UBA1707TS datasheet(11/36 Pages) PHILIPS

11 / 36 page

1999 Feb 17

Philips Semiconductors

Product speciﬁcation

Cordless telephone, answering machine

line interface

UBA1707

The EHI input can also be used for pulse dialling or

(voltage at pin EHI is LOW or open-circuit), the voltage

regulator is switched off and the capacitor at pin REG is

internally disconnected to prevent its discharge. As a

result, the voltage stabilizer will have negligible switch-on

delay after line interruptions. This minimizes the

contribution of the IC to the current waveform during pulse

dialling or register recall.

When the UBA1707 is in power-down mode (bit PD at

logic 1), the TPDARL transistor is forced to be turned off

whatever the voltage applied at pin EHI.

SET IMPEDANCE

In the audio frequency range, the dynamic impedance

between pins LN and GND (illustrated in Fig.8) is mainly

determined by the ZSET impedance.

The impedance introduced by the external TNSW transistor

connected between pin GND and the negative line

terminal (LN

−) is negligible.

Fig.8

Equivalent impedance between

LN and GND.

Leq =CREG × RSLPE × RP

RP = internal resistance = 35 kΩ.

handbook, halfpage

GND

SLPE

RSLPE

CREG

REG

ZSET

4.7

µF

619

Ω

Vref

LEQ

MGL215

TRANSMIT AMPLIFIER (PINS TXI+ AND TXI

−)

The UBA1707 has symmetrical transmit inputs TXI+ and

TXI

−. The input impedance between pins TXI+ or TXI− and

GND is 21 k

Ω. The voltage gain from pins TXI+ or TXI− to

pin LN is set at 11.6 dB with 600

Ω line load (Zline) and

619

Ω set impedance. The inputs are biased at

× Vd ≅ 1.4 V, with Vd representing the diode voltage.

Automatic gain control is provided on this amplifier for line

loss compensation.

RECEIVE AMPLIFIER (PINS RXI AND RXO; BIT RXM)

The receive amplifier (see Fig.9) has one input (RXI) and

one output (RXO). The input impedance between pins

RXI and GND is 21 k

Ω. The rail-to-rail output stage is

designed to drive a 500

µA peak current. The output

impedance at pin RXO is approximately 100

Ω.

The voltage gain from pin RXI to pin RXO is set at 37.9 dB.

This gain value compensates typically the attenuation of

the anti-sidetone network (see Fig.10). The output as well

as the input are biased at 2

× Vd ≅ 1.4 V. Automatic gain

control is provided on this amplifier for line loss

compensation. This amplifier can be muted by activating

the receive mute function (bit RXM at logic 1).

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