Things to consider for step up DC-DC converter - Page 1
Forum section: electronics / beginners

author: nitish111
author_rank: Contributor
timestamp: July 21, 2017, 08:39:19 pm
content: I have a system working at 5 V. In the circuit I am using DCA-20PC-3-DC4-RL-C to display current through a load.http://www.murata-ps.com/data/meters/dca20pc.pdfAfter ordering it I realized that its recommended supply voltage is 8V-36 when I wanted to order the one with 5V. Even though its recommended voltage is 8V and above it seems to run fine with 5V. Then I ordered a DC to DC converter chip so that I can boost voltage to ~9V such that I can power the ammeter within the spec. I ordered AP3012 because it seemed to work and easy to configure. I even ordered recommended component mentioned in typical applications. Then I soldered the converter onto a perf board and tested it. The output voltage was around 9V. Then I connected the ammeter to power it. The ammeter turned on but when I checked the output of the converter it dropped down to ~6.4 V. I also had a similar problem with LT3580 when I wanted to boost voltage from Li-ion battery to ~7V to power one of the circuit which consumed around ~100mA.I am not sure what am I doing wrong and why there is a drop in the voltage when load is connect since I bought recommended components. Is there something I am not considering while soldering? My question is what are the things we should consider while working with these type of circuits?

author: Zero999
author_rank: Super Contributor
timestamp: July 22, 2017, 03:42:58 pm
content: Are you sure the DC:DC converter can output enough current? The data sheet says the current could be as high as 150mA.

author: nitish111
author_rank: Contributor
timestamp: July 24, 2017, 03:04:43 pm
content: It should be able to. Ammeter consumes around 30 mA. I believe it should be able to output 30 mA at 9 V. I just wanted to know if there are any thumb rule like certain component need to be near some pin or traces have to be this much thick and so forth.

author: suicidaleggroll
author_rank: Super Contributor
timestamp: July 24, 2017, 03:17:16 pm
content: That's a 1.5 MHz converter, layout is critical. Unfortunately the datasheet doesn't show a recommended layout, so you'll have to do your best. Keep loop areas small, decoupling caps close, etc. What does the circuit look like now?

author: nitish111
author_rank: Contributor
timestamp: July 24, 2017, 03:29:05 pm
content: I am just testing the component. I have a test circuit on a breadboard. I will keep that in mind while layouting DC to DC converter.

author: suicidaleggroll
author_rank: Super Contributor
timestamp: July 24, 2017, 04:30:58 pm
content: A breadboard? Meaning you have the controller on some SOT to DIP style adapter, and your caps, diode, inductor, and feedback resistors are located inches away and connected through the solderless breadboard rows? That won't work, you can't breadboard a 1.5 MHz DC/DC converter, you need a proper PCB with a proper layout, surface mount components located millimeters from the IC leads, etc.

author: nitish111
author_rank: Contributor
timestamp: July 25, 2017, 03:00:35 pm
content: Got it thanks. For these type of circuits to perform as mentioned by the manufacturers layout is one of the crucial elements.Are there any reference material or application notes on these types of stuff.

author: suicidaleggroll
author_rank: Super Contributor
timestamp: July 25, 2017, 08:15:10 pm
content: Sure, here are a couple:http://cds.linear.com/docs/en/application-note/an136f.pdfhttp://www.ti.com/lit/an/snva638a/snva638a.pdfhttp://www.ti.com/lit/an/slva773/slva773.pdf

author: nitish111
author_rank: Contributor
timestamp: August 23, 2017, 11:34:37 pm
content: Hello Everyone, I want to thank you everyone in this community. Finally I was able to get desired result from DC to DC converter:phew:. Now I know importance of traces, its size, placement of the components for these kind of circuits. Circuit works great. I tested the board and @ 7V, it can generate 106V and it can handle 40 mA which exceeds my requirement. I haven't tested the board to its limits. I just wanted to share my success story. Hope to ask you more questions and learn more in future.