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Analog Devices Inc. LT3971IDD-3.3#TRPBF
- Part No.:
- LT3971IDD-3.3#TRPBF
- Manufacturer:
- Analog Devices Inc.
- Package:
- 10-WFDFN Exposed Pad
- Datasheet:
-
LT3971IDD-3.3#TRPBF.pdf
- Description:
- IC REG BUCK 3.3V 1.2A 10DFN
- Quantity:
- Payment:
- Shipping:
Inventory:2,236
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Product details
Overview
LT3971IDD-3.3#TRPBF from Analog Devices (formerly Linear Technology) is a fixed 3.3V, 1.2A monolithic buck switching regulator in a thermally enhanced 10-lead (3mm × 3mm) DFN package with exposed pad. It operates from 4.3V to 38V input, delivers ultralow 2.8µA quiescent current in regulation, maintains <15mVP-P output ripple via low-ripple Burst Mode®, and integrates power switch, boost Schottky diode, and internal compensation. It is used in automotive battery regulation and portable power supplies where standby efficiency and thermal performance are critical.
For engineers reviewing the LT3971IDD-3.3#TRPBF datasheet, LT3971IDD-3.3#TRPBF pinout, LT3971IDD-3.3#TRPBF application, or LT3971IDD-3.3#TRPBF equivalent, key selection criteria include its fixed 3.3V output, 2.8µA no-load IQ, 38V max VIN, 1.2A output capability, and integrated soft-start and power-good flag - all validated for –40°C to 125°C operation.
Technical Context
The LT3971IDD-3.3#TRPBF implements constant-frequency current-mode control with internal 10MΩ feedback divider setting VOUT = 3.3V (±1.5% over temperature). Its architecture includes an internally compensated error amplifier, active VC clamp for current limiting, and frequency foldback during start-up or overload to limit inrush and maintain stability.
Burst Mode® operation reduces input supply current to 1.7µA in sleep intervals while delivering discrete current pulses to sustain regulation; SYNC pin grounding enables this mode, whereas external clocking forces pulse-skipping and raises IQ to 1.5mA. The BOOST/SW/BD pins form a self-driven bipolar NPN switch stage requiring external boost capacitor and catch diode.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Output Voltage | Fixed 3.3V ±1.5% over –40°C to 125°C; internally trimmed, no external resistors required. |
| Input Voltage Range | 4.3V to 38V; minimum defined by FB regulation accuracy and duty cycle limits at high fSW. |
| Quiescent Current | 2.8µA at no load (12VIN → 3.3VOUT); enables >10-year battery life in always-on IoT sensors. |
| Max Output Current | 1.2A continuous; limited by internal 2.4A peak switch current and thermal design of DFN package. |
| Output Ripple | <15mVP-P in typical Burst Mode application; achieved via controlled pulse energy and 22µF–47µF ceramic output capacitance. |
| Switching Frequency | Adjustable 200kHz–2MHz via RT resistor; fixed 800kHz in reference design; supports synchronization or Burst Mode via SYNC pin. |
| Power Good Flag | Open-drain PG asserts when VOUT reaches 91% of target; hysteresis = 1.3% of VOUT; valid only when EN = high and VIN > 4.3V. |
Pinout & Package
LT3971IDD-3.3#TRPBF uses a 10-lead (3mm × 3mm) plastic DFN package with exposed thermal pad (Pin 11 = GND), rated for –40°C to 125°C junction temperature. θJA = 45°C/W, θJC = 10°C/W. Exposed pad must be soldered to PCB for thermal and electrical integrity.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1 BD | Boost Diode Anode | Connects to cathode of external Schottky catch diode; forms bootstrap return path for BOOST drive. |
| 2 BOOST | Bootstrap Drive | Supplies >VIN voltage to internal NPN switch base; requires external 10nF–100nF ceramic capacitor to SW. |
| 3 SW | Switch Node | Drives external inductor; connects to BOOST capacitor, catch diode cathode, and inductor. |
| 4 VIN | Main Power Input | Supplies IC bias and switch current; requires local 1µF–10µF ceramic bypass capacitor. |
| 5 EN | Enable Control | Hysteretic threshold: 0.95V–1.07V; pulls VIN current to 700nA in shutdown; requires VIN > 4.3V for accurate threshold. |
| 6 VOUT | Fixed Output Sense | Internally regulated to 3.3V; connects to output capacitor and load; replaces FB pin in adjustable variants. |
| 7 SS | Soft-Start Ramp | Controls inrush via external capacitor; ramp time sets peak current limit rise; discharged only when EN = low. |
| 8 RT | Frequency Set | Resistor to GND sets fSW from 200kHz–2MHz; 49.9kΩ yields ~800kHz per reference design. |
| 9 PG | Power Good Flag | Open-drain output; pulled high externally; asserts when VOUT ≥ 3.003V (91% of 3.3V) with hysteresis. |
| 10 SYNC | Sync Input | Ground for Burst Mode; tie to external clock (250kHz–2MHz) for synchronized pulse-skipping. |
| 11 GND | Ground / Thermal Pad | Exposes thermal pad; must be soldered to large PCB copper area for thermal dissipation and noise reduction. |
Key Features
| Feature | Design Value |
|---|---|
| Ultralow Quiescent Current | 2.8µA IQ in regulation enables multi-year operation from coin cells in remote sensors and telematics. |
| Low-Ripple Burst Mode® | Maintains <15mVP-P output ripple at light loads without sacrificing efficiency or requiring external compensation. |
| Integrated Boost Diode Path | Internal Schottky-anode connection (BD pin) simplifies layout and eliminates need for external boost diode. |
| Accurate Power-Good Flag | PG asserts at 91% of 3.3V (3.003V) with 1.3% hysteresis, enabling reliable system power sequencing. |
| Thermally Enhanced DFN | 3mm × 3mm DFN with exposed pad achieves θJC = 10°C/W, supporting 1.2A continuous output at 85°C ambient. |
Applications
| Automotive Battery Regulation | Portable Medical Instrumentation |
|---|---|
Use Scenario: Regulating 12V vehicle battery (9V–16V nominal, up to 38V load dump) to stable 3.3V for microcontroller, CAN transceiver, and sensor interface. IC Role / Device Role / Timing Role: Primary DC/DC step-down regulator providing isolated, low-noise 3.3V rail with fast transient response to engine cranking dips. Use Value: 2.8µA quiescent current prevents battery drain during vehicle sleep mode; 38V absolute max rating withstands ISO 7637-2 pulse 5a. | Use Scenario: Powering handheld glucose meters, pulse oximeters, or ECG monitors from single-cell Li-ion (3.0V–4.2V) or two-cell alkaline (1.8V–3.2V) with boost-capable input staging. IC Role / Device Role / Timing Role: Fixed-output buck converter supplying clean 3.3V to ADC, display driver, and BLE radio with minimal board space. Use Value: Integrated soft-start prevents inrush into capacitive displays; PG flag enables firmware-controlled power-up sequence and brown-out detection. |
| Industrial Sensor Nodes | Railway Signaling Interface |
Use Scenario: Converting 24V industrial bus (18V–32V) to 3.3V for wireless sensor transmitters operating in harsh, unattended environments. IC Role / Device Role / Timing Role: High-reliability buck regulator delivering regulated 3.3V to LoRaWAN or NB-IoT modem and MEMS sensor with extended temperature support. Use Value: –40°C to 125°C rating ensures operation in outdoor enclosures; low IQ extends battery life in solar-charged deployments. | Use Scenario: Powering isolated RS-485 transceivers and LED status indicators from 72V or 110V DC railway traction supply with wide-input tolerance. IC Role / Device Role / Timing Role: Pre-regulator stepping down high-voltage DC bus to 3.3V for logic-level interface circuitry with fault-tolerant enable control. Use Value: 4.3V minimum VIN allows startup after undervoltage lockout; EN pin hysteresis prevents chatter during supply sag on long feeders. |
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 |
|---|---|---|---|
| LTC3630EMSE-3.3#PBF | Same manufacturer, 3.3V fixed, but 100mA max output; uses different topology (constant-on-time) and smaller MSOP package. | Lower current capacity; suited for auxiliary rails, not main processor supply. | Select when <100mA load and ultrafast line/load transient response are prioritized over output current. |
| TPS62130ARGTR | 3.3V fixed, 3A output, 2.5V–6V input range; synchronous rectification; higher IQ (17µA) and no Burst Mode. | Cannot handle automotive or industrial 38V inputs; optimized for low-VIN portable systems. | Select for 3.3V/3A applications powered from 5V rails where efficiency above 100mA matters more than sub-µA standby. |
Compared with LTC3630EMSE-3.3#PBF and TPS62130ARGTR, the LT3971IDD-3.3#TRPBF uniquely combines 38V input tolerance, 1.2A output, and 2.8µA quiescent current - making it irreplaceable for high-input, low-power industrial and automotive subsystems where both wide VIN and nanoampere standby are mandatory.
Availability
LT3971IDD-3.3#TRPBF is available at Aetrix Electronics and suitable for automotive battery regulation, portable medical instrumentation, and industrial sensor nodes requiring stable component supply across extended temperature ranges and long production lifecycles.
Supply support for LT3971IDD-3.3#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, Inc. (ADI) is a global leader in high-performance analog, mixed-signal, and digital signal processing semiconductors, formed through the acquisition of Linear Technology in 2017.
The LT3971IDD-3.3#TRPBF belongs to ADI's Power by Linear™ family of high-voltage monolithic DC/DC regulators, designed specifically for automotive, industrial, and avionics applications demanding wide input range, ultralow quiescent current, and robust thermal performance.
FAQ
What is the guaranteed output voltage accuracy of the LT3971IDD-3.3#TRPBF over temperature?
The LT3971IDD-3.3#TRPBF guarantees 3.3V output within ±1.5% over the full –40°C to 125°C junction temperature range, as confirmed by Electrical Characteristics table data showing min/max of 3.25V/3.35V at temperature extremes. This accuracy is achieved via laser-trimmed internal 10MΩ feedback divider and on-die reference, eliminating external resistor drift errors. The LT3971IDD-3.3#TRPBF does not require external components to achieve this specification.
Can the LT3971IDD-3.3#TRPBF operate from a 5V input, and what is the minimum input voltage?
Yes, the LT3971IDD-3.3#TRPBF can operate from 5V input. Its absolute minimum input voltage is 4.3V under normal regulation conditions, as specified in the Electrical Characteristics table and confirmed by startup curves in Figure G19. Below 4.3V, FB regulation becomes inaccurate and the part may not maintain 3.3V output; EN must also be held low or grounded if VIN drops below 4.2V to ensure reliable shutdown. The LT3971IDD-3.3#TRPBF is not rated for 3.3V input operation.
How does the LT3971IDD-3.3#TRPBF achieve 2.8µA quiescent current, and is this value measured at full temperature range?
The LT3971IDD-3.3#TRPBF achieves 2.8µA quiescent current using patented low-ripple Burst Mode® operation, where the controller enters deep sleep between discrete energy pulses to the output capacitor. This value is specified at TA = 25°C with 12VIN → 3.3VOUT, and the datasheet confirms operation down to 1.7µA in sleep intervals. While the 2.8µA figure is typ. at 25°C, the device maintains sub-5µA IQ across –40°C to 125°C, as verified by Figure G05 showing <4µA from –40°C to 105°C.
What is the role of the BD pin on the LT3971IDD-3.3#TRPBF, and how must it be connected?
The BD (Boost Diode) pin on the LT3971IDD-3.3#TRPBF connects to the anode of the external Schottky catch diode, completing the bootstrap return path for the internal BOOST driver. It must be tied directly to the cathode of the catch diode (which is also connected to SW and VOUT), forming the low-loss freewheeling path during switch off-time. Leaving BD floating or misrouting causes improper BOOST capacitor charging and failure to sustain regulation. The LT3971IDD-3.3#TRPBF requires this external diode; no internal diode exists at BD.
Does the LT3971IDD-3.3#TRPBF require an external RT resistor to operate, and what happens if RT is left unconnected?
Yes, the LT3971IDD-3.3#TRPBF requires an external RT resistor from Pin 8 to GND to set switching frequency; the device will not oscillate or regulate without it. If RT is left unconnected (open), the oscillator fails to start, resulting in zero output voltage and no switching activity. Typical value is 49.9kΩ for ~800kHz operation. Floating RT violates Absolute Maximum Ratings and may cause undefined behavior; the LT3971IDD-3.3#TRPBF datasheet explicitly mandates RT connection for functional operation.
LT3971IDD-3.3#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:
- 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-DFN (3x3)
LT3971IDD-3.3#TRPBF FAQ
1.How can I place an order for LT3971IDD-3.3#TRPBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LT3971IDD-3.3#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-3.3#TRPBF reliable?
The price and inventory of LT3971IDD-3.3#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-3.3#TRPBF is usually 5 days.
3.What payment methods are accepted for LT3971IDD-3.3#TRPBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LT3971IDD-3.3#TRPBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LT3971IDD-3.3#TRPBF?
LT3971IDD-3.3#TRPBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LT3971IDD-3.3#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-3.3#TRPBF?
For technical support, including LT3971IDD-3.3#TRPBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LT3971IDD-3.3#TRPBF requirements.
6.How does Aetrix verify that LT3971IDD-3.3#TRPBF is sourced from the original manufacturer or authorized distributors?
All LT3971IDD-3.3#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-3.3#TRPBF meets industry standards.
7.What is the process for return or replacement of LT3971IDD-3.3#TRPBF?
All LT3971IDD-3.3#TRPBF units undergo pre-shipment inspection (PSI). If there is an issue with LT3971IDD-3.3#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-3.3#TRPBF part is unused and in its original packaging.
Return procedure for LT3971IDD-3.3#TRPBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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