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Linear technology LTC2410 precision 24-bit adc (qty.2)
Linear Tech LTC2410 Precision 24-bit ADC (Qty.2)
Build a 6 digit DVM, or N2PK VNA!
On offer are 2 new LTC2410 precision 24 bit analogue to digital converters (ADC) by Linear Technology.
These are great for instrumentation projects, being some of the best performing converters available anywhere. 24 bits means 16,777,216 levels which is extraordinary resolution, providing a correspondingly huge dynamic range.
With such small steps, noise could be a real problem, but the chip itself has RMS noise of just 0.16ppm and by clocking at a multiple of the 50Hz line frequency, mains noise based is rejected by 110dB. Common mode DC rejection is even higher at 140dB.
Of course, to obtain full performance from these parts, a good quality voltage reference is required, along with well regulated supplies. The parts are billed as 'micropower' chips, taking just 200uA while running, and a tenth of that in sleep mode, making them ideal for battery powered applications.
They are physically small (0.6mm pitch SSOP) and will take some skill/experience with SMD devices to mount. Seven of the sixteen pins are connected to ground, so only nine other connections are needed and it is just about possible to do 'ugly style' without a dedicated PCB if you are a masochist (like me ;-).
These converters are not fast - you wouldn't use them to capture rapidly changing signals, such as audio waveforms. Instead they excel at, or close to, DC where they have both superb accuracy and high precision.
However, by hooking up one of these 24 bit converters, with accuracy and linearity around a part per million, a 6 digit instrument is achievable, matching the performance of high end test gear. (As a fan of precision techniques, I found the Linear Technology Application Note #86 absolutely fascinating, see "A Standards Lab Grade 20-Bit DAC with 0.1ppm/ C Drift - The Dedicated Art of Digitizing One Part Per Million".)
Perhaps the most famous project using these in the Ham world is the Vector Network Analyser (VNA) by Paul, N2PK, an excellent and novel design. The N2PK architecture does a direct conversion to DC, then uses the huge resolution of the LTC2410 to provide a dynamic range comparable to a multi-conversion superhet. Simple and elegant, full details are online:
* Main Page: http://n2pk.com/
* Architecture: http://n2pk.com/VNA/VNAarch.html
* Schematics+: http://n2pk.com/VNA/n2pk_vna_pt_2_ver_b2.pdf
[By comparison, most lab VNAs use the Superhet principle, which gives great dynamic range but is relatively complex to implement (see Scotty Sprowls' design at http:// /ssavectoranal/vector.html). Simpler approaches usually use the nice 'VNA on a chip', the AD8302 from Analog Devices but these compromise on the dynamic range (< 60dB, restricted by the chip).]
These fine parts will find many uses in precision test gear projects, with good code samples and applications in the datasheet .
http:// /pc/downloadDocument.do?navId=H0,C1,C1155,C1001,C1152,P1851,D2557
