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Analog Devices Inc. LT3971IMSE-3.3#PBF
- Part No.:
- LT3971IMSE-3.3#PBF
- Manufacturer:
- Analog Devices Inc.
- Package:
- 10-TFSOP, 10-MSOP (0.118", 3.00mm Width) Exposed Pad
- Datasheet:
-
LT3971IMSE-3.3#PBF.pdf
- Description:
- IC REG BUCK 3.3V 1.2A 10MSOP
- Quantity:
- Payment:
- Shipping:
Inventory:168
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Product details
Overview
LT3971IMSE-3.3#PBF from Analog Devices (formerly Linear Technology) is a fixed-output 3.3V, 1.2A monolithic buck switching regulator in a thermally enhanced 10-lead MSOP package. It operates from 4.3V to 38V input, delivers ultralow 2.8µA quiescent current in regulation, and maintains <15mVP-P output ripple via low-ripple Burst Mode® operation - ideal for automotive battery-powered systems requiring long standby life.
For engineers reviewing the LT3971IMSE-3.3#PBF datasheet, LT3971IMSE-3.3#PBF pinout, LT3971IMSE-3.3#PBF application, or LT3971IMSE-3.3#PBF equivalent, key selection criteria include its guaranteed 3.3V ±1.5% output accuracy over –40°C to 125°C, 700nA shutdown current, power good flag, soft-start control, and internal compensation eliminating external loop components.
Technical Context
The LT3971IMSE-3.3#PBF implements constant-frequency current-mode control with internal 10MΩ feedback divider setting VOUT = 3.3V. Its bipolar NPN switch (0.33Ω RDS(ON) equiv.) is driven by a bootstrap circuit using the BOOST and BD pins, enabling full saturation across the 4.3–38V input range.
Burst Mode® operation activates below ~92mA load, reducing supply current to 1.7µA during sleep cycles while maintaining tight output regulation. Frequency foldback during startup and overload limits peak inductor current, and the open-drain PG pin asserts when VOUT reaches 91% of nominal - all without external timing or sensing components.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Output Voltage | Fixed 3.3V ±1.5% over –40°C to 125°C; eliminates external resistor divider and phase-lead capacitor |
| Max Output Current | 1.2A continuous; supports industrial sensors and microcontroller rails without derating at 125°C junction |
| Quiescent Current | 2.8µA at no load (12VIN→3.3V); enables >10-year battery life in always-on IoT nodes |
| Input Voltage Range | 4.3V to 38V; covers 12V/24V automotive batteries including cold-crank and load-dump transients |
| Switching Frequency | Adjustable 200kHz–2MHz via RT pin; 800kHz typical in reference design for optimal size/efficiency tradeoff |
| Shutdown Current | 700nA; reduces system standby power to negligible levels when EN pin is pulled low |
| Power Good Flag | Open-drain PG asserts high when VOUT ≥ 91% of 3.3V; provides reliable power sequencing signal for MCUs/FPGAs |
Pinout & Package
LT3971IMSE-3.3#PBF uses a 10-lead plastic MSOP package (3mm × 3mm footprint) with exposed pad (Pin 11) soldered to PCB for thermal performance (θJA = 45°C/W).
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1 BD | Boost Diode Anode | Connects to cathode of external Schottky diode; forms bootstrap return path for high-side drive |
| 2 BOOST | Bootstrap Drive | Supplies >VIN voltage to internal NPN switch base; requires 10nF ceramic capacitor to SW |
| 3 SW | Switch Node | Drives external inductor; connects to BOOST capacitor and catch diode cathode |
| 4 VIN | Main Power Input | Supplies IC bias and switch current; requires local 10µF ceramic bypass to GND |
| 5 EN | Enable Control | Hysteretic 1.005V rising threshold; pulls low to achieve 700nA shutdown current |
| 6 VOUT | Fixed Output Sense | Internally regulated to 3.3V; connects directly to output capacitor and load (no FB divider needed) |
| 7 SS | Soft-Start Ramp | Controls inrush current via external capacitor; disables soft-start if left floating |
| 8 RT | Frequency Set | Resistor-to-GND sets switching frequency from 200kHz–2MHz; 49.9kΩ = 800kHz |
| 9 PG | Power Good Flag | Open-drain output; sinks current until VOUT reaches 3.003V (91% of 3.3V) |
| 10 SYNC | Sync Input | Ground for Burst Mode; tie to external clock (250kHz–2MHz) for synchronized pulse-skipping |
Key Features
| Feature | Design Value |
|---|---|
| Ultralow Quiescent Current | 2.8µA regulating 12VIN → 3.3VOUT; enables multi-year operation on coin cells or supercaps |
| Low-Ripple Burst Mode® | Maintains <15mVP-P output ripple at light loads; avoids audible noise and EMI spikes of conventional burst modes |
| Internal Compensation | Eliminates external Type-II/III compensation network; reduces BOM count and layout sensitivity |
| Accurate Power Good Flag | PG asserts within 100ms of VOUT reaching 3.003V; provides deterministic reset timing for downstream logic |
| Thermally Enhanced Package | Exposed pad (Pin 11) must be soldered to PCB copper; achieves θJC = 10°C/W for 1.2A continuous operation |
Applications
| Automotive Body Control Module | Industrial Sensor Node |
|---|---|
|
Use Scenario: Powers MCU, CAN transceiver, and analog front-end in door module operating from 9–16V battery with 30-day sleep mode. IC Role / Device Role / Timing Role: Primary 3.3V power rail regulator with integrated PG signaling for safe MCU wake-up sequence. Use Value: 2.8µA IQ extends battery life beyond 5 years; 38V max input withstands load-dump transients per ISO 7637-2. |
Use Scenario: Supplies wireless sensor node (BLE SoC + MEMS accelerometer) deployed in remote locations with primary Li-SOCl₂ battery. IC Role / Device Role / Timing Role: Always-on buck converter delivering regulated 3.3V during 99.9% duty-cycle sleep intervals. Use Value: 700nA shutdown current preserves battery capacity during firmware updates; internal 3.3V setpoint ensures ±1.5% accuracy without calibration. |
| Portable Medical Monitor | Railway Signaling Interface |
|
Use Scenario: Powers ECG front-end and display controller in handheld patient monitor requiring FDA-compliant low-power design. IC Role / Device Role / Timing Role: Main 3.3V supply with soft-start limiting inrush into large display capacitors during power-on. Use Value: SS pin-controlled ramp prevents brownout of MCU during cold start; PG flag synchronizes display initialization. |
Use Scenario: Converts 72VDC track supply to 3.3V for FPGA-based signaling logic in wayside equipment with wide ambient temperature range. IC Role / Device Role / Timing Role: High-input-voltage buck regulator supporting –40°C to 125°C operation without derating. Use Value: 4.3V min input enables regulation down to brownout conditions; exposed-pad MSOP sustains 1.2A at 125°C ambient. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar fixed-output buck regulator applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| LT8609SIV#PBF | 42V input, 2A output, 2.5µA IQ, synchronous rectification, 3mm × 4mm LQFN | Higher current, lower IQ, but requires external feedback resistors for 3.3V; no internal VOUT divider | Select when >1.2A load or synchronous efficiency >92% is required; rework needed for feedback network |
| TPS62840DGRR | 6V input, 1A output, 0.35µA IQ, 2.0V–5.5V adjustable output, 2mm × 2mm WSON | Lower input range, ultra-low IQ, but cannot support automotive 12V/24V or 38V transients | Select only for battery-powered sub-6V systems where 38V tolerance is unnecessary; incompatible with 12V+ inputs |
Compared with LT3971IMSE-3.3#PBF, LT8609SIV#PBF offers higher current and slightly lower quiescent current but lacks the integrated 3.3V divider and requires layout changes for feedback. TPS62840DGRR achieves dramatically lower IQ but fails to meet the 38V input requirement, making it unsuitable for automotive or industrial 24V rail applications.
Availability
LT3971IMSE-3.3#PBF is available at Aetrix Electronics and suitable for automotive battery regulation, industrial sensor nodes, and portable medical monitors requiring stable component supply across extended temperature ranges and long production lifecycles.
Supply support for LT3971IMSE-3.3#PBF 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
Analog Devices acquired Linear Technology in 2017 and maintains full product support, documentation, and manufacturing continuity for the LT3971 family.
The LT3971 series was designed specifically for high-input-voltage, ultralow-quiescent-current DC/DC conversion in automotive, industrial, and battery-backed systems where reliability across –40°C to 125°C is mandatory.
FAQ
What is the guaranteed output voltage accuracy of the LT3971IMSE-3.3#PBF over temperature?
The LT3971IMSE-3.3#PBF guarantees 3.3V output with ±1.5% tolerance across the full –40°C to 125°C junction temperature range, as confirmed by electrical characteristics tables in the official datasheet. This accuracy is achieved via laser-trimmed internal 10MΩ feedback resistors and a precision 1.19V reference, eliminating drift-related calibration needs in automotive and industrial deployments.
Can the LT3971IMSE-3.3#PBF operate from a 40V input transient?
No - the LT3971IMSE-3.3#PBF has an absolute maximum VIN rating of 38V. While brief transients up to 38V are permissible, sustained operation above this violates Absolute Maximum Ratings and risks permanent damage. For 40V+ environments, external clamping (e.g., TVS diode) or upstream pre-regulation is required before the LT3971IMSE-3.3#PBF input.
Does the LT3971IMSE-3.3#PBF require an external catch diode?
Yes - the LT3971IMSE-3.3#PBF requires an external Schottky diode connected between SW and VOUT (cathode to SW, anode to VOUT). The internal boost Schottky is only for gate-drive bootstrapping; it does not replace the power-path catch diode. Diode selection must prioritize <1µA reverse leakage at 3.3V to preserve ultralow IQ performance.
How is soft-start configured on the LT3971IMSE-3.3#PBF?
Soft-start on the LT3971IMSE-3.3#PBF is controlled by an external capacitor from SS (Pin 7) to GND. A typical 1nF capacitor yields ~1ms ramp time; larger values increase ramp duration linearly. The SS pin is automatically released when EN rises above 1V, and actively discharged only during shutdown - ensuring repeatable inrush control across power cycles.
Is the LT3971IMSE-3.3#PBF pin-compatible with other LT3971 variants in the same package?
Yes - the LT3971IMSE-3.3#PBF shares identical pinout and footprint with LT3971IMSE#PBF (adjustable), LT3971IMSE-5#PBF (5V fixed), and LT3971IMSE16#PBF (16-lead MSOP). However, VOUT (Pin 6) functionality differs: LT3971IMSE-3.3#PBF regulates Pin 6 to 3.3V, while the adjustable version uses Pin 6 as FB input - direct substitution requires schematic review.
LT3971IMSE-3.3#PBF Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc.
- Series:
- -
- Package/Case:
- 10-TFSOP, 10-MSOP (0.118", 3.00mm Width) Exposed Pad
- Packaging:
- Tube
- Product Status:
- Active
- Function:
- Step-Down
- Output Configuration:
- Positive
- Topology:
- Buck
- Output Type:
- Fixed
- Number of Outputs:
- 1
- Voltage - Input (Min):
- 4.3V
- Voltage - Input (Max):
- 38V
- Voltage - Output (Min/Fixed):
- 3.3V
- Voltage - Output (Max):
- -
- Current - Output:
- 1.2A
- Frequency - Switching:
- 200kHz ~ 2MHz
- Synchronous Rectifier:
- No
- Operating Temperature:
- -40°C ~ 125°C (TJ)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 10-MSOP-EP
LT3971IMSE-3.3#PBF FAQ
1.How can I place an order for LT3971IMSE-3.3#PBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LT3971IMSE-3.3#PBF on Aetrix. Our sales agent will provide a competitive quotation and guide you through the order confirmation once you accept the terms.
2.Are the price and stock information for LT3971IMSE-3.3#PBF reliable?
The price and inventory of LT3971IMSE-3.3#PBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LT3971IMSE-3.3#PBF is usually 5 days.
3.What payment methods are accepted for LT3971IMSE-3.3#PBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LT3971IMSE-3.3#PBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LT3971IMSE-3.3#PBF?
LT3971IMSE-3.3#PBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LT3971IMSE-3.3#PBF order is processed, you will receive an email with the shipment details and tracking number.
Note: Tracking information may take up to 24 hours to appear. Express delivery typically takes 3–5 business days.
5.How can I obtain technical support or documentation for LT3971IMSE-3.3#PBF?
For technical support, including LT3971IMSE-3.3#PBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LT3971IMSE-3.3#PBF requirements.
6.How does Aetrix verify that LT3971IMSE-3.3#PBF is sourced from the original manufacturer or authorized distributors?
All LT3971IMSE-3.3#PBF products on Aetrix are procured from qualified distributors and authorized channels. Our dedicated quality assurance team conducts strict verification, including traceability checks and, if necessary, third-party testing. This ensures that LT3971IMSE-3.3#PBF meets industry standards.
7.What is the process for return or replacement of LT3971IMSE-3.3#PBF?
All LT3971IMSE-3.3#PBF units undergo pre-shipment inspection (PSI). If there is an issue with LT3971IMSE-3.3#PBF, returns or replacements are accepted under the following conditions:
1.Quantity discrepancies, incorrect items, or visible external defects (such as breakage or corrosion), acknowledged by Aetrix.
2.The issue is reported within 90 days of delivery.
3.The LT3971IMSE-3.3#PBF part is unused and in its original packaging.
Return procedure for LT3971IMSE-3.3#PBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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