Micro-Cap Tutorial: Highside MOSFET PWM PMOS

Exploring pulse width modulation (PWM) with P-Channel MOSFET (PMOS) places as a highside load switch. This placement arrangement is relatively common for basic three-phase motor controls. We also talk about why highside modulation is more difficult to manage in applications...the input voltage has to match the supply voltage. Often times, customers will require provisions for the supply voltage to vary by up to twice the nominal (e.g., 24.0 V max operating, with 12.0 V nominal). It becomes possible for gate-source maximum voltages to be violated if the required supply variance is not taken into account. Because of the difficulties, when highside topology is needed, people tend to prefer using an N-Channel MOSFET that is driven by a charge pump. They do that to solve the supply variance issue and N-Channel devices often cost less (and perform more efficiently). However, the cost of the charge pump and accessory components can outweigh the benefits. I'm indifferent to method of implementation as long as overall product works within required tolerances (according to customer specification) and the components are low cost for short term and long term (warranty spend). Motor Control Note: Some six-step commutation pre-driver applications work just fine using highside P-Channel devices; such as Toshiba's TB9061AFNG. That's a reliable and low cost commutation logic and pre-driver product.