If a system has the following step response:
$y(t) = 1 - [A e^{(−t/T1)} + (1-A) e^{(−t/T2)}]$$$\begin{align} y(t) &= 1 - \Big(A e^{−t/T_1} + (1-A) e^{−t/T_2}\Big) \\ &= 1 - A e^{−t/T_1} - (1-A) e^{−t/T_2} \\ \end{align}$$
and I know the values of A$A$, T1$T_1$ and T2$T_2$, can I transform this to a discrete-time IIR filter analytically? If there is no analytical solution, is it possible to say how many poles/zeros the IIR filter should have?
I've done it numerically by using the Prony's method on the impulse response, but I'm hoping there is a more direct way.