Next-Gen Digital Signal Controller ICs Offer 4X More Memory

May 1, 2010 12:00 PM
Sam Davis, Editor-in-Chief

MICROCHIP TECHNOLOGY'S 16-bit Digital Signal Controller (DSC) ICs were hailed as the next generation of digitally controlled power-supply ICs in 2006 when they were first introduced. Fig. 1 shows a block diagram of the initial offering of DSCs. Now, there is a new generation of DSCs with improved performance that has the block diagram shown in Fig. 2.

The 2010 version of the DSCs provides up to four times the memory, compared to the company's previous SMPS & digital power conversion families. Additionally, you can configure the new DSCs for various topologies, giving power-supply designers freedom to optimize them for specific applications.

The best way to understand the functions of these DSCs is to examine the simplified version in Fig. 3., which shows the basic internal digital control configuration for a switch-mode power supply. These devices are configured within the supply's feedback loop, so speed is critical because the A/D converter (ADC) and processor must sample the output and react as quickly as possible to any changes. In operation, the ADC samples the power supply's output voltage and sends the digital result to the processor that controls a pulse width modulator (PWM). Then, an external power stage rectifies the PWM output and produces a filtered dc output.

Compared with analog supplies, DSC ICs provide extensive fault monitoring, better transient response, and lower-cost redundancy options. In addition, the digital approach eliminates a power supply's drift and need for temperature compensation. This digital technique can program operational settings, which eliminates the manual tweaking of power-supply adjustments. DSC ICs perform these tasks primarily using firmware.

The eight new DSCs shown in the table enable several completely independent digital control loops. These dsPIC33F GS series digital-power DSCs enable digital control loops with 12 to 18 high-speed, 1-ns resolution PWMs and one or two 10-bit, on-chip ADCs, providing 2 to 4 million samples per second (MSPS) for low latency and high-resolution control. They range from 64 to 100 pins and 32 to 64 KB Flash memory. These DSCs feature interactive peripherals that both minimize the intervention of the processor and are able to handle the real-time needs of high-speed current-mode control.

Implementing high-speed, precision digital control loops for digital power conversion applications requires a high-performance DSP engine, along with specialized digital power peripherals. Microchip's 16-bit dsPIC33F GS Series DSCs provide on-chip peripherals specifically designed for high-performance, digital power supplies. These peripherals include high-speed PWMs, ADCs, and analog comparators. Thus, the newly expanded dsPIC33F GS family supports applications such as induction cooking, uninterruptible power supplies, solar and pure sine-wave inverters, intelligent battery chargers, power factor correction, HID lighting, fluorescent lighting, LED lighting, and ac-dc and dc-dc power converters.

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