PBL386502SHT datasheet(12/16 Pages) ERICSSON

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PBL 386 50/2

receive output via the resistor R

RX, is dc

biased with +1.25V. This makes it

possible to compensate for currents

floating due to dc voltage differences

between RSN and the CODEC output

without using any capacitors. This is

done by connecting a resistor R

R be-

tween the RSN terminal and ground.

With current directions defined as in

figure 14, current summation gives:

where V

CODEC is the reference voltage of

the CODEC at the receive output.

From this equation the resistor R

R can be

calculated as

For values on I

RSN, see table 3.

The resistor R

R has no influence on the

ac transmission.

SLIC

RSN [µA]

PBL 386 50/2

-155

Table 3. The SLIC internal bias current

with the direction of the current defined

as positive when floating into the terminal

RSN.

Programmable overhead voltage(POV)

With the POV function the overhead

voltage can be increased.

If the POV pin is left open the overhead

voltage is internally set to 3.2 V

Peak in off-

The current limit (reference C in figure

13) is adjusted by connecting a resistor,

LC, between terminal PLC and ground

according to the equation:

LC =

1000

LProg + 4

where R

LC is in kΩ for ILProg in mA.

A second, lower battery voltage may be

connected to the device at terminal

VBAT2 to reduce short loop power

dissipation. The SLIC automatically

switches between the two battery supply

voltages without need for external

control. The silent battery switching

occurs when the line voltage passes the

value |VB2| - 40·I

L - (VOHVirt -1.3),

if I

L > 6 mA.

For correct functionality it is important

to connect the terminal VBAT2 to the

second power supply via the diode D

VB2

in figure 12.

An optional diode D

BB connected

between terminal VB and the VB2 power

supply, see figure 12, will make sure that

the SLIC continues to work on the

second battery even if the first battery

voltage disappears.

If a second battery voltage is not used,

VBAT2 is connected to VBAT on the

SLIC and C

VB2, DBB and DVB2 are removed.

Metering applications

For designs with metering applications

please contact Ericsson Microelectronics

for assistance.

CODEC Receive Interface

The PBL 386 50/2 SLIC have got a

completely new receive interface at the

four wire side which makes it possible to

reduce the number of capacitors in the

applications and to fit both single and

dual battery feed CODECs. The RSN

terminal, connecting to the CODEC

−=

−

RSN

RRX

CODEC

1 25

125

RSN

CODEC

−−

−

125

Battery Feed

The PBL 386 50/2 SLIC emulate

resistive loop feed, programmable

between 2·50

Ω and 2·900 Ω, with

adjustable current limitation. In the

current limited region the loop current

has a slight slope corresponding to

2·30 k

Ω, see figure 13 reference B.

The open loop voltage measured

between the TIPX and RINGX terminals

is tracking the battery voltage V

Bat. The

signalling headroom, or overhead voltage

TRO, is programmable with a resistor ROV

connected between terminal POV on the

SLIC and ground. Please refer to section

“Programmable overhead voltage(POV)”.

The battery voltage overhead, V

OH,

depends on the programmed signal

overhead voltage V

TRO. VOH defines the

TIP to RING voltage at open loop

conditions according to V

TR(at IL = 0 mA)

= |V

Bat| - VOH.

Refer to table 2 for typical values on

OH and VOHVirt. The overhead voltage is

changed when the line current is ap-

proaching open loop conditions. To

ensure maximum open loop voltage,

even with a leaking telephone line, this

occurs at a line current of approximately

6 mA. When the overhead voltage has

changed, the line voltage is kept nearly

constant with a steep slope correspond-

ing to 2·25

Ω(reference G in figure 13).

The virtual battery overhead, V

OHVirt, is

defined as the difference between the

battery voltage and the crossing point of

all possible resistive feeding slopes, see

figure 13 reference J. The virtual battery

overhead is a theoretical constant

needed to be able to calculate the

feeding characteristics.

SLIC

OH(typ)

OHVirt(typ)

[V]

PBL 386 50/2 3.0 +V

TRO

4.9 +V

TRO

Table 2. Battery overhead.

The resistive loop feed (reference D in

figure 13) is programmed by connecting

a resistor, R

SG, between terminals PSG

and VBAT according to the equation:

Feed =

SG + 2·10

+ 2R

200

where R

Feed is in Ω for RSG and RF in Ω.

10203040

off-hook

on-hook

Rov (KΩ)

Figure 11. Programmable overhead voltage (POV). R

L = 600 Ω or ∞.

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