U4082B Datasheet, PDF (12/13 Pages) ATMEL Corporation – Low-voltage Voice-switched IC for Hands-free Operation

UNISONIC TECHNOLOGIES CO., LTD
U4082B
LINEAR INTEGRATED CIRCUIT
„ FUNCTIONAL DESCRIPTION(Cont.)
* Switch to idle quickly,
The current sources are turned off,
The internal 2kΩ resistor is switched in
Discharging the capacitor to VB with a time = 2kΩ x CT.
* Switching to idle slowly
The current sources are turned off
The switch at the 2kΩ resistor is open
Discharging the capacitor to VB through the external resistor RT with a time=RT x CT.
MICROPHONE AMPLIFIER
While the inverting input and the output are pinned out, pins 10/11,the microphone amplifier, has the
non-inverting input internally connected to VB. This amplifier’s open loop gain is typically 80dB when f<100Hz, and
the gain bandwidth is typically 1MHz. Its maximum output swing (p-p) is typically 1 volt. MCI’s input bias current is
typically 40nA out of the pin.
HYBRID AMPLIFIER
At HTO+, HTO-, and HTI, the two hybrid amplifiers provide the two-to-four wire converter for interfacing to the
telephone line. The first amplifier’s gain is set by external resistor, and the first amplifier’s output drives the second
amplifier (gain of -1).
FILTER
The external components determined the operation of the filter circuit.
POWER SUPPLY, VB, and CHIP DISABLE
For normal operation the power supply voltage is to be between 3.5v and 6.5v, but with reduced operation the
V_CC is possible 2.8 volts. VB’s output voltage is ~ (Vcc-0.7)/2, and also provides the AC ground.
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QW-R108-020.A