TWL1106

VOICEBAND AUDIO PROCESSOR (VBAP)

SLWS094 – JUNE 2001

3

POST OFFICE BOX 655303

detailed description

power up/reset

An external reset must be applied to the active-low RESET terminal while MCLK is active to ensure reset at

power up.

reference

A precision band-gap reference voltage is generated internally and supplies all required references to operate

the transmit and receive channels.

phase-locked loop

The phase-locked loop generates the internal clock frequency required for internal digital filters and modulators

by phase locking to 2.048-MHz master clock input.

PCM interface

The PCM interface transmits and receives data at the PCMO and PCMI terminals, respectively. The data is

transmitted or received at the MCLK speed once on each PCMSYN cycle. The PCMSYN can be driven by an

external source that is derived from the master clock and used as an interrupt to the host controller.

microphone input

The microphone input circuit consists of two differential input/differential output amplifiers (MIC Amp 1 and

MIC Amp 2). MIC Amp 1 is a low-noise differential amplifier capable of an externally set gain. MIC Amp 2 is a

differential amplifier with a fixed gain of 6 dB.

analog modulator

The transmit channel modulator is a third-order sigma-delta design.

transmit filter

The transmit filter is a digital filter designed to meet Consultive Committee on International Telegraphy and

Telephony (CCITT) G.714 requirements. The TWL1106 device operates in either the 13-bit linear or 8-bit

companded

µ-law mode.

receive filter

The receive (RX) filter is a digital filter that meets CCITT G.714 requirements. The TWL1106 device operates

in either the 13-bit linear or 8-bit

µ-law companded mode, which is selected at the LINSEL input.

receive volume control

In linear mode, the three least significant bits of the 16-bit PCMI data sample is used to control volume. The

volume range is –18 dB to 3 dB in 3-dB steps.

digital modulator and filter

The second-order digital modulator and filter convert the received digital PCM data to the analog output required

by the earphone interface.

earphone amplifiers

EAROUT is recommended for use as a differential output; however, it can be connected in single-ended

topology as well. Clicks and pops are suppressed from the differential output.