When the maximum number of bits output from a PRNG is equal to the 2^blocksize, the resulting output delivers the mathematically expected security level that the key size would be expected to generate, but the output can be distinguished from a true random number generator. When the maximum number of bits output from this PRNG is less than 2^blocksize, the expected security level is delivered and the output appears to be indistinguishable from a true random number generator. In the next revision, limiting the total number of generate requests and the bits provided per generate request will show security strength.

Dual_EC_DRBG is part of the standard though it is not cryptographically secure due to a kleptographic NSA backdoor.

NIST SP 800-90A Rev.1 is essentially NIST SP 800-90A with the Dual_EC_DRBG removed.

CTR_DRBG, another PRNG, is based on a block cipher running in counter mode and whilst its design is uncontroversial, it has been proven to be weaker than others in distinguishing an attack.

The standards for statistical testing of new CSPRNG designs are maintained by NIST along with a good reference of standard CSPRNGs.