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Analog Devices Inc. LT3971IDD#TRPBF
- Part No.:
- LT3971IDD#TRPBF
- Manufacturer:
- Analog Devices Inc.
- Package:
- 10-WFDFN Exposed Pad
- Datasheet:
-
LT3971IDD#TRPBF.pdf
- Description:
- IC REG BUCK ADJ 1.2A 10DFN
- Quantity:
- Payment:
- Shipping:
Inventory:1,674
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Product details
Overview
LT3971IDD#TRPBF from Analog Devices (formerly Linear Technology) is a 38V, 1.2A monolithic synchronous step-down regulator in a thermally enhanced 10-lead (3mm × 3mm) DFN package with exposed pad. It delivers ultralow 2.8µA quiescent current in regulation, supports adjustable switching frequency from 200kHz to 2MHz via RT pin, and integrates a 0.33Ω bipolar NPN switch, boost Schottky diode, and power good flag. It is designed for automotive battery regulation and portable industrial power supplies requiring wide VIN (4.3V–38V) and high light-load efficiency.
For engineers reviewing the LT3971IDD#TRPBF datasheet, LT3971IDD#TRPBF pinout, LT3971IDD#TRPBF application, or LT3971IDD#TRPBF equivalent, key selection criteria include its 2.8µA no-load IQ, 91% VOUT power-good threshold, internal compensation, soft-start capability via SS pin, and compatibility with low-leakage Schottky catch diodes to maintain sub-15mV output ripple in Burst Mode operation.
Technical Context
The LT3971IDD#TRPBF implements constant-frequency current-mode control with internal slope compensation and an actively clamped VC node for fast transient response and loop stability. Its oscillator frequency is set by an external RT-to-GND resistor and is synchronizable externally via the SYNC pin - though grounding SYNC enables low-ripple Burst Mode, while synchronization triggers pulse-skipping and raises quiescent current to 1.5mA at light loads.
It uses a bipolar NPN main switch driven from either VIN or BOOST, where the BOOST pin voltage must exceed SW by ≥1.4V to ensure full saturation. The EN pin features a precise 1.005V rising threshold with 30mV hysteresis, and shutdown reduces input current to 700nA. Power good (PG) signals when FB reaches 91% of regulation voltage and remains valid only when VIN > 4.3V and EN is high.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Input Voltage Range | 4.3V to 38V - supports direct connection to 12V/24V automotive batteries and industrial rails without pre-regulation. |
| Max Output Current | 1.2A - sufficient for powering microcontrollers, sensors, and communication ICs in compact systems. |
| Quiescent Current | 2.8µA at no load - enables multi-year battery life in always-on IoT and telematics applications. |
| Switching Frequency | 200kHz to 2MHz - adjustable via RT resistor; higher frequencies allow smaller magnetics but reduce max VIN/VOUT ratio. |
| Feedback Reference | 1.19V ±1.3% over temperature - sets output voltage accuracy for external resistor dividers or fixed variants. |
| Power Good Threshold | 91% of regulated VOUT - provides reliable system reset signaling with 20mV hysteresis. |
| Shutdown Current | 700nA - enables deep-sleep modes in energy-harvesting and wake-on-event designs. |
Pinout & Package
LT3971IDD#TRPBF is housed in a 10-lead (3mm × 3mm) plastic DFN package with exposed thermal pad (Pin 11), which must be soldered to PCB ground for optimal thermal performance (θJA = 45°C/W, θJC = 10°C/W).
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1 BD | Boost Diode Anode | Connects to cathode of external Schottky diode; forms bootstrap path for BOOST drive. |
| 2 BOOST | Bootstrap Drive | Supplies elevated gate drive to internal NPN switch; requires capacitor to SW. |
| 3 SW | Switch Node | Output of internal power switch; connects to inductor, catch diode, and BOOST capacitor. |
| 4 VIN | Main Input Supply | Provides power to internal circuitry and switch; must be locally bypassed with ceramic capacitor. |
| 5 EN | Enable Control | Hysteretic input (1.005V rise, 0.975V fall); pulls device into 700nA shutdown when low. |
| 6 FB | Feedback Sense | Regulated to 1.19V; connects to resistor divider tap for adjustable output voltage. |
| 7 SS | Soft-Start Ramp | Controls inrush current via external capacitor; ramp rate determines startup dI/dt. |
| 8 RT | Frequency Set | Resistor-to-GND sets switching frequency from 200kHz to 2MHz per datasheet table. |
| 9 PG | Power Good Flag | Open-drain output active-high when VOUT reaches 91% of target; requires pull-up resistor. |
| 10 SYNC | External Clock Sync | Ground for Burst Mode; tie to clock source for synchronization (increases IQ to 1.5mA at light load). |
Key Features
| Feature | Design Value |
|---|---|
| Ultralow Quiescent Current | 2.8µA IQ in regulation enables >10-year battery life in always-on sensor nodes. |
| Low-Ripple Burst Mode | Maintains <15mVP-P output ripple at light loads while sustaining high efficiency down to µA-level output currents. |
| Integrated Boost Diode | On-die Schottky eliminates external boost diode, reducing BOM count and layout area in space-constrained designs. |
| Internal Compensation | Eliminates need for external compensation network - simplifies design and improves robustness across operating conditions. |
| Thermally Enhanced DFN | 3mm × 3mm DFN with exposed GND pad achieves θJC = 10°C/W - supports 1.2A continuous output without heatsink. |
Applications
| Automotive Body Control Module | Industrial IoT Sensor Node |
|---|---|
Use Scenario: Powering CAN transceiver, microcontroller, and LIN interface from 12V battery rail with cold-crank tolerance down to 4.3V. IC Role / Device Role / Timing Role: Primary buck regulator delivering stable 3.3V/5V supply; manages start-up under low-VIN transients and maintains regulation during load dumps. Use Value: 2.8µA quiescent current prevents battery drain during vehicle sleep mode; PG flag enables safe MCU reset sequencing. | Use Scenario: Long-life remote environmental monitor powered by coin cell or energy harvester, requiring multi-year operation. IC Role / Device Role / Timing Role: Main system regulator enabling ultra-low-power sleep states; Burst Mode minimizes average current draw while maintaining output regulation. Use Value: Sub-15mV ripple ensures clean analog sensor readings; soft-start prevents inrush-induced brownouts in weak-source systems. |
| Portable Medical Diagnostic Device | Rail-to-Rail Industrial PLC I/O Module |
Use Scenario: Battery-powered handheld ultrasound or glucose meter needing reliable 3.3V supply across varying battery SOC (8V–32V). IC Role / Device Role / Timing Role: High-efficiency step-down converter with fast transient response to handle pulsed RF or ADC loads. Use Value: 1.2A output supports peak-current peripherals; internal compensation ensures stable loop behavior without tuning. | Use Scenario: DIN-rail mounted controller supplying isolated logic rails from unregulated 24V industrial bus with EMI constraints. IC Role / Device Role / Timing Role: Pre-regulator feeding downstream LDOs or isolated DC/DC; operates continuously across wide ambient temperature range (–40°C to 125°C). Use Value: Wide 4.3V–38V input handles brownouts and surges; exposed-pad DFN ensures thermal reliability in sealed enclosures. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar step-down regulator applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| LTC3630EMS#TRPBF | Lower 3.6V min VIN; 100mA max output; integrated MOSFETs; no BOOST pin or external diode support. | Better suited for low-current, low-VIN point-of-load applications; lacks automotive-grade input range and high-current capability. | Select when output current ≤100mA and input never exceeds 20V; not drop-in for LT3971IDD#TRPBF's 1.2A/38V use cases. |
| TPS54202DRCT | 2.5V–17V input; 2A output; 500kHz–2.2MHz sync-capable; 25µA IQ in Eco-mode; no integrated boost diode. | Higher IQ than LT3971IDD#TRPBF at light loads; requires external bootstrap diode; lower max VIN limits automotive use. | Prefer for cost-sensitive consumer applications with ≤17V input; avoid where 38V surge immunity or sub-3µA IQ is required. |
Compared with LTC3630EMS#TRPBF and TPS54202DRCT, the LT3971IDD#TRPBF uniquely combines 38V input tolerance, 1.2A output, and 2.8µA quiescent current in a thermally optimized DFN - making it the only viable choice for high-reliability, wide-input, ultra-low-power industrial and automotive buck conversion.
Availability
LT3971IDD#TRPBF is available at Aetrix Electronics and suitable for automotive body control modules, industrial IoT sensor nodes, portable medical diagnostic devices, and rail-to-rail industrial PLC I/O modules requiring stable component supply across extended temperature and long product lifecycles.
Supply support for LT3971IDD#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 legacy of high-performance power management ICs with rigorous automotive and industrial qualification.
The LT3971 product line was engineered for wide-input, ultralow-IQ DC/DC conversion in harsh environments - targeting automotive battery regulation, portable instrumentation, and always-on industrial monitoring systems.
FAQ
What is the minimum input voltage required for LT3971IDD#TRPBF to regulate a 3.3V output?
The LT3971IDD#TRPBF requires a minimum input voltage of 4.3V to maintain accurate feedback regulation. Below this, the internal error amplifier cannot sustain regulation - even if the duty cycle would theoretically support lower VIN. For reliable 3.3V output startup and dropout behavior, ensure VIN stays above 4.3V under all operating conditions, including cold-crank events. This specification is explicitly guaranteed across the full –40°C to 125°C junction temperature range.
Can LT3971IDD#TRPBF operate without an external catch diode?
No, the LT3971IDD#TRPBF requires an external Schottky catch diode connected between SW and VOUT. While it integrates an on-die boost Schottky diode (BD pin), the main power path relies on an external diode to conduct inductor current during switch-off periods. Omitting it will cause catastrophic failure due to unclamped inductive kickback. Use a low-leakage (<1µA reverse current) Schottky diode such as DFLS2100 to preserve the 2.8µA quiescent current performance.
How does the SYNC pin affect efficiency and noise performance in LT3971IDD#TRPBF?
Grounding the SYNC pin enables low-ripple Burst Mode operation, achieving 2.8µA quiescent current and <15mVP-P output ripple at light loads. Connecting SYNC to an external clock forces pulse-skipping mode, raising quiescent current to 1.5mA and increasing output ripple - beneficial only when deterministic switching is required for EMI filtering. For maximum efficiency and lowest noise, SYNC must remain grounded; floating or pulling high is undefined and may cause erratic behavior.
What is the purpose of the SS pin on LT3971IDD#TRPBF, and how is it configured?
The SS (soft-start) pin on LT3971IDD#TRPBF controls inrush current by ramping the internal current limit during startup. A capacitor from SS to GND sets the ramp time - typical values range from 1nF to 10nF depending on desired dI/dt. The SS pin is only actively discharged when EN is low; it floats high when EN goes high. For inputs >25V, add a 100kΩ series resistor to prevent overstress. Leaving SS unconnected disables soft-start, risking high peak inductor current at turn-on.
Does LT3971IDD#TRPBF support adjustable output voltage, and what is the feedback reference voltage?
Yes, the LT3971IDD#TRPBF supports fully adjustable output voltage from 1.19V to 30V using an external resistor divider on the FB pin. Its internal reference is precisely trimmed to 1.19V ±1.3% over temperature, enabling high-accuracy regulation. The standard formula applies: R1 = R2 × ((VOUT / 1.19V) − 1). For best light-load efficiency, use MΩ-range resistors (e.g., 1MΩ + 182kΩ for 3.3V) and add a 10pF phase-lead capacitor from FB to VOUT to stabilize the loop.
LT3971IDD#TRPBF Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc.
- Series:
- -
- Package/Case:
- 10-WFDFN 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-DFN (3x3)
LT3971IDD#TRPBF FAQ
1.How can I place an order for LT3971IDD#TRPBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LT3971IDD#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 LT3971IDD#TRPBF reliable?
The price and inventory of LT3971IDD#TRPBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LT3971IDD#TRPBF is usually 5 days.
3.What payment methods are accepted for LT3971IDD#TRPBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LT3971IDD#TRPBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LT3971IDD#TRPBF?
LT3971IDD#TRPBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LT3971IDD#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 LT3971IDD#TRPBF?
For technical support, including LT3971IDD#TRPBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LT3971IDD#TRPBF requirements.
6.How does Aetrix verify that LT3971IDD#TRPBF is sourced from the original manufacturer or authorized distributors?
All LT3971IDD#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 LT3971IDD#TRPBF meets industry standards.
7.What is the process for return or replacement of LT3971IDD#TRPBF?
All LT3971IDD#TRPBF units undergo pre-shipment inspection (PSI). If there is an issue with LT3971IDD#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 LT3971IDD#TRPBF part is unused and in its original packaging.
Return procedure for LT3971IDD#TRPBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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