L7556, L7557 Low-Power SLICs
with Battery Switch
Data Sheet
January 2000
Functional Description
Table 2. Input State Coding
B0 B1
BS
State/Definition
1
1
1
Powerup, Forward Battery. Normal talk and battery feed state. Pin PT is positive with respect
to PR. On-hook transmission is enabled. VBAT1 is applied to entire circuit.
1
1
0
Powerup, Forward Battery. Normal talk and battery feed state. Pin PT is positive with respect
to PR. On-hook transmission is enabled.
For the L7556 only, VBAT2 is applied to tip/ring drive amplifiers.
For the L7557 only, the device compares the magnitude of VBAT2 to the voltage necessary to
maintain proper loop current. Then the device automatically applies VBAT2 to tip/ring drive am-
plifiers when possible, not affecting the desired dc template.
1
0
0
0
1
1
2-Wire Wink. Pins PT and PR are put at the same potential (near ground). VBAT1 is applied to
entire circuit.
Disconnect. The tip and ring amplifiers are turned off, and the SLIC goes to a high-impedance
state (>100 kΩ).VBAT1 is applied to entire circuit.
Table 3. Supervision Coding
Pin NLC
Pin NRDET
Pin RGDET
1 = ring ground
0 = no ring ground
0 = off-hook
1 = on-hook
0 = ring trip
1 = no ring trip
Absolute Maximum Ratings (TA = 25 °C)
Stresses in excess of the Absolute Maximum Ratings can cause permanent damage to the device. These are
absolute stress ratings only. Functional operation of the device is not implied at these or any other conditions in
excess of those given in the operational sections of the data sheet. Exposure to Absolute Maximum Ratings for
extended periods can adversely affect device reliability.
Parameter
Symbol
VCC
Value
7.0
Unit
V
5 V Power Supply
Battery (Talking) Supply
VBAT1
VBAT2
—
–63
V
Auxiliary Battery Supply
–63
V
Logic Input Voltage
–0.5 to +7.0
–7.0 to +7.0
165
V
Analog Input Voltage
—
V
Maximum Junction Temperature
Storage Temperature Range
Relative Humidity Range
TJ
°C
°C
%
V
Tstg
–40 to +125
5 to 95
RH
Ground Potential Difference (BGND to AGND)
PT or PR Fault Voltage (dc)
PT or PR Fault Voltage (10 x 1000 µs)
Current into Ring Trip Inputs
—
±3
VPT, VPR
VPT, VPR
IRTSP, IRTSN
(VBAT1 – 5) to +3
(VBAT1 – 15) to +15
±240
V
V
µA
Note: The IC can be damaged unless all ground connections are applied before, and removed after, all other connections. Furthermore, when
powering the device, the user must guarantee that no external potential creates a voltage on any pin of the device that exceeds the
device ratings. Some of the known examples of conditions that cause such potentials during powerup are the following:
1. An inductor connected to tip and ring can force an overvoltage on VBAT through the protection devices if the VBAT connections chatter.
2. Inductance in the VBAT leads could resonate with the VBAT filter capacitors to cause a destructive overvoltage.
6
Lucent Technologies Inc.
AGERE [ AGERE SYSTEMS ]
