How to avoid validating control inside UpdatePanel when the whole page is being PostBack

 Hi,
 I have a page with multiple UpdatePanels, some controls inside of those UpdatePanels have RequiredFieldValidator associated with them. Some times I have to PostBack the page with the button, that is outside of these UpdatePanels. But when I do the page PostBack all the controls that require validation within these UpdatePanels get triggered. How can I allow some of the validations to happen and others to be susspended on page's PostBack.
 Please advise.

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