How do I drive a MOSFET H-bridge with ADuM3220s?
Two ADuM3220 dual isolated gate drivers can be used to isolate an H-bridge. The high-side switches need to be PMOS devices. One device drives the low-side switches and the other drives the high-side switches. The low-side ADuM3220 is ground referenced to the isolated ground. The high-side ADuM3220’s VDD2 is connected to the bridge voltage. Its GND2 supply needs to be a gate voltage lower than the bridge voltage. A Zener diode from VDD2 to GND2 is a possible implementation. The Zener should be biased to at least the ADuM3220’s maximum IDD2 with a resistor from the high-side ADuM3220’s GND2 to the isolated ground. Refer to the link below for a more detailed explanation and schematics.
Hello! Why is that there's no Rgs in this design? Thanks
Sometimes designers add a bleeder resistor from the gate to source of power devices in a half-bridge, or H-bridge configuration. This lets the designer know where the gate will float to in case of an unpowered or unattached gate driver. These bleeder resistors are often a good idea, but are not absolutely necessary. The values are usually in the range of 10kΩ to 100kΩ.
The design linked to above uses PMOS devices in the H-bridge. This is usually not desired because of the lower electron mobility in PMOS vs. NMOS devices. This design is better created using ADuM3223 gate drivers and NMOS power devices. The outputs of the ADuM3220 cannot be driven much above VDDO, so a bleeder resistor that pulled the PMOS gates high (off) would not be possible.