L7556, L7557 Low-Power SLICs
with Battery Switch
Data Sheet
January 2000
Electrical Characteristics
(continued)
Table 5. 2-Wire Port
Parameter
Tip or Ring Drive Current:
= dc + Longitudinal + Signal Currents
Signal Current
Longitudinal Current Capability per Wire
1
dc Loop Current Limit
2
:
R
LOOP
= 100
Ω
Programmability Range
Accuracy (20 mA < I
LIM
< 40 mA)
Min
65
15
8.5
—
5
—
Typ
—
—
15
I
LIM
—
—
Max
—
—
—
—
45
±12
Unit
mA
mArms
mArms
mA
mA
%
V
kΩ
kΩ
kΩ
Ω
Powerup Open Loop Voltage Levels (includes external diode):
|V
BAT
+ 8.4| |V
BAT
+ 7.9| |V
BAT
+ 7.4|
Differential Voltage
Disconnect State:
PT Resistance (V
BAT
< V
PT
< 0 V)
PR Resistance (V
BAT
< V
PR
< 0 V)
Ground Start State:
PT Resistance
dc Feed Resistance (for I
LOOP
below regulation level)
Loop Resistance Range (–3.17 dBm overload into 600
Ω;
not
including protection):
I
LOOP
= 20 mA at V
BAT2
= –48 V
I
LOOP
= 20 mA at V
BAT2
= –24 V
Longitudinal to Metallic Balance—
IEEE
3
Std. 455 (See
4
:
50 Hz to 1 kHz
1 kHz to 3 kHz
Metallic to Longitudinal Balance:
200 Hz to 4 kHz
RFI Rejection (See Figure 7.)
5
:
0.5 Vrms, 50
Ω
Source, 30% AM Mod 1 kHz
500 kHz to 100 MHz
100
100
100
95
143
133
143
115
—
—
—
135
1885
685
—
—
—
—
Ω
Ω
64
60
46
75
70
—
—
—
—
dB
dB
dB
—
–55
–45
dBV
1. The longitudinal current is independent of dc loop current.
2. Current-limit I
LIM
is programmed by a resistor, R
PROG
, from pin I
PROG
to DCOUT. I
LIM
is specified at the loop resistance where current limiting
begins (see Figure 19). Select R
PROG
(kΩ) =1.67 x I
LIM
(mA).
3.
IEEE
is a registered trademark of The Institute of Electrical and Electronics Engineers, Inc.
4. Longitudinal balance of circuit card will depend on loop series resistance matching (see Figure 23 and Figure 24).
5. This parameter is not tested in production. It is guaranteed by design and device characterization.
8
Lucent Technologies Inc.
AGERE [ AGERE SYSTEMS ]
