TEA1064A View Datasheet(PDF) - Philips Electronics

Part Name

Description

Manufacturer

TEA1064A

Low voltage versatile telephone transmission circuit with dialler interface and transmit level dynamic limiting

Philips Electronics 

Philips Semiconductors

Low voltage versatile telephone transmission circuit

with dialler interface and transmit level dynamic limiting

Product specification

TEA1064A

handbooIkp, h5alfpage

(mA)

4

MGR059

3

2

1

0

2

3

4 Vp (V)

lline = 15 mA; R16 = 392 Ω; R15 = 0 Ω; valid for MUTE = 0 and 1.

Line current has very little influence

Fig.4 Minimum supply current for peripherals (Ip)

as a function of the peripheral supply

voltage (Vp).

The maximum AC output swing on the line at low line

currents is influenced by R16 (limited by current) and the

maximum output swing on the line at high line currents is

influenced by the DC voltage VLN-SLPE (limited by voltage).

In both these situations, the internal dynamic limiter in the

sending channel prevents distortion when the microphone

input is overdriven. The maximum AC output swing on LN

is shown in Fig.5; practical values for R16 are from 200 to

600 Ω and this influences both the maximum output swing

at low line currents and the supply capabilities.

The SLPE pin is the ground reference for peripheral

circuits, therefore inputs MUTE, PD and DTMF are also

referenced to SLPE.

Active microphones can be supplied between VCC1 and

VEE. Low-power circuits that provide only MUTE and/or PD

inputs to the TEA1064A also can be powered from VCC1.

However VCC1 cannot be used for circuits that provide

DTMF signals to the TEA1064A because VCC1 is referred

to ground.

If the line current lline exceeds ICC1 + 0.25 mA, the voltage

converter shunts the excess current to SLPE via LN;

where ICC1 ≈ 1.3 mA, the value required by the IC for

normal operation.

The DC line voltage on LN is:

VLN = VLN-SLPE + (ISLPE × R9)

VLN = Vref + ([Iline − ICC1 − 0.25 × 10−3 A] × R9)

in which

Vref = 3.3 V ± 0.25 V is the internal reference voltage

between VCC2 and SLPE; its value can be adjusted by

external resistor RVA

R9 = external resistor between SLPE and VEE (20 Ω in

basic application).

With R9 = 20 Ω, this results in:

VLN = 3.57 ± 0.25 V at lline = 15 mA

VLN = 4.17 ± 0.3 V at lline = 15 mA,

RVA(REG-SLPE) = 33 kΩ

VLN = 4.57 ± 0.35 V at lline = 15 mA,

RVA(REG-SLPE) = 20 kΩ

The preferred value for R9 is 20 Ω. Changing R9

influences microphone gain, DTMF gain, the gain control

characteristics, sidetone, and the DC characteristics

(especially the low voltage characteristics).

In normal conditions, ISLPE >> (ICC1 + 0.25 mA) and the

static behaviour is equivalent to a voltage regulator diode

with an internal resistance of R9. In the audio frequency

range the dynamic impedance is determined mainly by R1.

The equivalent impedance of the circuit in the audio

frequency range is shown in Fig.6.

The internal reference voltage VCC2-SLPE can be increased

by external resistor RVA(REG-SLPE) connected between

REG and SLPE. The supply voltage VCC2-SLPE is shown as

a function of RVA(REG-SLPE) in Fig.7. Changing the

reference voltage influences the output swing of both

sending and receiving amplifiers.

At line currents below 8 mA (typ.), the DC voltage dropped

across the circuit is adjusted to a lower level automatically

(approximately 1.8 V at 2 mA). This gives the possibility of

operating more telephone sets in parallel with DC line

voltages (excluding polarity guard) down to an absolute

minimum of 1.8 V. At line currents below 8 mA (typ.), the

circuit has limited sending and receiving levels.

March 1994

7

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