The LTC3625 and LTC3625-1 are supercapacitor chargers like the lower current 150mA LTC3225 and LTC3225-1, and the higher current 2A linear LTC4425. However, aside from the ability to charge two series supercaps with automatic cell balancing and low Iq there is not much resemblance between the ICs. The LTC3225 is a charge-pump based IC that may buck or boost charge. It works best for low-current charging from 3.3V, three “AA” or Lithium-Ion battery sources. The LTC4425 is a constant current-constant voltage linear charger with ideal diode onboard. It works best when high peak power or low average power is required from 5V USB, Li-Ion or a current-limited 2.7V - 5.5V supply. The LTC3625 is best if higher current charging is needed for faster charge times or if a high efficiency, high peak power boosted supply is needed from a current limited source like a battery. Other differences include the following  for the LTC3625 as compared to LTC4425: the LTC3625 may both buck and boost charge, LTC4425 is buck only; the LTC4425 max charge current is 2A continuous compared to 1A for the LTC3625; there are different per-cell voltage and top-off voltages for the supercaps; the LTC3625 will balance while charging; no LDO mode as with LTC4425; no charge current monitoring via the PROG pin; no thermal limit on the LTC3625; requires three external components in the minimum operating configuration, C_IN, RPROG, and the inductor while the LTC4425 requires two, C_IN and RPROG; and the LTC3625 is in a larger DFN package due to different topology. The primary differences between the LTC3625 compared to the charge-pump based LTC3225 are: higher charge current; higher efficiency due to the switchmode architecture, each converter operates at ~90% efficiency; V_IN power failure indicator; and the LTC3625 again is in a larger footprint and package.