The rise of programmable analogue chips

Many companies are now taking on the challenge of specifying and supporting programmable analogue chips.

Ask any engineer about programmable chips and he/she will almost certainly think of FPGAs for implementing complex digital logic. But the world in which we live is essentially analogue in nature.

Readers of Programmable Logic Designline will know that the road to launching a new digital FPGA company is strewn with the corpses of failed challengers. The attempts to create programmable analogue devices are rarely discussed.

For many good reasons, system architects decide to convert "real-world" analogue inputs into the digital domain as quickly as possible. Digital processing can be fast and accurate, and is free from the problems associated with voltage and temperature drift that affect analogue chips.

Analogue is tricky—sometimes it's darned tricky—as I know after several years of marketing customer-specific mixed-signal devices. For example, the specification of an analogue to digital converter has a wide range of parameters: input level, offset error, resolution bits, integral non-linearity, monotonicity, throughput rate and settling time, voltage/temperature coefficients and output voltage noise/slew rate/levels/drive.

Maxim Integrated recently announced the MAX11300 device. This features a 12bit ADC and 12bit DAC along with an analogue switch matrix. The ADC operates up to 400ks/s while the DAC provides a conversion in 40µs. There are 20 analogue ports that can be accessed and measured by the product or used as either digital or analogue outputs. The switch matrix is controlled by what Maxim call PIXI technology, and the chip is programmed on power-up via an SPI link.

MAX11300 devices provide a neat solution to interfacing in control or industrial applications where equipment uses a range of different supply voltages. Designers can select each pin to interface over a ten volt range and at voltages from -10V to 10V. The chip can also monitor its internal temperature and (using an additional sensor) the external temperature. The temperature limits can be programmed into the device, and it can use one of the output ports to flag an out-of-range condition to the system processor.

Designers use a GUI that provides simple drag-and-drop and interconnect features. The flexibility built into the selection of the mixed signal port assignment will simplify the printed circuit board layout.

Maxim lists diverse applications that require a mix of analogue and digital functionality, such as motor control and RF amplifier bias control for base stations. This single chip solution looks to me to be a product that can solve a wide range of interfacing and data conversion problems.

Silego Technology has released another new analogue product. It offers small programmable arrays of analogue components under the branding GreenPAK. The latest device, GreenPAK4, includes analogue components such as an 8bit ADC with two DACs, a voltage reference, oscillators, digital comparators/Pulse Width Modulators, and a tiny amount of programmable digital logic. While designers can program parts using a GUI during the design phase, the production parts have the design customised into NVM by Silego rather than being field-programmable devices. The company lists consumer, wearables, PC and peripherals among the applications for the devices.

- Paul Dillien
  EE Times