LT3971EMSE#PBF - 38V, 1.2A, 2MHz Buck Regulator | Analog Devices
MPN: LT3971EMSE#PBF ✓ Active| Qty | Unit Price | Extended |
|---|---|---|
| 1 | $10.55 | $10.55 |
| 10 | $9.45 | $94.50 |
| 100 | $8.2 | $820.00 |
| 500 | $7.1 | $3,550.00 |
| 1,000 | $6.25 | $6,250.00 |
LT3971EMSE#PBF Overview
A buck (step-down) switching regulator is a type of DC-DC converter that efficiently reduces a higher DC input voltage to a lower DC output voltage by rapidly switching a power transistor and storing energy in an inductor. Buck regulators occupy the middle tier of the power-management hierarchy: DC-DC converter -> switching regulator -> buck converter -> power management IC. They are preferred over linear regulators in high-ratio step-down applications because they avoid the large (VIN-VOUT) x IOUT power dissipation inherent to LDOs, achieving typical efficiencies of 85-95%.
Key features of the LT3971EMSE#PBF include low ripple Burst Mode operation for high efficiency at light loads, an accurate 1V threshold enable pin (with 700nA shutdown current), a soft-start pin for controlled inrush current, and a power-good flag that signals when VOUT reaches 91% of the programmed value. The internal compensation and 1.2A switch current rating simplify design while reducing external BOM count. The 10-pin MSOP exposed pad package provides a low thermal-resistance path, supporting full 1.2A operation in industrial temperature grades (E: 0C to 125C junction, -40C to 125C by design).
Typical applications include automotive battery regulation, industrial 24V bus point-of-load conversion, distributed power systems, portable battery-powered equipment, and always-on alarm/keep-alive supplies where the 2.8uA quiescent current is critical. When designing with the LT3971EMSE#PBF, choose the inductor and input/output capacitors based on the programmed switching frequency and load transients; higher switching frequencies permit smaller inductors but trade off switch losses.
Drop-in alternatives for LT3971EMSE#PBF — 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 LT3971EMSE#PBF (same form factor and footprint) — differing in Package, Switching Frequency, Topology, Operating Temperature Range, Quiescent Current.
Quick Comparison Tool — Select alternative parts for side-by-side comparison:
LT3971EMSE-3.3#PBF
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View Datasheet →LT3971EMSE-5#PBF
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LT3971IMSE#PBF
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LT3971IMSE-3.3#PBF
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LT3971IMSE-5#PBF
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LM2841YMK-ADJL
✅ Drop-In✓ In Stock
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View Datasheet →LT3971EMSE#PBF Maximum Ratings & Electrical Characteristics
| Topology | Buck (Step-Down) |
| Input Voltage Range | 4.3 V to 38 V |
| Output Voltage Range | 1.19 V to 30 V (adjustable) |
| Maximum Output Current | 1.2 A |
| Switching Frequency | 200 kHz to 2 MHz (adjustable) |
| Quiescent Current | 2.8 uA (Burst Mode, no load) |
| Shutdown Current | 700 nA (EN low) |
| Enable Threshold | 1 V (accurate) |
| Operating Junction Temperature | -40C to +125C (E grade by design, characterized 0C to 125C) |
| Package | 10-TFSOP / 10-MSOP (0.118", 3.00 mm) Exposed Pad |
| Package Code | MSE (MSOP-10EPD) |
| Mounting Type | Surface Mount |
| Soft-Start Pin | Yes (SS capacitor controls inrush) |
| Power Good Flag | Yes (asserts at 91% of VOUT) |
| Lead-Free / RoHS | Yes (PBF suffix indicates lead-free) |
LT3971EMSE#PBF Pin Configuration
| Pin 1 | EN — Enable pin (1V accurate threshold); drive high to enable, low to shutdown (700nA Iq) |
| Pin 2 | VIN — Input supply voltage (4.3V to 38V) |
| Pin 3 | SW — Switch node - connected to inductor |
| Pin 4 | BST — Bootstrap pin for high-side gate drive |
| Pin 5 | PGND — Power ground |
| Pin 6 | RT — Timing resistor - sets switching frequency 200kHz to 2MHz |
| Pin 7 | SS — Soft-start - capacitor to GND sets inrush time |
| Pin 8 | PG — Power good flag - open-drain output, asserts at 91% of VOUT |
| Pin 9 | FB — Feedback (adjustable version); VOUT = 1.19V x (1 + R1/R2) |
| Pin 10 | AGND — Analog ground |
| Pin 11 | EP — Exposed pad (thermal) - solder to PCB ground pour |
Typical Applications
LT3971EMSE#PBF is suitable for 6 applications: Automotive 12V Battery Point-of-Load, Industrial 24V Bus Distributed Power, Battery-Powered Portable Equipment, Always-On Alarm and Keep-Alive Supply, Distributed Power Systems, General-Purpose 5V/3.3V System Rails.
Automotive 12V Battery Point-of-Load
The LT3971EMSE#PBF is well suited for automotive 12V battery rails because its 38V maximum input withstands 24V jump-start transients and load-dump events, while its 2.8uA quiescent current is critical for always-on modules that must not drain the battery when the ignition is off. The 1.2A switch can power infotainment processors, CAN transceivers, or sensor clusters directly from VBAT. Compared to an LDO, the buck topology dissipates far less heat at large VIN-VOUT deltas, enabling smaller PCB area and lighter thermal management.
Recommended
Industrial 24V Bus Distributed Power
On industrial 24V bus systems, the LT3971EMSE#PBF operates directly from the bus without a pre-regulator, providing isolated point-of-load rails for sensors, actuators, and PLC I/O. Its 4.3V to 38V input accommodates the 18V to 32V industrial envelope including transients, while the 200kHz to 2MHz programmable frequency allows designers to balance efficiency against component size. The integrated soft-start prevents inrush into large bulk capacitors when many modules power up simultaneously on the same backplane.
Recommended
Battery-Powered Portable Equipment
The LT3971EMSE#PBF is excellent for portable battery-powered equipment because its 2.8uA quiescent current extends standby life when the load is sleeping, and its 700nA shutdown current (EN low) further reduces drain during shipping or storage. The adjustable switching frequency up to 2MHz enables tiny chip inductors under 4.7uH, reducing solution footprint for handheld instruments. Burst Mode operation eliminates audible switching noise at light loads, important for medical and audio accessories.
Recommended
Always-On Alarm and Keep-Alive Supply
For always-on alarm and keep-alive circuits that must operate for years on a primary cell or backup battery, the LT3971EMSE#PBF's 2.8uA Iq ensures negligible standby drain while maintaining a regulated output to RTCs, tamper detectors, and supervisory MCUs. The enable pin allows the main system to switch off the regulator entirely when in deep sleep, dropping quiescent current to 700nA. Power-good flag simplifies coordination with the host MCU's reset sequencing.
Recommended
Distributed Power Systems
In distributed power architectures, the LT3971EMSE#PBF serves as a downstream POL (point-of-load) converter placed at each load, stepping down an intermediate 12V or 24V bus to local MCU voltages (3.3V, 5V, 1.8V). Its small MSOP-10EPD footprint and high switching frequency minimize PCB area per converter. The accurate 1V EN threshold permits direct connection to a GPIO without level translation, simplifying sequencing in multi-rail FPGA or DSP power trees.
Recommended
General-Purpose 5V/3.3V System Rails
As a general-purpose 5V or 3.3V system rail source, the LT3971EMSE#PBF (used in its adjustable variant or the -3.3/-5 fixed variants) supplies microcontrollers, sensors, and communication ICs across a wide input range. Its 1.2A switch rating covers typical MCU plus peripheral loads, while Burst Mode ensures high efficiency at light loads common in idle or sleep modes. The integrated compensation eliminates the loop compensation network that simpler bucks require, reducing BOM and design time.
Recommended
Recommended Products Summary
Engineering reference data for LT3971EMSE#PBF — comparison, design guidance, and compliance information.
Selection Guide
Comparison with Alternatives
| Parameter | This Product | LT3971EMSE-3.3#PBF | LT3971EMSE-5#PBF | LT3971IMSE#PBF | LT3971IMSE-3.3#PBF | LT3971IMSE-5#PBF | LM2841YMK-ADJL |
|---|---|---|---|---|---|---|---|
| Package | MSOP-10EPD (MSE) | MSOP-10EPD (MSE) - same | MSOP-10EPD (MSE) - same | MSOP-10EPD (MSE) - same | MSOP-10EPD (MSE) - same | MSOP-10EPD (MSE) - same | MSOP-10EPD - same footprint |
| Brand | Analog Devices | Analog Devices | Analog Devices | Analog Devices | Analog Devices | Analog Devices | Texas Instruments |
| Input Voltage Range | 4.3 V to 38 V | 4.3 V to 38 V | 4.3 V to 38 V | 4.3 V to 38 V | 4.3 V to 38 V | 4.3 V to 38 V | 4.5 V to 42 V |
| Output Voltage | 1.19 V to 30 V (adjustable) | 3.3 V (fixed) | 5 V (fixed) | 1.19 V to 30 V (adjustable) | 3.3 V (fixed) | 5 V (fixed) | 0.765 V to 34 V (adjustable) |
| Maximum Output Current | 1.2 A | 1.2 A | 1.2 A | 1.2 A | 1.2 A | 1.2 A | 0.3 A |
| Quiescent Current | 2.8 uA | 2.8 uA | 2.8 uA | 2.8 uA | 2.8 uA | 2.8 uA | 20 uA (typ) |
| Switching Frequency Range | 200 kHz to 2 MHz | 200 kHz to 2 MHz | 200 kHz to 2 MHz | 200 kHz to 2 MHz | 200 kHz to 2 MHz | 200 kHz to 2 MHz | 550 kHz to 1.5 MHz |
| Junction Temperature Range | -40C to +125C (E grade by design) | -40C to +125C (E grade by design) | -40C to +125C (E grade by design) | -40C to +125C (I grade guaranteed) | -40C to +125C (I grade guaranteed) | -40C to +125C (I grade guaranteed) | -40C to +125C |
Key Differentiators
- Industry-leading 2.8uA quiescent current (vs LM2841YMK-ADJL)
- Wide VIN to 38V handles 24V industrial transients (vs TPS563201)
- Up to 2MHz switching frequency with internal compensation (vs LM2841YMK-ADJL)
- Accurate 1V enable threshold and 700nA shutdown current (vs TPS563201)
Design Notes
Estimated: at VIN=24V, VOUT=5V, and 1.2A load, the LT3971EMSE#PBF dissipates roughly (24-5)V x 1.2A x (1/eta - 1). Assuming 88% efficiency yields about 3.1W of waste heat. The MSE-10EPD package with proper PCB copper pour (>=1 square inch of 2oz copper tied to the exposed pad) typically achieves 40-45 C/W theta_JA, producing a junction temperature rise of approximately 130C above ambient. Derate load or add thermal relief if the design operates near full load at high VIN.
Place the input capacitor (>= 2.2uF X7R ceramic) as close as possible between VIN and PGND, with the return path short and wide. Place the bootstrap capacitor (>= 0.1uF) between BST and SW, also close to the IC. Keep the FB/ADJ trace short and away from the SW node to minimize noise injection. The exposed pad must be soldered to a continuous ground plane with thermal vias for proper heat sinking and EMI performance.
Do not exceed the absolute maximum VIN of 38V; transients above this will damage the part. The EN pin has a precise 1V threshold - if driving from a noisy GPIO, add a small RC filter (10k/100nF) to prevent false triggering. The SS capacitor must be present; without it, large inrush currents can trigger the current limit and create startup instability. Always respect the BST-to-SW voltage rating (typically 4V); design with margin for transient spikes on the SW node.
Separate power ground (PGND) and analog ground (AGND) at the IC pins, then tie them together at a single point under the exposed pad to avoid ground bounce coupling into the FB/ADJ node. Use a 4-layer PCB if possible, with the inner layer dedicated to a quiet ground plane beneath the feedback trace. Keep the inductor and input capacitor loop area minimal to reduce high-frequency ringing on the SW node.
Compliance Information
PBF suffix indicates lead-free / RoHS-compliant per Analog Devices part numbering convention. E grade (standard) is not AEC-Q100 qualified; automotive applications should request ADI automotive-grade variants. Halogen-free status not confirmed in provided data.
