UNISONIC TECHNOLOGIES CO., LTD

U4082B

LINEAR INTEGRATED CIRCUIT

UNISONICTECHNOLOGIESCO.,LTD

12 of 13

www.unisonic.com.tw

QW-R108-020.A

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