PBL38650-2 查看數據表（PDF） - Ericsson

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PBL38650-2

Subscriber Line Interface Circuit

Ericsson  

PBL 386 50/2

Figure 7. Tipx voltage.

VBExt

R

S

RLRTo

TIPX

PBL 386 50/2

RINGX

Notes

1. The overhead voltage can be adjusted with the ROV resistor

for higher levels e.g. min 3.1 VPeak and is specified at the

two-wire port with the signal source at the four-wire

receive port.

2. The two-wire impedance is programmable by selection of

external component values according to:

ZTRX = ZT/|G2-4S α RSN| where:

ZTRX = impedance between the TIPX and RINGX

terminals

Z = programming network between the VTX and RSN

T

terminals

G2-4S = 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).

3. Higher return loss values can be achieved by adding a

reactive component to RT, the two-wire terminating

impedance programming resistance, e.g. by dividing RT

into two equal halves and connecting a capacitor from the

common point to ground.

4. The overhead voltage can be adjusted with the ROV

resistor for higher levels e.g. min 1.6 V and is specified

Peak

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 = 0.5 (or 0.25 see

2-4S

pin PTG). The overhead voltage is dependent on G and

2-4S

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 RF and resistors RP impact

the insertion loss as explained in the text, section

Transmission. The specified insertion loss is for RF = RP = 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 (ERX = 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

(ERX = 0).

9. Previous state must be active - loop or ground key

detector.

10. If |VBExt| ≥ |VBat + 2 V|, where VBat is the voltage at VBAT pin,

the current ILeak is limited to ≈ 5mA.

7

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