Dear Ashok Gaur,
I welcome you to CiteHR. With reference to your query, one must use the right term as a professional (as distinct from a 'layman'); and since there is no such terminology in vogue, kindly refrain from using the term "suspension allowance".
What you probably mean is "Subsistence Allowance", which is granted to an employee during his suspension so that he can take care of the sustenance of himself and his family. In the absence of any income during the suspension period, the survival of the employee and his family shall be at stake. Thus, this is a welfare provision.
Generally, in Govt. and PSUs which have standardized and legally compliant HR rules, the Suspension allowance is 50% of the "salary", which is later enhanced to 75% after three months of suspension, in accordance with Sec. 10-A - "Payment of Subsistence Allowance" of the Industrial Employment (Standing Order) Act 1946. An organization can allow better terms than the one prescribed.
Warm regards.