le9500 Zarlink Semiconductor, le9500 Datasheet - Page 3

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

PRODUCT DESCRIPTION
The Le9500 device is optimized to provide battery feed, ringing, and supervision on short Plain Old Telephone Service (POTS)
loops. This device provides power ringing to the subscriber loop through amplification of a low-voltage input. It also provides
forward and reverse battery feed states, on-hook transmission, a low-power scan state, ground start (tip open), and a forward
disconnect state.
The Le9500 device requires a 3.3V V
use of a lower-voltage battery in the off-hook condition, thus minimizing short-loop off-hook power.
The following two batteries are used:
1. A high-voltage operation and ringing battery (V
2. A lower-voltage talk battery (V
Loop closure, ring trip, and ground start detection is available. The loop closure detector has fixed threshold with hysteresis. The
ring trip detector requires a single-pole filter, thus minimizing external components required. The ring trip threshold at a given
battery voltage is fixed and with hysteresis. Ground start detection also has fixed threshold with hysteresis.
The DC current limit is set and fixed by a logic-controllable pin. Ground or open applied to this pin sets the current limit at the low
or high value.
This device is designed for ultra-low power in all operating states.
Forward and reverse battery active states are used for off-hook conditions. Since this device is designed for short-loop
applications, the lower-voltage V
breaking the AC path. Rate of battery reversal may be ramped to control switching time.
The magnitude of the overhead voltage in the forward and reverse active states has a typical default value of 7.2 V, allowing for
an on-hook transmission of an undistorted signal of 3.14 dBm into 900 Ω. Additionally, this allows sufficient overhead for 500 mV
of meter pulse if desired. This overhead is fixed. The ring trip detector is turned off during active states to conserve power.
Because on-hook transmission is not allowed in the scan state, an on-hook transmission state is defined. This state is functionally
similar to the active state, except the tip ring voltage is derived from the higher V
In the on-hook transmission states with a primary battery whose magnitude is greater than a nominal 56.5 V, the magnitude of
the tip-to-ground and ring-to-ground voltage is clamped at less than 56.5 V.
To minimize on-hook power, a low-power scan state is available. In this state, all functions except off-hook supervision are turned
off to conserve power. On-hook transmission is not allowed in the scan state.
In the scan state with a primary battery whose magnitude is greater than a nominal 56.5 V, the magnitude of the tip-to-ground
and ring-to-ground voltage is clamped at less than 56.5 V.
A forward disconnect state is provided, where all circuits are turned off and power is denied to the loop.
The device offers a ring state, in which a power ring signal is provided to the tip/ring pair. During the ring state, user-supplied low-
voltage ring signals are input to the device’s RING
either or both include certain DC offset. Both inputs should reference to Vref. The two signals are amplified to produce the power
ring signal. The input signal or signals may be a sine wave or filtered square wave to produce a sine wave or trapezoidal output.
The Ring Trip detector is active during the ring state. The flexibility makes the device ideal to directly interface to DOCSIS
compliant cable modem gateway products.
This feature eliminates the need for a separate external ring relay, associated external circuitry, and a bulk ringing generator.
The device offers a ground start state. In this state, the tip drive amplifier is turned off. The device presents a high impedance
(>100 kΩ) to PT and a current-limited battery (V
The NSTAT loop current detector is used for ring ground detection. In the ground start state, since the loop current is common
state, the loop closure threshold is reduced in half, thus maintaining loop supervision at specified levels.
Upon reaching the thermal shutdown temperature, the device will enter an all off state. Upon cooling, the device will re-enter the
state it was in prior to thermal shutdown. Hysteresis is built in to prevent oscillation.
Data control is via a parallel unlatched control scheme.
Circuitry is added to the Le9500 device to minimize the inrush of current from the V
on- to off-hook transition, thus saving in power supply design cost.
V
–85 V for Le9500B, or –100V for Le9500C and Le9500D.
For Le9500D during ringing only this voltage may be extended to –145 V. The supply has to be externally adjustable. It has
to be adjusted back to no more than -100 V for other operation states. Further, when –145 V is used for ringing special care
should be applied to prevent certain faults from happening such as tip to ring, tip or ring to ground.
V
BAT1
BAT2
is used for active state powering.
is used for scan, on-hook transmission, ground start, and power ringing. It can be a maximum of –75 V for Le9500A,
BAT2
BAT2
CC
is applied during the forward and reverse active
):
and battery to operate eight operating states. A battery switch is included to allow for
BAT1
BAT1
INP/N
Zarlink Semiconductor Inc.
) to PR. The voltage on PR is clamped to be less than 56.5 V in magnitude.
):
inputs. The input signals can be differential or single-ended, and can
3
BAT1
CC
rather than V
supply and to the battery supply during an
states.
Battery reversal is quiet, without
BAT2
.