IR2121PBF - 5V Low-Side Gate Driver with OCP | Infineon
MPN: IR2121PBF ✗ End of Life| Qty | Unit Price | Extended |
|---|---|---|
| 1 | $2.52 | $2.52 |
| 10 | $2.21 | $22.10 |
| 100 | $1.85 | $185.00 |
| 500 | $1.52 | $760.00 |
| 1,000 | $1.28 | $1,280.00 |
IR2121PBF Overview
A gate driver IC is a power-management semiconductor that sits between a low-power control signal (typically from a microcontroller or PWM controller) and a power switching device (MOSFET or IGBT). Its primary role is to translate a logic-level command into a high-current drive that can rapidly charge and discharge the gate capacitance of the power switch, thereby minimizing switching losses and preventing shoot-through. Within the broader hierarchy, gate drivers belong to power management ICs, then to PMIC gate drivers, and finally to the semiconductor family.
Key features include a current-limit programming input that allows the system designer to set the OCP threshold with an external resistor, an open-drain FAULT output that pulls low when an over-current event is detected and latches the driver off, CMOS/LSTTL-compatible logic inputs down to 2.5 V, and a high-pulse-current buffer output stage designed for minimum cross-conduction. Typical propagation delay is 150 ns, allowing the part to operate efficiently at PWM frequencies up to several hundred kilohertz.
The IR2121PBF is built on Infineon's proprietary high-voltage CMOS process, which integrates the level-shifting, protection logic, and output driver stages onto a single die. The output stage uses a complementary push-pull topology with controlled rise and fall times to limit EMI while still providing the in-rush current needed to switch large gate charges. The OCP comparator monitors the voltage across an external current-sense resistor and, when the threshold is exceeded, the FAULT pin is asserted and the gate output is latched low until the input is cycled.
Typical applications include low-side switching of IGBTs and power MOSFETs in motor drives, solenoid drivers, DC-DC converters, lighting ballasts, and general-purpose switch-mode power supplies where fault reporting is required. The wide supply range also makes it suitable for industrial 24 V bus-derived rails.
A critical design consideration when using the IR2121PBF is to choose the current-sense resistor value carefully so that the OCP trip point sits comfortably above the maximum normal load current yet well below the saturation limit of the switching device. Also ensure the FAULT pin is pulled high with a pull-up resistor, since it is an open-drain output.
This page consolidates distributor pricing, pin-compatible drop-in alternatives, and practical design notes beyond what is captured in the manufacturer datasheet alone.
Drop-in alternatives for IR2121PBF — same package, pin-to-pin compatible. Different-package parts requiring PCB rework are excluded.
Quick Comparison Tool — Select alternative parts for side-by-side comparison:
IR2121PBF
✅ Drop-In✓ In Stock
$1.28 / Unit
View Datasheet →IR2121PBF Maximum Ratings & Electrical Characteristics
| Configuration | Low-Side |
| Number of Outputs | 1 |
| Supply Voltage (Vcc) | 12 V to 18 V |
| Logic Input Compatibility | CMOS / LSTTL, down to 2.5 V |
| Peak Source Current | 1.6 A (typical) |
| Peak Sink Current | 3.3 A (typical) |
| Propagation Delay | 150 ns (typical) |
| Over-Current Protection | Programmable, with latched FAULT output |
| FAULT Output Type | Open-drain, active-low |
| Input Type | Non-Inverting |
| Operating Temperature | -40C to +125C |
| Package | 8-Pin PDIP (0.300 inch, 7.62 mm) |
| Mounting Type | Through-Hole |
| Technology | Latch-immune CMOS |
| Lead-Free (Pbf) | Yes (PBF suffix) |
| RoHS Status | Compliant |
IR2121PBF Pin Configuration
| Pin 1 | VCC — Logic and driver supply voltage (12 V to 18 V) |
| Pin 2 | IN — Logic input (CMOS/LSTTL compatible, non-inverting) |
| Pin 3 | GND — Ground reference |
| Pin 4 | NC — Not connected (per datasheet) |
| Pin 5 | CS — Current-sense input for programmable OCP comparator |
| Pin 6 | FAULT — Open-drain fault output, active-low (latched) |
| Pin 7 | NC — Not connected (per datasheet) |
| Pin 8 | OUT — Gate drive output to power MOSFET or IGBT |
Typical Applications
IR2121PBF is suitable for 6 applications: Low-Side IGBT Switch in Motor Drive, Solenoid and Relay Driver, DC-DC Converter Low-Side Synchronous Rectifier Driver, Switch-Mode Power Supply Primary-Side Switch Driver, Lighting Ballast and LED Driver Stage, Industrial 24 V Bus Switching and Protection.
Low-Side IGBT Switch in Motor Drive
The IR2121PBF drives the low-side IGBT in half-bridge motor drive stages where fault reporting is mandatory. With 1.6 A source and 3.3 A sink peak currents, it charges and discharges the IGBT gate charge within a few hundred nanoseconds, reducing switching losses at PWM frequencies up to 20 kHz. The integrated programmable OCP comparator monitors the IGBT collector current via an external shunt and asserts a latched FAULT output when the threshold is exceeded, protecting the IGBT from short-circuit events during motor stall or winding faults. The 12 V to 18 V supply range matches the standard 15 V gate-drive rail used in industrial 24 V bus systems.
Recommended
Solenoid and Relay Driver
The IR2121PBF is well suited to driving DC solenoid coils and automotive relay coils where a single low-side switch with fault protection is required. Its 3.3 A sink current handles the inductive kick when the solenoid is de-energized, while the open-drain FAULT pin signals the host microcontroller if the coil current exceeds the programmed OCP threshold. The CMOS-compatible 2.5 V input accepts logic from 3.3 V microcontrollers without level shifting, simplifying the BOM in 12 V and 24 V automotive subsystems. Latch-immune CMOS construction ensures the driver survives repetitive load-dump transients on the VCC rail.
Recommended
DC-DC Converter Low-Side Synchronous Rectifier Driver
In isolated and non-isolated DC-DC converter topologies, the IR2121PBF drives the synchronous rectifier MOSFET on the low side of the secondary. Its 150 ns propagation delay maintains timing accuracy across the converter's duty cycle, while the 1.6 A source current rapidly charges the synchronous MOSFET gate to minimize body-diode conduction losses. The over-current protection feature is invaluable in buck and forward converters where a shorted synchronous FET would otherwise draw catastrophic current from the input bus. The 8-pin PDIP package also simplifies hand-prototyping of through-hole converter boards.
Recommended
Switch-Mode Power Supply Primary-Side Switch Driver
The IR2121PBF drives the primary-side switching MOSFET in flyback and forward SMPS topologies up to a few hundred watts. With its high sink current capability, it pulls the MOSFET gate low quickly to limit turn-off switching losses, while the 12 V to 18 V VCC range supports bootstrapping from an auxiliary winding. The integrated OCP provides cycle-by-cycle current limiting that is essential for primary-side regulation. The latch-immune CMOS process ensures the driver tolerates the high dV/dt transients present across the primary-side MOSFET drain in hard-switched topologies.
Recommended
Lighting Ballast and LED Driver Stage
In fluorescent lamp ballasts and high-power LED drivers, the IR2121PBF drives the low-side power switch that commutates the inductor or lamp current. The 1.6 A source current is sufficient to switch most MOSFETs used in 40 W to 150 W ballast stages, while the OCP comparator protects against lamp rectification failure, a common end-of-life fault in fluorescent ballasts. The 8-pin PDIP package is preferred in this application because through-hole soldering withstands the high operating temperatures inside enclosed luminaires better than equivalent SOIC parts.
Recommended
Industrial 24 V Bus Switching and Protection
The IR2121PBF is commonly deployed as the low-side driver in industrial 24 V systems that require rugged fault protection. Its 12 V to 18 V supply range can be derived directly from a 24 V rail with a local linear regulator, while the latch-immune CMOS process survives the inductive transients found in factory automation environments. The OCP latch and FAULT pin integrate cleanly with PLC-style discrete I/O modules, providing a hard-wired fault signal back to the controller. Operating temperature range of -40C to +125C supports outdoor and unconditioned cabinet installations.
Recommended
Recommended Products Summary
Engineering reference data for IR2121PBF — comparison, design guidance, and compliance information.
Selection Guide
Comparison with Alternatives
| Parameter | This Product | IR2121PBF | IR2127SPBF |
|---|---|---|---|
| Package | 8-PDIP (0.300 inch) | 8-PDIP - same | 8-SOIC - different footprint |
| Brand | Infineon | Infineon Technologies | Infineon Technologies |
| Configuration | Low-Side | Low-Side | Low-Side / High-Side driver |
| Supply Voltage | 12 V to 18 V | 12 V to 18 V | 12 V to 18 V |
| Peak Source Current | 1.6 A | 1.6 A | 2.0 A |
| Peak Sink Current | 3.3 A | 3.3 A | 4.0 A |
| Over-Current Protection | Yes, programmable, latched FAULT | Yes, programmable, latched FAULT | No integrated OCP |
| Propagation Delay | 150 ns | 150 ns | 150 ns |
Key Differentiators
- Integrated programmable OCP with latched FAULT output (vs IR2127SPBF)
- Through-hole PDIP package for hand-prototyping and high-voltage clearance (vs IR2127SPBF)
- Wide CMOS/LSTTL input compatibility down to 2.5 V (vs IR2127SPBF)
Design Notes
Place a 1 uF ceramic decoupling capacitor as close as possible to the VCC pin (pin 1) and a 100 nF high-frequency bypass cap on the same node. The 8-pin PDIP benefits from a ground plane on the component side; route the CS trace (pin 5) directly to the shunt resistor with minimal loop area to avoid noise-induced false OCP trips. Keep the FAULT pull-up resistor (typically 10 kOhm to VCC) close to pin 6 to preserve noise margin when the open-drain output is asserted.
Do not assume the FAULT pin will reset automatically - the IR2121PBF latches the fault and requires IN to be cycled low-to-high to release the latch per the Infineon datasheet. When setting the OCP threshold, account for the shunt resistor tolerance (1% or better recommended) and the input bias current on the CS pin, otherwise the trip point may drift 10-15% from the calculated value. Avoid leaving the CS pin floating, as it will cause spurious FAULT assertions from PCB leakage.
Estimated: at 100 kHz switching frequency, 1 nC gate charge, and 18 V VCC, the IR2121PBF internal dissipation is roughly P = VCC x Qg x fsw = 18 x 1e-9 x 1e5 = 1.8 mW, which is negligible. The thermal limitation in practice is the output stage sourcing into a partially discharged gate at low supply voltages; verify with a worst-case Vgs=10V turn-on scenario when driving very large MOSFETs (Qg > 50 nC). The PDIP-8 theta_JA of approximately 100 C/W provides adequate margin for these low-power dissipation levels.
Compliance Information
RoHS and lead-free status per PBF suffix in the MPN and Infineon product page. AEC-Q100 not applicable - this part is qualified to industrial level only per the datasheet cover page.
