TLV320AIC22
DUAL VOIP CODEC
SLAS281B – JULY 2000 – REVISED JUNE 2002
19
POST OFFICE BOX 655303
DALLAS, TEXAS 75265
power down and reset (continued)
There are two ways to reset the TLV320AIC22:
D By pulling the RESET pin low, or
D By writing to the software reset bits in control registers 2 and/or 7 to reset either codec
Asserting the RESET pin low puts the device into a default state with default register settings. After deasserting
the RESET pin, the user should wait a minimum of 10
s before sending control or conversion data to the device.
The default register settings are described in the sections titled suggested configuration sequence and register
map. After a software reset has been removed, control and conversion data can be sent in the next frame.
Asserting a software reset by programming register 2 puts register 1, 2, 3, 4, 5, and 15 in their default settings
and resets codec 1.
Asserting a software reset by programming register 7 puts register 6–14, 16, and 17 in their default settings and
resets codec 2.
microphone bias
To operate Electret microphones properly, a bias voltage and current are provided. Typically, the current drawn
by the microphone is on the order of 100
A to 800 A and the bias voltage is specified across the microphone
at 2.5 V. The bias has good power-supply noise rejection in the audio band, can source 4-mA max current, and
can be shared between all the microphones.
microphone amplifiers
There are three microphone preamplifiers, one each for the handset, headset, and speakerphone microphones.
The input signals for the handset and headset amps typically are less than 20 mVrms, 100 mV max. The input
signals for the speakerphone amp typically are less than 2 mVrms, 20 mV max. The amplifiers have a differential
input to minimize noise and EMC immunity problems. Three values for the gain for the handset and headset
microphones and four values for the gain for the speakerphone microphone are selectable via the I2C or serial
interface to cater to the requirements in Europe and North America. The frequency response is flat, up to 8 kHz.
Table 3. Gain Settings
INPUT
GAIN SETTINGS
Handset microphone preamp (HSINP,M)
0 dB, 14 dB, 23 dB, or mute
Headset microphone preamp (HDINP,M)
0 dB, 14 dB, 23 dB, or mute
Speakerphone microphone preamp (MCINP,M)
0 dB, 20 dB, 32 dB, 42 dB, or mute
By default, the echo gain for the handset and headset are 14 dB. Therefore, a connection exists between the
handset and headset inputs (microphones) and their respective outputs (speakers) in order to implement
sidetone.
driver amplifiers
There are two driver amplifiers that are meant to drive a 150-
handset or headset speakers, differentially. The
drive amplifier is differential, to minimize noise and EMC immunity problems. The frequency response is flat,
up to 8 kHz.
speakerphone amplifiers
The speakerphone speaker impedance is 8
. The drivers are capable of providing a 5-V peak-to-peak
differential signal, which means that the peak power is about 390 mW. The differential drive amplifier achieves
this and minimizes noise and EMC immunity problems. The frequency response is flat, up to 8 kHz.