LUCL9500AGF-DT datasheet(22/32 Pages) AGERE

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Preliminary Data Sheet

September 2001

High-Voltage Ringing SLIC for VoIP Applications

L9500A

Agere Systems Inc.

Applications (continued)

dc Loop Current Limit

Current limit may be chosen from two discrete values,

25 mA or 40 mA, depending on if VPROG is grounded

(25 mA) or left floating (40 mA). Note that there is a

12.5 k

Ω slope to the I/V characteristic in the current-

limit region; thus, once in current limit, the actual loop

current will increase slightly, as loop length decreases.

The above describes the active mode steady-state cur-

rent-limit response. There will be a transient response

of the current-limit circuit upon an on- to off-hook transi-

tion. Typical active mode transient current-limit

response is given in Table 19.

Table 19. Typical Active Mode On- to Off-Hook Tip/

Ring Current-Limit Transient Response

Overhead Voltage

Active Mode

Overhead is fixed to a nominal 7.0 V, which is adequate

for an on-hook transmission of 3.14 dBm into 900

Ω

with additional head room for a 500 mV PPM signal.

Scan Mode

If the magnitude of the primary battery is greater than

51 V, the magnitude of the open loop tip-to-ring open

loop voltage is clamped typically between 44 V and

51 V. If the magnitude of the primary battery is less

than a nominal 51 V, the overhead voltage will track the

magnitude of the battery voltage, i.e., the magnitude of

the open circuit tip-to-ring voltage will be 4 V to 6 V less

than battery. In the scan mode, overhead is unaffected

by VOVH.

On-Hook Transmission Mode

If the magnitude of the primary battery is greater than

51 V, the magnitude of the open loop tip-to-ring open

loop voltage is clamped typically between 41 V and

49 V. If the magnitude of the primary battery is less

than a nominal 51 V, the overhead voltage will track the

magnitude of the battery voltage, i.e., the magnitude of

the open circuit tip-to-ring voltage will be 6 V to 8 V less

than battery. In the scan mode, overhead is unaffected

by VOVH.

Ring Mode

In the ring mode, to maximize ringing loop length, the

overhead is decreased to the saturation of the tip ring

drive amplifiers, a nominal 4 V. The tip to ground volt-

age is 1 V, and the ring to VBAT1 voltage is 3 V. In the

ring mode, overhead is unaffected by VOVH.

During the ring mode, to conserve power, the receive

input at RCVN/RCVP is deactivated. During the ring

mode, to conserve power, the ACC amplifier in the

transmit direction at VITR is deactivated. However, the

AX amplifier at VTX is active during the ring mode; dif-

ferential ring current may be sensed at VTX during the

ring mode.

Loop Range

The dc loop range is calculated using:

RL =

– 2RP – RDC

VBAT2 is typically applied under off-hook conditions for

power conservation and SLIC thermal considerations.

The L9500 is intended for short-loop applications and,

therefore, will always be in current limit during off-hook

conditions. However, note that the ringing loop length

rather than the dc loop length will be the factor to deter-

mine operating loop length.

Parameter

Value

Unit

dc Loop Current:

Active Mode

RLOOP = 100

Ω On- to Off-hook

Transition t < 5 ms

ILIM + 60

dc Loop Current:

Active Mode

RLOOP = 100

Ω On- to Off-hook

Transition t < 50 ms

ILIM + 20

dc Loop Current:

Active Mode

RLOOP = 100

Ω On- to Off-hook

Transition t < 300 ms

ILIM

VBAT2

VOH

–

ILIMIT

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