Data Sheet

IDC7 Bluetooth Module
Model: IDC747
Page: 12 Copyright IOT747 Ref: IDC747-DTS-V003
IOT747, 122 Ross Street, Cambridge, CB1 3BU, United Kingdom
Check www.iot747.com for updates. Email: [e-mail] Back to TOC
IDC747 Module
Product Information Data Sheet
Ref: IDC747-DTS-V003
Latest Update: July 20, 2021
122 Ross Street, CB13BU
Cambridge, United Kingdom
www.iot747.com
Connecting Speakers
The analogue output is not AC coupled. The analogue output circuit comprises a DAC, a buffer with
gain-setting, a low-pass filter and a class AB output stage amplifier. The output is available as a
differential signal between SPKR_LN and SPKR_LP for the left channel, and between SPKR_RN and
SPKR_RP for the right channel. The amplifiers expect a load impedance of 16 to 32 Ohms. Peak
voltage output depends on the gain setting though one should expect no more than a peak to peak
voltage of 1.5V with a DC offset of around 1.2V at maximum gain.
External Amplifier Support
The module is designed to provide direct speaker drive. In the case where higher Audio
power is required, it can drive an external amplifier. On the module, a PIO (refer to UART
Control Manual) goes High when an Audio Link is active. That PIO can be used for turning
ON and OFF an external amplifier.
The Speaker outputs are DC coupled to the Bluetooth IC internal to the module. The
speaker outputs are referenced to 1.8V. It is recommended connecting the module to an
external amplifier in a differential configuration for enhanced noise immunity. In this
configuration common mode noise is rejected by the amplifier configuration.
USB supply configuration:
In many applications supply noise can significantly degrade audio performance. This is
especially true in USB powered applications or where a USB source is used to charge a
battery powered application. USB supplies vary significantly with noise levels and supply
stability. In addition to steady state noise levels from USB supplies the plugging and
unplugging of USB chargers can cause large supply transients that ripple through the supply
chain to cause clicking and popping in the audio domain. It is recommended following good
noise immunity pcb design practices, ground isolation, short residual current return paths
and the use of ferrite bead and large decoupling capacitors on USB supply connections.