PCA1070 Просмотр технического описания (PDF) - Philips Electronics
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PCA1070 Datasheet PDF : 36 Pages
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Philips Semiconductors
Multistandard programmable analog
CMOS transmission IC
Product specification
PCA1070
FUNCTIONAL DESCRIPTION
All values in the Chapter “Functional description” are
typical unless stated otherwise.
Line interface
DC VOLTAGE DROP
Power for the PCA1070 and its peripheral circuits is
obtained from the telephone line. The IC develops its own
supply voltage at VDD and regulates its DC voltage drop
between pins SLPE and VSS. This voltage (VSLPE) can be
programmed via the I2C-bus interface between
3.1 to 5.9 V and is default at 4.7 V (see Table 8).
The DC line voltage at pin LN can be calculated using the
following equation:
VLN = VSLPE + (Iline − ILN) × RLN-SLPE
where:
ILN = DC bias current flowing into pin LN
(≈3 mA if Iline > 17 mA)
RLN-SLPE = external 20 Ω resistor between
LN and SLPE.
At line currents below 6 mA the DC voltage VSLPE is
automatically adjusted to a lower value. This means that
the operation of more sets, connected in parallel, is
possible with reduced sending and receiving levels and
relaxed performance. At line currents below 16 mA the DC
bias current ILN is reduced from ≈3 mA to a lower value to
ensure maximum possible transmit level capability under
all line current conditions.
SET IMPEDANCE
In normal conditions Iline >> ILN and the static behaviour is
equivalent to a voltage regulator diode with a series
resistor RLN-SLPE. In the audio frequency range the
dynamic impedance ZLN is determined mainly by the
internal component Zset = Ra + (Rb // C). The equivalent
impedance ZLN is shown in Fig.3. The values of Ra, Rb
and C can be programmed via the I2C-bus interface
(see Tables 9, 10 and 11).
handbook, halfpage
RLN-SLPE
SLPE
Leq
VSLPE
CP CREG CLSI
REG LSI
RP
RLSI
LN
Ca
Zset
Ra
Rb C
MGE342 VSS
Fig.3 Equivalent impedance ZLN.
where:
Ca = DC blocking capacitor (influence negligible at
f ≥ 300 Hz for given value of CLSI)
CLSI = capacitor at pin LSI (100 nF)
CP = internal capacitor (12 nF)
CREG = capacitor at pin REG (470 nF)
Leq = artificial inductor
(= RP × RLN-SLPE × CREG = 10.1 H at VSLPE = 4.7 V)
RLN-SLPE = DC slope resistance (20 Ω)
RP = internal resistor (1075 kΩ at VSLPE = 4.7 V)
RLSI = internal resistor (240 kΩ).
SUPPLY FOR PERIPHERAL CIRCUITS
The supply voltage VDD can be used for peripheral
circuitry. The supply capabilities depend on the
programmed DC voltage drop VSLPE and on several other
parameters as given in the following equation:
VDD = VSLPE − (IDD + Ip + IVP) × RSLPE−VDD
where:
IDD = internal current consumption PCA1070 (2.3 mA)
Ip = current to peripheral circuitry
IVP = current taken from VP for electret microphone
RSLPE−VDD = external resistor between SLPE and VDD.
1997 Jun 20
5
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