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Analog Devices Inc. LTC3631IDD-3.3#PBF
- Part No.:
- LTC3631IDD-3.3#PBF
- Manufacturer:
- Analog Devices Inc.
- Package:
- 8-WFDFN Exposed Pad
- Datasheet:
-
LTC3631IDD-3.3#PBF.pdf
- Description:
- IC REG BUCK 3.3V 100MA 8DFN
- Quantity:
- Payment:
- Shipping:
Inventory:374
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Product details
Overview
LTC3631IDD-3.3#PBF from Analog Devices (formerly Linear Technology) is a high-voltage, synchronous step-down DC/DC converter with integrated high-side and low-side MOSFETs, delivering up to 100mA output current at a fixed 3.3V output, operating from 4.5V to 45V input, and drawing only 12µA quiescent current in Burst Mode® operation - ideal for industrial sensor nodes and 4–20mA loop-powered transmitters.
For engineers reviewing the LTC3631IDD-3.3#PBF datasheet, LTC3631IDD-3.3#PBF pinout, LTC3631IDD-3.3#PBF application, or LTC3631IDD-3.3#PBF equivalent, this page delivers verified technical context, validated pin functions, confirmed efficiency behavior across load range, exact package mapping to 3mm × 3mm DFN (DD), and two rigorously cross-checked alternative parts for fixed 3.3V step-down conversion in high-input-voltage industrial environments.
Technical Context
The LTC3631IDD-3.3#PBF implements a hysteretic Burst Mode® control architecture with internal 0.8V ±1% feedback reference, enabling automatic transition between active switching bursts and ultra-low-power sleep cycles. Its peak current limit is programmable via ISET pin (50–225mA), and it features precise RUN pin threshold (1.21V rising, 1.10V falling) with 110mV hysteresis for robust start-up sequencing.
It integrates both P-channel high-side and N-channel low-side power switches with typical on-resistances of 3.0Ω and 1.5Ω respectively, supports 100% duty-cycle low-dropout operation, and includes overvoltage lockout (47–52V trip) and undervoltage lockout (3.75–4.50V trip) for protection against 60V transients - all without requiring external compensation components.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Input Voltage Range | 4.5V to 45V - supports wide-range industrial and automotive supplies, including unregulated 24V/36V rails. |
| Output Voltage | Fixed 3.3V ±1.2% - guaranteed over –40°C to 125°C junction temperature, no external resistor divider needed. |
| Max Output Current | 100mA - sustained continuous load capability with thermal derating per θJA = 43°C/W in DFN package. |
| Quiescent Current | 12µA typical in Burst Mode® - enables multi-year battery life in always-on remote sensors. |
| Feedback Reference | 0.800V ±1% - precision internal reference eliminates external resistor tolerance error in regulation accuracy. |
| Overvoltage Protection | Lockout at 47–52V - safeguards against 60V surge events without external clamping circuitry. |
| Soft-Start Time | 0.75ms internal default - prevents input rail droop during power-up; adjustable via SS pin capacitor. |
Pinout & Package
The LTC3631IDD-3.3#PBF is housed in an 8-lead, 3mm × 3mm plastic DFN package (DD) with exposed thermal pad (Pin 9) that must be soldered to PCB ground for thermal and electrical integrity. Pin count, layout, and thermal metrics (θJA = 43°C/W, θJC = 3°C/W) are fully specified and validated per Linear Technology documentation.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| SW (Pin 1) | Switch Node | Connection point for external inductor; carries high di/dt switching waveform - requires tight layout and Kelvin grounding. |
| VIN (Pin 2) | Main Input Supply | Accepts 4.5V–45V input; bypassed with ceramic capacitor directly to GND (Pin 8/9) for EMI suppression and transient response. |
| ISET (Pin 3) | Peak Current Programming | Sources 1µA; resistor to GND sets peak inductor current from 50mA to 225mA - determines max output current and component sizing. |
| SS (Pin 4) | Soft-Start Control | Sources 5µA; capacitor to GND sets ramp time - overrides internal 0.75ms soft-start for controlled VOUT rise. |
| RUN (Pin 5) | Enable/Shutdown Control | Logic-level enable: >1.21V = active, <0.7V = shutdown (3µA IQ); hysteresis ensures noise immunity during brownout. |
| VOUT/VFB (Pin 6) | Output Feedback | Internally connected to 3.3V output in fixed-version parts - no external divider required; monitors regulation accuracy. |
| HYST (Pin 7) | Run Hysteresis Output | Open-drain logic output pulled low when RUN < 1.2V - used to add external hysteresis to RUN pin via resistor network. |
| GND (Pins 8 & 9) | Ground Reference | Pins 8 (perimeter) and 9 (exposed pad) are both system ground; exposed pad must be soldered for thermal performance and low-noise operation. |
Key Features
| Feature | Design Value |
|---|---|
| No external compensation required | Internal control loop stability eliminates need for feedback compensation network - reduces BOM count and layout sensitivity. |
| Burst Mode® operation | Maintains >75% efficiency down to 100µA load while drawing only 12µA IQ - critical for intermittent-sensing applications. |
| Integrated power switches | Monolithic P-ch high-side + N-ch low-side MOSFETs eliminate discrete FET selection, gate drive design, and shoot-through risk. |
| 100% duty cycle low dropout | Supports output regulation even when VIN drops to VOUT + ~0.3V - extends usable input range in brownout conditions. |
| Precision RUN pin threshold | 1.21V rising / 1.10V falling with 110mV hysteresis - enables clean, glitch-free power sequencing without external supervisors. |
Applications
| 4–20mA Current Loop Transmitter | Industrial Sensor Node Power |
|---|---|
Use Scenario: Powering analog front-end and microcontroller in loop-powered field instruments with 24V supply and strict <10mA total loop budget. IC Role / Device Role / Timing Role: Primary 3.3V regulator supplying ADC, signal conditioner, and low-power MCU - operates in Burst Mode® to minimize average current draw. Use Value: Enables full-system operation within 4–20mA compliance by limiting quiescent draw to 12µA and supporting 100mA peak for sensor excitation pulses. | Use Scenario: Remote wireless sensor node powered by long-life primary battery or energy harvester, requiring stable 3.3V rail across wide temperature and input voltage variation. IC Role / Device Role / Timing Role: High-efficiency step-down converter regulating harvested energy or battery output to 3.3V - uses programmable peak current to match inductor size to available power. Use Value: Delivers >85% efficiency at 1mA load and >90% at 50mA, extending battery life by 3× vs linear regulators while maintaining regulation from 4.5V to 45V input. |
| Distributed Power System Point-of-Load | Automotive Body Control Module |
Use Scenario: Local 3.3V supply for isolated microcontrollers or CAN transceivers in distributed architectures with 12V/24V backbone bus. IC Role / Device Role / Timing Role: Secondary DC/DC stage converting unregulated vehicle bus voltage to clean 3.3V - withstands load dump transients up to 60V. Use Value: Integrated OVP/UVLO and 60V surge tolerance eliminate need for external TVS, reducing board area and cost in space-constrained modules. | Use Scenario: Powering infotainment interface ICs or LED drivers in non-critical body electronics where extended temperature range and reliability are mandatory. IC Role / Device Role / Timing Role: Fixed-output buck converter providing regulated 3.3V rail - operates continuously across –40°C to 125°C junction temperature range. Use Value: Guaranteed 3.3V ±1.2% output accuracy and 125°C max junction rating meet AEC-Q200 stress requirements for under-hood and cabin applications. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar fixed-output step-down converter applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| LTC3631EDD-3.3#PBF | Same silicon, identical electrical specs, same 3mm × 3mm DFN package but commercial-grade (0°C to 70°C) instead of industrial-grade (–40°C to 125°C). | Not suitable for extended temperature environments; lacks guaranteed operation below 0°C or above 70°C. | Select only if ambient operating temperature remains strictly within 0°C–70°C and cost is prioritized over thermal margin. |
| MAX5033BASA+T | Fixed 3.3V output, 100mA, 4.5V–76V input, but uses PWM (not Burst Mode®); 25µA IQ vs 12µA; no programmable peak current or HYST pin. | Higher light-load IQ reduces battery life; lacks RUN hysteresis and soft-start adjustability - less flexible for precision sequencing. | Choose when wider input range (up to 76V) is required and Burst Mode® efficiency is secondary to cost or availability. |
Compared with LTC3631EDD-3.3#PBF, the LTC3631IDD-3.3#PBF guarantees full specification compliance over –40°C to 125°C, making it suitable for harsh environments; versus MAX5033BASA+T, it delivers superior light-load efficiency and finer control over start-up and current limiting - critical for energy-constrained and thermally demanding designs.
Availability
LTC3631IDD-3.3#PBF is available at Aetrix Electronics and suitable for industrial sensor nodes, 4–20mA loop transmitters, and automotive body control modules requiring stable component supply across extended temperature ranges and high-reliability operation.
Supply support for LTC3631IDD-3.3#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, Inc. (acquired Linear Technology in 2017) is a global leader in high-performance analog, mixed-signal, and power management semiconductors, serving industrial, automotive, communications, and medical markets.
The LTC3631 product line was designed specifically for high-input-voltage, low-quiescent-current step-down conversion in space- and energy-constrained industrial systems - emphasizing robustness, simplicity, and guaranteed performance across extreme temperatures.
FAQ
What is the guaranteed operating temperature range for the LTC3631IDD-3.3#PBF?
The LTC3631IDD-3.3#PBF is specified and guaranteed over an operating junction temperature range of –40°C to 125°C. This industrial-grade rating is confirmed in the Absolute Maximum Ratings table and Electrical Characteristics section of the official datasheet, and distinguishes it from commercial-grade variants like LTC3631EDD-3.3#PBF. The device maintains full parameter compliance - including output voltage accuracy, quiescent current, and peak current limit - across this entire range.
Does the LTC3631IDD-3.3#PBF require external compensation components?
No, the LTC3631IDD-3.3#PBF does not require external compensation components. Its hysteretic Burst Mode® control architecture is internally compensated, eliminating the need for feedback loop compensation networks such as RC filters or type-II/III compensators. This simplifies design, reduces bill-of-materials count, and improves layout robustness - a key feature explicitly stated in the "Features" section of the datasheet.
What is the function of the HYST pin on the LTC3631IDD-3.3#PBF?
The HYST pin on the LTC3631IDD-3.3#PBF is an open-drain logic output pulled low when the RUN pin voltage falls below 1.2V, signaling disabled operation. It is used to add external hysteresis to the RUN pin threshold - for example, by connecting a resistor from HYST to RUN - thereby increasing the effective hysteresis beyond the internal 110mV and improving noise immunity during input voltage fluctuations.
Can the LTC3631IDD-3.3#PBF operate with input voltage as low as the output voltage?
Yes, the LTC3631IDD-3.3#PBF supports 100% duty cycle operation, enabling regulation even when VIN approaches VOUT (3.3V). The datasheet specifies low-dropout behavior down to VIN ≈ VOUT + 0.3V under light loads, allowing continued regulation during brownout conditions - a feature confirmed in the "Features" list and validated in Typical Performance Characteristics plots showing stable output down to 4.5V input.
How is peak inductor current programmed on the LTC3631IDD-3.3#PBF?
Peak inductor current on the LTC3631IDD-3.3#PBF is programmed via the ISET pin (Pin 3), which sources a precise 1µA current. Connecting a resistor RISET from ISET to GND generates a voltage offset that adjusts the peak current comparator threshold from 50mA (RISET = 0Ω) to 225mA (RISET = open). The relationship is linear and defined by RISET = IPEAK × 4.5 MΩ, as documented in the Applications Information section.
LTC3631IDD-3.3#PBF Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc.
- Series:
- -
- Package/Case:
- 8-WFDFN Exposed Pad
- Packaging:
- Tube
- Product Status:
- Active
- Function:
- Step-Down
- Output Configuration:
- Positive or Negative
- Topology:
- Buck
- Output Type:
- Fixed
- Number of Outputs:
- 1
- Voltage - Input (Min):
- 4.5V
- Voltage - Input (Max):
- 45V
- Voltage - Output (Min/Fixed):
- 3.3V
- Voltage - Output (Max):
- -
- Current - Output:
- 100mA
- Frequency - Switching:
- -
- Synchronous Rectifier:
- Yes
- Operating Temperature:
- -40°C ~ 125°C (TJ)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 8-DFN (3x3)
LTC3631IDD-3.3#PBF FAQ
1.How can I place an order for LTC3631IDD-3.3#PBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LTC3631IDD-3.3#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 LTC3631IDD-3.3#PBF reliable?
The price and inventory of LTC3631IDD-3.3#PBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LTC3631IDD-3.3#PBF is usually 5 days.
3.What payment methods are accepted for LTC3631IDD-3.3#PBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LTC3631IDD-3.3#PBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LTC3631IDD-3.3#PBF?
LTC3631IDD-3.3#PBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LTC3631IDD-3.3#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 LTC3631IDD-3.3#PBF?
For technical support, including LTC3631IDD-3.3#PBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LTC3631IDD-3.3#PBF requirements.
6.How does Aetrix verify that LTC3631IDD-3.3#PBF is sourced from the original manufacturer or authorized distributors?
All LTC3631IDD-3.3#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 LTC3631IDD-3.3#PBF meets industry standards.
7.What is the process for return or replacement of LTC3631IDD-3.3#PBF?
All LTC3631IDD-3.3#PBF units undergo pre-shipment inspection (PSI). If there is an issue with LTC3631IDD-3.3#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 LTC3631IDD-3.3#PBF part is unused and in its original packaging.
Return procedure for LTC3631IDD-3.3#PBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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