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STMicroelectronics Solutions for ADSL Line Interfaces

TA0313

The TS612 comes in SO20 plastic batwing package which increases its power dissipation capability to

2.7W at room temperature. It features a power-down or stand-by function in order to minimize the

consumption when the modem is not in communication.

Power Supply

Remote ADSL modem terminals must be designed to be easily connected to a PC. For such applications,

the driver should use a +12V single power supply, which is available via standard PCI connectors. Note

that the TS613 and TS612 can also be powered by a dual power supply at +/-6V.

Figure 4 shows a single +12V supply circuit with the TS613 as a remote terminal transmitter in differential

mode. Note that one could also use the TS612 in exactly the same schema.

The driver is biased with a mid-supply (nominally +6V) in order to maintain the DC component of the

signal at +6V. This allows a maximum dynamic range between 0 and +12 V. Several options are possible

in order to provide this bias supply—such as for example, a virtual ground using an operational amplifier,

or, the cheapest solution, a two-resistor divider. A high resistance value is required to limit the current

consumption. On the other hand, the current must be high enough to bias the inverting input of the driver.

If we consider the positive input’s bias current (15µA max) as 1% of the current through the resistance

divider (1.5mA), two 3.9k

Ω resistors are sufficient to keep a stable mid-supply .

Figure 3: Thermal considerations: power dissipation of the drivers vs. room temperature

Figure 4: Implementation of the TS613 as a differential line driver with a +12V single supply

-40

-30

-20

-10

0

102030

4050

6070

80

Room Temperature (°C)

0

1

2

3

4

5

½R1

R4

R2

_

+

_

+

Vi

Vi

Vo

Vo

3

2

6

5

1

7

4

GND

8

+12V

25

100Ω

1:2

Hybrid

&

Transformer

GND

+12V

3k9

3k9

10µ

100n

100n

100n

1k

1k

12.5

Ω

10n

1µ

_

+

_

+

Vi

Vi

Vo

Vo

3

2

6

5

1

7

4

GND

8

+12V

25

Ω

100Ω

1:2

Hybrid

&

Transformer

GND

+12V

3k9

3k9

10µ

100n

100n

100n

1k

1k

10n

1µ

12.5

Ω

½R1

½R1

R4

R2

_

+

_

+

Vi

Vi

Vo

Vo

3

2

6

5

1

7

4

GND

8

+12V

25

100Ω

1:2

Hybrid

&

Transformer

GND

+12V

3k9

3k9

10µ

100n

100n

100n

1k

1k

12.5

Ω

10n

1µ

_

+

_

+

Vi

Vi

Vo

Vo

3

2

6

5

1

7

4

GND

8

+12V

25

Ω

100Ω

1:2

Hybrid

&

Transformer

GND

+12V

3k9

3k9

10µ

100n

100n

100n

1k

1k

10n

1µ

12.5

Ω

½R1