In an embodiment, a method includes: receiving a first plurality of digital codes from a TDC; generating a coarse histogram from the first plurality of digital codes; detecting a peak coarse bin from the plurality of coarse bins; after receiving the first plurality of digital codes, receiving a second plurality of digital codes from the TDC; and generating a fine histogram from the second plurality of digital codes based on the detected peak coarse bin, where a fine histogram depth range is narrower than a coarse histogram depth range, where a lower fine histogram depth is lower or equal to a lower coarse peak depth, and where a higher fine histogram depth is higher or equal to a higher coarse peak depth.