L7556, L7557 Low-Power SLICs
with Battery Switch
Data Sheet
January 2000
Pin Information
V
BAT2
I
PROG
NC
L
BAT
BS1
BS2
31
4
V
CC
RCVP
RCVN
LCTH
DCOUT
V
BAT1
PR
CF2
CF1
5
6
7
8
9
10
11
12
13 14
VITR
3
2
1
32
30
29
28
27
26
SN
XMT
B1
NLC
NRDET
RTSP
RTSN
PT
BGND
32-PIN PLCC
NC
25
24
23
22
20
DCR
21
15
ICM
BS
16
RGDET
17
B0
18
AGND
19
AGND
12-2548.q (F)
Figure 2. Pin Diagram (PLCC Chip)
Table 1. Pin Descriptions
Pin
1
2
3
4
4
5
6
7
8
9
10
Symbol Type
Description
V
BAT2
—
Auxiliary Battery Supply.
Negative high-voltage battery, lower in magnitude than
V
BAT1
, used to reduce power dissipation on short loops.
I
PROG
I
Current-Limit Program Input.
A resistor to DCOUT sets the dc current limit of the
device.
BS
I
Battery Switch.
See Table 2 for description.
NC
—
No Connection (L7556 Only).
Do not use as a tie point.
L
BAT
O
Lower Battery in Use (L7557 Only).
When high, this open-collector output indicates
the device has switched to V
BAT2.
To use, connect a 100 kΩ resistor to V
CC
.
V
CC
—
+5 V Power Supply.
RCVP
I
Receive ac Signal Input (Noninverting).
This high-impedance input controls the ac
differential voltage on tip and ring.
RCVN
I
Receive ac Signal Input (Inverting).
This high-impedance input controls the ac differ-
ential voltage on tip and ring.
LCTH
I
Loop Closure Threshold Input.
Connect a resistor to DCOUT to set off-hook thresh-
old.
DCOUT
O
dc Output Voltage.
This output is a voltage that is directly proportional to the absolute
value of the differential tip/ring current.
V
BAT1
—
Battery Supply.
Negative high-voltage power supply, higher in magnitude than V
BAT2
.
4
Lucent Technologies Inc.
AGERE [ AGERE SYSTEMS ]
