UBA1707 NXP Semiconductors, UBA1707 Datasheet - Page 8

• Manufacturer Part Number: UBA1707
• Description: Cordless Telephone, Answering Machine Line Interface
• Manufacturer: NXP Semiconductors

Philips Semiconductors
The DC line current flowing into the set is determined by
the exchange supply voltage (V
resistance (R
(R
the voltage introduced by the transistor (TN
line interrupter (see Fig.5). With a line current below I
(8 mA with Z
(V
means that more sets can operate in parallel with DC line
voltages (excluding the polarity guard) down to 1.2 V.
At line current below I
and receive levels. This is called the low voltage area.
Figure 6 shows in more details how the UBA1707, in
association with some external components, manages the
line interrupter (TN
In on-hook conditions (voltage at pin EHI is LOW), the
voltage at pin LCC is pulled-up to the supply voltage level
(V
of the R
are switched off. The TN
the R
guarantee a high on-hook impedance.
1999 Feb 17
ref
CC
line
Cordless telephone, answering machine
line interface
) is automatically adjusted to a lower value. This
) to turn off the TP
) and the set (R
LVI
PLD
resistor from the LN line terminal in order to
resistor, the TN
SET
exch
= 619 ), the internal reference voltage
), the DC resistors of the telephone line
SW
SET
low
external transistor).
DARL
), the reference voltage (V
, the circuit has limited transmit
ON-HOOK
transistor. As a result, because
SW
and TN
exch
transistor disconnects
), the feeding bridge
ON-HOOK
SW
) used as
transistors
ref
) and
low
8
In off-hook conditions (voltage at pin EHI is HIGH), an
operational amplifier drives (at pin LCC) the base of
TP
association with TN
TN
deep saturation. A virtual ground is created at pin LVI
because of the operational amplifier. A DC current (I
sourced from pin LVI into the R
generate a voltage source. Thus the voltage between pin
GND and the negative line terminal (LN ) becomes:
V
The voltage V
can be calculated as follows:
V
Where:
CE
line
I
I
DARL
line
ZSET
SW
(TN
= line current
transistor. The TN
V
= current flowing through Z
which forms a current amplifier structure in
ref
SW
+ R
) = R
line
SLPE
LVI
between the line terminals LN+ and LN
SW
I
(I
LVI
. The line current flows through
line
ON-HOOK
+ V
I
CE
ZSET
LVI
(TN
) + V
transistor is forced into
resistor in order to
SET
ON-HOOK
Product specification
CE
.
(TN
UBA1707
)
SW
R
)
LVI
LVI
I
LVI
) is