Make your music pop with TPA3138D2 and PIC18F57Q43

AudioAmp 5 Click is based on the TPA3138D2, an inductor-less stereo class-D audio amplifier from Texas Instruments. It has many features that make this IC an attractive solution for battery-powered and stand-alone active speakers. It is very flexible regarding the PSU voltage: it can work with voltages within the range of 3.5V to 14.4V. With only 3.5V at the PSU connector, it can still deliver 1W of power to a 6Ω load (per channel). However, its nominal operating voltage is 12V, reaching up to 10W of power to the connected 6Ω speaker, with only 1% of Total Harmonic Distortion (THD). The TPA3138D2 IC features a set of protections, including output short circuit, over-temperature, under-voltage, and over-voltage protection. These protections will be reported at the SD/FAULT (EN) I/O pin if any of these protections are activated. The TPA3138D2 IC can also detect a constant DC current at the output. When a DC detection event occurs, the outputs are turned OFF, protecting the connected speakers. Very often, a DC detection event can be triggered when the circuit is powered up, so it is advisable to hold the EN pin to a LOW logic level for a short period, preventing faulty DC detection reports and loud pops. The output stage of the TPA3138D2 operates in Bridge-Tied Load (BTL) topology. This means there are two outputs per channel: inverted and non-inverted (OUTN and OUTP). Class-D amplifier produces the sound by modulating the pulse-with of the output voltage. It offers a choice of two PWM modulation schemes,

selectable by the MODE_SEL pin of the IC. This pin is routed to the mikroBUS™ RST pin, labeled as MDS on this Click board™. By default, a resistor pulls the MDS pin to a LOW logic level. When the MDS pin is set to a LOW logic level, the TPA3138D2 uses the BD Modulation scheme. This scheme reduces the need for a typical LC reconstruction filter at the output. While there is no input, both OUTN and OUTP are in phase, with a 50% duty cycle. There is no current through the speaker in this case. The duty cycle will increase at the OUTP and decrease at the OUTN simultaneously when the positive half-phase of the audio signal is applied at the input. For the negative half-phase at the input, the opposite will happen. The greater the difference in pulse width, the greater the current through the connected speaker. When the MDS pin is set to a HIGH logic level, the TPA3138D2 uses the 1SPW Modulation scheme. This scheme allows low idle current and better overall efficiency at the expense of increased THD. Both OUTP and OUTN are held in phase at about 15% duty cycle. As the input signal is applied, one output is driven to the GND while the other output increases. The modulation takes place through this single output, reducing the switching losses. Again, the positive half-phase will cause the OUTN to be driven to GND, while the negative half-phase of the input signal causes the OUTP to be driven to GND. The SD/FAULT pin allows the host MCU to enable/disable outputs. Pulling this pin to a

LOW logic level makes the outputs muted, and the TPA3138D2 IC enters the low-current state, reducing the supply current to the absolute minimum level. Muting the TPA3138D2 before cutting down the power supply reduces the pops and clicks that might appear in this case. The SD/FAULT pin is routed to the mikroBUS™ CS pin labeled EN on this Click board™, and a resistor pulls it to a HIGH logic level. There is a selectable input gain on Audio Amp 5 click. Applying a LOW logic level to the GAIN_SEL pin sets the input gain to 20dB. A HIGH logic level sets the input gain to 26dB. This allows matching the input signal to reach the optimal output level. This pin is routed to the mikroBUS™ PWM pin labeled as GS and pulled to the LOW logic level by a resistor. The external PSU should be connected to the VIN terminal. A line-level audio source can be connected to the LINE IN 3.5mm jack stereo connector, while the speakers should be connected to the angled spring terminals labeled OUTL and OUTR. These terminals have their polarities marked on the top overlay. This Click board™ can operate with either 3.3V or 5V logic voltage levels selected via the VCC SEL jumper. This way, both 3.3V and 5V capable MCUs can use the communication lines properly. However, the Click board™ comes equipped with a library containing easy-to-use functions and an example code that can be used, as a reference, for further development.

PIC18F57Q43 Curiosity Nano evaluation kit is a cutting-edge hardware platform designed to evaluate microcontrollers within the PIC18-Q43 family. Central to its design is the inclusion of the powerful PIC18F57Q43 microcontroller (MCU), offering advanced functionalities and robust performance. Key features of this evaluation kit include a yellow user LED and a responsive

mechanical user switch, providing seamless interaction and testing. The provision for a 32.768kHz crystal footprint ensures precision timing capabilities. With an onboard debugger boasting a green power and status LED, programming and debugging become intuitive and efficient. Further enhancing its utility is the Virtual serial port (CDC) and a debug GPIO channel (DGI

GPIO), offering extensive connectivity options. Powered via USB, this kit boasts an adjustable target voltage feature facilitated by the MIC5353 LDO regulator, ensuring stable operation with an output voltage ranging from 1.8V to 5.1V, with a maximum output current of 500mA, subject to ambient temperature and voltage constraints.