RT8299AZSP - 3A, 24V Synchronous Step-Down Converter | Richtek
MPN: RT8299AZSP ✓ Active| Qty | Unit Price | Extended |
|---|---|---|
| 1 | $1.65 | $1.65 |
| 10 | $1.42 | $14.20 |
| 100 | $1.05 | $105.00 |
| 500 | $0.82 | $410.00 |
| 1,000 | $0.66 | $660.00 |
| 3,000 | $0.59 | $1,770.00 |
RT8299AZSP Overview
What is a synchronous step-down converter? A synchronous buck regulator is a type of switched-mode power supply (SMPS) that uses both a high-side and a low-side MOSFET (often integrated) to convert a higher DC input voltage to a lower DC output voltage. Compared to an asynchronous buck (with a freewheeling diode), a synchronous buck replaces the diode with a MOSFET, which dramatically reduces conduction loss, raises efficiency (typically 90%+), and eliminates the rectifier reverse-recovery loss. Within the broader taxonomy, a buck converter is a DC/DC converter, which is a sub-category of voltage regulator, itself part of power management ICs. The RT8299 family is targeted at distributed point-of-load (POL) rails where high efficiency at moderate current is required.
Key specifications include the 3 V-24 V input range, 0.8 V-15 V adjustable output, 3 A continuous load, fixed 500 kHz switching frequency, internal high-side and low-side MOSFETs, and SOP-8EP package with an exposed thermal pad for improved heat spreading. Current-mode control eases loop compensation, while internal soft-start reduces inrush current at power-up.
Architecturally, the RT8299 integrates a high-side N-MOSFET, a low-side N-MOSFET, a 0.8 V reference, an error amplifier, a PWM controller, and protection circuitry (OCP, OVP, UVLO, thermal shutdown) into one die. The exposed pad on the SOP-8EP package reduces thermal resistance to roughly 40 C/W (per the manufacturer datasheet thermal table), enabling full 3 A output at elevated ambient temperatures with proper board layout.
Typical applications include 12 V bus to 3.3 V/5 V point-of-load conversion for industrial controllers, consumer electronics (set-top boxes, LCD TVs), USB Type-C powered devices, distributed POL supplies in networking equipment, and battery-powered systems running from 2- to 4-cell Li-ion packs (8.4 V-16.8 V nominal). At light loads the device still operates in forced-PWM, so efficiency is moderate at very low currents.
When designing with the RT8299AZSP, choose an inductor with low DCR (typically 2.2 µH to 4.7 µH), use ceramic input and output capacitors rated for the switching ripple current, and keep the high-current loop (IN-SW-PGND) tight on the PCB. Ensure the exposed pad is soldered to a copper area of at least 1 sq inch for the full 3 A continuous rating.
This page synthesizes distributor pricing, drop-in same-package alternatives, and practical design guidance not found in the manufacturer datasheet.
Drop-in alternatives for RT8299AZSP — 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 RT8299AZSP (same form factor and footprint) — differing in Continuous Output Current, Control Mode, Input Voltage Range, Operating Temperature Range, Output Voltage Range.
Quick Comparison Tool — Select alternative parts for side-by-side comparison:
RT8299AS-A
✅ Drop-In📋 Reference alternative (not in catalog)
RT8299ZLSP
✅ Drop-In ⚠️ Specs Unverified📋 Reference alternative (not in catalog)
MP1484EN-LF-Z
✅ Drop-In📋 Reference alternative (not in catalog)
MP1584EN-LF-Z
✅ Drop-In📋 Reference alternative (not in catalog)
AOZ1282CI
✅ Drop-In✓ In Stock
$0.55 / Unit
View Datasheet →RT8299AZSP Maximum Ratings & Electrical Characteristics
| Topology | Synchronous Step-Down (Buck) |
| Input Voltage Range | 3 V to 24 V |
| Output Voltage Range | 0.8 V to 15 V (Adjustable) |
| Continuous Output Current | 3 A |
| Switching Frequency | 500 kHz (fixed) |
| Reference Voltage | 0.8 V |
| Control Mode | Current Mode (PWM) |
| Internal MOSFETs | High-side + Low-side N-channel (integrated) |
| Operating Temperature Range | -40 C to +85 C |
| Package | SOP-8 with Exposed Pad (SOP-8EP) |
| Package Dimensions | 3.90 mm body width (0.154 inch) |
| Mounting Type | Surface Mount |
| Protection Features | Cycle-by-cycle OCP, OVP, UVLO, Thermal Shutdown |
| Soft-Start | Internal |
| RoHS Status | Compliant |
RT8299AZSP Pin Configuration
| Pin 1 | BOOT — Bootstrap capacitor for high-side gate drive |
| Pin 2 | EN — Enable input (active-high) |
| Pin 3 | GND — Analog ground |
| Pin 4 | SW — Switch node (connected to internal high-side/low-side MOSFETs) |
| Pin 5 | SW — Switch node (continuation - both SW pins must be connected on PCB) |
| Pin 6 | IN — Input supply voltage |
| Pin 7 | IN — Input supply voltage (continuation) |
| Pin 8 | PGND — Power ground (also exposed pad, must be soldered to ground plane) |
Typical Applications
RT8299AZSP is suitable for 6 applications: 12 V Industrial Point-of-Load Regulation, Consumer Set-Top Box and LCD TV Power, USB Type-C Powered Device Rails, Networking and Telecom Point-of-Load, 2- to 4-Cell Li-Ion Battery Powered Systems, Distributed LED Driver Rails.
12 V Industrial Point-of-Load Regulation
The RT8299AZSP converts a 12 V or 24 V industrial bus rail to 3.3 V or 5 V logic rails for PLC controllers, sensor modules, and HMI displays. Its 3 A continuous output at 24 V VIN supports MCU + companion IC loads simultaneously, while 500 kHz switching keeps the external inductor compact (2.2-4.7 µH). The integrated high-side/low-side MOSFETs eliminate the need for an external Schottky, reducing BOM cost and board area. Cycle-by-cycle OCP and thermal shutdown protect against industrial fault conditions such as output short circuits or fan failure.
Recommended
Consumer Set-Top Box and LCD TV Power
The RT8299AZSP is well suited for set-top boxes and LCD TV mainboards where a 12 V or 19 V adapter rail must be dropped to 5 V/3.3 V for SoC, memory, and tuner ICs. Its 3 A capability covers the combined digital core + DDR power budget of typical STB SoCs, while the 0.8 V reference supports low-voltage core rails. Fixed-frequency 500 kHz switching makes EMI compliance (FCC/CE) easier to manage than variable-frequency solutions. The SOP-8EP package fits low-profile consumer enclosures with standard 0.154 inch SOIC pad layout.
Recommended
USB Type-C Powered Device Rails
In USB Type-C powered devices (PD sourcing 5 V/3 A or higher), the RT8299AZSP can step down the negotiated bus voltage (typically 5 V, 9 V, 15 V, or 20 V) to system rails. Its 24 V input maximum comfortably tolerates 20 V USB-PD profiles plus transient overshoot, while the 0.8 V minimum reference supports direct generation of low-voltage MCU rails. 3 A continuous output is sufficient to power radio modules, microcontrollers, and sensor clusters in compact USB-C peripherals. Internal soft-start prevents inrush that could trip USB-PD current-limit thresholds at attach.
Recommended
Networking and Telecom Point-of-Load
The RT8299AZSP supports distributed point-of-load conversion in routers, switches, and small-cell base stations where a 12 V or 24 V backplane rail feeds multiple POL regulators. Each POL converts the bus voltage to local 3.3 V/1.8 V/1.2 V rails for ASICs, FPGAs, and PHYs. The 500 kHz switching frequency balances efficiency (90%+ typical) and external-component size, while the integrated synchronous MOSFETs reduce PCB real estate versus discrete designs. Cycle-by-cycle current limit prevents fault propagation across the backplane.
Recommended
2- to 4-Cell Li-Ion Battery Powered Systems
Portable systems running from 2-cell (8.4 V max) or 3-cell (12.6 V max) Li-ion battery packs benefit from the RT8299AZSP's 3 V-24 V input range. The 3 V minimum safely covers depleted-battery operation while the 24 V maximum tolerates fully-charged 4-cell packs plus transient ringing. At 12 V to 5 V conversion the device achieves 92% efficiency at 1 A, extending battery runtime. Integrated synchronous MOSFETs minimize external parts count - critical for compact handheld designs - and internal soft-start prevents inrush that would trip low-voltage protection circuits.
Recommended
Distributed LED Driver Rails
In LED lighting systems (architectural, signage, and display backlighting), the RT8299AZSP can supply constant-voltage rails that downstream constant-current LED drivers convert to per-string current. Its 24 V input range supports long LED-string runs from a 24 V distribution bus, while the 3 A output drives multiple LED driver ICs in parallel. The fixed 500 kHz frequency and synchronous architecture keep EMI low - important when drivers are co-located with sensitive RF/wireless control modules. Wide operating temperature (-40 C to +85 C) suits outdoor and industrial lighting installations.
Recommended
Recommended Products Summary
Engineering reference data for RT8299AZSP — comparison, design guidance, and compliance information.
Selection Guide
Comparison with Alternatives
| Parameter | This Product | RT8299AS-A | RT8299ZLSP | MP1484EN-LF-Z | MP1584EN-LF-Z | AOZ1282CI |
|---|---|---|---|---|---|---|
| Brand | Richtek | Richtek | Richtek | Monolithic Power Systems | Monolithic Power Systems | Alpha & Omega Semiconductor |
| Package | SOP-8EP | SOP-8EP | SOP-8EP | SOIC-8EP | SOIC-8EP | SOIC-8EP |
| Topology | Synchronous Buck | Synchronous Buck | Synchronous Buck | Asynchronous Buck | Asynchronous Buck | Synchronous Buck |
| Input Voltage Range | 3 V - 24 V | 3 V - 24 V | 3 V - 24 V | 4.5 V - 18 V | 4.5 V - 28 V | 4.5 V - 18 V |
| Output Current | 3 A | 3 A | 3 A | 3 A | 3 A | 3 A |
| Switching Frequency | 500 kHz | 500 kHz | 500 kHz | 385 kHz (fixed) | Up to 1.5 MHz adj. | 500 kHz |
| Output Voltage Range | 0.8 V - 15 V | 0.8 V - 15 V | 0.8 V - 15 V | 0.8 V - 16 V | 0.8 V - 21 V | 0.8 V - 15 V |
| Efficiency at 12 V → 5 V / 1 A (typical) | ~92% | ~92% | ~92% | ~85% (async) | ~83% (async) | ~91% |
| RoHS / Lead-Free | Compliant | Compliant | Compliant | Compliant | Compliant | Compliant |
Key Differentiators
- True synchronous buck topology with both high-side and low-side MOSFETs integrated (vs MP1584EN-LF-Z)
- Wider 3 V to 24 V input range than typical 3 A SOP-8EP competitors (vs MP1484EN-LF-Z / AOZ1282CI)
- Higher switching frequency (500 kHz) than older 3 A buck families (vs MP1484EN-LF-Z (385 kHz fixed))
Design Notes
The RT8299AZSP delivers up to 3 A continuous output. At VIN = 12 V, VOUT = 5 V, and 3 A load, power dissipation is approximately (12 V - 5 V) × 3 A = 21 W. The SOP-8EP package has a junction-to-ambient thermal resistance (θJA) of roughly 40 C/W with a 1 sq inch copper pour, yielding a junction temperature rise of 840 C above ambient - well beyond the 85 C operating limit. Design MUST limit continuous load to keep VIN-VOUT × IOUT below ~2.5 W, OR use a much larger copper area / multi-layer board / external heatsink. Always derate for VIN ≥ 15 V with high output currents.
PCB layout is critical for switching regulator performance. Place the input ceramic capacitor (22 µF X7R or larger) as close as possible to pins 6/7 (IN) and pin 8 (PGND) to minimize the high-frequency switching loop. Keep the SW traces short and wide to reduce EMI and voltage spikes. Route the BOOT trace away from SW and connect the bootstrap capacitor (typically 100 nF) directly between BOOT (pin 1) and SW (pin 4/5). Use a single ground plane with PGND and GND connected at one point under the exposed pad.
Do not skip the bootstrap capacitor between BOOT and SW - without it the high-side MOSFET will not turn on and the regulator will fail to start. Do not exceed the absolute maximum VIN rating of 26 V (per datasheet); transients above this damage the internal MOSFETs. Ensure the EN pin (pin 2) is not left floating - pull it high through a 100 kΩ resistor for always-on operation, or to a logic signal for sequenced startup. Do not use electrolytic output capacitors with high ESR - ceramic X7R is required for stable loop compensation.
The 500 kHz fundamental and its harmonics can radiate from the SW node and the input loop. To minimize EMI: (1) keep the SW node copper area minimal to reduce antenna effect, (2) place the input capacitor's ground return directly under the IC exposed pad, (3) shield the SW node with ground copper on adjacent layers, and (4) use a shielded inductor rather than an open drum-core. For CE/FCC Class B compliance, a small π-filter (LC) on the input is often sufficient at 3 A load.
The recommended inductor range is 2.2 µH to 4.7 µH; lower inductance gives faster transient response and smaller size but higher ripple current. Choose an inductor saturation current rated at least 30% above the peak current (IOUT + VIN/(2 × L × fSW)). For 12 V → 5 V at 3 A with 3.3 µH and 500 kHz: peak current = 3 A + (12 V - 5 V) × (1 - 5/12) / (2 × 3.3 µH × 500 kHz) ≈ 3.6 A. Select an inductor with ISAT ≥ 4.5 A for safe margin.
Compliance Information
RoHS compliant per LCSC listing. Industrial operating temperature -40 C to +85 C. Not AEC-Q100 qualified; for automotive applications consider TI LMR16006X-Q1 or similar AEC-Q100 3 A buck parts. Halogen-free status and conflict-mineral declaration not explicitly found in the provided data - marked unknown.
