PBL 386 50/2
R
V
BExt
S
TIPX
PBL 386 50/2
R
LRTo
RINGX
Figure 7. Tipx voltage.
Notes
1.
The overhead voltage can be adjusted with the R
OV
resistor
for higher levels e.g. min 3.1 V
Peak
and is specified at the
two-wire port with the signal source at the four-wire
receive port.
The two-wire impedance is programmable by selection of
external component values according to:
Z
TRX
= Z
T
/|G
2-4S
α
RSN
| where:
Z
TRX
= impedance between the TIPX and RINGX
terminals
Z
T
= programming network between the VTX and RSN
terminals
G
2-4S
= transmit gain, nominally = 0.5 (or 0.25 see pin
PTG)
α
RSN
= receive current gain, nominally = 200 (current
defined as positive flowing into the receivesumm-
ing node, RSN, and when flowing from ring to tip).
Higher return loss values can be achieved by adding a
reactive component to R
T
, the two-wire terminating
impedance programming resistance, e.g. by dividing R
T
into two equal halves and connecting a capacitor from the
common point to ground.
The overhead voltage can be adjusted with the ROV
resistor for higher levels e.g. min 1.6 V
Peak
and is specified
at the four-wire transmit port, VTX, with the signal source
at the two-wire port. Note that the gain from the two-wire
port to the four-wire transmit port is G
2-4S
= 0.5 (or 0.25 see
pin PTG). The overhead voltage is dependent on G
2-4S
and
POV setting.
5.
Pin PTG = Open sets transmit gain to nom. -6.02dB
Pin PTG = AGND sets transmit gain to nom. -12.04 dB
Secondary protection resistors R
F
and resistors R
P
impact
the insertion loss as explained in the text, section
Transmission. The specified insertion loss is for R
F
= R
P
= 0.
6. The specified insertion loss tolerance does not include
errors caused by external components.
7. The level is specified at the two-wire port.
8. The two-wire idle noise is specified with the port
terminated in 600
Ω
(R
L
) and with the four-wire receive
port grounded (E
RX
= 0; see figure 6).
The four-wire idle noise at VTX is specified with the two-
wire port terminated in 600
Ω
(R
L
). The noise specification
is referenced to a 600
Ω
programmed two-wire impedance
level at VTX. The four-wire receive port is grounded
(E
RX
= 0).
9. Previous state must be active - loop or ground key
detector.
10. If |V
BExt
|
≥
|V
Bat
+ 2 V|, where V
Bat
is the voltage at V
BAT
pin,
the current I
Leak
is limited to
≈
5mA.
2.
3.
4.
7
ERICSSON [ ERICSSON ]
