Philips TEA1081T-C2, TEA1081-C2 Datasheet

DATA SH EET

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

September 1994

INTEGRATED CIRCUITS

Philips Semiconductors

TEA1081

Supply circuit with power-down for telephone set peripherals

September 1994 2

Philips Semiconductors Product speciﬁcation

Supply circuit with power-down for telephone set peripherals

TEA1081

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.

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.

QUICK REFERENCE DATA

ORDERING INFORMATION

SYMBOL PARAMETER CONDITIONS MIN. TYP. MAX. UNIT

operating DC line voltage 2.5 − 12.0 V

DC output voltage 2.0 − 10.0 V

∆V

LN-O

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)

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

THD=2%

− 1.5 − V

INT

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

PD = LOW; VSP= V

− 0.8 1.4 mA

amb

operating ambient temperature −25 − +70 °C

TYPE NUMBER

PACKAGE

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 3

Philips Semiconductors Product speciﬁcation

Supply circuit with power-down for telephone set peripherals

TEA1081

BLOCK DIAGRAM

Fig.1 Block diagram.

handbook, full pagewidth

MLC166

1/2 V

POWER-

DOWN

REFERENCE

CURRENT

8 4

SP PD

TR2

TR1

0.5 V

TEA1081

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

Fig.2 Pin configuration.

age

1 2 3 4

8 7 6 5

SP QS VA IF

LN VN AD PD

TEA1081

MLC167

September 1994 4

Philips Semiconductors Product speciﬁcation

Supply circuit with power-down for telephone set peripherals

TEA1081

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.

(1)

Table 1 Explanation of formula (1).

The internal current (I

INT

) at IO = 0 mA is typically 0.8 mA at VLN = 4 V and reaches a maximum of 1.4 mA at VLN=12V.

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).

SYMBOL DESCRIPTION

input current

internal series resistance

LNmin

minimum instantaneous line voltage (1.4 V at IO = 5 mA)

LN(P)

required peak level of AC line voltage

LNI1RS

× V

LNminVLN P()

V()++=

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

(2)

Table 2 Explanation of formula (2).

EGULATED OUTPUT VOLTAGE (SEE FIG.4)

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.

SYMBOL DESCRIPTION

line voltage

input current

internal series resistance

LNI1RS

0.5+×()– V()=

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

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

handbook, halfpage

010

MLC168

2468

(V)

V (V)

(1)

(2)

(3)

September 1994 5

Philips Semiconductors Product speciﬁcation

Supply circuit with power-down for telephone set peripherals

TEA1081

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

LINEmin

) that is available for

the telephone set

• The specified minimum input current (I

LNmin

) for the

speech/transmission circuit.

That is I

1max

= I

LINEmin

− I

LNmin

At V

LN(rms)

< 150 mV, the input current I1is approximately:

I1=I

INT

+k×IO (mA)

Where:

INT

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

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.

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

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

handbook, halfpage

210

MLC169

468

(1)

(2)

(3)

(V)

V (V)

R = 100 kΩ

75 kΩ

50 kΩ

Input current at V

LN(rms)

= 1 V and without R

approximates to: I1 = I

INT

+2×IO (mA)

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

Omax

Where:

LINEmin

is the minimum line current of the telephone set;

LNmin

is the specified minimum input current of the

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.

Ampliﬁer decoupling: AD (pin 3)

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

Omin

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

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

SPmin

during line interruptions. When VO<V

SPmin

, SP should be 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.

LINEminILNmin

– I

INT

–

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