am79231 ETC-unknow, am79231 Datasheet - Page 20

• Manufacturer Part Number: am79231
• Description: Intelligent Subscriber Line Interface Circuit Islic
• Manufacturer: ETC-unknow

Table 2.
Table 3.
20
Disconnect
Standby
Tip Open
Active High Battery
Active Low Battery
On-Hook Transmission
(OHT), Fixed Longitudinal
Voltage
Operating Mode
Mode Descriptions
Driver Descriptions
Control bits RD1, RD2, and RD3 do not affect the operating mode of the Am79231. These signals
usually perform the following functions.
Driver
R1
R2
This mode disconnects both A and B output amplifiers from the AD and BD outputs. The
A and B amplifiers are shut down and the Am79231 selects the low battery voltage at the
VBL pin. In the Disconnect state, the currents on IMT and ILG represent the voltages on
the SA and SB pins, respectively. These currents are scaled to produce voltages across
RMTi and RLGi of
The power amplifiers are turned off. The AD output is driven by an internal 250 Ω (typical)
resistor, which connects to ground. The BD output is driven by an internal 250 Ω (typical)
resistor, which connects to the high battery (BATH) at the VBH pin, through a clamp circuit,
which clamps at –50 V with respect to BGND. For VBH values above –55 V, the open-
circuit voltage, which appears at this output is ~VBH + 5 V. If VBH is below –55 V, the
voltage at this output is –50 V. The battery selection for the balance of the circuitry on the
chip is VBL. Line supervision remains active. Current limiting is provided on each line to
limit power dissipation under short-loop conditions as specified in the “Am79231 Current-
Limit Behavior” section. In external ringing, the standby ISLIC state is selected.
In this mode, the AD (Tip) lead is opened and the BD (Ring) lead is connected to a clamp,
which operates from the high battery on VBH pin and clamps to approximately –50 V with
respect to BGND through a resistor of approximately 250 Ω (typical). The battery selection
for the balance of the circuitry on the chip is VBL. To prevent excessive power dissipation,
the current in the Ring lead is limited by an internal current source to 30 mA.
amplifiers deliver the full power level determined by the programmed DC-feed conditions.
Active High Battery mode is enabled during a call in applications when a long loop can
be encountered.
conditions. VBL, the low negative battery, is selected in the Active Low Battery mode. This
is typically used during the voice part of a call.
In the On-Hook Transmission, Fixed Longitudinal Voltage mode, battery connections are
as shown in Table 1. The longitudinal voltage is fixed at –30 V to allow compliance with
safety specifications for some classes of products.
A logic 1 on RD1 turns the R1 driver on and operates a relay connected between the R1
pin and VCCD. R1 drives the ring relay.
A logic 1 on the RD2 signal turns the R2 driver on and routes current from the R2 pin to
the RYE pin. In the option where the RYE pin is connected to ground, the R2 pin can sink
current from a relay connected to VCCD.
Another option is to connect the RYE pin to the BD (Ring) lead through a diode and connect
a test load between R2 and the AD (Tip) lead. This technique avoids the use of a relay to
connect a test load. However, it does not isolate the subscriber line from the linecard. The
test load must be connected to the Am79231 side of the protection resistor to avoid
damage to the R2 driver.
In the Active High Battery mode, battery connections are as shown in Table 1. Both output
Both output amplifiers deliver the full power level determined by the programmed DC-feed
Am79231 Data Sheet
V
--------- -
400
SA
and
V
-------- -
400
SB
, respectively.
Description
Description