TWL1110

VOICE-BAND AUDIO PROCESSOR (VBAP

™)

SLWS103 – NOVEMBER 2000

5

POST OFFICE BOX 655303

functional description

power on/reset

The power for the various digital and analog circuits is separated to improve the noise performance of the

device. An external reset must be applied to the active low/RESET terminal to guarantee reset upon power on

and to bring the device to an operational state. After the initial power-on sequence the device can be functionally

has a pin-selectable power up in the default mode option. The hardwired pin-selectable PWRUPSEL function

allows the VBAP to power up in the default mode and to be used without a microcontroller.

reference

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

operate the transmit and receive channels. The reference system also supplies bias voltage for use with an

electret microphone at terminal MBIAS. An external precision resistor is required for reference current setting

at terminal REXT.

to seven control registers:

There are two power up modes which may be selected at the PWRUPSEL terminal: (1) The PWRUPSEL state

interface or controlling device, the programmable functions are fixed at the default gain levels, and functions

such as the sidetone and DTMF are not accessible. (2) The PWRUPSEL state (ground at terminal 20) causes

up the device.

phase-locked loop (PLL)

The phase-lock loop generates the internal clock frequency required for 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 PCMCLK speed once every PCMSYN cycle. The PCMCLK can be tied directly

to the 128-kHz or 2.048-MHz master clock (MCLK). The PCMSYN can be driven by an external source or

derived from the master clock and used as an interrupt to the host controller.

microphone amplifiers

The microphone input is a switchable interface for two differential microphone inputs. The first stage is a

low-noise differential amplifier that provides a gain of 23.5 dB. The second-stage amplifier has a selectable gain

of 6 or 18 dB.