ADPCM CODEC
Application Notes
 

Documents

Description

These notes describe the design of analog interface circuits between ADPCM CODECs and acoustic devices (speakers or microphones). The design method for the interface circuit is shown so that the voice signal level corresponds to the operational characteristics of ADPCM CODEC input or output level.

The interface circuit examples of the ADPCM CODEC are indicated in Fig. 1 and Fig. 2.

Fig. 1 : Applies to Example for MSM7540/7540L/7560/7560L
Fig. 2 : Applies to Example for MSM7570/7570L/7590L

The differences between the groups of devices are as follows:
1. The devices in the later group provides an AIN1+ pin for using
      the first stage amplifier as a differential amplifier.
2. The devices in the later group provide the differential output
      pins (SAO+ and SAO–) for driving a sounder or
      other acoustic devices other than speakers.
3. The devices of the later group have built-in programmable-gain side-tone signal
      paths.