U4091BM-N Datasheet, PDF (7/38 Pages) ATMEL Corporation – PROGRAMMABLE TELEPHONE AUDIO PROCESSOR

U4091BM-N
3. Ringing:
During ringing, the supply for the system is fed into VB via the Ringing Power
Converter (RPC). Normally, the speaker amplifier in single-ended mode is used
for ringing. The frequency for the melody is generated by the DTMF/Melody
generator.
4. External supply:
In an answering machine, the chip is powered by an external supply via pin VB.
The answering machine connections can be directly made to U4091BM-N. The
answering machine is connected to the pin AMREC. For the output AMREC, an
AGC function is selectable via the serial bus. The output of the answering
machine will be connected to the pin AMPB, which is directly connected to the
switching matrix. This enables the signal to be switched to every desired output.
Figure 4. Supply Generator
V R _L
SENSE
10 Ω
C
1 µF
IND
R
+
-
R
300 k Ω
V
5.5 V
V_MPS
-
+
3.3 V
470 µF
V_MP
+
47 µF
-
5.5 V
V_B
220 µF
Ringing Power
Converter (RPC)
Ringing Frequency
Detector (RFD)
The RPC transforms the input power at VRING (high voltage/low current) into an equiv-
alent output power at VB (low voltage/high current) which is capable of driving the low-
ohmic loudspeaker. The input impedance at VRING is adjustable from 3 kΩ to 12 kΩ by
RIMPA (ZRING = RIMPA/100) and the efficiency of the step-down converter is approxi-
mately 65%.
The U4091BM-N provides an output signal for the microcontroller. This output signal is
always double the value of the input signal (ringing frequency). It is generated by a cur-
rent comparator with hysteresis. The levels for the on-threshold are programmable in 16
steps, the off-level is fixed. Every change of the comparator output generates a high
level at the interrupt output INT. The information can then be read out by means of a
serial bus with either normal or fast read mode. The block RFD is always enabled.
Table 1. Threshold Level
RINGTH[0:3]
0
V_RING
7V
15
22 V
Step
1V
7
4666B–CORD–08/04