U4089B-P_05 Datasheet, PDF (4/26 Pages) ATMEL Corporation – Monolithic Integrated Feature Phone Circuit

Table 2-1. Pin Description (Continued)
Pin
Symbol Function
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 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. Maximum gain change is 6 dB.
31
IREF
Internal reference current generation; RREF = 62 kΩ; IREF = 20 µA
32
STO
Side-tone reduction output. Output resistance is approximately 300Ω. Maximum load impedance is 10 kΩ.
33
V_M
Reference node for microphone-earphone and loudspeaker amplifier. Supply for electret microphone
(IM ≥ 300 mA).
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 kΩ.
44
G_T
A resistor from this pin to GND sets the amplification of microphone and DTMF signals; the input
amplifier can be muted by applying V_MP to G_T.
Note: Filters against electromagnetic interference (EMI) are located at pins MIC1, MIC2, RECIN and STI.
4 U4089B-P
4518C–CORD–10/05