AD8531ART Analog Devices, AD8531ART Datasheet - Page 13

• Manufacturer Part Number: AD8531ART
• Description: Low Cost, 250 ma Output Single-supply Amplifiers
• Manufacturer: Analog Devices

REV. B
Direct Access Arrangement for Telephone Line Interface
Figure 42 illustrates a +5 V only transmit/receive telephone line
interface for 600
transmission of signals on a transformer coupled 600
differential manner. Amplifier A1 provides gain that can be
adjusted to meet the modem output drive requirements. Both
A1 and A2 are configured to apply the largest possible signal on
a single supply to the transformer. Because of the high output
current drive and low dropout voltage of the AD8531/AD8532/
AD8534s, the largest signal available on a single +5 V supply is
approximately 4.5 V p-p into a 600
Amplifier A3 is configured as a difference amplifier for two
reasons: (1) It prevents the transmit signal from interfering with
the receive signal and (2) it extracts the receive signal from the
transmission line for amplification by A4. A4’s gain can be
adjusted in the same manner as A1’s to meet the modem’s input
signal requirements. Standard resistor values permit the use of
SIP (Single In-line Package) format resistor arrays. Couple this
with the AD8531/AD8532/AD8534’s 8-lead SOIC or TSSOP
footprint and this circuit offers a compact, cost-sensitive solution.
transmission systems. It allows full duplex
transmission system.
line in a
–13–
Figure 42. A Single-Supply Direct Access Arrangement
for Modems
TO TELEPHONE
600
Z
A1, A2 = 1/2 AD8532
A3, A4 = 1/2 AD8532
O
LINE
MIDCOM
671-8005
1:1
T1
6.2V
6.2V
10k
R11
10k
10k
R9
360
R12
AD8531/AD8532/AD8534
R3
2
3
10k
10k
10k
A3
R10
ADJUST
R5
R6
Tx GAIN
P1
1
1
2k
7
A1
A2
10k
R13
9.09k
R2
6
5
2
3
14.3k
6
5
R14
10k
A4
R1
Rx GAIN
ADJUST
10 F
2k
7
0.1 F
P2
C1
+5V DC
0.1 F
C2
R7
10k
R8
10k
TRANSMIT
RECEIVE
TxA
RxA