Extreme Processing Thresholds: Low Price

Friday, March 26th, 2010 by Robert Cravotta

[Editor's Note: This was originally posted on the Embedded Master

Exploring processing thresholds is a tricky proposition. There is a certain amount of marketing specmanship when you are releasing a product that extends some limit of a processing option – say price, power, performance, or integration. It is helpful to understand how the supplying semiconductor vendor is able to meet the new threshold so you can better understand how those trade-offs will or will not affect any design you might choose to consider that new part in.

To lead off this series, I am looking at processors that cross new low price thresholds because there have been a handful of announcements for such parts in the past few months. Texas Instruments’ 16-bit MSP430 represent the lowest public cost parts which start at $0.25. Moving up the processing scale points our attention to NXP’s 32-bit Cortex-M0 processors which start at $0.65. Rounding out the top end of the batch of new value-priced processors is STMicroelectronics’ 32-bit Cortex-M3 processors which start at $0.85.

In looking at these announcements, be aware that the pricing information is not an apples-to-apples comparison. While all of the parts of the announced processor families can address a range of applications spaces and overlap with each other, each of these specific announcements is significant to a different application space. What is most relevant with each of these processors is that each potentially crosses a cost threshold for a given level of processing capacity such that existing designs using a processor at that same price point, but delivering less capability, can now consider incorporating new features with a larger processor than was available before at that price point. The other relevant opportunity is that there are applications that were not using processors before because they cost too much that can now economically implement a function with a processor.

When looking at these types of announcements, there are a few questions you might want to get answers for. For example, what volume of parts must you purchase to get that price? The Cortex-M0 and -M3 pricing is for 10,000 units. This is a common price point for many processor announcements, but you should never assume that all announced pricing is at that level. For example, the MSP430 announcement pricing is for 100,000 units. The announced 1,000 unit pricing for the MSP430G2001 is $0.34. To get an idea of how much volume purchasing can drop the price, VC Kumar, MSP430 MCU product marketing at Texas Instruments, shares that the pricing for the G2001 part drops to around $0.20 at 1,000,000 units. Fanie Duvenhage, Director Product Marketing/Apps/Architecture for the Security, Microcontroller & Technology Development Division at Microchip points out that since around five years ago, very high-volume, small microcontrollers have been available for a unit price in the $0.10 to $0.15 range. So there is a wide range of processing options at a variety of price points.

So how what do these suppliers have to do to be able to sell their processors for these lower prices? According to Joe Yu, Strategic Business Development at NXP Semiconductors, choosing the right core with the right process technology has the largest impact on lowering the price threshold of a processor. The packaging choice represents the second largest impact on pricing thresholds. After that, reducing Flash, then RAM, and then individual features are choices that a processor supplier can make to further lower the pricing point.

VC Kumar shares that the latest MSP430 part price point uses the same process node as other MSP430 devices. The lower price point is driven by smaller on chip resources and by taking into account what are the boundary conditions that the processor will have to contend with. By constraining the boundary conditions, certain value-priced parts can use less expensive, but lower fidelity IP blocks for different functions. As an example, standard MSP430 parts can include a clock module configuration that supports four calibrated frequencies with ±1% accuracy while the value-line sister parts use a clock module configuration that supports a single calibrated frequency and no guarantee for the ±1% accuracy.

Another area of controversy for processors that push the low-end of the pricing model is how much on-chip resources they provide. To reach these price points, the on-chip resources are quite constrained. For example, the Cortex-M3 part includes 16-kbytes of Flash, while the Cortex-M0 part includes 8-kbytes of Flash. The MSP430 part includes 512-bytes of Flash and 128-bytes of SRAM. These memory sizes are not appropriate for many applications, but there are growing areas of applications, including thermometers, metering, and health monitoring that might be able to take advantage of these resource constrained devices.

One thing to remember when considering those devices at the lowest end of the pricing spectrum is that they might represent a new opportunity for designs that do not currently use a processor. Do not limit your thinking to tasks that processors are already doing or you might miss out on the next growth space. Are you working on any projects that can benefit from these value-priced processors or do you think they are just configurations that give bragging rights to the supplier without being practical for real world use?

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