THS6032

LOW-POWER ADSL CENTRAL-OFFICE LINE DRIVER

SLOS233C – APRIL1999 – REVISED MARCH 2000

21

POST OFFICE BOX 655303

APPLICATION INFORMATION

shutdown function (continued)

1 k

Ω

To Internal

Output

Node

Q2

+IN

Pin

–IN

Pin

To Output

Drive

Circuitry

Q1

Q3

Q4

Q5

Q6

+VCC(H)

IBIAS–1

IBIAS–2

DGND

QS1

IBIAS–S1

IBIAS–S2

QS2

QS3

QS4

Shut–Down Circuitry

Active

Load

Active

Load

CC(H)

–V

Figure 44. Simplified THS6032 Input Stages

Because the DGND pin voltage is effectively at a noninverting terminal, any signal or voltage fluctuation at this

node is amplified by the THS6032. This could possibly cause a noisy output to appear during shutdown

operation. Figure 45 shows the frequency response of the THS6032 due to an input signal at the DGND

terminal. The maximum DGND voltage signal which the THS6032 will follow linearly during shutdown operation

is less than

±4 V. With this dynamic range capability, it is recommended that the DGND pin be as noise-free

as possible to ensure proper transmission line termination.

Figure 45

–6

–5

–4

–3

–2

–1

0

1

2

3

DGND OUTPUT AMPLITUDE

vs

FREQUENCY

f – Frequency – Hz

100 k

1 M

10 M

100 M

VCC(H) = ± 15 V

VCC(L) = ± 5 V

RL = 25 Ω

VSD = +10 V

VI = DGND Pin

VO(PP) = 0.2 V

VO(PP) = 2 V