fastcomponents
Newbie level 5
driving p channel mosfet
Hi,
we're currently designing a servo controller for these motors that we've started getting made up **broken link removed**. The idea is to make a 'servo beater' for robotics applications, retailing at $15 - $20. Basic specs to include a variety of gearboxes (and nominal RPM outputs 40 ~ 250RPM), quadranture encoding, RSXXX, I2C, SPI, PWM, analogue, arbitrary (absolute & relative) positioning commands, arbitrary torque output commands, temperature overload control / feedback... etc.
To keep the costs down, and becuase we simply don't have board space for a driver, we wanted to drive the MOSFET H-bridge direct from our MCU. For the N-channel MOSFETS (currently Fairchild FDFS6N303), we're proposing to use a 10k pulldown, and a 100R series drive resistor.
I'm a little unsure though what to do about the P-Channel (currently a Fairchild FDFS2P103). Is that simply the case of a 10k pullup, and a 100R series drive resistor?
Quick specs - motor stall current is about 1.5A. Supply voltage is 4-6v, pwm switching is variable between 2 and 8khz to minimise audio noise approaching discontinuous operation, and switching loss at higher power levels. Are there any other gotcha's for driving this motor that anyone can think of?
I've tried hunting high and low for some info on direct drive of P-channel MOSFETS, but all the Microchip designs seem to use drivers (presumably becuase of the voltage levels involved).
Thanks, Tom.
Fast Components - the best way to buy components!
**broken link removed**
Hi,
we're currently designing a servo controller for these motors that we've started getting made up **broken link removed**. The idea is to make a 'servo beater' for robotics applications, retailing at $15 - $20. Basic specs to include a variety of gearboxes (and nominal RPM outputs 40 ~ 250RPM), quadranture encoding, RSXXX, I2C, SPI, PWM, analogue, arbitrary (absolute & relative) positioning commands, arbitrary torque output commands, temperature overload control / feedback... etc.
To keep the costs down, and becuase we simply don't have board space for a driver, we wanted to drive the MOSFET H-bridge direct from our MCU. For the N-channel MOSFETS (currently Fairchild FDFS6N303), we're proposing to use a 10k pulldown, and a 100R series drive resistor.
I'm a little unsure though what to do about the P-Channel (currently a Fairchild FDFS2P103). Is that simply the case of a 10k pullup, and a 100R series drive resistor?
Quick specs - motor stall current is about 1.5A. Supply voltage is 4-6v, pwm switching is variable between 2 and 8khz to minimise audio noise approaching discontinuous operation, and switching loss at higher power levels. Are there any other gotcha's for driving this motor that anyone can think of?
I've tried hunting high and low for some info on direct drive of P-channel MOSFETS, but all the Microchip designs seem to use drivers (presumably becuase of the voltage levels involved).
Thanks, Tom.
Fast Components - the best way to buy components!
**broken link removed**