Track and Hold Time versus Source Output Impedance

The figure below shows a simplified acquisition path.

During the tracking phase, the AFE tracks the input signal during the tracking time shown below:

t_TRACK = n × C_IN × (R_ON+Z_SOURCE)/1000

• Tracking time expressed in ns and Z_SOURCE expressed in Ω.
• n depends on the expected accuracy
• R_ON= 2 kOhm

  Table 1. Number of Tau:n

  Resolution (bits)	12	13	14	15	16
  RES	0	2	3	4	5
  n	8	9	10	11	12

The AFEC already includes a tracking time of 15 t_{AFE Clock.}