to 1
Multiplexer ^V3
Vo
V_REF
D/A 1
2
34
RGS1
RGS2
V_REF1 ^CFIL
V_REF2
V_REF3
*Optional Bal Net Connection
20031A–010
Figure 9a. Am79Q4457JC Device
(Channel 1 Shown)
SLAC Products
29