Bluetooth Audio Module
6.9 Analog Output stage
The output stage digital circuitry converts the signal from 16-bit per sample, linear PCM of
variable sampling frequency to a 2Mbits/s 5-bit multi-bit bit stream, which is fed into the analogue
output circuitry.
The output stage circuit is comprised a DAC with gain setting and class AB amplifier. The output
is available as a differential signal between SPKR_LN and SPKR_LP for the right channel, as
Figure 14 shows, and between SPKL_RN and SPKL_RP for the left channel.
Figure 15: Speaker output
6.10 USB
This is a full speed (12M bits/s) USB interface for communicating with other compatible digital
devices. The module acts as a USB peripheral, responding to request from a master host
controller, such as a PC.
The USB interface is capable of driving a USB cable directly. No external USB transceiver is
required. The device operates as a USB peripheral, responding to requests from a master host
controller such as a PC. Both the OHCI and the UHCI standards are supported. The set of USB
endpoints implemented can behave as specified in the USB section of the Bluetooth
specification v2.1+EDR or alternatively can appear as a set of endpoints appropriate to USB
audio devices such as speakers.
The module has an internal USB pull-up resistor. This pulls the USB_DP pin weakly high when
module is ready to enumerate. It signals to the USB master that it is a full speed (12Mbit/s) USB
device.
Shanghai Ehong Technologies Inc
