Philips TEA1081T, TEA1081 Datasheet

INTEGRATED CIRCUITS

DATA SH EET

TEA1081

Supply circuit with power-down for telephone set peripherals

Product speciﬁcation Supersedes data of February 1988 File under Integrated Circuits, IC03

Philips Semiconductors

September 1994

Philips Semiconductors Product speciﬁcation

Supply circuit with power-down for

TEA1081

telephone set peripherals

FEATURES

• High input impedance for audio signals

• Low DC series resistance

• High output current

• Large audio signal handling capability

• Low distortion

• Two modes of operation:

– output voltage that follows the DC line voltage – regulated output voltage

• Power-down input

• Low number of external components.

QUICK REFERENCE DATA

SYMBOL PARAMETER CONDITIONS MIN. TYP. MAX. UNIT

∆V

LN-O

operating DC line voltage 2.5 − 12.0 V DC output voltage 2.0 − 10.0 V voltage drop from line to output IO=0mA − 0.5 − V internal series resistance − 20 −Ω output current (pin 7) VLN=4V

TEA1081 −−30 mA TEA1081T −−20 mA

LN(rms)

INT

amb

AC line voltage (RMS value) VLN=4V; IO=15mA;

internal supply current VLN=4V; IO= 0 mA;

operating ambient temperature −25 − +70 °C

GENERAL DESCRIPTION

The TEA1081 is an integrated circuit for use in line-powered telephone sets to supply peripheral circuits for extended dialling and/or loudspeaker facilities.

The IC uses a part of the surplus line current normally drawn by the voltage regulator of the speech/transmission circuit. A power-down function isolates the IC from its load and reduces the input current.

− 1.5 − V

THD=2%

− 0.8 1.4 mA

PD = LOW; VSP= V

ORDERING INFORMATION

PACKAGE

TYPE NUMBER

NAME DESCRIPTION VERSION

TEA1081 DIP8 plastic dual in-line package; 8 leads (300 mil) SOT97-1

TEA1081T SO8 plastic small outline package; 8 leads; body width 3.9 mm SOT96-1

September 1994 2

Philips Semiconductors Product speciﬁcation

Supply circuit with power-down for telephone set peripherals

BLOCK DIAGRAM

handbook, full pagewidth

0.5 V

1/2 V

TR1

TEA1081

TR2

POWER-

DOWN

REFERENCE

CURRENT

TEA1081

Fig.1 Block diagram.

PINNING

SYMBOL PIN DESCRIPTION

LN 1 positive line terminal VN 2 negative line terminal AD 3 ampliﬁer decoupling PD 4 power-down input IF 5 low-pass ﬁlter input VA 6 output voltage adjustment QS 7 power supply output SP 8 supply input; power-down circuit

MLC166

age

LN VN AD PD

1 2 3 4

TEA1081

Fig.2 Pin configuration.

MLC167

September 1994 3

Philips Semiconductors Product speciﬁcation

Supply circuit with power-down for telephone set peripherals

FUNCTIONAL DESCRIPTION

The TEA1081 is a supply interface between telephone line and peripheral devices in the telephone set. The high input impedance of the circuit allows direct connection to the telephone line (via a diode bridge). An inductor function is obtained by amplifier A1, resistor RS (see Fig.1) and an external low-pass RC filter.

Under the control of amplifier A2, transistor TR1 supplies peripheral devices and transistor TR2 minimizes line signal distortion by momentarily diverting input current to ground whenever the instantaneous value of the line voltage drops below the output voltage.

Internal circuits are biased by a temperature and line voltage compensated reference current source.

The power-down circuit isolates the supply circuit from external circuitry.

Line terminals: LN and VN (pins 1 and 2)

The input terminals LN and VN can be connected directly to the line. The minimum DC line voltage required at the input is expressed by formula (1); see also Table 1.

LNI1RS

× V

LNminVLN P()

V()++=

Table 1 Explanation of formula (1).

SYMBOL DESCRIPTION

R V

LNmin

input current internal series resistance minimum instantaneous line voltage

(1.4 V at IO = 5 mA)

LN(P)

The internal current (I

required peak level of AC line voltage

) at IO = 0 mA is typically 0.8 mA

INT

at VLN = 4 V and reaches a maximum of 1.4 mA at VLN=12V.

(1)

TEA1081

The output voltage follows the line voltage and is expressed by formula (2); see also Table 2.

LNI1RS

Table 2 Explanation of formula (2).

SYMBOL DESCRIPTION

EGULATED OUTPUT VOLTAGE (SEE FIG.4)

line voltage input current internal series resistance

The circuit operates in this mode when an external resistor (RV) is connected between QS and VA (see Fig.6).

The output voltage is held constant at VO = 2 × I6× RV (V) as soon as the line voltage VLN>(2×I6×RV+I1×RS+ 0.5) (V)

The control current I6 is typically 20 µA.

handbook, halfpage

(V)

010

2468

(2)

(1)

0.5+×()– V()=

MLC168

(3)

V (V)

(2)

Supply terminals: QS and VA (pins 7 and 6)

Peripheral devices are supplied from QS (pin 7). Two modes of output voltage regulation are available.

OUTPUT VOLTAGE FOLLOWS LINE VOLTAGE (SEE FIG.3) The TEA1081 operates in this mode when there is no

external resistor (RV) between QS and VA (see Fig.6).

September 1994 4

Application without RV. (1) I1 = 5 mA. (2) I1 = 20 mA. (3) I1 = 30 mA; not valid for TEA1081T.

Fig.3 Output voltage as a function of line voltage.

Philips Semiconductors Product speciﬁcation

Supply circuit with power-down for telephone set peripherals

75 kΩ

50 kΩ

V (V)

MLC169

handbook, halfpage

(V)

RV connected between QS and VA. (1) I1 = 5 mA. (2) I1 = 20 mA. (3) I1 = 30 mA; not valid for TEA1081T.

(1)

(2)

(3)

210

468

R = 100 kΩ

Fig.4 Output voltage as a function of line voltage.

TEA1081

Input current at V approximates to:

I1 = I

+2×IO (mA)

INT

The maximum supply current (within the specified output current limits) available for peripheral devices is shown by:

Omax

-----------------------------------------------------------

LINEminILNmin

Where:

is the minimum line current of the telephone set;

LINEmin

is the specified minimum input current of the

LNmin

speech/transmission circuit.

Input low-pass ﬁlter: IF (pin 5)

The input impedance between LN and VN at audio frequencies is determined by the filter elements C (between pins 1 and 5), RL (between pins 5 and 7) and the internal resistor RS(typical value 20 Ω).

At audio frequencies the TEA1081 behaves as an inductor of the value LI= CL× RL× RS (H). The typical value of LI at CL = 2.2 µF and RL = 100 kΩ is 4.4 H.

= 1 V and without R

LN(rms)

– I

–

INT

Input and output currents I1 and IO (pins 1 and 7)

The maximum available current into pin 1 (I

) is

determined by:

• The minimum line current (I

) that is available for

LINEmin

the telephone set

• The specified minimum input current (I

LNmin

) for the

speech/transmission circuit. That is I At V

LN(rms)

I1=I

INT

1max

= I

LINEmin

− I

LNmin

< 150 mV, the input current I1is approximately:

+k×IO (mA)

Where:

= internal supply current (0.8 mA at VLN= 4 V);

INT

k = correction factor (k < 1.1 for the specified output

current range). With large line signals the instantaneous line voltage may

drop below VO+ 0.4 V. Normally (when VLN>VO+ 0.4 V), instantaneous current flows from LN to QS (pin 1 to pin 7) to the output load.

When VLN<VO+ 0.4 V, the instantaneous current is diverted to pin 2 to prevent distortion of the line signal.

Ampliﬁer decoupling: AD (pin 3)

To ensure stability, a 68 pF decoupling capacitor is required between AD (pin 3) and LN (pin 1).

< 1.5 mA, a 47 pF capacitor has to be added

If I

Omin

between AD (pin 3) and VA (pin 6).

Power-down inputs: PD and SP (pins 4 and 8)

During pulse dialling or register recall, or if the input current to pin 1 is insufficient to maintain the output current, the supply to peripheral devices can be switched off by activating the PD input at pin 4. With PD = HIGH, the input current is reduced to 40 µA (typ.) at V

= 4 V and the

internal circuits are isolated from the load at QS (pin 7). The power-down circuit is supplied via the SP input (pin 8).

SP can be wired to QS in conditions where VO>V during line interruptions. When VO<V

, SP should be

SPmin

wired to an external supply point (e.g. to VCC of the TEA1060 family circuit).

When power-down is not required, the PD and SP inputs can be left open-circuit.

September 1994 5

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