isolated switching regulator - Page 1
Forum section: electronics / beginners

author: LaserTazerPhaser
author_rank: Regular Contributor
timestamp: June 04, 2019, 10:44:02 pm
content: What are a few decent commonly available switching transformer isolated 5v voltage regulators which can step down high side power rails to 5v for powering a small isolated signal circuit?Preferably not from Linear Tech since they tend to be very costly and commonly very specialized.

author: ignislion
author_rank: Contributor
timestamp: June 05, 2019, 07:20:50 am
content: tl494 mc34063

author: Dave
author_rank: Super Contributor
timestamp: June 05, 2019, 08:29:57 am
content: Are we talking about a mains powered circuit? Please specify input voltage range and output power.For mains powered flyback converters, take a look at the TinySwitch series from Power Integrations. They tend to befairly cheap.I think the biggest cost is going to be sourcing a switching transformer to go with it. Those are usually custom wound for the job, so finding the right ones in low quantity is going to be a bit tricky.

author: LaserTazerPhaser
author_rank: Regular Contributor
timestamp: June 07, 2019, 11:48:38 am
content: Does it matter if 10uF cap is an electrolytic or MLCC? Ceramic caps have very low esr which can cause ringing.https://www.analog.com/media/en/technical-documentation/data-sheets/LT8302.pdf

author: ogden
author_rank: Super Contributor
timestamp: June 07, 2019, 12:04:39 pm
content: Question: "Preferably not from Linear Tech since they tend to be very costly"Answer:https://www.analog.com/media/en/technical-documentation/data-sheets/LT8302.pdfNot from Linear Tech but Analog Devices, right?Unless you are planning *huge* volume, take DC-DC module likeCRE1S0505SC, 2.7$/qty1:

author: LaserTazerPhaser
author_rank: Regular Contributor
timestamp: June 07, 2019, 12:34:25 pm
content: Quote from: ogden on June 07, 2019, 12:04:39 pmI looked into DC converters prior to this post glad you posted this series. I already had the LT IC and transformer in cart and circuit layed out, it wasen't routed. Going with a CRE1S1205SC it would be nice if they took a larger input range but its going to run from a 12v adapter.

author: ogden
author_rank: Super Contributor
timestamp: June 07, 2019, 01:02:49 pm
content: B careful, check specs regarding input voltage. Most of those requires regulated input. This one i did mention is 5v in 5v out.

author: Jeroen3
author_rank: Super Contributor
timestamp: June 07, 2019, 01:51:25 pm
content: You didn't provide much details:Side A voltage? Side B voltage?A-B voltage?A-B dV/dt?Power?Anyway, I recently used some Murata NXF1 units, and they are nice. Cheap and small. Quickly integrated.https://nl.mouser.com/datasheet/2/281/kdc_nxf1-1315413.pdfBut I think they either can't handle poor reflow/esd production, or don't handle high dV/dT very well. Since I had two prototypes fail on me. (no production units)

author: mariush
author_rank: Super Contributor
timestamp: June 07, 2019, 01:53:00 pm
content: How much current?If you already have 5v and you only need 10-30mA you could use something like ADUM5010 (digital isolator)..https://www.digikey.com/product-detail/en/analog-devices-inc/ADUM5010ARSZ-RL7/ADUM5010ARSZ-RL7CT-ND/3821204It's not cheap at 3$ in 100pcs but it takes minimal space and you don't need custom switching transformers etc.. maybe just some ceramic caps and inductor at output for extra filteringThere's ADUM5000 that can do 100mA but it's 6-8$... at that pount it becomes cheaper to get a module with transformer.

author: LaserTazerPhaser
author_rank: Regular Contributor
timestamp: June 08, 2019, 08:13:05 pm
content: Does the CRE1S1205SC need any other filter capacitors on its output or is the 4.7uH & 4.7uF filter adaquate for ~75mA?

author: ogden
author_rank: Super Contributor
timestamp: June 08, 2019, 08:44:06 pm
content: Quote from: LaserTazerPhaser on June 08, 2019, 08:13:05 pmHard to tell unless you provide more info, like max ripple allowed. At least tell what is "adequate" for you, or tell more about circuit you plan to power from that thing. Those modules have 30mV pp ripple w/o any filter, load regulation is 10%. Kinda awful specs if we compare to ANY switching regulator. Some may find it adequate out of the box, others would not use such for w/o postregulator.