Could check this by raising or lowering the amperage load and see if the 
problem stabilizes.

I think you should also be able to see the output of the switch go from 
discontinuous  (ringing on turn off) to continuous if this is happening.

Mark

Bob Blick wrote:
> On Thu, 8 Jul 2010 15:11:33 -0400, "microsoftwarecontrol" said:
>   
>> Using TI boost buck, in boost mode. it is unsteady, some time heating up 
>> and take almost double amount current. Output V is fine and out current
>> is 
>> always near 1 A. Just input I, sometime increasing for unknown reason 
>> to me.
>>
>> Any one knows what it is and how to fix it?
>>
>>     
>
> Are you using an approved type of inductor? Because what pops into mind
> is that your are transitioning to continuous mode and the quick
> inductance drop puts you in and out of a parasitic state of loop
> instability. You can either use a bigger inductor of the same type, or
> go to one that is more forgiving with continuous DC.
>
> Cheerful regards,
>
> Bob
>
>   
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