Hi,
Further to superlative’s post, I would like to power the A-Star micro with a 5.0v regulated supply on the VCC line, but also be able to sometimes connect the USB cable to receive commands from the PC, or to reprogram it. The USB is not always connected, so the device must also be able to be powered from the 5.0 supply.
The A-Star is controlling a set of 16 addressable LEDs, so I need 800ma (max) to power the LEDs.These LEDs don’t like more than 5.0v, so my idea is that I power the board + the LEDs from a 5.0v 1A regulated supply. However, from the schematic, it looks like if VIN is not connected, then the USB power (VBUSF) will also be connected to VCC.
(Note: The docs state “The board features a power selection circuit that allows both USB and VIN to be connected at the same time; if this is done, the A-Star will draw power from USB.” and also “It will draw power from VIN only if USB is disconnected.”; but looking at the schematic, I think the P-Channel MOSFET will switch OFF when VIN > VBUSF, and so the board will be powered from the onboard regulator if VIN and VBUS are both connected. Am I correct?)
Is it safe to do this, or is there some way or other components I can use to ensure the board is never powered from the USB port?
(I don’t really want to use a >5v supply plus a hefty 1A regulator for the LEDs.)