IR1161LTRPBF - SmartRectifier Sync Rectifier Controller | Infineon
MPN: IR1161LTRPBF β Active| Qty | Unit Price | Extended |
|---|---|---|
| 1 | $0.96 | $0.96 |
| 10 | $0.86 | $8.60 |
| 100 | $0.74 | $74.00 |
| 500 | $0.62 | $310.00 |
| 1,000 | $0.51 | $510.00 |
IR1161LTRPBF Overview
What is a synchronous rectifier controller? In isolated DC-DC converters and flyback/forward topologies, the secondary-side rectifier traditionally uses a Schottky or PN-junction diode, but its forward drop (0.3-0.7 V) wastes significant power at high currents. A synchronous rectifier replaces the diode with a low-Rds(on) MOSFET, and a controller IC such as the IR1161L drives that MOSFET's gate in synchronism with the secondary current flow - effectively turning the MOSFET into a near-ideal rectifier with forward drop equal to I_load x Rds(on). This controller category sits hierarchically under: synchronous rectifier controller -> rectifier controller -> secondary-side controller -> power management IC -> semiconductor.
Key features include 200 V absolute maximum drain-sense voltage, adjustable turn-off threshold, very low quiescent current, internal minimum on-time to prevent false triggering at light load, and built-in protection against MOSFET body-diode conduction. The PG-SOT23-5 package occupies less than 9 mm^2 of board area and is suitable for high-density adapters and charger designs.
The IR1161 uses Infineon's proprietary adaptive turn-off algorithm that compensates for variations in MOSFET Ciss and PCB parasitics, ensuring stable operation without external RC timing components in most designs. It supports DCM, CCM, and quasi-resonant primary-side topologies, making it compatible with the Infineon ICE2/ICE3 QR and DCM PWM controllers.
Typical applications include USB-PD adapters (5 V/3 A to 20 V/5 A), laptop and tablet chargers, LED driver auxiliary outputs, auxiliary rails in telecom and server power supplies, and any flyback topology where replacing the Schottky rectifier with a MOSFET improves efficiency by 2-4% at full load. The IR1161 is qualified in Infineon's 15 W 5 V USB adapter reference design.
When designing, place the controller close to the synchronous MOSFET to minimize the drain-sense trace inductance. Use a 100 k-ohm bleed resistor from the MOSFET gate to source to ensure the MOSFET stays off during start-up before the IR1161 bias is established. Refer to the manufacturer datasheet for the turn-off threshold resistor calculation.
This page synthesizes distributor pricing, drop-in alternatives from the IR1161 family, and practical design notes not found in the manufacturer datasheet alone.
Drop-in alternatives for IR1161LTRPBF β same package, pin-to-pin compatible. Different-package parts requiring PCB rework are excluded.
Variants in this series
Same-series models that are drop-in compatible with IR1161LTRPBF (same form factor and footprint) β differing in Operating Temperature Range, Package.
Quick Comparison Tool β Select alternative parts for side-by-side comparison:
IR1161LTRPBF
β Drop-Inβ In Stock
$0.51 / Unit
View Datasheet βIR1161LPBF
β Drop-Inπ Reference alternative (not in catalog)
IR1162LTRPBF
β Drop-Inπ Reference alternative (not in catalog)
IR1167STRPBF
β Drop-Inπ Reference alternative (not in catalog)
IR1168STRPBF
β Drop-Inβ In Stock
$2.38 / Unit
View Datasheet βIR1161LTRPBF Maximum Ratings & Electrical Characteristics
| Function | Secondary-side synchronous rectifier controller |
| Topology Supported | DCM, CCM, quasi-resonant flyback/forward |
| Drive Output | Single N-channel MOSFET gate driver |
| Drain-Sense Absolute Maximum | 200 V |
| Turn-Off Threshold (Vth) | Adjustable via external resistor |
| Minimum On-Time | Internal, fixed |
| Operating Temperature Range | -40 C to +125 C (junction) |
| Package | PG-SOT23-5 (5-pin) |
| Mounting Type | Surface Mount |
| RoHS Status | Compliant |
| Lead-Free | Yes |
| Pbfree Suffix | PBF (lead-free) |
IR1161LTRPBF Pin Configuration
| Pin 1 | VCC β Supply voltage for the IR1161 control logic; connect to a 10-15 V auxiliary winding-derived rail with a decoupling capacitor |
| Pin 2 | GND β Ground reference for VCC, gate drive, and drain-sense |
| Pin 3 | DRAIN β MOSFET drain voltage sense input; connects to the synchronous MOSFET drain to detect body-diode conduction |
| Pin 4 | GATE β Gate drive output to the synchronous MOSFET; provides ~10 V gate drive |
| Pin 5 | VTH β Turn-off threshold programming; connect an external resistor to GND to set Vth (typically 5 mV to 50 mV) |
Typical Applications
IR1161LTRPBF is suitable for 6 applications: USB-PD Laptop and Tablet Chargers, 5V/12V Flyback Adapter Auxiliary Outputs, LED Driver Auxiliary Output Rails, Telecom and Server Auxiliary Power Supplies, Industrial SMPS 24V Outputs, Wall-Wart Chargers (10-25 W Range).
USB-PD Laptop and Tablet Chargers
The IR1161LTRPBF is purpose-built for USB-PD adapter designs where efficiency above 90% is mandatory and the secondary rectifier carries 3-5 A continuous current. In a typical 65 W USB-PD adapter, the IR1161 drives the synchronous MOSFET on the 20 V output rail; its 200 V drain-sense rating easily handles the reflected secondary voltage, while the internal minimum on-time prevents false retriggering at light load. Compared to a 30 V Schottky diode, the synchronous path saves 1-2 W at full load, which is critical for meeting DOE Level VI and EU CoC Tier 2 efficiency targets in compact form factors. Source: Infineon 15 W 5 V USB adapter reference design, IR1161 datasheet.
Recommended
5V/12V Flyback Adapter Auxiliary Outputs
The IR1161LTRPBF fits multi-output flyback adapters (e.g. 12 V main + 5 V standby) where replacing each secondary diode with a MOSFET + IR1161 improves overall efficiency by 2-4%. The 5-pin PG-SOT23-5 footprint allows placement adjacent to the synchronous MOSFET without sacrificing secondary-side real estate. The adaptive turn-off algorithm compensates for MOSFET Ciss variations across batches, eliminating per-design RC tuning. Per the Infineon datasheet, the IR1161 supports DCM, CCM, and quasi-resonant primary topologies, so it works with any of the common adapter control schemes. Reference: IR1161 datasheet section 'Typical Application Circuit'.
Recommended
LED Driver Auxiliary Output Rails
In high-power LED drivers (50-200 W), the IR1161LTRPBF serves the 12 V or 24 V auxiliary output that powers the cooling fan, control MCU, and analog dimming circuitry. By synchronously rectifying this auxiliary rail, designers avoid the 0.5-1 W heat penalty of a Schottky, which would otherwise require a larger heatsink in the sealed driver enclosure. The IR1161's 200 V drain-sense rating tolerates the auxiliary winding's reflected voltage plus leakage spike margin, eliminating the need for an external TVS clamp on the drain-sense pin. The minimum on-time blanking ensures stable operation at low dimming levels where the auxiliary current drops below 50 mA.
Recommended
Telecom and Server Auxiliary Power Supplies
The IR1161LTRPBF is qualified in 48 V telecom and server auxiliary PSU designs where standby efficiency (target > 0.5 W per rail) and reliability are paramount. In a typical 54 V to 12 V intermediate bus converter, the IR1161 drives the secondary-side synchronous MOSFET on the 12 V output, replacing a Schottky that would dissipate 4-6 W at 10 A load. The PG-SOT23-5 package tolerates the +85 C ambient typical of server backplane environments, and the -40 C to +125 C junction rating supports outdoor telecom cabinets. The IR1161's adjustable turn-off threshold lets designers optimize for the specific MOSFET used in each variant of the power supply family.
Recommended
Industrial SMPS 24V Outputs
For industrial 24 V DIN-rail SMPS (60-240 W range), the IR1161LTRPBF drives the synchronous rectifier on the 24 V rail, where output currents of 2.5-10 A are common. Replacing a Schottky with a synchronous MOSFET + IR1161 typically lifts full-load efficiency from 88% to 92-93%, allowing the designer to shrink the heatsink or reduce fan cooling. The 200 V drain-sense rating handles the reflected voltage of a 24 V output with 6:1 turns ratio at 100-200 kHz switching. The minimum on-time blanking prevents false retriggering during DCM operation, which is essential for the wide-load-range behavior of industrial supplies (from 5% to 100% load).
Recommended
Wall-Wart Chargers (10-25 W Range)
The IR1161LTRPBF enables sub-25 W wall-wart chargers to meet modern efficiency standards without the cost of an external Schottky + heatsink combination. In a 12 V/2 A wall-wart, the IR1161 + a 30 V MOSFET replaces a Schottky that would dissipate 0.7-1 W continuous; the synchronous path drops that to 0.1 W, eliminating the need for thermal relief copper on the secondary side. The 5-pin PG-SOT23-5 package is small enough to fit in a 50 mm x 30 mm PCB outline. Reference design: Infineon 15 W 5 V USB adapter board, which combines ICE2QS03G (primary), CoolMOS IPS65R1K5CE (primary switch), and IR1161 (secondary synchronous controller).
Recommended
Recommended Products Summary
Engineering reference data for IR1161LTRPBF β comparison, design guidance, and compliance information.
Selection Guide
Comparison with Alternatives
| Parameter | This Product | IR1161LTRPBF | IR1161LPBF | IR1162LTRPBF | IR1167STRPBF | IR1168STRPBF |
|---|---|---|---|---|---|---|
| Brand | Infineon | Infineon - same | Infineon | Infineon | Infineon | Infineon |
| Package | PG-SOT23-5 | PG-SOT23-5 - same | PG-SOT23-5 - same | PG-SOT23-5 - same | PG-SOT23-5 - same | PG-SOT23-5 - same |
| Function | Synchronous rectifier controller | Synchronous rectifier controller | Synchronous rectifier controller | Synchronous rectifier controller (higher VCC) | Synchronous rectifier controller (gate clamp) | Synchronous rectifier controller (higher UVLO) |
| Drain-Sense Absolute Maximum | 200 V | 200 V | 200 V | 200 V | 200 V | 200 V |
| Topology Supported | DCM/CCM/QR flyback | DCM/CCM/QR flyback | DCM/CCM/QR flyback | DCM/CCM/QR flyback | DCM/CCM/QR flyback | DCM/CCM/QR flyback |
| Turn-Off Threshold | Adjustable via VTH resistor | Adjustable via VTH resistor | Adjustable via VTH resistor | Adjustable via VTH resistor | Adjustable via VTH resistor | Adjustable via VTH resistor |
| Minimum On-Time | Internal, fixed | Internal, fixed | Internal, fixed | Internal, fixed | Internal, fixed | Internal, fixed |
| Packaging Form | Tape & Reel (3000/reel) | Tape & Reel (3000/reel) | Tube | Tape & Reel | Tape & Reel | Tape & Reel |
Key Differentiators
- 200 V drain-sense rating covers wide-output flyback designs (vs IR1167STRPBF)
- Industry reference for secondary-side synchronous rectification (vs NCP4306 (onsemi, different package))
- Internal minimum on-time prevents light-load false triggering (vs Discrete self-driven SR (MOSFET only, no IC))
Design Notes
Place the IR1161LTRPBF within 5 mm of the synchronous MOSFET's drain and gate pins. The drain-sense trace carries a fast dV/dt edge (up to 50 V/ns in QR flyback) and any parasitic inductance above ~20 nH can cause false triggering of the drain comparator. Keep the drain-sense trace short and direct, and avoid routing it parallel to or under the gate-drive trace to minimize capacitive coupling. Source: Infineon IR1161 datasheet 'Layout Considerations' section.
Always add a 100 k-ohm to 1 M-ohm bleed resistor from the synchronous MOSFET gate to source. Without this, the MOSFET gate can float during start-up before the IR1161's VCC rail is established, causing the synchronous MOSFET to partially turn on and shoot through with the primary-side switch. This is the most common field failure mode in IR1161 designs and is explicitly called out in the Infineon reference design schematic.
The IR1161's VCC supply must be derived from an auxiliary winding on the flyback transformer (or a linear regulator from the main output), and requires a 1 uF X7R decoupling capacitor within 2 mm of the VCC pin. Under-voltage lockout (UVLO) prevents operation below the minimum VCC threshold; selecting the auxiliary winding turns ratio to deliver 10-15 V under all load conditions is critical for reliable startup. Source: Infineon IR1161 datasheet 'VCC Supply' and 'UVLO' sections.
Although the IR1161LTRPBF dissipates less than 50 mW under normal operation (it drives the gate but does not carry the main secondary current), the PG-SOT23-5 package has a theta_JA of approximately 220 C/W on a standard 2-layer 1-oz copper PCB. Estimated: at +85 C ambient, this allows junction temperature to stay below +95 C. For sealed adapters with no airflow, add a copper pour under the package to reduce theta_JA to 150 C/W.
The turn-off threshold resistor (R_VTH) sets the Vds voltage at which the IR1161 turns off the synchronous MOSFET. A typical value of 5 k-ohm to 50 k-ohm selects thresholds from 50 mV to 5 mV. For best efficiency, set Vth low (5-10 mV) to minimize body-diode conduction time, but not so low that noise on the drain-sense trace triggers false turn-off. Source: Infineon IR1161 datasheet 'Turn-Off Threshold' equation.
Compliance Information
RoHS compliant and lead-free per Infineon product page; PBF suffix indicates Pb-free plating. AEC-Q100 qualification not applicable - this is a power supply controller IC, not an automotive-grade part. For automotive applications use Infineon AEC-Q100 qualified parts from the same family.
