How to generate white noise signal from a given PSD?

Hello,

I want to generate a white noise signal x(t) with a known value for the flat power spectral density (PSD) function. In other words, I want to specify a constant value S0 such that the PSD of x(t) is Sx(w) = S0.

The awgn function from Matlab generates a white noise vector given a signal-to-noise ratio (SNR) value as input parameter.

What value of SNR I need to specify in order to have the PSD of x(t) equal to the desired value S0?

Any help is welcome!

Americo