TLV320AC40, TLV320AC41

3-V VOICE-BAND AUDIO PROCESSORS (VBAP

™)

SLWS045A – JUNE 1996 – REVISED APRIL 1997

2

POST OFFICE BOX 655303

description

The TLV320AC40 and TLV320AC41 voice-band audio processor (VBAP) integrated circuits perform the

transmit encoding (A /D conversion) and receive decoding (D/A conversion) together with transmit and receive

filtering for voice-band communications systems. Cellular telephone systems are targeted in particular;

however, these integrated circuits can function in other systems including digital audio, telecommunications,

and data acquisition.

These devices are pin-selectable for either of two modes — companded and linear — providing data in two

formats. In the companded mode, data is transmitted and received in 8-bit words. In the linear mode, 13 bits

of data, and either three bits of gain-setting control data, or three 0 bits of padding (to create a16-bit word), are

sent and received.

The transmit section is designed to interface directly with an electret microphone element. The microphone input

signal (MICIN) is buffered and amplified with provision for setting the amplifier gain to accommodate a range

of signal input levels. The amplified signal is passed through antialiasing and bandpass filters. The filtered signal

is then applied to the input of a compressing analog-to-digital converter (COADC) when companded mode is

selected. Otherwise, the analog-to-digital converter performs a linear conversion. The resulting data is then

clocked out of DOUT as a serial data stream.

The receive section converts a frame of serial data on DIN to analog through an expanding digital-to-analog

converter (EXDAC) when the companded mode is selected; otherwise, a linear conversion is performed. The

analog signal then passes through switched capacitor filters, which provide out-of-band rejection, (sin x)/x

correction functions, and smoothing. The filtered signal is sent to the earphone amplifier. The earphone amplifier

has a differential output with adjustable gain and is designed to minimize static power dissipation.

A single on-chip high-precision band-gap circuit generates all voltage references, eliminating the need for

virtual ground for all the amplifier circuits and the microphone bias circuit. Another reference voltage, MICBIAS,

can supply bias current for the microphone.

The TLV320AC4xC devices are characterized for operation from 0

°C to 70°C. The TLV320AC4xI devices are

characterized for operation from – 40

°C to 85°C.