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Analog Devices Inc. LT3991IMSE-3.3#TRPBF
- Part No.:
- LT3991IMSE-3.3#TRPBF
- Manufacturer:
- Analog Devices Inc.
- Package:
- 10-TFSOP, 10-MSOP (0.118", 3.00mm Width) Exposed Pad
- Datasheet:
-
LT3991IMSE-3.3#TRPBF.pdf
- Description:
- IC REG BUCK 3.3V 1.2A 10MSOP
- Quantity:
- Payment:
- Shipping:
Inventory:3,286
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Product details
Overview
LT3991IMSE-3.3#TRPBF from Analog Devices (formerly Linear Technology) is a 55V input, 1.2A fixed-output step-down DC/DC regulator in thermally enhanced 10-pin MSOP package, featuring 2.8µA quiescent current in regulation, low-ripple Burst Mode operation (<15mVP-P), and internal 3.3V feedback divider. It serves as primary power conversion IC in automotive battery-supplied systems requiring ultra-low standby power.
For engineers reviewing the LT3991IMSE-3.3#TRPBF datasheet, LT3991IMSE-3.3#TRPBF pinout, LT3991IMSE-3.3#TRPBF application, or LT3991IMSE-3.3#TRPBF equivalent, key selection criteria include its guaranteed –40°C to 125°C junction temperature range, 3.3V ±1.5% output accuracy over temperature, 700nA shutdown current, power good flag with 91% VOUT threshold, and compatibility with external frequency synchronization up to 2MHz.
Technical Context
The LT3991IMSE-3.3#TRPBF implements constant-frequency current-mode control with internal compensation, enabling fast transient response and stable loop behavior without external type-II/III networks. Its bipolar NPN switch features 0.44Ω on-resistance and integrates a boost Schottky diode drive path for gate saturation at high input voltages.
Burst Mode operation reduces no-load input current to 2.8µA while maintaining output ripple below 15mVP-P; switching frequency is programmable from 200kHz to 2MHz via RT pin resistor and synchronizable externally from 250kHz to 2MHz. The EN pin has 1.01V rising threshold with 30mV hysteresis, and PG asserts open-drain when VOUT reaches 91% of nominal 3.3V.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Input Voltage Range | 4.3V to 55V - supports direct connection to 12V/24V/48V automotive and industrial rails without pre-regulation. |
| Output Voltage | 3.3V ±1.5% (–40°C to 125°C) - fixed internal 10MΩ divider eliminates external resistors and improves accuracy vs. adjustable variants. |
| Max Output Current | 1.2A continuous - limited by thermal design in MSOP package; peak switch current ≥2.3A ensures margin under pulse loads. |
| Quiescent Current | 2.8µA at no load (12VIN→3.3VOUT) - enables >10-year battery life in always-on telematics and sensor nodes. |
| Shutdown Current | 700nA - reduces system standby drain to negligible levels when EN is pulled low. |
| Switching Frequency | 200kHz–2MHz (RT-programmable) - allows optimization of inductor size (e.g., 12µH @ 400kHz) vs. efficiency tradeoff. |
| Output Ripple | <15mVP-P in Burst Mode - meets EMI-sensitive requirements without additional filtering in typical 47µF output cap designs. |
Pinout & Package
LT3991IMSE-3.3#TRPBF uses a 10-lead plastic MSOP package with exposed pad (Pin 11 = GND), θJA = 45°C/W, θJC = 10°C/W. Soldering the exposed pad to PCB copper is mandatory for thermal performance.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| BD (1) | Boost Diode Anode Connection | Connects to cathode of external Schottky diode; forms bootstrap path for switch drive voltage above VIN. |
| BOOST (2) | Internal Switch Drive Supply | Provides elevated voltage to saturate bipolar NPN switch; requires external capacitor between BOOST and SW. |
| SW (3) | Power Switch Output | Drives inductor and connects to BOOST capacitor; carries high di/dt switching current - needs short, low-inductance layout. |
| VIN (4) | Main Power Input | Supplies internal circuitry and switch; must be locally bypassed with ≥1µF ceramic capacitor near pin. |
| EN (5) | Enable Control Input | Hysteretic 1.01V/0.975V threshold; pulls low to reduce supply current to 700nA; requires VIN >4.3V for valid operation. |
| VOUT (6) | Fixed 3.3V Output Sense | Internally regulated to 3.3V; connects to internal 10MΩ divider - no external FB resistors required. |
| SS (7) | Soft-Start Control | Controls inrush current via external RC ramp; discharged only during EN low - prevents output overshoot at startup. |
| RT (8) | Frequency Set Resistor | Resistor to GND sets switching frequency (e.g., 118kΩ = 400kHz); enables precise EMI band placement. |
| PG (9) | Power Good Flag | Open-drain output active low until VOUT reaches 91% of 3.3V; requires external pull-up for system sequencing. |
| SYNC (10) | External Clock Input | Accepts 250kHz–2MHz clock; forces pulse-skipping mode if driven - increases IQ to 1.5mA but eliminates beat frequencies. |
Key Features
| Feature | Design Value |
|---|---|
| Ultralow Quiescent Current | 2.8µA IQ in regulation enables multi-year operation from coin cells or supercaps in IoT edge sensors. |
| Low-Ripple Burst Mode | Maintains <15mVP-P output ripple at light loads without sacrificing efficiency - critical for noise-sensitive analog circuits. |
| Integrated Boost Diode Drive | Eliminates need for external charge pump; supports full 55V input with robust switch saturation using single Schottky diode. |
| Accurate Power Good Flag | PG asserts when VOUT reaches 91% of 3.3V (±1.5%) - provides reliable power sequencing signal for microcontrollers and FPGAs. |
| Thermally Enhanced MSOP | Exposed pad + 10-pin MSOP delivers 10°C/W junction-to-case resistance - sustains 1.2A output at 85°C ambient without heatsink. |
Applications
| Automotive Body Control Module | Industrial Sensor Node |
|---|---|
Use Scenario: Powers MCU, CAN transceiver, and analog front-end in door module operating from 9–16V battery with cold-crank down to 4.3V. IC Role / Device Role / Timing Role: Primary 3.3V power rail regulator with integrated PG signaling for safe MCU boot sequence. Use Value: 2.8µA quiescent current prevents battery drain during vehicle sleep mode; 55V rating withstands load-dump transients. |
Use Scenario: Supplies 3.3V to low-power wireless sensor (LoRaWAN/NB-IoT) powered by LiSOCl₂ battery with 15-year shelf life. IC Role / Device Role / Timing Role: Standby-optimized DC/DC converter enabling years of maintenance-free operation. Use Value: 700nA shutdown current extends battery life beyond 10 years; fixed 3.3V output eliminates resistor tolerance drift errors. |
| Portable Medical Monitor | Railway Signaling Interface |
Use Scenario: Powers ECG analog signal chain and ARM Cortex-M4 in handheld diagnostic device with USB/CR2032 dual-source capability. IC Role / Device Role / Timing Role: High-PSRR, low-noise 3.3V supply ensuring ADC reference stability and amplifier SNR. Use Value: <15mVP-P ripple avoids aliasing in 24-bit delta-sigma ADCs; Burst Mode maintains efficiency across 10µA–1.2A dynamic load. |
Use Scenario: Converts 72V/110V railway traction battery to isolated 3.3V logic supply for train control safety PLCs. IC Role / Device Role / Timing Role: Input-stage buck regulator preceding isolated DC/DC for functional safety compliance. Use Value: 55V absolute max rating accommodates 110V nominal rail with 25% tolerance; –40°C to 125°C grade meets EN50155 extended temp requirement. |
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 |
|---|---|---|---|
| LT8609SIV-3.3#TRPBF | 42V max input, 2.5A output, 2.5µA IQ, integrated inductor option available; uses MOSFET switch instead of bipolar. | Better suited for space-constrained designs where board area is premium; lower max input limits use in 48V+ systems. | Select when footprint reduction or higher output current is prioritized over 55V input capability. |
| TPS63020DSJR | Buck-boost topology, 1.8–5.5V input, 3.3V fixed output, 22µA IQ, 1.2A output; no PG flag or SYNC pin. | Required where input may drop below 3.3V (e.g., single-cell Li-ion); lacks automotive-grade temp range and low-IQ performance. | Choose only for battery-powered systems with sub-4V minimum input - not a drop-in replacement for LT3991IMSE-3.3#TRPBF. |
Compared with LT8609SIV-3.3#TRPBF and TPS63020DSJR, the LT3991IMSE-3.3#TRPBF uniquely combines 55V input tolerance, 2.8µA quiescent current, and automotive-grade temperature range in a fixed 3.3V output configuration - making it irreplaceable in high-voltage industrial and automotive always-on subsystems.
Availability
LT3991IMSE-3.3#TRPBF is available at Aetrix Electronics and suitable for automotive body electronics, industrial sensor nodes, portable medical monitors, and railway signaling interfaces requiring stable component supply across extended temperature and long product lifecycles.
Supply support for LT3991IMSE-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. (acquired Linear Technology in 2017) is a global leader in high-performance analog, mixed-signal, and power management semiconductors, serving precision instrumentation, automotive, industrial, and communications markets.
The LT3991 family was designed specifically for ultralow-quiescent-current, high-input-voltage DC/DC conversion in automotive and industrial environments where reliability across –40°C to 125°C and immunity to load-dump transients are mandatory.
FAQ
What is the guaranteed operating temperature range for LT3991IMSE-3.3#TRPBF?
The LT3991IMSE-3.3#TRPBF is specified and guaranteed over the industrial temperature range of –40°C to 125°C junction temperature. This rating is confirmed in the Absolute Maximum Ratings table and Electrical Characteristics section of the official datasheet, with all performance parameters assured across this full range - unlike the 'E' grade which is only guaranteed from 0°C to 125°C.
Does LT3991IMSE-3.3#TRPBF require external feedback resistors to set the 3.3V output?
No, the LT3991IMSE-3.3#TRPBF does not require external feedback resistors. It integrates an internal 10MΩ resistor divider and associated phase-lead capacitor to regulate the VOUT pin precisely to 3.3V. This eliminates resistor tolerance errors and simplifies layout - a key distinction from the adjustable LT3991 variant which uses the FB pin and external resistors.
How does the power good (PG) flag behave on LT3991IMSE-3.3#TRPBF?
The PG pin on LT3991IMSE-3.3#TRPBF is an open-drain output that remains low until the VOUT pin reaches 91% of its nominal 3.3V (i.e., ~3.003V). It becomes valid only when EN is high and VIN exceeds 4.3V. An external pull-up resistor is required to generate a logic-high signal for system power sequencing - consistent with standard PG implementations in Analog Devices regulators.
Can LT3991IMSE-3.3#TRPBF synchronize to an external clock, and what is the impact on quiescent current?
Yes, LT3991IMSE-3.3#TRPBF accepts external synchronization from 250kHz to 2MHz on the SYNC pin. However, when synchronized, it operates in pulse-skipping mode at light loads - increasing quiescent current from 2.8µA (Burst Mode) to 1.5mA. For ultralow-IQ applications, SYNC must be grounded to enable true low-ripple Burst Mode operation.
What package type and thermal characteristics apply to LT3991IMSE-3.3#TRPBF?
The LT3991IMSE-3.3#TRPBF uses a 10-lead plastic MSOP package with exposed pad (Pin 11 = GND). Its thermal resistance is θJA = 45°C/W and θJC = 10°C/W. The exposed pad must be soldered to PCB copper for effective heat dissipation - failure to do so degrades thermal performance and risks exceeding maximum junction temperature under 1.2A load.
LT3991IMSE-3.3#TRPBF Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc.
- Series:
- -
- Package/Case:
- 10-TFSOP, 10-MSOP (0.118", 3.00mm Width) 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):
- 55V
- 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-MSOP-EP
LT3991IMSE-3.3#TRPBF FAQ
1.How can I place an order for LT3991IMSE-3.3#TRPBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LT3991IMSE-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 LT3991IMSE-3.3#TRPBF reliable?
The price and inventory of LT3991IMSE-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 LT3991IMSE-3.3#TRPBF is usually 5 days.
3.What payment methods are accepted for LT3991IMSE-3.3#TRPBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LT3991IMSE-3.3#TRPBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LT3991IMSE-3.3#TRPBF?
LT3991IMSE-3.3#TRPBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LT3991IMSE-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 LT3991IMSE-3.3#TRPBF?
For technical support, including LT3991IMSE-3.3#TRPBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LT3991IMSE-3.3#TRPBF requirements.
6.How does Aetrix verify that LT3991IMSE-3.3#TRPBF is sourced from the original manufacturer or authorized distributors?
All LT3991IMSE-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 LT3991IMSE-3.3#TRPBF meets industry standards.
7.What is the process for return or replacement of LT3991IMSE-3.3#TRPBF?
All LT3991IMSE-3.3#TRPBF units undergo pre-shipment inspection (PSI). If there is an issue with LT3991IMSE-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 LT3991IMSE-3.3#TRPBF part is unused and in its original packaging.
Return procedure for LT3991IMSE-3.3#TRPBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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