FAA AIM 5-2-7 para b.1:
1. Unless specified otherwise, required obstacle clearance for all departures, including diverse, is based on the pilot crossing the departure end of the runway at least 35 feet above the departure end of runway elevation, climbing to 400 feet above the departure end of runway elevation before making the initial turn, and maintaining a minimum climb gradient of 200 feet per nautical mile (FPNM), unless required to level off by a crossing restriction, until the minimum IFR altitude. A greater climb gradient may be specified in the DP to clear obstacles or to achieve an ATC crossing restriction.
http://www.faraim.org/aim/aim-4-03-14-302.html
8260.43F Departure Procedure (DP) Program
DPs must not require a turn prior to reaching 400 feet above the departure end of runway (DER) elevation. See Order 8260.3 and Order 8260.58, United States Standard for Performance Based Navigation (PBN) Instrument Procedure Design, when a turn is required within two nautical miles (NM) of departure end runway (DER).
No turns are allowed in the ICA (Initial Climb Area) 400' above DER.