U4089B Datasheet, PDF (4/25 Pages) ATMEL Corporation – MONOLITHIC INTEGRATED FEATUREPHONE CIRCUIT

Pin Description
Pin Symbol Function
1
DTMF Input for DTMF signals. Also used for the answering machine and hands-free input.
3
MIC 2 Non-inverting input of microphone amplifier
4
MIC 1 Inverting input of microphone amplifier
6
IND
The internal equivalent inductance of the circuit is proportional to the value of the capacitor at this pin. A resistor
connected to ground may be used to reduce the DC line voltage.
7
V_L Line voltage
8
GND Reference point for DC- and AC-output signals
9
SENSE
A small resistor (fixed) connected from this pin to V_L sets the slope of the DC characteristic and also affects the line-
length equalization characteristics and the line current at which the loudspeaker amplifier is switched on.
10
V_B Unregulated supply voltage for peripheral circuits (voice switch); limited to typically 7 V
11
SAO Output of loudspeaker amplifier
13
V_MP Regulated 3.3 V supply voltage for peripheral circuits. The maximum output current is 2 mA.
Control input for selection of line impedance
1) 600 W
20 IMPSEL 2) 900 W
3) Mute of second transmit stage (TXA); also used for indication of external supply (answering machine);
last chosen impedance is stored
21 TSACL Time constant of anti-clipping of speaker amplifier
22
GSA
Current input for setting the gain of the speaker amplifier. Adjustment characteristic is logarithmical.
For RGSA > 2 MW, the speaker amplifier is switched off.
23
SA I Speaker amplifier input (for loudspeaker, tone ringer and hands-free use)
Three-state input of transmit mute:
1) Speech condition; inputs MIC1/MIC2 active
24 MUTX 2) DTMF condition; input DTMF active. A part of the input signal is passed to the receiving amplifier as a
confidence signal during dialing.
3) Input DTMF used for answering machine and hands-free use; receive branch is not affected.
25
ATAFS
Attenuation of acoustical feedback suppression. Maximum attenuation of the AFS circuit is set by a resistor at this
pin. Without the resistor, AFS is switched off.
26 INLDT Input of transmit level detector
27 INLDR Input of receive level detector
28 TLDT Time constant of transmit level detector
29 TLDR Time constant of receive level detector
30
AGA
Automatic gain adjustment with line current. A resistor connected from this pin to GND sets the starting point.
Max. gain change is 6 dB.
31
IREF Internal reference current generation; RREF = 62 kW; IREF = 20 µA
32
STO Side tone reduction output. Output resistance is approximately 300 W. Maximum load impedance is 10 kW.
33
V_M Reference node for microphone, earphone and loudspeaker amplifier. Supply for electret microphone (IM £ 300 µA).
36
STI Input for side-tone network
39 RECO Output of receiving amplifier
40
G_R
A resistor connected from this pin to GND sets the receiving amplification of the circuit; amplifier RA1 can be
muted by applying V_MP to G_R
41 TTXA Time constant of anti-clipping in transmit path
42 RECIN Input of receiving path; input impedance is typically 80 kW
44
G_T
A resistor from this pin to GND sets the amplification of the microphone and DTMF signals; the input amplifier can
be muted by applying V_MP to G_T.
4 U4089B-M
4570A–CORD–04/03