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Analog Devices Inc. LT3971EDD#PBF
- Part No.:
- LT3971EDD#PBF
- Manufacturer:
- Analog Devices Inc.
- Package:
- 10-WFDFN Exposed Pad
- Datasheet:
-
LT3971EDD#PBF.pdf
- Description:
- IC REG BUCK ADJ 1.2A 10DFN
- Quantity:
- Payment:
- Shipping:
Inventory:16,063
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Product details
Overview
LT3971EDD#PBF 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 used in automotive battery-powered systems requiring high efficiency at light loads.
For engineers reviewing the LT3971EDD#PBF datasheet, LT3971EDD#PBF pinout, LT3971EDD#PBF application, or LT3971EDD#PBF equivalent, key selection considerations include its 4.3V–38V input range, 1.19V–30V programmable output, Burst Mode® operation with <15mVP-P ripple, soft-start control via SS pin, and accurate 1V enable threshold with 30mV hysteresis.
Technical Context
The LT3971EDD#PBF employs a current-mode control architecture with internal compensation for fast transient response and stable loop behavior across wide line/load conditions. Its oscillator is resistor-programmable (RT pin) and synchronizable (SYNC pin), enabling precise frequency setting between 250kHz and 2MHz while maintaining low jitter in PWM mode.
Burst Mode® operation reduces no-load supply current to 2.8µA by disabling non-essential circuitry between regulated energy bursts, keeping output ripple below 15mVP-P. The integrated boost circuit drives the internal switch using a capacitor-connected BOOST pin, ensuring full saturation of the 0.33Ω NPN transistor even at high duty cycles.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Input Voltage Range | 4.3V to 38V - supports direct connection to 12V/24V/36V automotive and industrial rails without pre-regulation. |
| Max Output Current | 1.2A - sufficient for powering microcontrollers, sensors, and interface ICs in compact embedded 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, lower frequencies improve VIN/VOUT ratio tolerance. |
| Feedback Reference | 1.19V ±1.3% - sets output voltage accuracy when using external resistor divider; enables 1.19V–30V programmable VOUT. |
| Enable Threshold | 1.01V typical with 30mV hysteresis - ensures clean, noise-immune startup/shutdown control with simple resistor-divider biasing. |
| Power Good Flag | Open-drain PG asserts when VOUT reaches 91% of target - provides reliable system-level power sequencing and fault detection. |
Pinout & Package
LT3971EDD#PBF uses a 10-lead (3mm × 3mm) plastic DFN package with exposed thermal pad (Pin 11 = GND). The exposed pad must be soldered to PCB 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 internal switch drive. |
| 2 (BOOST) | Bootstrap Drive Voltage | Provides >VIN voltage to fully saturate internal NPN switch; requires external capacitor to SW and VOUT. |
| 3 (SW) | Switch Node | Drives external inductor and catch diode; carries high di/dt switching current and must be routed with minimal loop area. |
| 4 (VIN) | Main Input Supply | Supplies internal circuitry and switch; requires local ceramic bypass capacitor (≥1µF) near pin. |
| 5 (EN) | Enable Control | Hysteretic 1V threshold enables shutdown (700nA IQ) or active operation; tie to VIN if unused. |
| 6 (FB) | Feedback Input | Regulated to 1.19V; connects to resistor divider tap for programmable output voltage configuration. |
| 7 (SS) | Soft-Start Control | Capacitor-to-GND ramps peak current limit at startup; prevents inrush current and output overshoot. |
| 8 (RT) | Frequency Set | Resistor-to-GND programs switching frequency from 200kHz to 2MHz; determines inductor/capacitor sizing tradeoffs. |
| 9 (PG) | Power Good Flag | Open-drain output signals VOUT ≥91% of regulation; requires external pull-up for logic-level signaling. |
| 10 (SYNC) | External Clock Sync | Ground for Burst Mode; connect to external clock (250kHz–2MHz) for synchronized pulse-skipping operation. |
Key Features
| Feature | Design Value |
|---|---|
| Ultralow Quiescent Current | 2.8µA IQ in regulation enables >10-year battery life in always-on sensor nodes and telematics modules. |
| Low Ripple Burst Mode® | Maintains <15mVP-P output ripple at light loads while achieving >85% efficiency down to 100µA output current. |
| Integrated Boost Diode | On-die Schottky eliminates need for external boost diode, reducing BOM count and PCB footprint in space-constrained designs. |
| Internal Compensation | Eliminates external compensation network, simplifying design and improving stability across temperature and component tolerances. |
| Thermally Enhanced DFN | 3mm × 3mm DFN with exposed GND pad achieves 10°C/W junction-to-case thermal resistance for reliable 1.2A operation. |
Applications
| Automotive Body Control Module | Industrial Sensor Transmitter |
|---|---|
|
Use Scenario: Powering CAN transceiver, microcontroller, and analog front-end in under-hood body control unit operating from 12V battery with cold-crank down to 4.5V. IC Role / Device Role / Timing Role: Primary DC/DC regulator delivering stable 3.3V/5V rail; manages start-up sequencing via EN and monitors health via PG flag. Use Value: 2.8µA quiescent current prevents battery drain during vehicle sleep mode; 38V absolute max rating withstands load-dump transients. |
Use Scenario: Providing regulated 3.3V supply to 4–20mA loop-powered pressure/temperature transmitter in hazardous-area field instrumentation. IC Role / Device Role / Timing Role: Isolated auxiliary supply generator; soft-start prevents inrush into capacitive isolation barriers; PG confirms rail readiness before sensor activation. Use Value: Adjustable frequency allows optimization for low EMI in intrinsically safe designs; wide input range accommodates varying loop voltage drops. |
| Portable Medical Monitor | Smart Energy Meter |
|
Use Scenario: Powering display controller, ADC, and BLE radio in handheld patient monitor powered by rechargeable Li-ion battery. IC Role / Device Role / Timing Role: Main system regulator supporting dynamic voltage scaling; Burst Mode extends runtime during standby intervals between measurements. Use Value: 1.2A output supports burst-mode wireless transmission; low-noise operation avoids interference with sensitive analog signal chains. |
Use Scenario: Generating 3.3V rail for metrology SoC and RTC in utility-grade electricity meter with 20+ year service life requirement. IC Role / Device Role / Timing Role: Long-life primary regulator; EN pin controlled by MCU to disable during deep-sleep cycles; PG ensures clean wake-up sequence. Use Value: 700nA shutdown current minimizes self-discharge of backup supercapacitor; 125°C rated operation ensures reliability in sealed outdoor enclosures. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar buck regulator applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| LMR36520RNXR | 65V input, 2A output, 26µA IQ, fixed 2.1MHz frequency, no SYNC or PG | Lacks power-good flag and external sync; better suited for high-input-voltage industrial SMPS where ultra-low IQ is secondary | Select LMR36520RNXR when input exceeds 38V or when fixed-frequency simplicity outweighs programmability and monitoring needs |
| TPS62840DRVR | 3V–18V input, 1A output, 0.35µA IQ, 1.8MHz fixed frequency, integrated PG | Narrower input range limits use to post-regulated supplies; superior IQ but incompatible with 24V/36V direct-battery inputs | Select TPS62840DRVR only for low-voltage battery-powered devices where sub-1µA IQ is critical and VIN ≤18V |
Compared with LMR36520RNXR and TPS62840DRVR, LT3971EDD#PBF uniquely balances 38V input capability, 1.2A output, 2.8µA IQ, and full feature set (PG, SYNC, SS, RT) in a 3mm × 3mm DFN-making it optimal for automotive and industrial systems needing robustness, longevity, and design flexibility.
Availability
LT3971EDD#PBF is available at Aetrix Electronics and suitable for automotive battery regulation, industrial sensor power supplies, and portable medical electronics requiring stable component supply across extended temperature ranges (–40°C to 125°C).
Supply support for LT3971EDD#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 its legacy of high-performance power management ICs with rigorous automotive and industrial qualification standards.
The LT3971 product line was designed for demanding off-battery and wide-input industrial power conversion, emphasizing ultralow quiescent current, fault resilience, and thermal efficiency in compact packages.
FAQ
What is the minimum input voltage required for LT3971EDD#PBF to regulate a 3.3V output?
The LT3971EDD#PBF requires a minimum input voltage of 4.3V for accurate feedback regulation, as specified in its Absolute Maximum Ratings and Electrical Characteristics tables. Below this, the FB pin reference may drift, and the internal switch cannot sustain proper duty cycle. For a 3.3V output, the practical dropout is higher-typically ~4.8V at full load-due to switch VCE(SAT) and diode forward drop. Always verify minimum VIN using the formula VIN(MIN) = (VOUT + VD) / (1 − fSWtOFF(MIN)) − VD + VSW for your chosen frequency and temperature.
Can LT3971EDD#PBF be synchronized to an external clock, and what impact does that have on quiescent current?
Yes, LT3971EDD#PBF supports external synchronization via the SYNC pin, accepting clocks from 250kHz to 2MHz. However, when synchronized, the device operates in 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 sacrifices battery life. For ultralow-IQ applications, ground the SYNC pin to retain Burst Mode® operation and its associated efficiency benefits.
How does the soft-start function work on LT3971EDD#PBF, and what capacitor value is recommended?
The LT3971EDD#PBF implements soft-start by ramping the internal current limit via the SS pin. A capacitor from SS to GND creates a linear voltage ramp that controls inrush current during startup. A typical value is 1nF, yielding ~1ms soft-start time; larger values (e.g., 10nF) extend ramp time for highly capacitive loads. For input voltages above 25V, add a 100kΩ series resistor to limit SS pin current. Do not float SS unless soft-start is intentionally disabled.
What is the purpose of the BD pin on LT3971EDD#PBF, and how should it be connected?
The BD (Boost Diode) pin on LT3971EDD#PBF connects to the anode of the external Schottky diode used in the bootstrap circuit. It must be tied directly to the VOUT node-never left floating or connected elsewhere. This connection completes the charge path for the BOOST capacitor during switch off-time, ensuring sufficient gate drive voltage for the internal NPN switch. Incorrect BD routing causes poor regulation, excessive heat, or startup failure.
Does LT3971EDD#PBF require an external feedback resistor divider, and what is the internal reference voltage?
Yes, LT3971EDD#PBF requires an external resistor divider from VOUT to GND with the tap connected to the FB pin. The internal reference voltage is 1.19V ±1.3%, and output voltage is calculated as VOUT = 1.19V × (1 + R1/R2). Use ≥1MΩ total divider resistance to minimize load on the output and preserve ultralow quiescent current. The LT3971EDD#PBF does not contain internal feedback resistors-those are only present in the fixed-output variants (e.g., LT3971EDD-3.3#PBF).
LT3971EDD#PBF Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc.
- Series:
- -
- Package/Case:
- 10-WFDFN Exposed Pad
- Packaging:
- Tube
- 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)
LT3971EDD#PBF FAQ
1.How can I place an order for LT3971EDD#PBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LT3971EDD#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 LT3971EDD#PBF reliable?
The price and inventory of LT3971EDD#PBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LT3971EDD#PBF is usually 5 days.
3.What payment methods are accepted for LT3971EDD#PBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LT3971EDD#PBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LT3971EDD#PBF?
LT3971EDD#PBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LT3971EDD#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 LT3971EDD#PBF?
For technical support, including LT3971EDD#PBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LT3971EDD#PBF requirements.
6.How does Aetrix verify that LT3971EDD#PBF is sourced from the original manufacturer or authorized distributors?
All LT3971EDD#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 LT3971EDD#PBF meets industry standards.
7.What is the process for return or replacement of LT3971EDD#PBF?
All LT3971EDD#PBF units undergo pre-shipment inspection (PSI). If there is an issue with LT3971EDD#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 LT3971EDD#PBF part is unused and in its original packaging.
Return procedure for LT3971EDD#PBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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