Power Supply

[Makaram]

Hey,
Currently using tl2575 buck to convert 12v to 3.3v for an automotive application.
Price is starting to become a critical issue and these sell for approx $3 a pop. Is there a better / cheaper alternative?
Would a linear regulator suit or would the efficiency be horrible at that voltage gap?
Any help would be most appreciated

Regards

Matt

 

[chemelec]

How Much Current?

 

[schmitt trigger]

When cost is an issue, stay away from propietary ICs. They may be high performance, but since they have got you as a captive customer, companies will charge you an arm and a leg.

Go the generic switcher route. The MC33063 is sourced by many vendors and thus very cheap. But as chemelec mentions, we need to know your current load.

 

[Makaram]

Current requirement probably 50mA - 100mA

 

[chemelec]

Current requirement probably 50mA - 100mA

Well since it Doesn't require a Low Drop Out Regulator, I would just use an LM317 (1.5 amp Max) or an LM317LZ (100 mA Max)

 

[Makaram]

So a linear voltage regulator at that current wouldnt be a problem with a 9V drop? With minimal heat sinking?

 

[MikeMl]

So a linear voltage regulator at that current wouldnt be a problem with a 9V drop? With minimal heat sinking?

(14.2-3.3)V *0.05A = 0.55W. A LM317T (TO220 with a tab) is going to get noticably hot if there is no heat sink, although likely not too hot. Can you bolt the tab to the car? Then you have an infinite heat sink

 

[ChrisP58]

I'll throw in my vote with Mr. schmitt for the MC33063. Widely available. About USD$ 0.30 even in small quantities.

 

[Makaram]

If a TO220 gets hot.. what is https://www.digikey.com/product-detail/en/LM317LCDR/296-17220-1-ND/668530 up to?

Surely that would be nearing temperatures comparable to the sun?

 

[schmitt trigger]

Since the OP is already comfortable working with switchmode power supplies, and he was only looking at reducing its cost, the MC33063 is a nice alternative to the pricey tl2575