Data Sheet

OP162/OP262/OP462

Rev. H | Page 17 of 20

Figure 45. Positive Slope Settling Time

Figure 46. Negative Slope Settling Time

DIRECT ACCESS ARRANGEMENT

Figure 47 shows a schematic for a 5 V single-supply transmit/

receive telephone line interface for 600 Ω transmission systems.

It allows full-duplex transmission of signals on a transformer-

coupled 600 Ω line. 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 differential

signal to the transformer. The largest signal available on a single

5 V supply is approximately 4.0 V p-p into a 600 Ω transmission

system. Amplifier A3 is configured as a difference amplifier to

extract the receive information from the transmission line for

amplification by A4. A3 also prevents the transmit signal from

interfering with the receive signal. The gain of A4 can be adjusted

in the same manner as A1 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 OP462 14-lead SOIC or TSSOP package and this circuit

offers a compact solution.

Figure 47. Single-Supply Direct Access Arrangement for Modems

10

0%

100

90

1µs

5mV

2V

10

0%

100

90

10

0%

100

90

1µs

2V

5mV

6.2V

6.2V

TRANSMIT

TXA

RECEIVE

RXA

2k

P1

TX GAIN

ADJUST

A1

A2

A3

A4

A1, A2 = 1/2 AD8532

A3, A4 = 1/2 AD8532

R3

360

Ω

ZO

600

Ω

R1

10k

Ω

R13

10k

Ω

R10

10k

Ω

R9

10k

Ω

R11

10k

Ω

C2

0.1

µF

C1

0.1

µF

10

µF

R12

10k

Ω

R7

10k

Ω

R8

10k

Ω

R5

10k

Ω

R6

10k

Ω

R14

14.3k

Ω

R2

9.09k

Ω

1:1

T1

TO TELEPHONE

LINE

1

2

3

7

6

5

2

3

1

6

5

7

P2

RX GAIN

ADJUST

2k

Ω

5V DC

MIDCOM

671-8005