Electronic – Driving high and low inputs of a MOSFET driver with a single PWM signal

There definitely are PN half bridge drivers, and a pmos for the high side is fine nowadays for not very high power applications, but you need to get the correct driver for it (some have the PN fets integrated, like the FAN7093).

It used to be that they had much lower performance than their counterpart n-type mosfets, so the drivers were made to use n-type for the high and low sides. N-type still have better performance because of their nature of using electrons instead of holes for conduction (electrons have higher mobility), but not as severely as before. On the other hand, P-type mosfets don't need a charge pump.

Take a look at this application note from Vishay: P-Channel MOSFETs, the Best Choice for High-Side Switching

An EE-Times article also talks about this: A primer on high-side FET load switches

Since I only need the high side output

It is OK to use only the high side output and use a freewheeling diode at the low side. But keep in mind that, a significant amount of losses in Buck Converter occurs on the freewheeling diode. If you use a MOSFET with sufficiently low R_ds,on resistance on the low side too, there will be less losses.

would it be sufficient to ground pins 3, 4 and LO

You must always connect the COM pin to the ground, because it is the GND pin of the IC. If you desire to use only high side, you should ground the pins LIN pin. But never ground the LO pin! It is an active output pin. It might be shorted and damage the IC. Even if it doesn't damage it, there may be a power loss on it.

Do I still need to connect Vcc to the supply?

Yes, of course. V_cc is always needed for powering the internal circuitry of the IC, and for boot-strapping the high side.

My suggestions:

• Don't use an electrolytic capacitor for C₁. They don't respond fast in high frequency circuits. Use a ceramic or film capacitor of at least 10nF; preferably 100nF.
• The rated reverse voltage of D_BOOT must be more that V_{HIGH_SIDE} - V_cc.
• C_BOOT should at least be around 100 times the input capacitance of the MOSFET (C_iss) to be driven, and should be a low ESR (e.g.; film) capacitor.
• The peek current on D_BOOT will be \$\dfrac{V_{cc}}{R_{BOOT}}\$. Choose R_BOOT and D_BOOT accordingly. Lower the value of R_BOOT, faster the capacitor will charge. The power loss on R_BOOT is independent of its value.
• C_BOOT will only see V_cc on it. No need to buy an high voltage capacitor for it. The high reverse voltage will be on D_BOOT. Make sure its reverse voltage rating is higher than the high side MOSFET drain voltage.