Doug S
Flashlight Enthusiast
Per the datasheet, the Max1675 and 1674 stepup ICs should be able to deliver a minimum of 80 and 160 mA at 3.3V respectively, at an input as low as 1.0V. Has anyone who has laid out a board using these ICs ever gotten this low Vin performance? As implemented in the MadMax and MadMax lite the output plummets to a much lower value for inputs below around 1.15V. The effect of this can be seen on all of the single 1 alkaline cell runtimes that various folks have done. This can be seen as the sharp change in slope of the runtime curves in the following examples: MM lite and MM Plus. Looking at the layout of the MM boards, it appears to me that Wayne has followed generally accepted guidelines for proper layout of a switching regulator. I remember a long time ago that Wayne complained about how quirky this IC was to work with [I don't remember if this was in a post or a private communication]. Using a MM lite board I varied the values of Cin, Cout, the inductor, and also deleted the forward diode [which is optional, BTW] and was unable to obtain any improvement in the low Vin performance. Has anyone managed to match the datasheet low Vin performance??