AFE58JD28: full scale ADC DATA is not 2^16 bits

Part Number: AFE58JD28

Hi ,

I iam using  AFE58JD28 with TGC mode:

CLAMP LEVEL= 2.24Vpp

LPF_PROG = 20 MHz

LNA_HPF_PROG = 100KHZ

 with input signl of :650KHZ pulse (30 pulses), unfortunately the max ADC data that i get at full sacle is ~26k bins and not 32768    [(2^16)/2].

what can i do to have full sacle of the ADC?

Thanks ,

Nadav