le9500 Zarlink Semiconductor, le9500 Datasheet - Page 16

• Manufacturer Part Number: le9500
• Description: Igh-voltage Ringing Slic Device For Volp Applications
• Manufacturer: Zarlink Semiconductor

APPLICATIONS
DC Loop Current Limit
Current limit may be chosen from two discrete values, 25 mA or 40 mA, depending on if V
(40 mA). Note that there is a 12.5 kΩ 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 state steady-state current-limit response. There will be a transient response of the current-limit
circuit upon an on- to off-hook transition. Typical active state transient current-limit response is given in Table 10.
Overhead Voltage
Active state
Overhead is fixed to a nominal 7.2 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 state
If the magnitude of the primary battery is greater than 51 V (but no more than 100 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 about 4V less than battery.
On-Hook Transmission state
If the magnitude of the primary battery is greater than 51 V (but no more than 100 V), the magnitude of the open loop tip-to-ring
open loop voltage is clamped typically between 41 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 to 8 V less than battery.
Ring state
In the ring state, to maximize ringing loop length, the overhead is decreased to the saturation of the tip ring drive amplifiers, a
nominal 4 V.
During the ring state, to conserve power, the receive input at RCVN/RCVP is deactivated. During the ring state, to conserve
power, the AAC amplifier in the transmit direction at VITR is deactivated. However, the AX amplifier at VTX is active during the
ring state; differential ring current may be sensed at VTX during the ring state.
DC Loop Range
The DC loop range can be calculated by using the following equation:
where:
V
V
R
R
BAT2
OH
DC
P
is protection resistor, typically 50 Ω.
is overhead voltage, typically 7.2V.
is DC feed impedance, typically 40 Ω.
is applied under off-hook conditions for power conservation and SLIC device thermal considerations.
Table 9. Typical Active state On-Hook to Off-Hook Tip/Ring Current-Limit Transient Response
DC Loop Current:
DC Loop Current:
DC Loop Current:
Active state
R
Active state
R
Active state
R
LOOP
LOOP
LOOP
= 100 Ω On- to Off-hook Transition t < 5 ms
= 100 Ω On- to Off-hook Transition t < 50 ms
= 100 Ω On- to Off-hook Transition t < 300 ms
Parameter
R
LOOP
Zarlink Semiconductor Inc.
=
------------------------------------- -
V
BAT2
I
LOOP
16
–
V
OH
– 2R
P
– R
DC
I
I
I
LIM
LIM
LIM
PROG
+ 60
+ 20
Value
is grounded (25 mA) or left floating
mA
mA
mA
Unit