UBA1702T View Datasheet(PDF) - Philips Electronics
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UBA1702T Datasheet PDF : 24 Pages
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Philips Semiconductors
Line interrupter driver and ringer
Product specification
UBA1702; UBA1702A
UBA1702A
The UBA1702A switch driver block is intended to generate
the appropriate signal to drive an external PNP interrupter.
The emitter and base of this PNP are respectively
connected to SDI and SDO. The EHI and DPI signals
control the state of this PNP.
The EHI pin is provided with high voltage capability. When
the voltage applied at pin EHI is HIGH, the switch driver
block will start and generate the appropriate signals to
switch on the external PNP interrupter.
When the telephone set is equipped with a mechanical
hook switch, pin EHI can be connected directly to pin SDI.
For electronic hook switch applications, the EHI pin can be
driven by the microcontroller output.
The EHI pin presents an impedance of 250 kΩ at low input
voltage. When the applied voltage at EHI goes above
approximately 30 V, the EHI input current remains
constant (see Fig.3) so that the EHI impedance increases.
The DPI is designed to switch on or off the external PNP
interrupter (providing EHI is HIGH). When the voltage
applied at pin DPI is HIGH, the switch driver block turns off
the external PNP interrupter. When the voltage applied at
pin DPI is LOW, the switch driver block turns on the
external PNP interrupter.
The external PNP interrupter is controlled by the current
flowing into pin SDO.
When the voltage applied at pin EHI is HIGH and the
voltage applied at pin DPI is LOW, pin SDO can be
considered as being connected to pin VEE via a 2.2 kΩ
resistor in order to create a base current for the external
PNP.
When the voltage applied at pin EHI and the one applied
at pin DPI are both HIGH, pin SDO can be considered as
being connected to pin SDI via a 1.1 MΩ pull-up resistor
while the impedance between SDI and VEE becomes very
high (a few MΩ).
When the voltage applied at pin EHI is LOW, whatever the
one applied at DPI is, pin SDO can be considered as being
connected to pin SDI via a 1.1 MΩ pull-up resistor while
the impedance between SDI and VEE becomes almost
infinite.
LINE CURRENT MANAGEMENT
(PINS SPI, SPO, CDA, CLA AND CDO)
The line current is measured by an internal 2 Ω resistor
and a sense circuit connected between the speech part
input and output (pins SPI and SPO). The circuit delivers
information about the hook switch status at the current
detection output (pin CDO) and controls the line current
limitation.
When the SPI current exceeds a certain level (3 mA), the
sense circuit injects some image of the SPI current into an
internal resistor (see Fig.1). The created voltage becomes
higher than an internal reference (approximately 0.3 V)
and CDO goes HIGH. This current detection level can be
increased by connecting a resistor between pins CDA
(current detection adjustment) and VEE. It is also possible
to connect a capacitor between pins CDA and VEE to filter
unwanted AC components of the line current signal. Line
current interruption during pulse dialling influences the
CDO output.
When the SPI current exceeds another current level
(45 mA), the sense circuit injects some image of the SPI
current into an internal resistor (see Fig.1). The created
voltage becomes higher than an internal reference
(approximately 0.4 V) and an internal signal is generated
in order to limit the current in the external interrupter thus
resulting in a line current limitation. This line current
limitation level can be increased up to a maximum value of
120 mA by connecting a resistor between pins CLA
(current limitation adjustment) and VEE.
When a PMOST (UBA1702) is used as an interrupter, the
SPI current equals the drain or source current of the
PMOST and thus also equals the line current.
When a PNP (UBA1702A) is used as an interrupter, the
SPI current equals the collector current of the PNP and
thus differs from the line current (the PNP base current
does not flow into the SPI pin).
1997 Sep 29
7
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