Planned order creating in past

Hi gurus,

Planned order is creating in past because of sales order, i.e. system is creating planned order taking information from sales order. Planned order is creating in past date as a result planned order can not be converted to production order because routing validity start date is in later date than the planned order dates. In this situation, what configuration parameters need to change so that no planned order can be created in past, i.e. even if requirement date of sales order is in past but planned order start date can not go before today's date.

Thanks in advance for answering.