U209B datasheet(13/34 Pages) ATMEL

13 / 34 page

U4090B

Preliminary Information

TELEFUNKEN Semiconductors

Rev. C1, 28-Oct-96

13 (34)

ATAFS (dB)

36 dB

ATAFSm

ATAFS

GSA

GSA (dB)

not usable

RATAFS

94 8957

Figure 8. Reducing speaker amplifier gain results in an equal reduction of AFS attenuation

LIDET

94 8958

Figure 9. Line detection with two comparators for speech mode

and pulse dialling

Line detection (LIDET)

The line current supervision is active under all operating

conditions

the

U4090B.

speech

mode

(PD = inactive) the line current comparator uses the same

thresholds as the comparator for switching off the entire

speaker amplifier. The basic behaviour is illustrated in

figure 13. Actual values of ILON/ILOFF vary slightly

with the adjustment of the DC-characteristics and the

selection of the internal line impedance.

When Power Down is activated (during pulse dialing), all

of the line current flows through the short circuiting

transistor QS (see figure 6). As long as IL is above typ.

1.6 mA, output LIDET is low. This comparator does not

use hysteresis.

LIDET

ILOFF

ILON

94 8959

Figure 10. Line detection in speech mode with hysteresis

U209B Datasheet(PDF) 13 Page - ATMEL Corporation

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