datasheetbank_Logo
Integrated circuits, Transistor, Semiconductors Search and Datasheet PDF Download Site

TEA1118AT View Datasheet(PDF) - Philips Electronics

Part Name
Description
View to exact match
TEA1118AT
Philips
Philips Electronics Philips
TEA1118AT Datasheet PDF : 24 Pages
1 2 3 4 5 6 7 8 9 10 Next Last
Philips Semiconductors
Versatile cordless transmisssion circuit
Product specification
TEA1118; TEA1118A
FUNCTIONAL DESCRIPTION
All data given in this chapter are typical values, except
when otherwise specified.
Supplies (pins LN, SLPE, VCC and REG)
The supply for the TEA1118 and TEA1118A and their
peripherals is obtained from the telephone line.
The ICs generate a stabilized reference voltage (Vref)
between pins LN and SLPE. This reference voltage is
equal to 3.35 V, is temperature compensated and can be
adjusted by means of an external resistor (RVA). It can be
increased by connecting the RVA resistor between
pins REG and SLPE (see Fig.11), or decreased by
connecting the RVA resistor between pins REG and LN.
The voltage at pin REG is used by the internal regulator to
generate the stabilized reference voltage and is decoupled
by a capacitor (CREG) which is connected to VEE.
This capacitor, converted into an equivalent inductance
(see Section “Set impedance”), realizes the set impedance
conversion from its DC value (RSLPE) to its AC value
(RCC in the audio-frequency range). The voltage at pin
SLPE is proportional to the line current. Figure 7 illustrates
the supply configuration.
The ICs regulate the line voltage at pin LN, and it can be
calculated as follows:
VLN = Vref + RSLPE × ISLPE
ISLPE = Iline ICC IP I* = Ish
where:
Iline: line current
ICC: current consumption of the IC
IP: supply current for peripheral circuits
I*: current consumed between LN and VEE
Ish: the excess line current shunted to SLPE (and VEE)
via LN.
The preferred value for RSLPE is 20 . Changing RSLPE will
affect more than the DC characteristics; it also influences
the transmit gain and the DTMF gain (TEA1118A only), the
gain control characteristics, the sidetone level and the
maximum output swing on the line.
The internal circuitry of the TEA1118 and TEA1118A is
supplied from pin VCC. This voltage supply is derived from
the line voltage by means of a resistor (RCC) and must be
decoupled by a capacitor CVCC. It may also be used to
supply peripheral circuits such as dialling or control
circuits. The VCC voltage depends on the current
consumed by the IC and the peripheral circuits as shown
by the formula (see also Figs 8 and 9). RCCint is the
internal equivalent resistance of the voltage supply point,
and Irec is the current consumed by the output stage of the
earpiece amplifier.
VCC = VCC0 RCCint × (IP Irec)
VCC0 = VLN RCC × ICC
The DC line current flowing into the set is determined by
the exchange supply voltage (Vexch), the feeding bridge
resistance (Rexch), the DC resistance of the telephone line
(Rline) and the reference voltage (Vref). With line currents
below 7.5 mA, the internal reference voltage (generating
Vref) is automatically adjusted to a lower value.
This means that more sets can operate in parallel with DC
line voltages (excluding the polarity guard) down to an
absolute minimum voltage of 1.6 V. At currents below
7.5 mA, the circuit has limited transmit and receive levels.
This is called the low voltage area.
Set impedance
In the audio frequency range, the dynamic impedance is
mainly determined by the RCC resistor. The equivalent
impedance of the circuits is illustrated in Fig.10.
Transmit amplifier (pins TX+, TXand GAT)
The TEA1118 and TEA1118A have symmetrical transmit
inputs. The input impedance between pins TX+ and TXis
equal to 62.5 k; the input impedance between pins
TX+/TXand VEE is equal 36.5 kΩ. The voltage gain from
pins TX+/TXto pin LN is set at 11.3 dB.
Automatic gain control is provided on this amplifier for line
loss compensation.
The gain of the TEA1118 can be decreased by connecting
an external resistor RGAT between pins GAT and REG.
The adjustment range is equal to 6 dB. A capacitor CGAT
connected between pins GAT and REG can be used to
provide a first-order low-pass filter. The cut-off frequency
corresponds to the time constant CGAT × (RGATint // RGAT).
RGATint is the internal resistor which sets the gain with a
typical value of 27 k.
Transmit mute (pin TMUTE; TEA1118A only)
The transmit amplifier can be disabled by activating the
transmit mute function. When TMUTE is LOW, the normal
speech mode is entered, depending on the level on MUTE.
When TMUTE is HIGH, the transmit amplifier inputs are
disabled while the DTMF input is enabled (no confidence
tone is provided). The voltage gain between LN and
TX+/TXis attenuated; the gain reduction is 80 dB.
1997 Jul 14
7
 

Share Link: 

datasheetbank.com [ Privacy Policy ] [ Request Datasheet ] [ Contact Us ]