Interestingly, for a company that also sells power management devices, the AD9361 data shows that it requires three rail voltages. Some are shown derived from external low drop out regulators (LDOs). Lime has integrated LDOs on-chip, making it possible to use a single supply, again reducing cost and board space.
Both data sheets mention programmable on-chip DSP (digital signal processing) to enhance their filter performance, along with Received Signal Strength Indicator (RSSI), Automatic Gain Control (AGC), and self-calibration capabilities. The companion baseband processor (BBP) can control the ADI device, while Lime has included an on-chip microcontroller and Direct Digital Frequency Synthesizers (DDFS), which can off-load tasks from the BBP, simplify calibration, and offer greater flexibility. The BBP is typically an FPGA or DSP processor, or may be a dedicated SoC for high volume applications such as residential and enterprise small cells.
ADI added an additional 12-bit auxiliary ADC that can be used for monitoring temperature or the transmit power output, and two 10-bit DACs for functions such as power amplifier bias generation, all of which again saves money.
The AD9361 is housed in a 10x10 mm CSP, while the LMS7002M uses an 11.5mm QFN square package. The penalty of a larger package may be driven by the higher number of signal pins that Lime brings out. Its philosophy is to give users access to intermediate points along the signal chain, so that external components such as filters, data convertors, or low noise amplifiers (LNAs) can be substituted if the system requirements need enhancements (more on this below).
The above discussions provide only a brief foray into the technical stuff, but there are bigger differences in the "soft" areas. For example, while ADI can support designers through its existing network, the Lime approach is for direct support supplemented by an open-source model as appropriate. That's an interesting approach for a semiconductor vendor, and with pioneering projects such as Arduino and Raspberry Pi setting new records every day, who would bet against it?
But the biggest difference that I found took a bit of digging. The AD9361 is stocked by distributors who show a sample price at $341 and list price of $175 in 1,000-plus quantities. The Lime press release said their part will be priced "aggressively" and invited customers to contact Lime directly. So I did. I was told that the LMS7002M will launch at no more than the cost of the current device, which samples at $110. That makes the ADI part three times the price. Not only that, but I was told the high-volume price will be so low that it will make it attractive to replace standard components such as dual 12-bit ADCs and DACs, DDFS, and programmable filters and mixers. (Remember I said that the user can access lots of intermediate points along the signal chain -- that's another reason why this was added and why the device has a fine granularity of power-down options.) All of this sounds like a disruptive attack on the wider analog market.
My conclusion is that ADI is targeting professional equipment and emerging applications in the range up to 6GHz, while Lime will service requirements in cost-driven designs and those using the lower frequency bands. The stage is set for explosive growth in applications like small cells, SDR, M2M, and white space. Now engineers have a real choice with regard to bringing exciting new wireless products to market.
Click here for more information on the AD9361.
Click here for more information on the LMS7002M.