I received a question regarding to the DCDC Operation Modes in the FRDM-KW40Z. I think this is a good topic to share in the community because it might be useful. KW40Z/KW30Z/KW20Z devices comes with an integrated DCDC module which is able to work in the next three modes: bypass, buck and boost.
In the FRDM-KW40Z, you are able to set a couple of jumpers to configure the DCDC in your desired mode(bypass, buck or boost). So, in the FRDM-KW40Z schematic, there is a table that can guide you about the jumper configuration to set each mode. This can also be found in the FRDMKW40ZUG.
The next image is the one shown in the FRDM-KW40Z schematic.
Moreover, in order to help user to look at the proper jumper configuration in the FRDM-KW40Z. Figure 11 to Figure 14 can be of reference in the FRDMKW40ZUG. Figure 11 is missing connection 5-6 of J22, however, it should be populated as indicated in the above table.
So, what is the difference between Buck auto mode and buck mode. Buck auto mode initializes the DCDC module as soon as power is supplied to the board, in the other hand, buck mode requires PSWITCH to be pressed in order to run the DCDC module.
Although this configuration is enough to start DCDC module. It is also recommended to configure DCDC by software in order to have optimum performance. DCDC software driver is part of the KW40Z Connectivity Software package, Heart Rate Sensor demo can be of reference for the configuration of the DCDC in buck mode.