2
AVR430
8124C-AVR-10/08
2 Hardware overview Please refer to schematics, layout and BOM available at http://www.atmel.com.
The MC300 motor con trol driver board is a power stage board intended for driving
BLDC and stepper motors. It has four half-bridges with independent control of high
and low sides. Each bridge has options for filtered/voltage divided feedback from its
output (EMF) and shunt resistor. There is also feedback from a common shunt
resistor, Vmotor (Vm) and Vneutral (Vn - center tap motor windings).
Four 8-pin 2,54mm (100mil) horizontal female pin header s on the left side of the
board form a system connector for device boards.
The board has an adjustable volta ge regulator for Vcc, 3.3V or 5V, and this voltage is
available on the system connector. A 5V regulator powers the Hall sensors. Vm, Vin
and Vcc each have their own LED to indicate power.
2.1 Specifications
MC300 maximum ratings with components as delivered:
Input:
• Vin: 10 – 20VDC
• Vm: 0 – 40VDC, Im
max
= 6A
Output ratings:
• Vcc = 3.3/5V, I
max
= 0.5A
• Vha = 5V, I
max
= 0.1A
The driver stage consists of four half-bridges capable of 40V / 30A (Warning! Other
components such as shunt resistors limit the maximum current to 6A).
2.1.1 Necessary precautions
The gate volta ge to the high side MOS is powered by a bootstrap capacitor. To
sustain the voltage over this capacitor the high side must be turned off for a short
time on a regular basis, allowing the capacitor to be recharged via a diode. Failing
to do so, for example. by keeping the high side perm anently on, will cause the gate
voltage on the high side MOS to drop and t he internal resistance to increase. If a high
current is going thru the high side MOS at this point the transistor will overhea t and be
destroyed. The fuse will not prevent this from happening.