LUCL9500AGF-DT datasheet(24/32 Pages) AGERE

24 / 32 page

Preliminary Data Sheet

September 2001

High-Voltage Ringing SLIC for VoIP Applications

L9500A

Agere Systems Inc.

Applications (continued)

Power Ring

The device offers a ring mode, in which a balanced

power ring signal is provided to the tip/ring pair. During

the ring mode, a user-supplied low-voltage ring signal

is input to the device’s RINGIN input. This signal is

amplified to produce the balanced power ring signal.

The user may supply a sine wave input, PWM input, or

a square wave to produce sinusoidal or trapezoidal

ringing at tip and ring.

Various crest factors are shown below for illustrative

purposes.

12-3346a (F)

Note: Slew rate = 5.65 V/ms; trise = tfall = 23 ms; pwidth = 2 ms;

period = 50 ms.

Figure 9. Ringing Waveform Crest Factor = 1.6

12-3347a (F)

Note: Slew rate = 10.83 V/ms; trise = tfall = 12 ms; pwidth = 13 ms;

period = 50 ms.

Figure 10. Ringing Waveform Crest Factor = 1.2

Sine Wave Input Signal and Sine Wave Power Ring

Signal Output

The low-voltage sine wave input is applied differentially

or single ended to the L9500 at pins RINGINP and

RINGINN. During the ring mode, the signals at pins

RINGINP and RINGINN are amplified and presented to

the subscriber loop. The differential gain from RINGIN

to tip and ring is a nominal 70.

When the device enters the ring mode, the tip/ring

overhead set at OVH and the scan clamp circuit are

disabled, allowing the voltage magnitude of the power

ring signal to be maximized. Additionally, in the ring

mode, the loop current limit is increased 2.5X the value

set by the VPROG voltage.

The magnitude of the power ring voltage will be a func-

tion of the gain of the ring amplifier, the high-voltage

battery, and the input signal at RINGIN. The input range

of the signal at RINGIN is 0 V to Vcc. As the input volt-

age at RINGIN is increased, the magnitude of the power

ring voltage at tip and ring will increase linearly, per the

gain of 70, until the tip and ring drive amplifiers begin to

saturate. Once the tip and ring amplifiers reach satura-

tion, further increases of the input signal will cause clip-

ping distortion of the power ring signal at tip and ring.

The ring signal will appear balanced on tip and ring.

That is, the power ring signal is applied to both tip and

ring, with the signal on tip 180

° out of phase from the

signal on ring.

It is recommended that the input level at RINGIN be

adjusted so that the power ring signal at tip and ring is

just at the edge or slightly clipping. This gives maxi-

mum power transfer with minimal distortion of the sine

wave. The tip side will saturate at a nominal 1 V above

ground. The ring side will saturate at a nominal 3 V

above battery. The input circuit for a sine wave along

with waveforms to illustrate the tip and ring saturation

is shown in Figure 9.

The point at which clipping of the power ring signal

begins at tip and ring is a function of the battery volt-

age, the input capacitor at RINGIN, and the input signal

at RINGIN and Vcc. During nonring modes, the sinusoi-

dal ringing waveform may be left on at RINGIN. Via the

state table, the ring signal will be removed from tip and

ring even if the low-voltage input is still present at

RINGIN.

TIME (s)

–80

–60

–40

–20

0.00

0.02 0.06

0.04 0.08

0.10

0.12

0.14

0.16

0.18

0.20

TIME (s)

–80

–60

–40

–20

0.00

0.02 0.06

0.04 0.08

0.10

0.12

0.14

0.16

0.18

0.20

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