5.1 Halfbridge Configuration
A common configuration used for the MCP14H2184 is a half-bridge (see Figure 5-1). In a half-bridge configuration the source of the high-side MOSFET (QH) and the drain of the low-side MOSFET (QL) are connected. That line (VS) is both the return for the high side in the gate driver IC as well as the output of the half-bridge. When QH is ON and QL is OFF, VS swings to high voltage, and when QH is OFF and QL is ON, VS swings to GND. Hence, the output switches from GND to high voltage at the frequency of IN and SD*, this line drives a transformer for a power supply, or a coil on a motor.
In this half-bridge configuration, high voltage DC is input to the MOSFETs, and converted to a high voltage switching signal to output to load (Figure 5-1). The MOSFETs operate in saturation mode and an important function of the gate driver is to turn ON the MOSFET quickly to minimize switching losses from the linear region of the MOSFET (turn ON and turn OFF). The MCP14H2184 has a typical rise/fall time of 40 ns/20 ns into a 1 nF load.
Another important function of the gate driver IC in the half-bridge configuration is to convert the logic signals of control (MCP14H2184 operates at logic 3V), to a voltage level and current capacity to drive the gate of the MOSFET and IGBT. This requires driving large currents initially to turn ON/turn OFF the MOSFET quickly. Also, the floating well of the high-side allows high voltage configurations during bootstrap operation.