ADuM4160 USB Isolator PCB panel
USB Isolator PCBs has arrived. In this article I will be talking about building and configuring one. The PCB was designed with hobbyist-friendly large size SMD packages and 10mil clearances and I hope it won’t be difficult to made one at home. The layout files are available from downloads section.
Let’s talk about parts procurement. This is a BOM at Mouser sans ADuM4160, LT1376-5, and PCB. This is BOM at Digi-Key, which includes LT1376-5. Last time I checked, Digi-Key was way more expensive. As far as ADuM4160, since no one sells it in single quantities right now (check this using FindChips), the easiest way to get it is to ask Analog Devices for a sample, they are generous folks.
Now, let’s discuss building the circuit. First of all, you need to understand one thing. This circuit is an isolator and consequently has two power rails and two grounds, marked GND and AGND. Don’t connect these two grounds together. Uplink side of ADuM4160 is powered from host USB bus, downlink power has to be provided form separate supply, usually wall wart. If you have 5V wall-wart capable of providing enough power to the USB device connected to the downlink port plus 10ma for isolator itself, you don’t need to build a regulator. Simply connect pad marked “Vin” to a pad marked “Vbus”. If your device is self-powered and have 3.3-5V supply, it can also be used to power downlink side of ADuM4160 by connecting it to “Vbus” pad.
If you decide to build a power supply it is very important to use wall wart which is center-positive(has “plus” contact in the center). If you reverse polarity, LT1376 will burn. Pads for pins 2 and 3 will be damaged as well so any subsequent repair will be difficult and will look ugly. Don’t ask me how I know. Also, if you have several wall warts, using one in 9-12V range would help the circuit to stay cool. Maximum input voltage is 25V, do not exceed it.
How to substitute parts. I used CDRH5D18 inductor from Sumida. Values from 6.2 to 12uH work well. You can use another inductor if it of “shielded” variety, fits into the pads and its current rating is 1A or more. Another important components are input and output capacitors. They have to be low-ESR tantalum, similar to AVX TPS, which I use. 24 ohm resistors on D+ and D- must be 1% accurate. D1 must be 30V 2A Shottky; the one I use (MBRS130) works very well and is cheap. Other parts are not critical.
The USB speed of the isolator has to be set manually using two jumpers, separate for uplink and downlink. They must be set to the same speed. Full speed will work for almost anything, excluding maybe USB keyboards and mice.
After the board is built, the easiest way to test is to connect an USB flash drive to the isolator and isolator to PC, make sure it gets detected, copy large archive to flash drive and try to unpack or run integrity check on this archive. If you end up with no errors, your USB isolator is ready to use.
If you have difficulties with this circuit, drop me a line and I will try to help.
Oleg.
I could not view your Digikey BOM. It states that I am not authorized, did you make it public?
It is public. However, I just checked and it turns out that you have to be a registered user at Digi-Key and be logged in to see it. I can download this BOM as .csv and e-mail it to you, if you’d like.
That would be great, I am a registered user there , maybe its just my issue… cant wait to get the boards I am using them for USB audio!
I sent you the BOM. Please keep me posted about your project progress – I am very curious about audio applications of this isolator!
For your DigiKey BOM the low ESR caps by Kemet are much cheaper than AVX comparables, here are the part numbers. 399-5300-1-ND for the 22uF 70mOhm ESR and 495-1582-1-ND which is 68uF 260mOhm ESR
Thanks! I’ll take a look at them.
Yeah I found out about this product from someone on DIYAUDIO.COM!
Hi Oleg:
From what I gather the Isolator (when no devices are attached) is not seen by the O/S (XP/7). There is no “Not Recognized “error, the Iso is not seen period…..which makes sense when you think about. I also read your FAQ using the jumper. Testing of unpacking files to a flash drive was successful. All devices so far are readily seen on both O/S’.
Perhaps I missed it,what is the purpose of the Vin and Vbus VIAs? Are they simply test points?
I appreciate that your target market may be more advanced than I.
That said, a couple of thoughts for consideration.
Under the “More details” link for the kit, add some tips as to identifying the parts. For those items “quantity one” and roughly the same size, it was a little challenging. I wish I had remembered that the Mouser/Digikey BOMS were listed. The Eagle files are very helpful as are the part markings on the board and the site’s large pictures. Perhaps re-shooting the top view of the fully populated board for better lighting?
Thanks for the support.
Terry
Hi Terry,
Thanks for your suggestions, I’ll add some more contents to make building easier.
Vin is routed to the barrel connector in case you want to solder a wire here. Vbus is power to the B-side( peripheral ), it can be used to power the isolator from the device’s 5V, if it’s available. It is also possible to connect Vin to Vbus, shut down or simply don’t populate the power supply and then power the isolator with 5V via barrel connector.
Let me know if you have more questions.
Oleg.
Hi Oleg, I see you are using 68uF and 22uF caps, where silkscreen text states 100uF and 10uF, so it is ok to use caps in the range of 10-22uF and 68-100 uF, right? And also, can you please say which size are they?
Thank you.
Caps are size D ( EIA7343 ). ESR is more important than capacity – the lower you can get the better. Also, if you don’t need that high of input voltage, you can use input cap with lower voltage rating which would give you more choices.
Do I need to use an adapter for the isolator?
Thanks
Yes, you need a power supply. Many different ones can be used – from wall warts to batteries. See also -> https://www.circuitsathome.com/adum4160-usb-isolator-assembly-guide