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Analog Devices Inc. LT3971IDD#PBF
- Part No.:
- LT3971IDD#PBF
- Manufacturer:
- Analog Devices Inc.
- Package:
- 10-WFDFN Exposed Pad
- Datasheet:
-
LT3971IDD#PBF.pdf
- Description:
- IC REG BUCK ADJ 1.2A 10DFN
- Quantity:
- Payment:
- Shipping:
Inventory:497
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Product details
Overview
LT3971IDD#PBF from Analog Devices (formerly Linear Technology) is a 38V input, 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 features integrated boost Schottky diode, power good flag, and soft-start. It is designed for automotive battery regulation and portable power systems requiring high efficiency at light loads.
For engineers reviewing the LT3971IDD#PBF datasheet, LT3971IDD#PBF pinout, LT3971IDD#PBF application, or LT3971IDD#PBF equivalent, key selection criteria include its 4.3V–38V input range, 1.19V feedback reference, 91% power-good threshold accuracy, and Burst Mode operation enabling <15mVP-P output ripple at no load - critical for always-on industrial and automotive subsystems.
Technical Context
The LT3971IDD#PBF implements constant-frequency current-mode control with internal compensation, enabling fast transient response and stable loop behavior across wide input/output conditions. Its bipolar NPN main switch (0.33Ω typical RCE(SAT)) is driven by an on-chip BOOST circuit that requires external capacitor biasing to exceed VIN - essential for full saturation at high duty cycles.
Burst Mode operation is activated automatically below ~92mA load, reducing supply current to 1.7µA during sleep intervals while maintaining regulation; SYNC pin grounding is mandatory for this mode. Frequency foldback occurs when FB voltage drops during startup or overload, limiting peak inductor current and preventing instability.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Input Voltage Range | 4.3V to 38V - supports direct connection to 12V/24V/36V automotive batteries without pre-regulation. |
| Quiescent Current | 2.8µA at no load - enables multi-year battery life in always-on telematics or sensor nodes. |
| Max Output Current | 1.2A continuous - sufficient for powering microcontrollers, CAN transceivers, and analog front-ends. |
| Switching Frequency | 200kHz to 2MHz (RT-programmable) - allows tradeoff between inductor size (e.g., 4.7µH @ 800kHz) and efficiency. |
| Feedback Reference | 1.19V ±15mV over temperature - sets output voltage accuracy when using external resistor divider. |
| Power Good Threshold | 91% of regulated VOUT - provides reliable system reset signaling with 20mV hysteresis. |
| Shutdown Current | 700nA - ensures negligible drain during deep sleep or vehicle ignition-off states. |
Pinout & Package
LT3971IDD#PBF uses a 10-lead (3mm × 3mm) plastic DFN package with exposed thermal pad (Pin 11 = GND), optimized for low θJA = 45°C/W and high power density in space-constrained layouts.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1 BD | Boost Diode Anode | Connects to cathode of external Schottky diode; forms bootstrap path for high-side drive. |
| 2 BOOST | Bootstrap Drive Voltage | Supplies >VIN voltage to internal NPN switch base; requires external capacitor to SW. |
| 3 SW | Switch Node | Drives inductor; connects to BOOST capacitor and catch diode cathode. |
| 4 VIN | Main Power Input | Supplies IC bias and switch current; must be locally bypassed with ≥1µF ceramic. |
| 5 EN | Enable Control | Hysteretic 1.005V rising / 0.975V falling threshold; pulls to GND for shutdown (700nA IQ). |
| 6 FB | Feedback Input | Regulated to 1.19V; connects to resistor divider tap for adjustable output voltage. |
| 7 SS | Soft-Start Control | Capacitor-to-GND ramps peak current limit; prevents inrush; floats to disable. |
| 8 RT | Frequency Set | Resistor-to-GND programs switching frequency (e.g., 49.9kΩ = 800kHz). |
| 9 PG | Power Good Flag | Open-drain output active low until VOUT reaches 91% of target; requires pull-up. |
| 10 SYNC | External Clock Sync | Ground for Burst Mode; tie to clock source for synchronization (increases IQ to 1.5mA). |
| 11 GND | Ground / Exposed Pad | Primary thermal and electrical ground; exposed pad must be soldered to PCB plane. |
Key Features
| Feature | Design Value |
|---|---|
| Ultralow Quiescent Current | 2.8µA regulating 12VIN to 3.3VOUT - extends battery runtime in infotainment standby and ADAS sensors. |
| Low Ripple Burst Mode | Output ripple <15mVP-P at no load - eliminates need for post-regulation LDOs in noise-sensitive analog rails. |
| Integrated Boost Schottky | On-die 770mV forward drop at 100mA - reduces BOM count and improves reliability vs. discrete boost diodes. |
| Accurate Enable Threshold | 1.01V ±30mV hysteresis - enables clean power sequencing with standard logic-level GPIOs. |
| Internal Compensation | No external compensation components required - simplifies layout and accelerates design validation. |
| Thermally Enhanced DFN | θJC = 10°C/W - supports 1.2A continuous output at TJ ≤ 125°C with minimal copper area. |
Applications
| Automotive Body Control Module (BCM) | Industrial IoT Sensor Node |
|---|---|
Use Scenario: Powering CAN transceiver, microcontroller, and LIN interface from 12V battery with ignition-off current budget <10µA. IC Role / Device Role / Timing Role: Primary buck regulator providing stable 3.3V rail; manages enable sequencing via vehicle wake-up signal. Use Value: 2.8µA quiescent current ensures compliance with ISO 16750-2 parasitic load limits; PG flag validates rail readiness before MCU boot. |
Use Scenario: Battery-powered vibration sensor transmitting data every 5 minutes via LoRaWAN. IC Role / Device Role / Timing Role: Main power converter delivering 3.3V to MCU and RF IC; enters Burst Mode between transmissions. Use Value: 1.7µA sleep current extends 2xAA alkaline battery life beyond 5 years; RT-programmable frequency optimizes inductor size for enclosure height. |
| Portable Medical Monitor | Railway Onboard Telematics |
Use Scenario: ECG front-end powered from rechargeable Li-ion with strict EMI requirements. IC Role / Device Role / Timing Role: Low-noise 3.3V supply; operates in fixed-frequency PWM above 500kHz to avoid sensitive audio bands. Use Value: Adjustable frequency avoids interference with ADC sampling clocks; integrated BOOST diode eliminates discrete component EMI source. |
Use Scenario: GPS/GSM module operating across 24V–110V DC train battery with cold-cranking dips to 6V. IC Role / Device Role / Timing Role: Wide-input buck regulator supporting 4.3V minimum start-up; PG signals valid rail after brown-out recovery. Use Value: 38V absolute max rating withstands load-dump transients; 91% PG threshold ensures deterministic system reset timing. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar step-down regulator applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| LMR36520RNXR | 65V input, 2A output, 26µA IQ, 1.2V reference, no integrated BOOST diode | Higher input voltage capability but higher quiescent current; requires external bootstrap diode | Choose for 48V industrial systems where 38V limit is insufficient; avoid if ultralow IQ is critical. |
| TPS62840DRVR | 6V input max, 1A output, 0.15µA IQ, 0.8V reference, DCS-Control topology | Far lower IQ but incompatible with automotive battery inputs; no BOOST circuit | Choose only for single-cell Li-ion or USB-powered devices; not suitable for LT3971IDD#PBF's 4.3–38V range. |
Compared with LMR36520RNXR and TPS62840DRVR, the LT3971IDD#PBF uniquely balances 38V operation, 2.8µA quiescent current, and integrated BOOST functionality - making it irreplaceable in automotive and wide-input industrial buck applications where both voltage range and ultra-low standby power are mandatory.
Availability
LT3971IDD#PBF is available at Aetrix Electronics and suitable for automotive battery regulation, portable medical monitors, and industrial IoT sensor nodes requiring stable component supply across extended temperature ranges (–40°C to 125°C).
Supply support for LT3971IDD#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) is a global leader in high-performance analog, mixed-signal, and power management semiconductors, serving automotive, industrial, and communications markets.
The LT3971IDD#PBF belongs to Linear's high-voltage monolithic buck regulator product line, engineered specifically for automotive and industrial applications demanding wide input range, ultralow quiescent current, and robust fault tolerance.
FAQ
What is the minimum input voltage required for LT3971IDD#PBF to regulate a 3.3V output?
The LT3971IDD#PBF requires a minimum input voltage of 4.3V to maintain accurate feedback regulation at any output voltage. For a 3.3V output, this corresponds to a practical dropout margin of ~1V under light load; actual minimum VIN depends on switching frequency and duty cycle constraints per the datasheet's VIN(MIN) equation. Below 4.3V, regulation is not guaranteed even if EN is asserted.
Can LT3971IDD#PBF operate without an external catch diode?
No - the LT3971IDD#PBF integrates a BOOST Schottky diode (anode on BD pin) but does not integrate the main catch diode. An external Schottky diode must be connected between SW and VOUT (cathode to SW, anode to VOUT) to provide the freewheeling path during switch off-time. Omitting it will cause catastrophic failure due to inductive kickback.
How does the LT3971IDD#PBF achieve 2.8µA quiescent current while regulating?
The LT3971IDD#PBF achieves 2.8µA quiescent current through low-ripple Burst Mode operation: it delivers discrete current pulses to the output capacitor, then enters deep sleep where most internal circuitry (oscillator, error amp, gate drivers) is disabled. During sleep, only a minimal bias current flows - resulting in 1.7µA consumption - while the output remains regulated by stored energy in the output capacitor.
Is the LT3971IDD#PBF pin-compatible with other LT3971 variants like LT3971EDD#PBF?
Yes - the LT3971IDD#PBF shares identical pinout, package dimensions (10-lead 3mm × 3mm DFN), and electrical specifications with the LT3971EDD#PBF. The only difference is temperature grade: IDD is rated for –40°C to 125°C junction, while EDD is rated for 0°C to 125°C. Both use LFJF marking and are mechanically and electrically interchangeable in industrial designs.
What is the purpose of the SS pin on the LT3971IDD#PBF, and how is it configured?
The SS (soft-start) pin on the LT3971IDD#PBF controls inrush current by ramping the internal peak current limit during startup. A capacitor (e.g., 1nF–10nF) is connected from SS to GND; the ramp time is proportional to capacitance. The SS pin is actively discharged only when EN is low. Leaving SS floating disables soft-start, causing immediate full-current startup - acceptable only in low-inductance, low-capacitance applications.
LT3971IDD#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)
LT3971IDD#PBF FAQ
1.How can I place an order for LT3971IDD#PBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LT3971IDD#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 LT3971IDD#PBF reliable?
The price and inventory of LT3971IDD#PBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LT3971IDD#PBF is usually 5 days.
3.What payment methods are accepted for LT3971IDD#PBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LT3971IDD#PBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LT3971IDD#PBF?
LT3971IDD#PBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LT3971IDD#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 LT3971IDD#PBF?
For technical support, including LT3971IDD#PBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LT3971IDD#PBF requirements.
6.How does Aetrix verify that LT3971IDD#PBF is sourced from the original manufacturer or authorized distributors?
All LT3971IDD#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 LT3971IDD#PBF meets industry standards.
7.What is the process for return or replacement of LT3971IDD#PBF?
All LT3971IDD#PBF units undergo pre-shipment inspection (PSI). If there is an issue with LT3971IDD#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 LT3971IDD#PBF part is unused and in its original packaging.
Return procedure for LT3971IDD#PBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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