U4084B Datasheet, PDF (4/26 Pages) TEMIC Semiconductors – Low-Voltage, Voice-Switched Circuit for Hands-Free Operation

U4084B
Pin Description
Pin Symbol
Function
1 GND Ground
2 NC Not connected
3 CD Chip disable.
A logic LOW (< 0.8 V) sets normal
operation. A logic HIGH (> 2.0 V)
disables the IC to conserve power.
The input impedance is nominally
90 kW.
4
V_S Supply voltage 2.8 to 6.5 V,
approximately @ 4 mA.
The AGC circuit reduces the receive
attenuator gain @ 25 dB.
Receive mode @ 2.8 V.
5
TO Transmit attenuator output.
The DC level is approximately V_B.
6
TI Transmit attenuator input.
Max. signal level is 350 mV_rms.
The input impedance is approxi-
mately 10 kW.
7 MICO Microphone amplifier output.
The gain is set by external resistors.
8 MIC Microphone amplifier input.
The bias voltage is approximately
V_B.
9 MUTE Mute input.
A logic LOW (< 0.8 V) sets normal
operation. A logic HIGH (> 2.0 V)
mutes the microphone amplifier
without affecting the rest of the
circuit. The input impedance is
nominally 90 kW.
10 VCI Volume control input.
When VCI = V_B, the receive attenu-
ator is at maximum gain in the
receive mode.
When VCI = 0.3 V_B, the receive
gain is 35 dB lower. This does not
affect the transmit mode.
Pin Symbol
Function
11
C_T Response time.
An RC at this pin sets the response
time for the circuit to switch modes.
12
V_B Output voltage ≈ V_S/2.
It is a system AC ground, and biases
the volume control. A filter cap is
required.
13 CPT An RC at this pin sets the time
constant for the transmit background
monitor.
14 TLI2 Transmit-level detector input on the
microphone/ speaker side.
15 TLO2 Transmit-level detector output on
the microphone/ speaker side, and
input to the transmit background
monitor.
16 RLO2 Receive-level detector output on the
microphone/ speaker side
17 RLI2 Receive-level detector input on the
microphone/ speaker side
18 RI Input receive attenuator and dial-
tone detector.
The max. input level is 350 mV_rms.
The input impedance is approxi-
mately 10 kW.
19 RECO Receive attenuator output.
DC level is approximately V_B.
20 TLI1 Transmit-level detector input on the
line side
21 TLO1 Transmit-level detector output on
the line side
22 RLO1 Receive-level detector output on the
line side, and input to the receive
background monitor
23 RLI1 Receive-level detector input on the
line side
24 CPR An RC at this pin sets the time
constant for the receive background
monitor
4 (26)
TELEFUNKEN Semiconductors
Preliminary Information
Rev. A1, 31-Jan-97