pbl386141 ETC-unknow, pbl386141 Datasheet - Page 13

• Manufacturer Part Number: pbl386141
• Description: Pbl 386 14/1 Subscriber Line Interface Circuit
• Manufacturer: ETC-unknow

Battery Switch
To reduce short loop power dissipation, a
second battery voltage, Off-hook, must be
connected to the device via an external
diode at terminal VBAT2. The SLIC auto-
matically switches between the two battery
supply voltages without need for external
control. The silent battery switching to VBAT
occurs when the line current is below 5.5
mA. This means that the current in the On-
hook battery is limited to 6 mA. To calculate
the switching voltage use this formula (See
formula C in Figure 16):
If metering is used see section Metering
Applications down below.
second power supply via the diode D
Figure 14. A diode D
VB and the VB2 power supply, see Figure
14, will make sure that the SLIC continues
to work on the second battery even if the
first battery voltage disappears.
ent batteries as shown in figure 12, note
that some current is sourced from VB (typ.
0.5 mA, internal bias current) when the line
current is sourced from VB2. The next chart
(figure 13) is showing what power dissipa-
tion the SLIC is using with different batter-
ies and variation of the line.
Metering Applications, TTX
It is very easy to use PBL 386 14/1 in
metering applications; simply connect a
suitable resistor (R
capacitor (C
metering source. Capacitor C
all DC-voltages that may be superimposed
on the metering signal. The metering signal
gain can be calculated from the equation:
V
Connect the terminal VBAT2 to the
The current commute between the differ-
G
Z
R
TR
T
TTX
4-2TTX
=| VB2 | -4.4 - 50 · I
.
=
Z
RSN
T
V
V
+ G
TTX
TR
TTX
) between pin RSN and the
2-4S
Z
=
LTTX
TTX
. (Z
BB
connected between
) in series with a
LTTX
LProg
+ 2R
TTX
decouples
F
)
B2
in
Figure 12. Chart describing current in Vbat and Vbat2.
Figure 13. Chart describing Power dissipation with different Vbat2.
V
Z
G
LTTX
TTX
where:
2-4S
mW
800
700
600
500
400
300
200
100
0
mA
30
25
20
15
10
is the wanted metering voltage
between the TIP and RING terminals
is the line impedance seen by the 12
or 16 kHz metering signal,
is the transmit gain through the SLIC,
i e 0.5.
5
0
0
0
1000
1000
2500
2500
I
B2
28 V
25 V
22 V
5000
5000
V
I
BAT 2
B
7500
7500
metering voltage up to 2.5 Vpeak (1.7 Vrms),
using AOV. Use following formula to
calculate the switching voltage of the Battery
Switch to get enough signal space.
V
V
voice
TTX
It is possible to mix voice voltage and
V
where:
TR
=| VB2 | -3.4 -V
is the voice voltage, normaly 1 V
is the the metering voltage in peak.
10000
10000
PBL 386 14/1
voice
-V
TTX
- 50 · I
LProg
peak
13