UC3726

The UC1726 Isolated Drive Transmitter, and its companion chip, the C1727 Isolated High Side IGBT Driver, provide a unique solution to driving solated power IGBTs. They are particularly suited to drive the high ide devices on a high voltage H-bridge. The UC1726 device transmits he drive logic and drive power, along with transferring and receiving fault nformation with the isolated gate circuit using a low cost pulse transformer.

This drive system utilizes a duty cycle modulation technique that gives instantaneous esponse to the drive control transitions, and reliably passes teady state, or DC conditions. High frequency operation, up to 750kHz, llows the cost and size of the coupling transformer to be minimized.

The UC1726 can be powered from a single V_CC supply which internally enerates a voltage reference for the logic circuitry. It can also be placed nto a low power shutdown mode that disables the internal reference. The C's logic circuitry can be powered from an external supply, VL, to minimize verall power dissipation. Fault logic monitors the Isolated High Side GBT Driver UC1727 for faults. Based on user defined timing, the C1726 distinguishes valid faults, which it responds to by setting the fault atch pin. This also disables the gate drive information until the fault reset in is toggled to a logic one.

The UC1726 operates over an 8 to 35 volt supply range. The typical VCC oltage will be greater than 28 volts to be compatible with the UC1727. he undervoltage lockout circuitry of the Isolated High Side IGBT Driver C1727 locks out the drive information during its undervoltage lockout.