Guys Thanks for the additional insights and comments. This is part of a Buck converter layout that I am designing per manufacturer recommended layout. It’s for an LT8619. recommended layout is below.
mfr layouts are always good… if you can fit the parts…
but …
alot of the times, the parts (caps) only fit if they are sh1tbox Y5V or Z5U toy grade capacitors, not X7R / X6S etc and since you are genelally suggested to use a shielded or semi shielded inductor, they dont fit in their layout either… But just try and maitain the paths and shape.
LT regulators are often over priced. but they do work. avoid Maxim
try for this one, Diodes Inc :
1/3 the price. diodes stuff works well.
Hey Glen
Thanks for the pointer on the Diodes Buck. Far cheaper than the AD LT8619. Will check it out might use that instead.
yeah all my regs are Diodes now… I do hi rel stuff, am pretty happy with them. unlike maxim wher eyou need to buy a 2A regulator to get a robust 1A regulator,. also their quantity pricing is pretty good. like a $2 Diodes Reg on Mouser is like 40c on the reel…
My SMPS regulators are TI and linear TI and Diodes.
In 2014 I was looking around to select Buck regulator. And I selected LM5017…LM5019 (100V input serie) and LM25017…LM25019 (the same but low voltage - 48V input).
I design very conservatively and I assume that any soft-start circuit can be cheated in some unusual conditions so I always select inductor with saturation current higher then IC max current limit.
So making 600mA output regulator with AP66200 I would select 3.7A choke, while doing the same with LM25017 1.3A choke is for me enough.
What I like in LM5017 serie is COT mode. COT is free of compensation problems (if using ceramic output capacitors you need to ensure ripple at FB input). COT for a step load change responds in single cycle while current mode regulators need 5…10 cycles to notice load change. Having direct dependency of Ton on Vin makes frequency almost constant.
Good move on “saturation current higher then IC max current limit.”. Many of the inductors now are soft saturation thought. I use now all Wurth inductors.
All the Diodes Inc regs I use are COT. There is also a Vishay SiC468 I use that is COT. good for FPGA VCCINT
@glenenglish . Hey so I did eventually try out the AP66200 you recommended. I wanted to try it out first so I have started with the the layout recommended in AP66200FVBW-EVM with just a few mods. Did’nt turn out as well as I expected. Just tested it out yesterday. PCB fab using JLCPCB and hand solder/ borrowed work reflow oven for assembly. I am not sure if I fried the chip but I am getting only 3V output instead of the 5V per the EVM data sheet. I thought maybe I may have some cold solder joints in the feedback resistor network so I desoldered and resoldered them and got the same result. Did you ever encounter this problem. ? I was thinking if I fried the chip then I should not get any output at all. I checked the output on VCC pin and get 4.75V which is close to the 4.8 from Data sheet. Any pointers? I will attach schematic and PCB when I get the chance