Digital-to-Analog Converter (DAC)

3.2 Digital-to-Analog Converter (DAC)

The C614 incorporates a two-pin pulse-density-modulated DAC which is capable of driving a 32 Ω loudspeaker directly. To drive loud speakers other than 32 Ω, an external impedance-matching circuit is required.

3.2.1Pulse-Density Modulation Rate

The rate of the master clock (MC) determines the pulse-density-modulation (PDM) rate, and this governs the output sampling-rate and the achievable DAC resolution. In particular, the sampling rate is determined by dividing the PDM rate by the required resolution:

Output sampling rate = PDM Rate ⎟2 (# DAC resolution bits)

PDM Rate

#DAC resolution bits

Set in ClkSpdCtrl register

Set in DAC control register

Address 0x3D

Address 0x34

For example, a 9 bit PDM DAC at 8 kHz sampling rate requires a PDM rate of 4.096 MHz.

There are four sampling rates which may be used effectively within the constraints of the C614 and the various software vocoders provided by Texas Instruments. These are: 7.2 kHz, 8 kHz, 10 kHz, and 11.025 kHz. Other sampling rates, however, may also be possible.

From the MC to the PDM clock, there is an optional divide-by-two in frequency. This option is controlled by the PDM clock divider in the interrupt/general control register. This means that the PDM rate can be set to run between

131.07kHz and 33.554 MHz in 131.07 kHz steps (the same as the MC). Or, the PDM rate can be set to run between 65.536 kHz and the maximum achievable CPU frequency (see Chapter 8, MSP50C614 Electrical Specifications) in 65.536 kHz steps. The PDM clock divider determines which of these two ranges apply. Within these ranges, it is the PLLM which sets the rate: ClkSpdCtrl, 0x3D. Refer to Section 3.2.3, PDM Clock Divider, for more information regarding the PDM clock divider and the available combinations of CPU clock rates vs sampling rates. (Section 2.9.3, Clock Speed Control Register, has more details regarding the PLLM.)

3.2.2DAC Control and Data Registers

The resolution of the PDM-DAC is selected using the control bits in the DAC control register (address 0x34). The available options are 8, 9, or 10 bits of res- olution. Bits 0 and 1 in the DAC control register control this option:

3-8

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Texas Instruments MSP50C614 Digital-to-Analog Converter DAC, Pulse-Density Modulation Rate, DAC Control and Data Registers
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MSP50C614 specifications

The Texas Instruments MSP50C614 is a microcontroller that belongs to the MSP430 family, renowned for its low power consumption and versatile functionality. Primarily designed for embedded applications, this microcontroller is favored in various industries, including consumer electronics, industrial automation, and healthcare devices.

One of the standout features of the MSP50C614 is its ultra-low power technology, which enables it to operate in various power modes. This makes it ideal for battery-powered applications, where energy efficiency is crucial. The MSP430 architecture allows for a flexible power management system, ensuring that energy is conserved while providing robust performance.

The MSP50C614 is equipped with a 16-bit RISC CPU that delivers high performance while maintaining low power usage. With a maximum clock frequency of 16 MHz, it can execute most instructions in a single cycle, resulting in swift operation and responsive performance. This microcontroller also comes with a generous flash memory capacity, allowing developers to store large amounts of code and data conveniently.

In terms of peripherals, the MSP50C614 is highly versatile. It features a range of digital and analog input/output options, including multiple timers, GPIO ports, and various communication interfaces like UART, SPI, and I2C. This extensive set of peripherals allows for seamless integration with other components and simplifies the design of complex systems.

The integrated 12-bit Analog-to-Digital Converter (ADC) stands out as a valuable characteristic of the MSP50C614. This feature enables the microcontroller to convert physical analog signals into digital data, making it particularly useful for sensing applications and real-time monitoring.

Another noteworthy technology employed in the MSP50C614 is its support for low-voltage operations. With a broad supply voltage range, this microcontroller can function efficiently in diverse environments and is suitable for low-power applications, enhancing its practicality.

Moreover, Texas Instruments provides software support in the form of Code Composer Studio and various libraries that make it easier for developers to program and utilize the MSP50C614 effectively.

In summary, the Texas Instruments MSP50C614 microcontroller is a powerful, low-power solution equipped with the features and technologies necessary for efficient operation in a wide array of applications. Its blend of performance, flexibility, and energy efficiency makes it a popular choice among engineers and designers looking to create innovative, sustainable designs in the rapidly evolving tech landscape.
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