600 V bootstrap — the DC-link ceiling
The IR21531STR is a half-bridge gate driver from Infineon (formerly International Rectifier) designed to drive a pair of N-channel MOSFETs in a synchronous half-bridge configuration. Its 600 V bootstrap rating sets the maximum DC-link voltage the high-side driver can float on — nominally suited for 230 VAC offline supplies, PFC stages, and motor-drive inverter rails where the bus sits below 400 VDC.
80 ns rise, 45 ns fall — switching-speed budget
At switching frequencies up to 100 kHz, these edges keep the overlap conduction period short enough that the driver's 10 V to 15.6 V supply rail can replenish the bootstrap capacitor between cycles without significant droop. The two drivers are internally matched for propagation delay, which simplifies dead-time calculation — the datasheet's timing diagrams are the reference for setting the RC network values that prevent shoot-through.
Industrial temperature grade — deployment envelope
The 8-SOIC package keeps the board footprint compact, though the 0.154-inch body width limits creepage between the high-side and low-side ground traces — a 4-layer PCB with a dedicated ground plane is the typical layout choice.
Infineon lists the IR21531STR as obsolete. The closest functional equivalent in the same family is the IR2153 — it shares the same half-bridge architecture, RC input, and 600 V bootstrap rating, but the IR21531 variant includes additional features such as shutdown capability. Pin compatibility should be verified against the respective datasheets before substituting. For new designs, the IR2153 or a newer-generation half-bridge driver from Infineon's current portfolio (e.g. the IRS series) is the recommended path.