U4092B Datasheet, PDF (13/32 Pages) TEMIC Semiconductors – Monolithic Integrated Feature Phone Circuit

TELEFUNKEN Semiconductors
ATAFS (dB)
ATAFS_m
ATAFS_a
RATAFS
RATAFS
U4092B
94 8957
not usable
GSA_o
GSA_a
36 dB
GSA (dB)
Figure 11 Reducing speaker amplifier gain results in an equal reduction of AFS attenuation
Ringing power converter (RPC)
Ringing frequency detector (RFD)
RPC transforms the input power at VRING (high voltage/
low current) into an equivalent output power at V_B (low
voltage/ high current), which is capable of driving the low
W ^{ohmic loudspeaker. Input impedance at VRING is fixed at}
5 k and the efficiency of the step down converter is
approx. 65%.
The U4092B offers an output signal for the
microcontroller, which is a digital representation of the
double ringing frequency. It is generated by a current
m ^{comparator with hysteresis. Input voltage VRING is}
transformed into a current via RTHA. Thresholds are 8 A
m and 24 A. RFDO and VRING are in phase. A second
comparator with hysteresis is used to enable the output
RFDO, as long as the supply voltage for the microprocessor
VMP is above 2.4 V (2.9 V).
Rev. A1: 24.01.1995
Preliminary Information
13