JSR01/02 Current & Resistor Wattage

[promixe]

heaveno Per-Anders,

Thanks for sharing a lot of great info on these regulator designs. I have a few basic questions:

My application would be having around 250-300mA continuous current at +24V. In the tech specs of JSR03 you indicate that it's capable of only 100mA continuous and 150mA peak. I also looked at your SSR01 design, which is capable of 1A and see in its BOM that you're using 0.6W resistors.

The question is, would I be OK with using SMD 1/4W resistors, 1.75W D44H11, 0.5A LM317M for my rated current/voltage? I'd feed an external 30VDC with an AC adapter, and then pre-regulate with LM317M, etc...

Thanks!

[peranders]

I write 1 A. You have read data belonging to the JSR02.

You can use any resistor type as you'll like as long as you not are exceeding the power limits.

[promixe]

I'm sorry, I meant JSR01/02 - basically all of the surface mount versions of your regulators. They are rated for 100mA continuous. Would they support 0.3A @24V continuous if I used 1/4W resistors and the SMD regs/transistors from my first post above?

Thanks!

[peranders]

It's only about the JSR01 since I'm out of stock of the JSR02. 300 mA is too much I'm afraid but the JSR03 or SSR01 will handle this.

[promixe]

Thanks for your replies.

Forgive my curiosity, but what exactly prevents the SMD versions handle that much current?
Where is the biggest bottleneck?
Is there a way to modify either the part selection and/or the boards to allow for my current draw requirement?

I have tight physical space requirements, hense SMD parts are a must, through hole is too bulky. How would you go about suiting the SMD versions to handling this much current? (at least theoretically, I'm not asking to modify your existing designs).

Thanks!!

[peranders]

The bottleneck is the pass element = heat

The pcb itself can handle 300 mA.

The JSR03/SSR01 isn't that big. How much space do you have?