AD USB Isolators

[JoeyG]

I'd like a USB Isolated connector to my 240W AC Mains controller running an MCU  connected to my  Laptop USB.

I like the ADUM4165 /66  USB Isolators however  I'm confused about the  following and which part to choose

ADuM4165 Clock Input from Host Side
ADuM4166 Clock Input from Peripheral Side

========
► Redriving and high speed data retiming for input jitter removal
and an open eye
► Flexible clock input options

ADuM4165 Clock Input from Host Side
ADuM4166 Clock Input from Peripheral Side
===========

https://www.analog.com/en/parametricsearch/11032#/

https://www.analog.com/media/en/technical-documentation/data-sheets/adum4165-4166.pdf

Any clues or pointers appreciated

[Psi]

Without looking closely.
It seems that the chip needs a clock and you have to decide if you would prefer to provide that from the PC or from the device.
However the datasheets says "clock or crystal" So if you use a crystal it doesn't matter anyway.

Take note of the crystal requirements

The crystal choice and implementation are critical to proper functioning of the circuit. To meet ADuM4165/ADuM4166 specifications,
a frequency tolerance of ≤50 ppm with ≤100 ppm stability is
required. When using the isolator across the full extended temperature range, ensure that the system is built using a crystal meeting these requirements across the desired operating temperature
range.
To comply with USB 2.0 requirements for suspend and resume,
the crystal oscillator must start up within 0.3 ms as the isolator
powers on initially or exits low power mode. To achieve this requirement, follow the PCB guidelines shown in Figure 21, together
with a typical crystal capacitance of 10 pF and capacitive loads
<10 pF to achieve timing specifications over temperature

[Nominal Animal]

I'd like a USB Isolated connector to my 240W AC Mains controller running an MCU  connected to my  Laptop USB.

First, verify your MCU has a High Speed (480 Mbit/s) USB 2.0 interface, and not a Full Speed (12 Mbit/s) one.  For Full Speed, ADuM3160/4160 suffices, and in a self-powered configuration, requires only four bypass capacitors and four 24Ω±1% resistors (on each USB data line), although additional ESD protection would be useful, too.  I've happily used these (in the form of ~ $10 eBay ADuM3160 isolators, after checking which DC-DC converter they use) with my own USB 2.0 Full Speed microcontrollers.

The difference between ADuM3165 and ADuM3166 is clearly shown on the datasheet: whether the clock source or crystal is on the host side, or on the device side.  Currently, ADuM3165 are in stock at Digikey and Mouser, but ADuM3166 are not.  If you prefer the inductive ADuM iCoupler isolators over the capacitive TI ISOUSB211 one, then I personally would consider using a PCB layout that allows either ADuM3165 or ADuM3166 to be used, by simply duplicating the 24 MHz crystal and load capacitors on both sides, and only populating one depending on which chip is used.  (The unused clock/crystal pins are grounds.)  ADuM4165 and ADuM4166 are pin-compatible, but have a different (larger) footprint.

In addition to ADuM3165/3166/4165/4166, there is also the TI ISOUSB211 isolator chip, which implements capacitive (as opposed to inductive/iCoupler) isolation, does not need a clock or crystal (the 24 MHz needed for retiming is internal), although thermal management is easier if you use external LDOs for 3.3V and 1.8V.  Figure 10-2 in the datasheet corresponds to your use case.  They also happen to be currently in stock at JLCPCB for PCB assembly, if you wanted to do a quick test board.  (I'd like to do one myself, but I'm only a poor hobbyist on the electronics side, and simply happen to use isolators a lot.  See this thread for my experiences.)

[thm_w]

Since its for a MCU, just buy one of the cheap $5 units from aliexpress: https://www.aliexpress.com/item/1005001369085297.html
They work OK.

https://www.eevblog.com/forum/dodgy-technology/some-more-audiophoolery-the-lan-silencer/msg5514193/#msg5514193

[perieanuo]

hi, i used https://www.olimex.com/Products/USB-Modules/USB-ISO/ for simple usb connections.
for mcu, should work for sure. for stuff like qualcomm hsusb mapping multiple ports on one usb connector, it doesn't.
so in your case it's ok
br, ovidiu

[Nominal Animal]

Both of the above are USB Full-Speed (12 Mbit/s) isolators based on ADuM3160, not USB High-Speed (480 Mbit/s) isolators like ADuM3165/3166/4165/4166 and TI ISOUSB211 are.

[voltsandjolts]

I'd like a USB Isolated connector to my 240W AC Mains controller running an MCU  connected to my  Laptop USB.

I suspect the simpler Full Speed isolators would be fine for that application.

[Nominal Animal]

I suspect the simpler Full Speed isolators would be fine for that application.

Like I said in my first reply, that is the first thing to check.

Personally, I have several Teensy 4.0/4.1/MicroMod MCUs with High Speed USB interfaces, and USB HS support is becoming quite common with ARM Cortex-M7 and RISC-V MCUs.  It is very nice when transferring data via USB Serial –– Teensy 4.x can sustain 25+ Mbytes/s or 200+ Mbits/s from Teensy 4.x to a Linux host using a trivial Arduino sketch, using actual data (random enough to pass BigCrunch test suite) ––, but for something like an USB HID device, is unnecessary even if supported.  Thus, I would definitely check first.

[voltsandjolts]

First, verify your MCU has a High Speed (480 Mbit/s) USB 2.0 interface, and not a Full Speed (12 Mbit/s) one.  For Full Speed, ADuM3160/4160 suffices...

Even if it is High Speed, a Full Speed connection will likely suffice in this low-bandwidth application. The High Speed interface will be capable of Full Speed operation, assuming USB compliant implementation.

[Nominal Animal]

Even if it is High Speed, a Full Speed connection will likely suffice in this low-bandwidth application.

Perhaps.  We do not have enough information from JoeyG to be certain, so checking this first is still the best option.

An one-directional full speed USB connection can (continously) transfer about 950,000 to 1,000,000 bytes of data payload per second.  When using a request-response protocol, the practically usable data bandwidth is much less, because the USB 2.0 connection is half-duplex and there are inherent latencies in sending and receiving individual USB packets.

The High Speed interface will be capable of Full Speed operation, assuming USB compliant implementation.

Of course.  All my HS MCUs work just fine over a FS connection, for example when using such an ADuM3160-based USB FS isolator.

I often use my Teensies that way, when experimenting with ideas using quick and dirty breadboard circuits, just to make sure I don't risk (the USB port on) my host computer.  USB ports should survive even VCC-GND shorts, but with my sausage fingers and bumbling and lack of luck, it is a cheap and easy way to be sure.

I even started a thread wondering digital isolators are not more widely used (in hobby designs).  Some of the counterpoints there might be informative for those reading this thread too.