This is a tranche of company's Rs 6,000 crore fund- raising which it had announced in November.
"The company has today allotted its 21st tranche of secured, redeemable, non-convertible debentures aggregating to Rs 225 crore," a company filing on BSE said.
The coupon rate on the bonds is 8.37 per cent per annum.
The company's stock closed 0.76 per cent higher at Rs 1,014.25 apiece on BSE.