Digitally-enhanced analogue controllers blend digital power, analogue loops

October 22, 2014 // By Graham Prophet
Claiming to combine the flexible control and telemetry aspects of digital power supply architectures with easy-to-use analogue control loops, Microchip’s MCP19118/9 provide simple analogue PWM control and a configurable MCU to yield the first PMBus compatible controller with up to 40V operation.

Microchip's latest Digitally Enhanced Power Analog (DEPA) controllers, the MCP19118 and MCP19119 provide simple yet effective analogue PWM control for DC-DC synchronous buck converters up to 40V, with the configurability of a digital MCU. They are positioned as the first devices to combine 40V operation and PMBus communication interfaces. These features enable quick power-conversion circuit development with an analogue control loop that is programmable in the integrated 8-bit PIC MCU core’s firmware. This integration and flexibility is suitable for power-conversion applications, such as battery-charging, LED-driving, USB Power Delivery, point-of-load and automotive power supplies.

Along with the rapidly growing popularity of digitally controlled power supplies, due to their configurability for a variety of operating conditions and topologies, power system designers also have an increasing need for the ability to report telemetry and conduct two-way communication (typically for monitoring and fault reporting), via standard communication interfaces such as PMBus. Additionally, the recently released USB charging specifications (USB Power Delivery and the USB type C connector) include variable charging voltages, which allow for rapid device charging, but add potentially difficult hardware requirements.

By integrating a supervisory microcontroller, the MCP19118/9 devices can create programmable power supplies. Key system settings—such as switching frequency (100 kHz to 1.6 MHz), current limits and voltage setpoints—can be adjusted on-the-fly during operation by issuing write commands to the registers in the device. One design can then be reused for additional applications, using firmware updates to change the configuration, which minimises design, production and inventory requirements across multiple platforms. The integrated MCU core can be used to monitor other parts of the application to sequence startup operations; intelligently manage faults, under-voltage or brown-out conditions; perform housekeeping functions; adjust power outputs in response to load requirements (such as battery charging or USB port power); and assisting with the module’s external interfaces (monitoring or delivering signals to the user or system). With integrated linear regulators, PWM generators, ADCs, MOSFET drivers, analogue error amplifiers and control-loop compensation, the MCP19118/9 devices provide a very compact circuit solution. Properly implemented, this system is capable of high conversion efficiency and excellent transient response for reduced system power losses, smaller heatsinks and longer battery life in portable applications. These DEPA devices can also provide data over the I²C interface, using customised SMBus or PMBus compatible commands.

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