ISL1536_14 Datasheet, PDF (7/9 Pages) Intersil Corporation – Dual Channel Central Office ADSL2+ Line Driver

Applications Information
Product Description
The ISL1536 consists of two sets of high-power line driver
amplifiers that can be connected for full duplex differential
line transmission. The amplifiers are designed to be used
with ADSL2+ signals up to 2.2MHz. Each amplifier has
identical positive gain connections resulting in optimum
common-mode rejection. A typical interface circuit
configuration is shown in Figure 15.
DRIVER
INPUT
+
-
R_F*
R_B
TIP
R_G*
DRIVER
INPUT
R_F*
-
R_B
+
R_F
R
Z_LINE
RING
RECEIVER
-
OUTPUT +
+
R_IN
RECEIVE
AMPLIFIERS ₊
R
-
RECEIVER
OUTPUT -
R_F
R_IN
*Values are internally
set for line driver
FIGURE 15. TYPICAL INTERFACE CIRCUIT CONFIGURATION
Integrated Components
ISL1536 integrates bias and feedback resistors, minimizing
the number of external components. The gain is fixed at
+12.85V/V.
The VBAB and VBCD pins also integrate a pair of 7.5kΩ and
50kΩ resistors on each port to bias the line driver for single
and dual supply usage. When powering the line driver with a
single supply, VBAB and VBCD pins are floated. When using
dual supplies, VBAB and VBCD pins are grounded.
Integration of these components in the line driver minimizes
assembly cost and board space.
Impedance Matching
R_B in Figure 15 depends on the line impedance and
transformer’s turns ratio. Line impedance is characterized to
be 100Ω across tip and ring. If a 1:N tranformer is used, R_B
can be calculated according to Equation 1:
⎝⎛ ^{R B}
=
1_----0_---0_--
N²
×
0.5_⎠⎞
(EQ. 1)
7
FN6508.4
February 15, 2013