engineeringtopics

November 1, 2011

Teardown: Castle Creations Phoenix ICELITE50

Filed under: Uncategorized — engineeringtopics @ 2:49 am

This brushless motor controller is rated for 6S (25V), 50A and includes a 5A switching BEC. This particular unit is being torn down because it smoked badly on a RIMFIRE 65cc motor. The RIMFIRE is a big motor. I was running it at 30V and about 30A on the bench, which the controller didn’t seem to mind. But one startup too many caused the controller to practically catch fire on startup.

There are two boards, each placed on both sides and then stacked via the connector. A heat spreader is atop the BEC, and also atop the lower MOSFET board.

The BEC is shown below. You can see the LT part on the right side. This is a LTC3824, high voltage step down controller. The SOIC8 below that is likely the P-channel MOSFET. The 5r6 is the inductor. Bottom left is probably an xtal.

 

On the flipside of this board, you find a SILABS part that is the 8051 25 MHz microcontroller. The 3 parts on the left are Intersil 6700 80V/1.25A half bridge drivers. Note the output to the MOSFETs are pins 5 (low side) and pin 7 (high side). The low side gates are driven with 27 ohm series R, while the high side gates are driven with 10 ohm series R

 

On the second board, we have 6 mosfets per side, for 12 total

These are Infineon OptiMOS MOSFETS (BSC019N04NS). They are rated for 40V and 100A, with 1.9 mOhm Rds(on). Notice on the bottom and top there are bus bars. These are tied to the battery. The lower left shows a 50 mOhm or so sense resistor in series with battery minus. Assuming 50A, this would give a 2.5V output for an ADC to read.

With 2 transistors paralleled, this would give about 1 mOhm Rds(on), and at 50A this would be about 2.5W per pair.

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