Power circuit for ESP8266  - Page 1
Forum section: electronics / projects

author: ErikNL
author_rank: Newbie
timestamp: October 29, 2018, 08:02:00 pm
content: Hi,This is my very first post here. I've been following the EEVblog for over a year, love the videos.For a while I've been tinkering with ESP8266 now, which is a lot of fun. I now came to a point where I could use some advice from people with actual knowledge about electronics(I'm a software developer with only basis knowledge of electronics design)What I want to do is create a circuit with which I can power the ESP8266 with either a doorbell transformer, supplying 8v, 12v or 24V AC, or usb power (5v dc) while also using a minimal amount of space on my board.While browsing mouser, I found the LMZM23600 series of DC/DC converters, of which the LMZM23600V3SILT seemed to fit the bill for me (https://nl.mouser.com/ProductDetail/595-LMZM23600V3SILT).Only downside was that I would have to convert DC into AC first, I thought I would be able to use a simple bridge rectifier for that, like to MB6S.To see if what I thought out would be usable, I created a small test board:Unfortunately, the circuit does not seem to do what I expected it to do. When I feed it with 8v AC, I only get 1,7v DC out of it. When I feed it directly with 5V DC, I only get 0,5v out of it.I was wondering if anyone here can spot what I'm doing wrong? And if I'm going the right way with my component selection or not?One thing to note is that the LMZM23600V3SILT is quite tricky to solder, I can't say I'm sure my soldering job is spot on, although I did solder 2 test boards and both give the same results.

author: floobydust
author_rank: Super Contributor
timestamp: October 29, 2018, 08:41:44 pm
content: I do not see it working well with only a 10uF filter capacitor and the 100Hz ripple coming out of the bridge rectifier. The LMZM23600 input voltage is then pulsing DC and you need some reservoir to hold up the voltage "in the valleys". I would add a big 470-1000uF 50V capacitor in parallel.But it should still work if providing 5VDC input unless the enable pin is not done properly.

author: TK
author_rank: Super Contributor
timestamp: October 29, 2018, 09:09:59 pm
content: If you have 5V from a USB port available it is simpler to use an LD1117 low drop regulator to get the 3.3V you need for the ESP module

author: ErikNL
author_rank: Newbie
timestamp: October 30, 2018, 07:45:31 pm
content: Thanks floobydust, that would indeed be a good idea, I've added a 470uF right after the MB6s (biggest one I had lying around) . The 10 an 33uF capacitors are there basically because they are in the recommended circuit in de datasheet:I also used that as a reference design for my test board:I connected mode to gnd, EN to vin and fb to vout, as in this design from the datasheet:With all that, I would think it should work, but I still only get around 1,7v DC out of it, when I connect 8V AC (through the MB6s) or 5V DC (yesterday I used a faulty 5V source, so that explains why I got 0,5v out of it)I'm now wondering if there's anything wrong with my circuit design or if it's just my soldering skills that are not good enough for these tiny parts.

author: floobydust
author_rank: Super Contributor
timestamp: October 30, 2018, 08:50:33 pm
content: I don't see keep-out zones defined by TI for this module.One caution with DC-DC modules is running traces/vias/copper pours underneath them, since the module itself is a PCB with vias, you can out short things on its underbelly.Notice the module PCB vias, are they shorting to any copper/solder/solder paste underneath?I haven't seen these modules but would look underneath them or maybe TI has better docs.But 1.7V is an oddball output voltage, so I might think the module took too much heat or is damaged.