Infineon Technologies IR3821AMTRPBF

Overview

IR3821AMTRPBF from Infineon Technologies is a highly integrated synchronous buck regulator with internal high- and low-side MOSFETs, delivering up to 9A continuous output current across 0.6V–12V output range from a 2.5V–21V input. It features fixed 300kHz switching frequency, 0.6V precision reference voltage, programmable over-current protection via OCSet pin, and pre-bias start-up capability-used in DDR memory power delivery and graphics card VRMs.

For engineers reviewing the IR3821AMTRPBF datasheet, IR3821AMTRPBF pinout, IR3821AMTRPBF application, or IR3821AMTRPBF equivalent, key selection criteria include its thermally enhanced 5mm×6mm QFN-15 package, dual UVLO thresholds (VCC and VC), hiccup-mode current limiting, and open-drain PGood reporting with external Vsns threshold programming.

Technical Context

The IR3821AMTRPBF implements voltage-mode PWM control with a fixed 300kHz oscillator and internal sawtooth ramp generator. Its error amplifier compares FB voltage against a 0.6V reference, driving trailing-edge modulated gate signals to integrated N-channel MOSFETs without external timing components.

Current sensing uses R_DS(on) of the low-side MOSFET (10.5–13.4mΩ typ.), eliminating sense resistors. Protection includes non-latched thermal shutdown at 140°C (20°C hysteresis), dual UVLO (VCC_UVLO_R = 4.0–4.4V; VC_UVLO_R = 3.1–3.5V), and programmable soft-start via SS pin capacitor.

Key Specifications

Pinout & Package

Package: 15-pin thermally enhanced Power QFN (5mm × 6mm, exposed thermal pad). Pin layout optimized for minimal loop inductance and thermal dissipation: separate AGnd (pins 4, 5, 15) and PGnd (pin 10), dedicated VC and VCC bias paths, and isolated SW node (pin 11).

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar synchronous buck regulator applications.

Compared with MP8765GQ-Z and TPS549D22, the IR3821AMTRPBF uniquely combines pre-bias start-up, dual UVLO, and external Vsns/OCSet programmability-making it optimal for DDR and server PoL applications requiring deterministic sequencing and fault resilience.

Availability

IR3821AMTRPBF is available at Aetrix Electronics and suitable for DDR memory power delivery, graphics card VRMs, and server point-of-load applications requiring stable component supply, long-term lifecycle support, and RoHS-compliant packaging.

Supply support for IR3821AMTRPBF includes scheduled delivery planning, volume procurement assistance, BOM continuity management, traceable sourcing, and lifecycle availability coordination for OEM customers, industrial embedded developers, connected-device designers, and electronics production programs.

Manufacturer

Infineon Technologies is a German semiconductor manufacturer specializing in power management, automotive, and industrial control ICs, with leadership in silicon-based power stages and integrated regulators.

The IR3821A belongs to Infineon's SupIRBuck™ family-designed specifically for high-efficiency, space-constrained point-of-load regulation in computing and storage infrastructure where integration, thermal performance, and sequencing reliability are critical.

FAQ

What is the minimum recommended output capacitance for stable operation at 9A?

The IR3821AMTRPBF requires ≥220μF total output capacitance with ≤5mΩ ESR for 9A operation at 300kHz. This is typically achieved using four 56μF/6.3V X5R MLCCs in parallel, placed close to the SW and PGnd pins to minimize loop inductance and ensure phase margin >45°.

Can the IR3821AMTRPBF operate with a 3.3V input supply?

No-the absolute minimum VIN is 2.5V, but the recommended operating VIN starts at 4.5V per datasheet Section 5. At 3.3V, VCC and VC UVLO thresholds (4.0V and 3.1V respectively) cannot be met, preventing gate driver activation and causing immediate shutdown.

How is the over-current threshold calculated using the OCSet pin?

The OCSet pin draws a fixed current (15–26μA typ.) that flows through an external resistor (R_OC) to the SW node. The current limit I_LIM ≈ (0.025V × R_{DS(on)_BOT}) / (R_OC × I_OCSET), where R_{DS(on)_BOT} = 10.5–13.4mΩ. For example, R_OC = 10kΩ yields ~9A limit at 25°C.

Does the IR3821AMTRPBF support forced PWM or power-save mode?

No-it operates exclusively in fixed-frequency voltage-mode PWM with no diode emulation or pulse-skipping mode. Light-load efficiency is maintained via low quiescent current (10mA VCC static), but the regulator does not enter discontinuous conduction mode or frequency foldback.