Agere Communications Inc.
7
Data Sheet
September 2001
L7585G Full-Feature, Low-Power SLIC and Switch
Operating States
The L7585 has 14 operating states. These states are
selected using 4 bits, B0—B3, according to the truth
table shown in Table 2. The operation of the L7585 is
undefined for unassigned states. Additionally, bit B4
independently operates the test-in access contacts so
that all states are available for self-test; and bit B5
independently operates a relay driver, regardless of the
status of bits B0—B4. All 6 bits are loaded via the par-
allel data interface and chip select lead NCS.
Table 2. B0—B3 Input State Coding
Table 3. B4—B5 Input State Coding
Forward Battery Active State
I
Normal talk and forward battery feed state.
I
All circuits are powered up and active.
I
Pin PT is positive with respect to pin PR (forward bat-
tery).
I
SW2, SW2a, SW4, and SW4a closed; SW1, SW3,
SW5, and SW6 open.
I
NDET reflects the status of the switchhook detector.
Ground Start/Tip Open State
I
Ground start idle supervision state.
I
Ring lead continuity test state (tone injected at the
receive port) in forward battery.
I
Same as forward battery active state, but with SW2
and SW2a open, and the tip drive amplifier powered
down.
I
Pin PT is high impedance (>100 k
).
I
The ring current limit is approximately equal to the
value programmed for the high-current active state
current limit. Current limit is achieved by reducing the
ring lead voltage only (see Table 6).
I
NDET indicates an off-hook when the ring current
(flowing into PR) is twice the value programmed for
the switchhook detector in the forward battery active
state.
B3 B2 B1 B0
1
1
1
1
1
1
1
1
1
0
1
0
1
0
State
1
1
0
0
1
1
0
1
0
1
0
1
0
1
Forward Battery Active
Ground Start/Tip Open
Ground Start/Tip Ground
Forward Battery Ring Open
Ringing (Battery Backed)
Disconnect State
Forward Battery Low-Current
Active State
High Impedance
Reverse Battery Active
Reverse Battery Tip Open
Ground Start/Tip Amplifier
Reverse Battery Ring Open
Ringing (Earth Backed)
Unassigned
Reverse Battery Low-Current
Active State
High Impedance
1
0
0
0
0
0
0
0
0
1
1
1
1
0
0
0
0
1
1
0
0
1
1
0
0
1
0
1
0
1
0
1
0
0
0
0
Bit
State
B4
1
0
1
0
Test-in contacts off.
Test-in contacts on.
Relay driver off.
Relay driver on.
B5