Bluetooth Audio Module
Ehong Technology Co., Ltd
The microphone bias characteristics include:
■ Power supply:
■ CSR8670 BGA microphone supply is VBAT (via SMP_VBAT) or VOUT_3V3 (via SMPS_3V3)
■ Minimum input voltage = Output v drop-out voltage
■ Maximum input voltage is 4.25V
■ Drop-out voltage:
■ 300mV maximum
■ Output voltage:
■ 1.8V or 2.6V
■ Tolerance 90% to 110%
■ Output current:
■ 70μA to 2.8mA
■ No load capacitor required
6.11. 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_A_N and SPKR_L_P for the right channel, as
Figure 6 shows, and between SPKL_B_N and SPKL_B_P for the left channel.
Figure 14: Speaker output
6.12. 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.
