Designing an Inductorwith ADS

[AMSA84]

Metal track slots; Designing an Inductor with ADS

Hi guys,

I am designing a converter where I need to design an inductor if the inductors that comes with the technology doesn't fill my needs. The technology is 0.13um. But first I've some questions:

1st - Normally, the inductors that comes with the technology are suitable for RF systems. Those coils can be used in a converter where the output current can get up to 100mA? In other words, how much current those coils can handle?

2nd - I read in some papers regading converters that the people who designed the converter have designed their own inductors. However, the inductor size is very big (it has of course) but when I say it is very big I am refering to width of the metal track - normally the width of the track is around 100um. In my technology the max allowed metal width is 10um. Question: How can they design the inductor violating the max width that the technology allows?

3rd - I have been told that if we exceed the metal with from the foundry, there, they insert some slots into the metal tracks (maybe because of the metal density or so, don't know what in concret). This is true? What are the implications if there is inserted some slots into the metal track, in this, of the inductor?

Kind regards.

 

[johnjoe]

1. consider the maximum current density of your metal in the specs.

2. place 10 x 10u metal traces in parallel

3. you can also insert slots on yourself. But if they are nice, they'll ask if it's ok that they will do. Also they just check design rules and give it back to you in case of violations. And yes, it's because of metal density.

 

[AMSA84]

Hi johnjoe and thanks for the reply.

Can you elaborate a little bit more the point number 2? I think that you understood wrong (from what I can tell from your answer).

What I meant when I said "How can they design the inductor violating the max width that the technology allows?" What I said violating, here what I meant was in the sense of creating a track with a width more than the technology allows being necessary in the factory to do some slots.

It was in this way that you understood what I asked?

Maybe you got it right and I thought that you don't.

If you understood and you are correct, then if I place a 10 x 10um metal traces in parallel, they must be placed together, placed together each other, tight. If so, it isn't the same as placing a single track with a width of 100um?

 

[johnjoe]

Ah ok, now I understand. It depends on your foundry. Some use special "inductor" layers which allow e.g. metal density violations (it's just a drc-layer, which tells drc not to check for example density errors). In general, it's explained in the tech. specs. Or you can ask directly your foundry.

10x10um: it's similar but larger, because between each trace you have to use some spacing (e.g. minimum spacing between traces). Also it depends on application, rf or converter etc.