Le79R241 Data Sheet
12
Zarlink Semiconductor Inc.
4.0 Pin Descriptions
Pin Name Type Description
AD, BD Output Provide the currents to the A and B leads of the subscriber loop.
BGND Ground Ground return for high and low battery supplies.
CREF +3.3 VDC
VCCD reference. It is the digital high logic supply rail, used by the Le79R241 ISLIC device to codec
interface.
GND Ground Analog and digital ground return for VCC.
HPA, HPB Output
These pins connect to CHP, the external high-pass filter capacitor that separates the DC loop-voltage
from the voice transmission path.
ILG Output
ILG is proportional to the common-mode line current (IAD–IBD), except in disconnect mode, where
ILG is proportional to the current into grounded SB.
IMT Output
IMT is proportional to the differential line current (IAD + IBD), except in disconnect mode, where IMT
is proportional to the current into grounded SA. The Le79R241 ISLIC device indicates thermal
overload by pulling IMT to CREF.
LD Input
The LD pin controls the input latch and responds to a 3-level input. When the LD pin is a logic 1 (C
REF
1), the logic levels on P1–P3 latch into the Le79241 control register bits that operate the
mode-decoder. When the LD pin is a logic 0 ( 0.6), the logic levels on P1–P3 latch into the Am79241
control register bits that control the relay drivers (RD1–RD3). When the LD pin level is at ~V
REF
± 0.3
V, the control register contents are locked.
P1–P3 Input Inputs to the latch for the operating-mode decoder and the relay-drivers.
R1 Output Collector connection for relay 1 driver. Emitter internally connected to BGND.
R2 Output Collector connection for relay 2 driver. Emitter internally connected to RYE
R3 Output Collector connection for relay 3 driver. Emitter internally connected to RYE.
RSN Input
The metallic current between AD and BD is equal to 500 times the current into this pin. Networks that
program receive gain and two-wire impedance connect to this node. This input is at a virtual potential
of VREF.
RSVD Reserved These pins are used during Zarlink testing. In the application, they must be left floating.
RYE Output Emitter connection for R2 and R3. Normally connected to relay ground.
SA, SB Input
Sense the voltages on the line side of the fuse resistors at the A and B leads. External sense resistors,
RSA and RSB, protect these pins from lightning or power-cross.
TMP,
TMN, TMS
Output
External resistors connected from TMP to TMS and TMN to VBL to offload excess power from the
Le79R241 ISLIC device.
VBH Battery (Power)
Connection to high-battery supply used for ringing and long loops. Connects to the substrate. When
only a single battery is available, it connects to both VBH and VBL.
VBL Battery (Power)
Connection to low-battery supply used for short loops. When only a single battery is available, this pin
can be connected to VBH.
VCC +5 V Power Supply Positive supply for low voltage analog and digital circuits in the Le79R241 ISLIC device.
VLB Input
Sets the DC longitudinal voltage of the Le79R241 ISLIC device. It is the reference for the longitudinal
control loop. When the VLB pin is greater than VREF, the Le79R241 ISLIC device sets the
longitudinal voltage to a voltage approximately half-way between the positive and negative power
supply battery rails. When the VLB pin is driven to levels between 0V and VREF, the longitudinal
voltage decreases linearly with the voltage on the VLB pin.
