Forums

spi RF attenuator

Started by John Larkin February 7, 2015
Who makes decent SPI programmable attenuators? I need DC to, say, 300
MHz or better.


-- 

John Larkin         Highland Technology, Inc
picosecond timing   laser drivers and controllers

jlarkin att highlandtechnology dott com
http://www.highlandtechnology.com

On Sat, 07 Feb 2015 09:22:37 -0800, John Larkin
<jlarkin@highlandtechnology.com> wrote:

>Who makes decent SPI programmable attenuators? I need DC to, say, 300 >MHz or better.
Well, I did find this... http://www.triquint.com/products/d/DOC-A-00000718 It's sure easy to program. -- John Larkin Highland Technology, Inc picosecond timing laser drivers and controllers jlarkin att highlandtechnology dott com http://www.highlandtechnology.com
Den l&#2013266168;rdag den 7. februar 2015 kl. 18.22.38 UTC+1 skrev John Larkin:
> Who makes decent SPI programmable attenuators? I need DC to, say, 300 > MHz or better. >
hittite ? http://hittite.com/products/index.html/category/247 -Lasse
On Sat, 07 Feb 2015 09:22:37 -0800, John Larkin wrote:

> Who makes decent SPI programmable attenuators? I need DC to, say, 300 > MHz or better.
Aeroflex and also general microwave (herley) http://ams.aeroflex.com/weinschel/PDFILES/wmod3200.pdf
On Sat, 07 Feb 2015 09:22:37 -0800, John Larkin
<jlarkin@highlandtechnology.com> wrote:

>Who makes decent SPI programmable attenuators? I need DC to, say, 300 >MHz or better.
Those RF guys are always annoying. This is rated DC to 4 GHz, but "DC blocking capacitors are required." http://www.triquint.com/products/p/TQP4M9072 The RF ports say that DC voltage is present, but they don't say how much. I once used a Hittite part, an absorbtive 8PST switch, that was rated DC to 4 GHz. Turned out they internally define "DC" as starting at 100 MHz. -- John Larkin Highland Technology, Inc picosecond timing laser drivers and controllers jlarkin att highlandtechnology dott com http://www.highlandtechnology.com
On Sat, 07 Feb 2015 09:28:32 -0800, John Larkin wrote:

> On Sat, 07 Feb 2015 09:22:37 -0800, John Larkin > <jlarkin@highlandtechnology.com> wrote: > >>Who makes decent SPI programmable attenuators? I need DC to, say, 300 >>MHz or better. > > Well, I did find this... > > http://www.triquint.com/products/d/DOC-A-00000718 > > It's sure easy to program.
Hell, you never said an IC chip. I was giving links to modules.
On Sat, 07 Feb 2015 09:28:32 -0800, John Larkin wrote:

> On Sat, 07 Feb 2015 09:22:37 -0800, John Larkin > <jlarkin@highlandtechnology.com> wrote: > >>Who makes decent SPI programmable attenuators? I need DC to, say, 300 >>MHz or better. > > Well, I did find this... > > http://www.triquint.com/products/d/DOC-A-00000718 > > It's sure easy to program.
http://vaunix.com/products/digital-attenuators/overview/
On Saturday, February 7, 2015 at 9:22:38 AM UTC-8, John Larkin wrote:
> Who makes decent SPI programmable attenuators? I need DC to, say, 300 > MHz or better.
My jellybean SPI attenuator of choice is the Mini-Circuits DAT-15R5-SP+. As usual, it's specified to work down to DC as long as your definition of DC is 0V. :( Also as usual, the data sheet tells you nothing about how it actually works. It'd be nice if someone built a digital pot like the AD5260 with response into the VHF range. I'm not sure why those have such a low 3 dB bandwidth. -- john, KE5FX
On 2/7/2015 12:28 PM, John Larkin wrote:
> On Sat, 07 Feb 2015 09:22:37 -0800, John Larkin > <jlarkin@highlandtechnology.com> wrote: > >> Who makes decent SPI programmable attenuators? I need DC to, say, 300 >> MHz or better. > > Well, I did find this... > > http://www.triquint.com/products/d/DOC-A-00000718 > > It's sure easy to program. > >
;) These RF bods can't be expected to use zero-ohm resistors like the rest of us. I've recently started putting zero-ohm resistors between linear regulators and their output reservoir caps. One recent test board had all the inverse-parallel diodes in backwards, leading to putting +15.5 V on the MCU's VDD pin. Too bad, so sad. The other good thing about that is that if the regulator has any stability issues (e.g. an LM1117 with a big polymer aluminum output cap) I can just put N milliohms in series and fix it. In hand-wired protos, I always wire and test the supplies first, then finish up. Cheers Phil Hobbs -- Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC Optics, Electro-optics, Photonics, Analog Electronics 160 North State Road #203 Briarcliff Manor NY 10510 hobbs at electrooptical dot net http://electrooptical.net
On Sat, 07 Feb 2015 14:34:35 -0500, Phil Hobbs
<hobbs@electrooptical.net> wrote:

>On 2/7/2015 12:28 PM, John Larkin wrote: >> On Sat, 07 Feb 2015 09:22:37 -0800, John Larkin >> <jlarkin@highlandtechnology.com> wrote: >> >>> Who makes decent SPI programmable attenuators? I need DC to, say, 300 >>> MHz or better. >> >> Well, I did find this... >> >> http://www.triquint.com/products/d/DOC-A-00000718 >> >> It's sure easy to program. >> >> >;) > >These RF bods can't be expected to use zero-ohm resistors like the rest >of us.
Nor can they be bothered to reveal the DC behavior of their parts.
> >I've recently started putting zero-ohm resistors between linear >regulators and their output reservoir caps. One recent test board had >all the inverse-parallel diodes in backwards, leading to putting +15.5 V >on the MCU's VDD pin. Too bad, so sad.
I never put reverse diodes across voltage regulators, and haven't suffered. I go try to remember to put 0R or milliohm resistors in series with regulators, so we can measure the currents. Sometimes it's good to know that stuff, like FPGA core power, for future reference.
> >The other good thing about that is that if the regulator has any >stability issues (e.g. an LM1117 with a big polymer aluminum output cap) >I can just put N milliohms in series and fix it.
I generally use tantalums on an 1117 output, voltage derated 2:1 or so. That seems to be very stable. We avoid wet aluminum lytics, because the ESR skyrockets below 0C.
> >In hand-wired protos, I always wire and test the supplies first, then >finish up.
Yeah, my protos sometimes include regulators, so that I don't need six bench supplies. -- John Larkin Highland Technology, Inc picosecond timing laser drivers and controllers jlarkin att highlandtechnology dott com http://www.highlandtechnology.com