NLP-5x Toolkits
Demo/Emulation Manual
18
P/N 80-0314-A
© 2009 Sensory Inc.
Audio Outputs
The NLP-5x has one PWM audio output and two DAC audio outputs, which can be used for stereo applications.
On the Demo/Emulation board, we have provided one audio jack for PWM (J6), and two audio jacks for DAC
outputs (J4 and J5).
DAC Amplifier and Volume Control
To amplify the NLP-5x's differential DAC outputs, we have provided a fully differential stereo audio amplifier, the
TPA6021A4 (U22). Because each channel has differential outputs (bridge-tied loads) there is no common
ground connection, so there are separate speaker jacks for each channel. Do not use a Y cable that shorts one
of the outputs of each channel together.
The volume of the DAC outputs is controlled with the dial (R88). When a shorting block is placed at Manual at
the “Audio Shutdown” header (JP3), the audio shutdown is controlled with this dial.
Adding Volume Control for PWM
To add volume control to the PWM output of the board:
Disconnect the speaker cord from the mini-plug jack on
the PCB.
Cut into one side of the cord and insert a 200 Ohm
potentiometer in series with the wire.
Microphone Circuit
There are two on-board microphones. To use the external microphone, plug the microphone cable into the
microphone jack. If you do, the on-board microphone will be disconnected from the circuit.
Microphone Power
The microphones are powered with VCCA. If you can power the microphones with a IO port, remove the
shorting block from MIC PWR (JP7), and connect the IO port to pin 2 of JP7.
Microphone Bias Resistors
MIC 1 has a 2.2K Ohms microphone bias resistor (R84), and MIC2 also has a 2.2K Ohms microphone bias
resistor (R85). If you need to change the value of microphone bias resistor, replace these resistors. For
selecting a microphone and bias resistor, refer to the design note – NLP-5x Microphone Selection Design Guide
(80-0318).
USB
There are three USB connectors on Demo/Emulation board. They are labeled “PC LOADER”, “DEBUG”, and
“APP USB”. “PC LOADER” is used to download the code and data into the Demo/Emulation board. The one
used for the application is “APP USB”. “DEBUG” is reserved for future use.
Mini-Plug
Speaker
