Half-bridge gate driver for 600 V bus applications
The Infineon IR21531S is a half-bridge gate driver IC designed to drive two N-Channel MOSFETs in a synchronous half-bridge configuration. Its 600 V bootstrap rating on the high side lets it directly drive the top FET in AC-DC converters, PFC stages, HID lamp ballasts, and motor drive inverters up to that bus voltage — no separate high-side supply needed. The input uses an RC input circuit, which sets the oscillator frequency with an external resistor and capacitor — a common approach for fixed-frequency half-bridge controllers where you want to set the switching frequency with two passives and no crystal.
Parametric fit — supply, timing, and temperature
Supply range is 10 V to 15.6 V, which matches the 12 V or 15 V bias rails found in most offline power supply and motor drive designs. The 80 ns typical rise time and 45 ns fall time are fast enough for switching frequencies up to several hundred kilohertz, but the asymmetric timing means the dead-time insertion between high-side and low-side on-times must accommodate the slower rise edge.
Infineon no longer manufactures this exact suffix in production volumes. The closest functional replacement is the IR2153 family — the IR21531S differs from the base IR21531 in package (the 'S' suffix denotes the SOIC-8 surface-mount variant) and possibly in minor electrical specs; the IR21531S datasheet should be compared against the IR2153(1) datasheet to confirm pin-compatibility and parametric match before substituting. The base IR21531 is also obsolete, so the search should extend to the IR2153 (without the '1') if a non-obsolete alternative is needed.