U4091BM TEMIC Semiconductors, U4091BM Datasheet - Page 5

• Manufacturer Part Number: U4091BM
• Description: Programmable Telephone Audio Processor
• Manufacturer: TEMIC Semiconductors

For line voltages below 2 V, the switches remain in
quiescent state as shown in the diagram.
2. When the chip is in power-down mode (Bit
3. During ringing, the supply for the system is fed into
4. In an answering machine, the chip is powered by an
V
Ringing Power Converter (RPC)
The RPC transforms the input power at VRING (high
voltage/ low current) into an equivalent 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 k
(ZRING = RIMPA / 100) and the efficiency of the step-
down converter is approximately 65%.
Rev. A1, 02-Jun-98
L
LOMAKE), e.g., during pulse dialing, all internal
blocks are disabled via the serial bus. In this condition,
the voltage regulators and their internal bandgap are
the only active blocks.
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.
external supply via Pin VB. The answering machine
connections can be directly put to U4091BM. The
answering machine is connected to the Pin AMREC.
For the output AMREC, an AGC function is select-
able 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, and thus
enables the signal to be switched to every desired
output.
R
1 F
C
10
R
SENSE
IND
300 k
R
+
–
V
Figure 3. Supply generator
W
+
+
–
–
to 12 k
Target Specification
3.3 V
5.5 V
5.5 V
W
14573
by RIMPA
470 F
47 F
220 F
V
V
MPS
V
MP
B
Ringing Frequency Detector (RFD)
The U4091BM 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 current 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.
Clock Output Divider Adjustment
The Pin OSCOUT is a clock output which is derived from
the crystal oscillator. It can be used to drive a micro-
controller or another remote component and thereby
reduces the number of crystals required. The oscillator
frequency can be divided by 1, 8, 16, 32. During power-on
reset, the divider will be reset to 1 until it is changed by
setting the serial bus.
Serial Bus Interface
The circuit is controlled by an external microcontroller
through the serial bus.
The serial bus is a bi-directional system consisting of a
one-directional clock line (SCL) which is always driven
by the microcontroller, and a bi-directional data-signal
line. It is driven by the microcontroller as well as from the
U4091BM (see fig. 23).
The serial bus requires external pull-up resistors as only
pull-down transistors (Pin SDA) are integrated.
WRITE:
A0 – A3: address of the destination register (0 to 15)
D0 – D7: content of the register
The data line must be stable when the clock is high. Data
must be shifted serially.
After 12 clock periods, the write indication is sent. Then,
the transfer to the destination register is (internally)
generated by a strobe signal transition of the data line
when the clock is high.
CLK[0:1]
RINGTH[0:3]
0
1
2
3
step
15
0
The data is a 12-bit word:
Divider
16
32
1
8
U4091BM
VRING
22 V
7 V
1 V
Frequency
3.58 MHz
447 kHz
224 kHz
112 kHz
5 (29)