Hittite - good products, horrible documentation? - Page 1
Forum section: electronics / rf-microwave

author: daqq
author_rank: Super Contributor
timestamp: November 10, 2016, 07:58:09 am
content: Hi guys,Is it just me, or does Hittite (bought by Analog Devices) seriously lack in the documentation department? I'm looking at some of their stuff and, well, the datasheets are vague and incomplete. See:http://www.analog.com/media/en/technical-documentation/data-sheets/hmc470A.pdfIt's seven pages, one of which is an automatically inserted Analog Devices page full of links and another one is the evaluation board layout. The package drawing is a crudely inserted JPG that suffered due to poor compression. There are helpful hints like:QuoteFor 60MHz is this 1nF? 1pF? 330pF? 10TF? Is there any formula to calculate this? Or a table? Or something?QuoteSo, is it a DC or AC coupled pin? I'm confused, if it requires a DC blocking capacitor, then the attenuator does not go from DC, but from some frequency.QuoteThen don't name them N/C?There are no timing diagrams, examples of waveforms (I'd love to see if there are any glitches during attenuation changes in the output signal) etc. Basically, the datasheet(s) assume that the user feels safe assuming a lot of stuff or does not care about a lot of stuff.A different device:QuoteWhat's "similar"? Is it 0.42 dB different with a peak at 712MHz? Does it spawn demons from pin 4 but otherwise works exactly the same?Basically it seems to me that the datasheets from Hitite are abridged versions really./rantBy the way, does anyone know of a small switchable attenuator ranging from 0-15dB attenuation, preferably with no external components? It needs to work at least in the 55-65 MHz range, beyond that I don't care, 50 Ohms IO, 2dB or smaller steps, parralel interface and preferably fast state changes without glitches.David

author: KE5FX
author_rank: Super Contributor
timestamp: November 10, 2016, 09:34:52 am
content: Suggest looking atwww.psemi.com- their data sheets aren't much better but their parts tend to be. Hittite is largely still GaAs oriented in an age where CMOS is making inroads into RF/microwave.

author: dmills
author_rank: Super Contributor
timestamp: November 10, 2016, 01:25:19 pm
content: Minicircuits have some switched attenuators that are happy in the 6M band, parallel or SPI variants are available, and they do work (You need the usual decoupling passives and a DC block cap in and out, should not be an issue at ~50MHz).I assume a QFN is acceptable packaging.Regards, Dan.

author: 1design
author_rank: Regular Contributor
timestamp: November 10, 2016, 03:12:01 pm
content: I used probably over 100 Hittite products over the years and the datasheets always had all the required information in them. So does this one.I never experienced any glitching while switching attenuators, they are just fets switching on and off. The capacitors are very basic RF calculations, do not belong in the datasheet as they are not part of the IC performance, but a design decision.With a basic understanding of how packages are made it is clear that those pins are internally N/C but good practice is to ground them so no stray voltage voltage forms on them in this case.The input and output pins are DC coupled so they need to be decoupled, again, standard practice with most components. It is matched to 50 ohms so a basic RC 1st order filter equation will give you the answer regarding capacitor size, but watch out for phase shifts if you are closer than a decade to the minimum frequency of interest.Minicircuits also works very well and have used plenty of their components over the years, again, you will have to do some work to match components to what you need the part to do in your specific case.BR

author: ebclr
author_rank: Super Contributor
timestamp: December 22, 2016, 01:04:48 pm
content: With the acquisition of Hittite Microwave, the industry's broadest portfolio of RF and Microwave Solutions are now available through Analog Devices's worldwideLet's wait, on the long run probably will have AD documentation quality on the survived products from Hittite

author: karoru
author_rank: Regular Contributor
timestamp: December 22, 2016, 03:23:22 pm
content: At least new designs, for older ones they could just slap AD logo on the first page (in best case via real wordprocessing, in worst case using some old scanned copy) and call it a day

author: eb4fbz
author_rank: Regular Contributor
timestamp: December 23, 2016, 10:04:29 pm
content: Quote from: 1design on November 10, 2016, 03:12:01 pmSame here, dozen of RF designs using Hittite ICs (att, lna, power amps, mixers, IQ mod/demods...) and never had a problem, their datasheets are fine and it's nice to have the I/Os equivalent circuit. Never had to contact their support department.

author: radar_macgyver
author_rank: Frequent Contributor
timestamp: December 24, 2016, 06:11:10 am
content: Their PLLs can be a pain to program. If you go by the datasheet and come up with values to program into the registers, things just don't work. The right way, apparently, is to use the eval board software, which generates a table of values that you write to the registers. Comparing these to the ones I had calculated from the data sheet reveals that bits marked "not used" in the data sheet had been flipped, and that was the only difference. Had this happen with an HMC834.

author: randsl
author_rank: Contributor
timestamp: January 17, 2017, 01:24:08 am
content: Usually Hittite chips works well without much effort "just out of the box".So far I've used about a dozen of those.I've had only one oscillation problem with one of the Ka band LNA due to lack of decoupling caps. I used the values used in the eval. board, but didn't work. Had to add few more to stop the oscillation. May be there was a contribution from the layout as well.However, for a novice designer, it may give the feeling of lack of documentation. But I think the real situation is the datasheet has all the information.