3

4655C–CORD–03/06

U4083B

3.

Functional Description Including External Circuitry

3.1

Pin 1: Chip Disable Digital Input (CD)

Pin 1 (chip disable) is used to power down the IC to conserve power or mute the IC or both.

Input impedance at Pin 1 is typically 90 k

Ω.

• Logic 0 < 0.8V

IC enabled (normal operation)

• Logic 1 > 2V

IC disabled

Figure 8-15 on page 12 shows the power supply current diagram. The change in differential gain

from normal operation to muted operation (muting) is more than 70 dB.

Switching characteristics are as follows:

• Turn-on time

t

• Turn-off time

t

They are independent of C

Voltages at Pins 2 and 3 are supplied from V

is disabled. The outputs, V

removing the signal from the speaker.

When signals are applied from an external source to the outputs (disabled), they must not

exceed the range between the supply voltage, V

3.2

Pins 2 and 3: Filtering, Power Supply Rejection

Power supply rejection is provided by capacitors C

dominant at high frequencies whereas C

to Figure 8-7 on page 9). The values of C

For example, a line-powered speakerphone (telephone amplifier) will require more filtering than

a system powered by regulated power supply.

The amount of rejection is a function of the capacitors and the equivalent impedance at Pin 3

and Pin 2 (see electrical characteristic equivalent resistance, R).

Apart from filtering, capacitors C

up, since the capacitors are charged up through the internal resistors (50 k

Ω and 125 kΩ) as

shown in the block diagram.

Figure 8-1 on page 7 shows the turn-on time versus C

The turn-on time is 60% longer when V

The turn-off time is less than 10 µs.