ST1S41PUR - 4A 18V Sync Step-Down DC-DC | STMicroelectronics
MPN: ST1S41PUR ✓ Active| Qty | Unit Price | Extended |
|---|---|---|
| 1 | $1.55 | $1.55 |
| 10 | $1.39 | $13.90 |
| 100 | $1.18 | $118.00 |
| 500 | $1.04 | $520.00 |
| 1,000 | $0.92 | $920.00 |
ST1S41PUR Overview
A buck (step-down) DC-DC converter is a switching voltage regulator that reduces a higher DC input voltage to a lower DC output voltage by rapidly switching an inductor and rectifying the resulting waveform. Unlike linear regulators that dissipate the VIN-VOUT difference as heat, buck converters achieve 90%+ efficiency even at large step-down ratios by storing energy in an inductor during the switch-on phase and releasing it during the switch-off phase. In the power management hierarchy, a buck converter is a DC-DC converter, which is a subset of voltage regulators, which belong to the broader power management IC category. Buck regulators are the workhorse of point-of-load conversion in modern digital systems.
Key features of the ST1S41PUR include 90% peak efficiency, internal soft-start with cycle-by-cycle current limiting, overcurrent protection, and thermal shutdown. The 850 kHz nominal switching frequency (programmable from 700 kHz to 1 MHz) permits the use of small inductors and ceramic output capacitors, enabling a sub-100 mm² total solution footprint. The exposed thermal pad on the DFN-8 package provides a low thermal resistance path for dissipating switch losses, supporting full 4 A continuous output without external heatsinking in well-designed layouts.
Typical applications include point-of-load regulation for FPGAs, microcontrollers, and ASICs, 12 V bus-powered distributed systems, industrial control boards, and consumer electronics requiring high step-down ratios. The 4 V minimum input also makes it suitable for USB Type-C PD and 5 V supply rails.
When designing, choose an inductor of approximately 4.7 µH for most VIN/VOUT combinations to maintain continuous-conduction mode. Place the input ceramic bypass capacitor directly adjacent to the PVIN pin and the exposed pad to a large ground copper pour to extract heat. This page synthesizes distributor pricing, drop-in alternatives, and practical design notes not found in the manufacturer datasheet alone.
Drop-in alternatives for ST1S41PUR — 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 ST1S41PUR (same form factor and footprint) — differing in Package, Input Voltage Range, Efficiency, Output Voltage Range, Switching Frequency.
Quick Comparison Tool — Select alternative parts for side-by-side comparison:
ST1S40PUR
✅ Drop-In ⚠️ Specs Unverified✓ In Stock
$0.72 / Unit
View Datasheet →ST1S50PUR
✅ Drop-In ⚠️ Specs Unverified✓ In Stock
$1.2 / Unit
View Datasheet →ST1S12GR
✅ Drop-In ⚠️ Specs Unverified✓ In Stock
$0.75 / Unit
View Datasheet →L7985TR
✅ Drop-In ⚠️ Specs Unverified✓ In Stock
$1.1 / Unit
View Datasheet →ST1S41PUR Maximum Ratings & Electrical Characteristics
| Topology | Synchronous Buck (Step-Down) DC-DC Converter |
| Input Voltage Range | 4.0 V to 18 V |
| Output Voltage Range | 0.8 V to VIN (adjustable) |
| Maximum Output Current | 4 A continuous |
| Switching Frequency | 850 kHz nominal (700 kHz to 1 MHz adjustable) |
| High-Side Switch Rds(on) | 95 mΩ |
| Low-Side Switch Rds(on) | 69 mΩ (synchronous rectifier) |
| Control Method | Peak Current-Mode PWM with Internal Compensation |
| Peak Efficiency | Up to 90% |
| Quiescent Current | 1.5 mA typical |
| Soft-Start | Internal |
| Protection Features | Overcurrent, Thermal Shutdown, Cycle-by-Cycle Current Limit |
| Operating Temperature Range | -40 °C to +125 °C junction |
| Package | VFQFPN-8 (3x3 mm) with exposed thermal pad |
| Mounting Type | Surface Mount |
| MSL Level | 1 |
| RoHS Status | Compliant |
ST1S41PUR Pin Configuration
| Pin 1 | VIN — Input supply voltage (4.0 V to 18 V) |
| Pin 2 | SW — Switch node — connect to output inductor |
| Pin 3 | GND — Ground return for internal MOSFETs and analog circuits |
| Pin 4 | FB — Feedback input for output voltage regulation (VREF=0.8 V) |
| Pin 5 | COMP — Compensation network node |
| Pin 6 | EN/SS — Enable input / soft-start control |
| Pin 7 | RT/FSET — Frequency set resistor (700 kHz to 1 MHz, 850 kHz nominal) |
| Pin 8 | BST — Bootstrap capacitor for high-side gate drive |
| Pin 9 | EPAD — Exposed thermal pad — connect to GND copper pour for heat dissipation |
Typical Applications
ST1S41PUR is suitable for 6 applications: FPGA Point-of-Load Converter, 12 V Industrial Distributed Power, USB Type-C / PD Powered Device Rails, DSP and ASIC Core Power, Telecommunications Card Power, Solid-State Drive and Storage Power.
FPGA Point-of-Load Converter
The ST1S41PUR provides a clean 0.8 V to 3.3 V core rail for FPGA core, GTX transceivers, and auxiliary voltages from a 5 V or 12 V system rail. With 4 A continuous output and 0.8 V minimum VOUT it directly serves low-voltage FPGA core supplies while its 95 mΩ/69 mΩ switches hold efficiency above 85% at typical load. The 850 kHz switching frequency keeps noise outside the baseband receiver range, and the exposed-pad DFN-8 footprint fits under a BGA package keep-out zone.
Recommended
12 V Industrial Distributed Power
Industrial PLC, motor-control, and instrumentation systems commonly distribute a 12 V or 24 V backplane rail that must be stepped down to 5 V, 3.3 V and 1.8 V for digital logic. The ST1S41PUR's 4 V to 18 V input range aligns directly with 12 V busses, and the 4 A output delivers up to 50 W at 12 V-to-1.8 V conversion. Internal cycle-by-cycle current limit and thermal shutdown provide fault resilience required in unattended industrial equipment running 24/7.
Recommended
USB Type-C / PD Powered Device Rails
USB-PD sources commonly negotiate 5 V, 9 V, 12 V, or 15 V at the sink; the ST1S41PUR's 4 V minimum input lets it operate directly from any negotiated PD voltage above 5 V. The 4 A output supplies USB-PD downstream devices such as SSDs, hubs, and active cables that require regulated 3.3 V or 5 V rails. Internal soft-start avoids inrush issues on PD attach events, and the synchronous rectifier yields high light-load efficiency suitable for USB suspend states.
Recommended
DSP and ASIC Core Power
DSPs, ASICs, and SoC devices typically require high-current sub-1 V core rails generated close to the device to minimize distribution losses. The ST1S41PUR can deliver 4 A into a sub-100 mm² solution with output rails from 0.8 V up, driven by its 850 kHz switching rate which permits small ceramic output capacitors without exceeding voltage ripple budgets. The peak-current-mode control provides the tight line/load regulation needed by core rails that power millions of transistors switching simultaneously.
Recommended
Telecommunications Card Power
In telecom and networking line cards, multiple isolated or non-isolated sub-rails (1.2 V, 1.8 V, 2.5 V, 3.3 V) must be derived from a 12 V or 5 V backplane. The ST1S41PUR's 4 A output, 850 kHz fixed-frequency operation, and small footprint suit densely packed line-card assemblies where every mm² of PCB area is premium. Cycle-by-cycle current limit and thermal shutdown comply with NEBS-style reliability expectations for telecom equipment.
Recommended
Solid-State Drive and Storage Power
SATA and NVMe SSDs require 3.3 V or 5 V rails from a host 12 V or 5 V supply with tight regulation for NAND flash programming. The ST1S41PUR's combination of 4 A output, 0.8 V minimum VOUT, and 90% efficiency at typical loads suits mainstream SSD power trees, including 12 V-to-3.3 V and 5 V-to-1.2 V conversion chains. The exposed thermal pad and internal thermal shutdown are essential in enclosed SSD cases with limited airflow.
Recommended
Recommended Products Summary
Engineering reference data for ST1S41PUR — comparison, design guidance, and compliance information.
Selection Guide
Comparison with Alternatives
| Parameter | This Product | ST1S40PUR | ST1S50PUR | ST1S12GR | L7985TR |
|---|---|---|---|---|---|
| Brand | STMicroelectronics | STMicroelectronics | STMicroelectronics | STMicroelectronics | STMicroelectronics |
| Package | VFQFPN-8 (3x3 mm) | VFQFPN-8 (3x3 mm) — same | VFQFPN-8 (3x3 mm) — same | VFQFPN-8 (3x3 mm) — same | VFQFPN-8 (3x3 mm) — same |
| Output Current | 4 A | 3 A (-25%) | 3 A (-25%) | 3 A (-25%) | 2 A (-50%) |
| Input Voltage Range | 4.0 V to 18 V | 4.0 V to 18 V | 4.0 V to 18 V | 2.5 V to 18 V (wider low end) | 4.5 V to 18 V |
| Switching Frequency | 850 kHz | 850 kHz | 850 kHz | 1.5 MHz | 1 MHz (adjustable) |
| High-Side Rdson | 95 mΩ | 95 mΩ | 165 mΩ (+74%) | 250 mΩ | 180 mΩ |
| Output Voltage Range | 0.8 V to VIN | 0.8 V to VIN | 0.8 V to VIN | 0.8 V to VIN | 0.8 V to VIN |
| Soft Start | Internal | Internal | Internal | Internal | Internal |
Key Differentiators
- Highest output current in ST's 3x3 mm DFN-8 buck family (vs ST1S40PUR)
- Lower high-side MOSFET Rdson at the same switching frequency (vs ST1S50PUR)
- Lower switching frequency than 1 MHz+ for better EMI margin (vs ST1S12GR (1.5 MHz))
Design Notes
At 4 A continuous load with 12 V input and 3.3 V output, internal MOSFET conduction losses are approximately 700 mW and switching losses add another 200–400 mW depending on frequency and layout. The DFN-8 (3x3 mm) exposed pad must be soldered to at least 1 cm² of ground copper pour on the top PCB layer and stitched with thermal vias to inner ground planes to keep the junction below the 125 °C rating. Estimated: theta_JA ≈ 40 °C/W on a 1-oz 1 cm² copper pour, derated further with reduced copper area.
Place the input ceramic bypass capacitor (minimum 22 µF X7R) within 2 mm of the VIN pin and the exposed pad to the closest ground copper plane. Keep the SW node trace short and minimize its copper area to reduce radiated EMI. The feedback trace should be routed away from the SW node and bypassed with a 10 nF capacitor from FB to GND. Use a four-layer PCB with a dedicated ground plane for any design that meets EN 55022 EMI limits on the first pass.
Do not attempt to operate the ST1S41PUR above 18 V input — the internal MOSFETs and bootstrap capacitor are rated for 18 V abs max. Avoid using electrolytic capacitors with high ESR at the output: only low-ESR ceramic or polymer capacitors produce the stable regulation loop expected by the internal compensation. The EN/SS pin must be tied above its 1.2 V logic-high threshold or left open (the part has internal pull-up); leaving it floating into a noisy environment can disable the converter unexpectedly.
Compliance Information
RoHS and REACH compliance per STMicroelectronics product page. Not AEC-Q100 qualified — for AEC-Q100 automotive grade, screen equivalent ST parts specifically.
