L7556, L7557 Low-Power SLICs
with Battery Switch
Data Sheet
January 2000
Electrical Characteristics (continued)
Table 5. 2-Wire Port
Parameter
Min
Typ
Max
Unit
Tip or Ring Drive Current:
—
—
15
—
—
—
= dc + Longitudinal + Signal Currents
65
15
mA
Signal Current
Longitudinal Current Capability per Wire1
mArms
mArms
8.5
dc Loop Current Limit2:
RLOOP = 100 Ω
—
5
—
ILIM
—
—
—
45
±12
mA
mA
%
Programmability Range
Accuracy (20 mA < ILIM < 40 mA)
Powerup Open Loop Voltage Levels (includes external diode):
Differential Voltage
|VBAT + 8.4| |VBAT + 7.9| |VBAT + 7.4|
V
Disconnect State:
143
133
—
—
PT Resistance (VBAT < VPT < 0 V)
PR Resistance (VBAT < VPR < 0 V)
100
100
kΩ
kΩ
Ground Start State:
PT Resistance
143
115
—
100
95
kΩ
dc Feed Resistance (for ILOOP below regulation level)
135
Ω
Loop Resistance Range (–3.17 dBm overload into 600 Ω; not
including protection):
—
—
—
—
ILOOP = 20 mA at VBAT2 = –48 V
ILOOP = 20 mA at VBAT2 = –24 V
1885
685
Ω
Ω
Longitudinal to Metallic Balance—IEEE 3 Std. 455 (See
Figure 6.)4:
—
—
64
60
75
70
dB
dB
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
—
—
46
—
dB
–55
–45
dBV
1. The longitudinal current is independent of dc loop current.
2. Current-limit ILIM is programmed by a resistor, RPROG, from pin IPROG to DCOUT. ILIM is specified at the loop resistance where current limiting
begins (see Figure 19). Select RPROG (kΩ) =1.67 x ILIM (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 ]
