u4090b-p ATMEL Corporation, u4090b-p Datasheet - Page 12

• Manufacturer Part Number: u4090b-p
• Description: U4090b-p Monolithic Integrated Feature Phone Circuit Emi Improved
• Manufacturer: ATMEL Corporation

3.3
12
Line Detection (LIDET)
U4090B-P
Figure 3-7.
Figure 3-8.
The line current supervision is active under all operating conditions of the U4090B-P. In speech
mode (PD = inactive), the line-current comparator uses the same thresholds as the comparator
for switching off the entire speaker amplifier. The basic behavior is illustrated in
page
and the selection of the internal line impedance.
When Power Down is activated (during pulse dialing), the entire line current flows through the
short-circuiting transistor QS (see
output LIDET is low. This comparator does not use hysteresis.
13. Actual values of ILON/ILOFF vary slightly with the adjustment of the DC characteristics
Reducing Speaker Amplifier Gain Results in an Equal Reduction of AFS
Attenuation
Line Detection with Two Comparators for Speech Mode and Pulse Dialing
ATAFS (dB)
ATAFS
ATAFS
GSA
IL
o
a
m
Figure 3-3 on page
R
GSA
ATAFS
a
R
ATAFS
8). As long as IL is above typically 1.6 mA,
36 dB
PD
GSA (dB)
not usable
LIDET
4741C–CORD–11/05
Figure 3-9 on