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 acquisitionZONE Products for the week of December 3, 2007
Semtech Says…
Semtech’s Latest Ultra-Small Sensing Platform Device Brings Industry-Leading Versatility and Value to Sensor Customers
SX8724 is only 4x4 mm, leverages ZoomingADC capability to directly connect to a wide range of pressure, temperature and magnetic sensors
Semtech Corp., a leading supplier of analog and mixed-signal semiconductors, announced the SX8724, an ultra-small sensor interface device that uses the company’s ZoomingADC signal amplification circuitry to directly connect to a wide array of pressure, temperature and magnetic sensors, making it one of the most versatile data acquisition devices available on the market.
The SX8724 enables electronics to be co-located with the sensor. With a digital output from the sensor, whether it be magnetic, pressure or chemical, manufacturers can provide a total solution to their customers. The device is designed to operate off a single Li-Ion battery without loss of its 16-bit precision even with a depleted battery.
The device features Semtech’s ZoomingADC, a 10-bit preamplifier with a programmable gain of between 0.1 and 1,000 and a 16-bit ADC. The preamplifier delivers the highest gain on the market giving designers the freedom to achieve a given level of sensitivity using lower cost, sensors.
The SX8724 interfaces directly with up to six sensors which can be a mix of pressure, magnetic and chemical, making the device truly a “sensing platform” which can be deployed across a manufacturer’s complete range of sensors.
“With an ability to directly read most Wheatstone bridge sensors and with flexible signal input, the SX8724 is the industry’s most versatile sensing solution,” said Michel Chevroulet, Sensing Product Group Manager for Semtech’s Wireless and Sensing Products Business Unit. “This flexibility and the focused amplification of our ZoomingADC technology allows customers to drive down the cost of their systems through the use of low-cost sensors.”
EN-Genius Says…
The ZoomingADC technology was acquired by Semtech from their purchase of Xemics SA in June 2005. Together with the wireless technology acquired at the same time the company became Semech’s Wireless & Sensing Products business unit.
The purpose of the technology is to maximize the use of an ADC. We see, regularly, the purchase of unnecessarily higher resolution ADCs because the design engineer cannot get his numbers in order. Control in this part is from the on-chip control logic driven from an I2C interface.
The architecture consists of a series of three differential programmable amplifiers followed by an ADC. There are 8 analog inputs (or 6 depending where you read on the data sheet) into a multiplexer which would, typically, be used for 4 (or 3) differential sensors such as bridges. The output of the mux is modulated by the sampling frequency and each of the last two amplifiers (they can be bypassed individually) is fed a reference voltage that is chosen from at the output of a 4-channel reference mux. Offsets can also be provided to the last two stages. The ADC is highly oversampled (typically the sampling frequency can be up to 1000 times the Nyquist rate of the inputs). The minimum typical sampling rate is 62.5 kHz while the maximum is 500 kHz. Decimation filtering is provided in the ADC.
Operation is bipolar (with a charge pump on chip) allowing for both positive and negative inputs to the ADC. The common mode range is from the higher of 3 V, or the battery voltage, -0.3 V to +0.3 V. Typical active current depends on resolution and sampling frequency but at 16 bits with 1 kHz it is a typical 250 µA. A sleep mode takes this down to a maximum of 1 µA.
The overall result is a part that can be programmed from 6 bits to 16 bits with very flexible gain (0.1x to 1000x in 10% steps) and offset (compensation up to 15x input FS). It should be straightforward for the external system controller (to which the digital outputs are being fed) to change settings for each pair of sensor inputs, as needed. Four digital GPIO lines are also provided and the part will be compatible with most Wheatstone bridge sensors.
Knowing as I do the originator of the suggested need for this sort of technology, I also have to say that the implementation is superb. The ability to maximize the span of an ADC’s inputs is a fundamental issue in data acquisition but little understood by many of the design engineers who are thrown into the analog pit, because the boss doesn’t want to hire a consultant for that little piece of circuitry. There is a premium on the part, but it is small and as a direct drop-in solution I doubt there will be little management or buyer resistance to it. The part is also small enough to have it embedded in a sensor’s enclosure. Being now in Semtech’s portfolio will make it a much easier sell -- rather than from a mostly R&D, fabless, operation in Neuchatel, Switzerland. The part should do fabulously and we will see it in many pressure and temperature sensor applications, particularly portable applications.
The SX8724 is in production in Pb-free MLPQ-16 priced at $2.42 in 10-k piece lots.
Data Sheet
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