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Analog Devices Inc. LT3971AIMSE#TRPBF
- Part No.:
- LT3971AIMSE#TRPBF
- Manufacturer:
- Analog Devices Inc.
- Package:
- 10-TFSOP, 10-MSOP (0.118", 3.00mm Width) Exposed Pad
- Datasheet:
-
LT3971AIMSE#TRPBF.pdf
- Description:
- IC REG BUCK ADJ 1.2A 10MSOP
- Quantity:
- Payment:
- Shipping:
Inventory:2,506
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Product details
Overview
The LT3971AIMSE#TRPBF from Analog Devices (formerly Linear Technology) is an adjustable-frequency monolithic buck switching regulator supporting 4.3V–38V input and delivering up to 1.3A output current with ultralow 2.8μA quiescent current in regulation. It features internal compensation, a 0.33Ω integrated switch, low-ripple Burst Mode operation (<15mVP-P), and a power good flag. It is widely used in automotive battery regulation and USB VBUS supplies requiring high light-load efficiency.
For engineers reviewing the LT3971AIMSE#TRPBF datasheet, LT3971AIMSE#TRPBF pinout, LT3971AIMSE#TRPBF application, or LT3971AIMSE#TRPBF equivalent, key selection criteria include its 2.8μA no-load IQ, 1.3A output capability, 200kHz–2MHz programmable frequency, 10-lead MSOP thermal performance, and precise 1V enable threshold-critical for always-on automotive and portable systems.
Technical Context
The LT3971AIMSE#TRPBF employs a constant-frequency current-mode control architecture with internal slope compensation and an oscillator set by an external RT resistor. Its fast transient response stems from the internally compensated error amplifier servoing the VC node, which directly controls peak switch current.
Burst Mode operation is enabled when SYNC is grounded, reducing input current to 1.7μA during sleep cycles while maintaining <15mVP-P output ripple via controlled pulse delivery. The device integrates a boost Schottky diode driver, 1.19V reference (LT3971A variant), and active VC clamping for overcurrent protection.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Input Voltage Range | 4.3V to 38V - supports wide automotive and industrial supply rails without pre-regulation |
| No-Load Quiescent Current | 2.8μA at 12VIN/3.3VOUT - enables multi-year battery life in always-on monitoring systems |
| Max Output Current | 1.3A - sufficient for powering microcontrollers, sensors, and USB peripherals directly |
| Switching Frequency | 200kHz to 2MHz - adjustable via RT resistor; higher frequencies allow smaller magnetics |
| Feedback Reference | 1.19V (LT3971A) - enables precise output programming from 1.19V to 30V using external resistive divider |
| Enable Threshold | 1.01V typical rising - accurate 1V logic-compatible shutdown with 30mV hysteresis prevents chatter |
| Power Good Flag | Open-drain PG asserts when FB reaches 91% of regulation - provides reliable system power sequencing signal |
| Package | 10-Lead MSOP with exposed pad - θJA = 45°C/W enables >1A operation without heatsink at 25°C ambient |
Pinout & Package
LT3971AIMSE#TRPBF is housed in a thermally enhanced 10-lead MSOP package (MSE) with exposed pad (Pin 11) soldered to PCB ground for optimal thermal performance (θJA = 45°C/W, θJC = 10°C/W).
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| BD (1) | Boost Diode Anode Connection | Connects to cathode of external Schottky; forms charge pump path for BOOST drive voltage |
| BOOST (2) | Internal Switch Gate Drive Supply | Provides >VIN voltage to fully saturate bipolar NPN switch; must be bypassed with 10nF ceramic |
| SW (3) | Switch Node | Drives external inductor and catch diode; high dv/dt node requiring tight layout and ground plane |
| VIN (4) | Main Power Input | Supplies IC bias and switch current; requires local 10μF ceramic + 100nF ceramic bypass |
| EN (5) | Enable Control Input | Hysteretic 1V threshold; pulls to GND for shutdown (700nA IQ); tie to VIN if always-on |
| FB (6) | Feedback Input | Regulated to 1.19V; connects to resistor divider tap; add 10pF phase lead capacitor to VOUT |
| SS (7) | Soft-Start Control | Capacitor to GND ramps peak current limit; discharged only when EN = low |
| RT (8) | Frequency Set Input | Resistor to GND programs fSW from 200kHz–2MHz per manufacturer's table |
| PG (9) | Power Good Output | Open-drain; pulled high externally; asserts when FB ≥ 91% of target (e.g., 1.083V for 3.3V out) |
| SYNC (10) | External Clock Input | Ground for Burst Mode; connect to external clock for synchronization (increases IQ to 1.5mA in light load) |
| GND (11) | Power & Signal Ground | Exposed pad - must be soldered to large PCB ground plane for thermal and EMI performance |
Key Features
| Feature | Design Value |
|---|---|
| Ultralow Quiescent Current | 2.8μA at no load ensures >10-year battery life in automotive telematics and IoT edge nodes |
| Low-Ripple Burst Mode | Maintains <15mVP-P output ripple at light loads while preserving >85% efficiency down to 100μA output current |
| Integrated Boost Schottky Driver | Eliminates need for external boost capacitor and diode in most designs, reducing BOM count and board area |
| Internal Compensation | Reduces design cycle time: no external Type II/III compensation network required for stable operation |
| Accurate Power Good Flag | PG asserts within ±2% of final output voltage, enabling reliable microcontroller reset and system sequencing |
| Thermally Enhanced MSOP | Exposed pad delivers 10°C/W junction-to-case resistance, supporting 1.3A continuous output at 85°C ambient |
Applications
| Automotive Battery Regulation | USB VBUS Power Supply |
|---|---|
Use Scenario: Regulating 9V–16V automotive battery to 3.3V/5V for infotainment MCU and CAN transceivers in start-stop vehicles. IC Role / Device Role / Timing Role: Primary buck converter providing always-on, low-IQ power with cold-crank immunity down to 4.3V input. Use Value: 2.8μA quiescent current prevents battery drain during weeks of vehicle inactivity; 38V abs max rating withstands load dump transients. | Use Scenario: Generating 5.15V USB VBUS from 12V automotive or 24V industrial rail for peripheral charging and enumeration. IC Role / Device Role / Timing Role: Fixed-output buck regulator with precise VOUT tolerance and PG signaling for USB compliance. Use Value: Internal 1.19V reference and external resistor divider enable 5.15V ±0.5% accuracy; PG flag confirms VBUS readiness before enumeration. |
| Industrial Sensor Node Power | Portable Medical Device Supply |
Use Scenario: Powering low-power wireless sensor nodes (BLE/Zigbee) operating from LiSOCl₂ primary cells or 24V loop-powered field devices. IC Role / Device Role / Timing Role: High-efficiency step-down regulator delivering regulated 3.3V with minimal standby loss. Use Value: 1.7μA Burst Mode sleep current extends 2000mAh cell life to >15 years; 200kHz–2MHz fSW allows optimization for size vs. efficiency. | Use Scenario: Providing clean, low-noise 3.3V power to ADCs, op-amps, and Bluetooth radios in handheld diagnostic tools. IC Role / Device Role / Timing Role: Primary DC/DC converter with soft-start and low output ripple for analog-sensitive subsystems. Use Value: <15mVP-P ripple in Burst Mode eliminates need for post-regulation LDOs; SS pin enables controlled inrush limiting during battery insertion. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar buck regulator applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| LT8609SIMSE#TRPBF | Lower 2.5μA IQ, 2.5A output, integrated MOSFETs, but requires external compensation and has no PG flag | Lacks power good signaling; better suited for space-constrained 2.5A apps where sequencing is handled externally | Choose LT8609S when higher current and lower IQ are critical and PG is not required |
| TPS54332DDAR | Higher 19μA IQ, 3.5A output, 3.5V–28V input, no integrated boost diode, requires external compensation | Not suitable for 36V+ inputs or ultralow-IQ battery apps; better for cost-sensitive industrial 24V systems | Choose TPS54332 when budget constraints outweigh IQ and 38V input requirements |
Compared with LT8609SIMSE#TRPBF and TPS54332DDAR, the LT3971AIMSE#TRPBF uniquely balances 38V input capability, 2.8μA IQ, integrated boost diode driver, and PG flag-making it optimal for automotive and long-life battery-powered systems where reliability and sequencing integrity are non-negotiable.
Availability
LT3971AIMSE#TRPBF is available at Aetrix Electronics and suitable for automotive battery regulation, USB VBUS power supplies, and industrial sensor node designs requiring stable component supply across extended temperature ranges (–40°C to 125°C).
Supply support for LT3971AIMSE#TRPBF 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 its high-performance power management portfolio with rigorous automotive and industrial qualification standards.
The LT3971A product line was designed specifically for ultralow-quiescent-current buck conversion in automotive, battery-powered, and always-on embedded systems-emphasizing efficiency at microamp loads and robustness across wide input voltage ranges.
FAQ
What is the minimum input voltage required for LT3971AIMSE#TRPBF to regulate a 3.3V output?
The LT3971AIMSE#TRPBF requires a minimum input voltage of 4.3V to operate, as specified in its absolute maximum ratings and electrical characteristics. At 3.3V output, the practical minimum input depends on duty cycle limits and switching frequency: for example, at 400kHz and 125°C, VIN(MIN) ≈ 4.8V due to tOFF(MIN) constraints. Always verify against the "Minimum Input Voltage" curves in the datasheet for your specific fSW and temperature conditions. The LT3971AIMSE#TRPBF will not regulate below 4.3V regardless of load or configuration.
Does LT3971AIMSE#TRPBF support synchronization to an external clock, and what impact does it have on efficiency?
Yes, the LT3971AIMSE#TRPBF supports external clock synchronization via the SYNC pin. When SYNC is tied to an external source (250kHz–2MHz), the device enters pulse-skipping mode at light loads instead of Burst Mode, increasing quiescent current from 2.8μA to 1.5mA. This trade-off improves EMI predictability but reduces light-load efficiency significantly. For best ultralow-IQ performance, SYNC must be grounded. The LT3971AIMSE#TRPBF datasheet explicitly states that Burst Mode operation requires SYNC = GND.
Can LT3971AIMSE#TRPBF be used to generate a 5.15V USB VBUS output, and how is accuracy ensured?
Yes, the LT3971AIMSE#TRPBF can generate 5.15V USB VBUS by configuring its FB pin with a precision resistor divider (e.g., R1 = 715kΩ, R2 = 20kΩ). Its 1.19V reference has ±1.2% initial tolerance over temperature, and using 1% resistors yields ≤±1.5% total output error. For tighter accuracy, the LT3971A-5 variant (e.g., LT3971AIMSE-5#TRPBF) offers 5.00V ±0.6% and built-in 10MΩ divider-enabling 5.15V with two external 1% resistors while maintaining ±0.7% overall accuracy. The LT3971AIMSE#TRPBF itself achieves this via standard FB configuration.
What thermal considerations apply to LT3971AIMSE#TRPBF in a 1.3A continuous application?
The LT3971AIMSE#TRPBF uses a 10-lead MSOP with exposed pad (θJA = 45°C/W, θJC = 10°C/W). At 12VIN/3.3VOUT/1.3A, typical power dissipation is ~1.2W. With 2 in² of 2-oz copper connected to the exposed pad, junction temperature rise is ~54°C above ambient-well within the –40°C to 125°C operating range. Thermal relief vias (≥6x 12-mil) under the pad and minimizing SW/GND loop area are essential. Derating is required above 85°C ambient; the LT3971AIMSE#TRPBF guarantees full 1.3A output only up to 125°C junction temperature.
How does the soft-start function work on LT3971AIMSE#TRPBF, and can it be disabled?
The LT3971AIMSE#TRPBF implements soft-start by ramping the internal current limit via the SS pin: a capacitor from SS to GND creates a linear voltage ramp, which controls peak switch current during startup. The SS pin is actively discharged only when EN is low; it floats high when EN rises. To disable soft-start, leave SS unconnected (floating). For inputs >25V, a 100kΩ series resistor between SS and capacitor is recommended to limit inrush. The LT3971AIMSE#TRPBF does not require external circuitry-soft-start duration is determined solely by CSS value and internal 1μA current source.
LT3971AIMSE#TRPBF Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc.
- Series:
- -
- Package/Case:
- 10-TFSOP, 10-MSOP (0.118", 3.00mm Width) Exposed Pad
- Packaging:
- Tape & Reel (TR)
- Product Status:
- Active
- Function:
- Step-Down
- Output Configuration:
- Positive
- Topology:
- Buck
- Output Type:
- Adjustable
- Number of Outputs:
- 1
- Voltage - Input (Min):
- 4.3V
- Voltage - Input (Max):
- 38V
- Voltage - Output (Min/Fixed):
- 1.19V
- Voltage - Output (Max):
- 30V
- 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
LT3971AIMSE#TRPBF FAQ
1.How can I place an order for LT3971AIMSE#TRPBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LT3971AIMSE#TRPBF 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 LT3971AIMSE#TRPBF reliable?
The price and inventory of LT3971AIMSE#TRPBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LT3971AIMSE#TRPBF is usually 5 days.
3.What payment methods are accepted for LT3971AIMSE#TRPBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LT3971AIMSE#TRPBF transactions.
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4.How is shipping managed for LT3971AIMSE#TRPBF?
LT3971AIMSE#TRPBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LT3971AIMSE#TRPBF 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 LT3971AIMSE#TRPBF?
For technical support, including LT3971AIMSE#TRPBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LT3971AIMSE#TRPBF requirements.
6.How does Aetrix verify that LT3971AIMSE#TRPBF is sourced from the original manufacturer or authorized distributors?
All LT3971AIMSE#TRPBF 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 LT3971AIMSE#TRPBF meets industry standards.
7.What is the process for return or replacement of LT3971AIMSE#TRPBF?
All LT3971AIMSE#TRPBF units undergo pre-shipment inspection (PSI). If there is an issue with LT3971AIMSE#TRPBF, 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 LT3971AIMSE#TRPBF part is unused and in its original packaging.
Return procedure for LT3971AIMSE#TRPBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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