PBL38772/1 데이터 시트보기 (PDF) - Ericsson
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PBL38772/1 Datasheet PDF : 24 Pages
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PBL 387 72
A
B
C
D
E
G
H
F
J
A:
IL (@VTR=0) = ILconst = ILProg
VTR [V]
RLC
=
500
ILProg
-
10.4
× ln(32
ILProg
×
ILProg)
B,C: IL = ILconst , VTR(@C) = VApp - RFEED × ILProg
D: RFEED = 2×25 Ω
E:
IL ≈ 5.5 mA , VTR = VApp - RFEED × 5.5 mA
F:
VApp (@IL = 0) = VTB - VF* - 3.7 V
* VF is the forward voltage drop across
diode DTB
G: IL ≈ 5 mA
H: RFEED = 2 × 25 Ω
J:
The On-hook voltage tracks the VBAT voltage up to |54.5| V, VTROpen = |VBat| – 4.5 V.
For VBAT > |54.5| V, VTROpen = 50 V.
Figure 12. Battery feed characteristics.
Ringing Voltage
When designing PBL 387 72/1 the object was to design a
robust ringing SLIC that supports balanced ringing and that
handles the high power dissipation and the different fault
conditions that may occur when ringing. For power handling
see section Power control.
Figure 13 shows a high level schematic of the ring loop.
The ring loop in the PBL 387 72/1 is designed as a voltage
amplifier. An internal feedback loop from the two-wire to the
input sets a predetermined voltage gain. The voltage gain
is adjusted to 94 by the AGC-R when ringing. The power
amplifiers are of the current feed type that makes it possible
to provide a reliable control of the ringing current. This
arrangement makes it possible to add a control device,
including an Automatic Gain Control unit, that provides
protecting functions, such as:
Automatic Gain Control-Ringing, AGC-R: If the amplifiers
that supply Tip and Ring are forced to saturation due to i.e.
variations of the VBat voltage or the VR input signal level,
the AGC-R will decrease the output signal. The shape of the
output signal is kept undistorted. This function guarantees
a low output impedance, approximately 2×20 Ω, and also
allows variations in the input signal and the VBat voltage.
Current limit: At off-hook or in fault conditions, i.e. Tip and
Ring are shorted, the control device will limit the ringing
current to approximately 10 mA above the programmed ring-
trip threshold.
16
EN/LZT 146 136 R1A © Ericsson Microelectronics, December 2001
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