LMC567: how to set input signal frequency for LMC567

Hi,

My customer is using LMC567 with 3.3V power supply, and set Center frequency=54.36KHz through pin5 Rt and pin6 Ct,

then apply an AC signal from pin3, when the AC signal frequency is between 27KHz and 27.4KHz, the output pin8 is active (have AC signal output),

but when the AC input signal frequency is out of 27KHz~27.4KHz, there is no output on pin8.

Questions:

How much frequency range for AC input signal can be accepted vs Center frequency?

What's the mean of L.D.B.W - largest detection bandwidth?

Best Regards

Sean Zhang