Mortgage lender HDFC Ltd on Monday said its board has approved raising funds through non-convertible debentures (NCDs) in tranches aggregating to Rs 57,000 crore. The board has cleared issuance of unsecured, redeemable, non-convertible debentures under a Shelf Placement Memorandum, aggregating Rs 57,000 crore, in various tranches, on a private placement basis, HDFC said in a regulatory filing.