Screaming Circuits: Most parts in place


Most parts in place

Mark Rules has made a bit of progress on his tiny motor controller. Someone suggested that he look at a rigid-flex board so that the driver could be wrapped around one of the motors. The idea would be to have the RS232 and MCU on one rigid board, the regulator and motor driver on a second rigid board and the connectors on a third rigid, all connected by flex. He looked at it for a while and then decided: "later."

Mr_early_layout For now, he has the placement of the four chips and all of the passives. The smallest parts  were going to be 0402, but it was getting a little tight under the board and he wanted to keep the MCU bypass cap close to the power and ground. The C-delay picked for the regulator was available in an 0201 size too, so both of those were moved to 0201 packages. Without the connectors, the whole layout measures about 1/2" x 1/2".

Right now, all the passives are under the board. As much as possible, though, none are directlyDfn8_w_stop_and_paste_w_viastr_1   under the chips. Keeping them out from directly under does take up a little more space, but it allows for easier routing of the RS232 BGA and leaves room for vias in the QFN pads for the regulator and motor driver. The big PIC won't need vias, but he may use that space for a connector.

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