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Analog Devices Inc. LT3991IMSE#TRPBF
- Part No.:
- LT3991IMSE#TRPBF
- Manufacturer:
- Analog Devices Inc.
- Package:
- 10-TFSOP, 10-MSOP (0.118", 3.00mm Width) Exposed Pad
- Datasheet:
-
LT3991IMSE#TRPBF.pdf
- Description:
- IC REG BUCK ADJ 1.2A 10MSOP
- Quantity:
- Payment:
- Shipping:
Inventory:2,242
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Product details
Overview
LT3991IMSE#TRPBF from Analog Devices (formerly Linear Technology) is a 55V, 1.2A monolithic step-down DC/DC regulator with ultralow 2.8µA quiescent current in regulation, internal 0.44Ω NPN switch, and programmable 200kHz–2MHz switching frequency. It delivers fixed 3.3V output in thermally enhanced 10-lead MSOP package and is used in automotive battery regulation and portable power supplies where low standby power is critical.
For engineers reviewing the LT3991IMSE#TRPBF datasheet, LT3991IMSE#TRPBF pinout, LT3991IMSE#TRPBF application, or LT3991IMSE#TRPBF equivalent, key selection criteria include input voltage range (4.3V–55V), soft-start control via SS pin, power-good flag timing (91% VOUT threshold), and Burst Mode operation enabling <15mVpp output ripple at light loads.
Technical Context
The LT3991IMSE#TRPBF implements constant-frequency current-mode control with internal compensation, fast transient response, and frequency foldback during startup or overload. Its bipolar NPN switch is driven by a BOOST pin requiring external Schottky diode and capacitor to generate gate drive above VIN.
Burst Mode operation reduces no-load supply current to 2.8µA while maintaining regulation; SYNC pin grounding enables low-ripple burst mode, whereas external clocking forces pulse-skipping with 1.5mA quiescent current. The EN pin features 1.01V rising threshold and 30mV hysteresis for reliable shutdown control.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Input Voltage Range | 4.3V to 55V - supports wide-range industrial and automotive battery inputs without pre-regulation |
| Output Voltage | Fixed 3.3V ±1.5% - internally trimmed; no external feedback resistors required |
| Max Output Current | 1.2A continuous - limited by internal 2.3A typical switch current limit and thermal design |
| Quiescent Current | 2.8µA at no load - enables >10-year battery life in always-on sensor nodes |
| Switching Frequency | 200kHz to 2MHz - set by RT resistor; synchronizable externally from 250kHz to 2MHz |
| Output Ripple | <15mVPP in Burst Mode - achieved with 47µF output capacitor and optimized layout |
| Power Good Threshold | 91% of regulated output - open-drain PG pin asserts high when VOUT reaches 3.003V (for 3.3V version) |
Pinout & Package
LT3991IMSE#TRPBF is housed in a 10-lead plastic MSOP package with exposed thermal pad (Pin 11 = GND), θJA = 45°C/W, θJC = 10°C/W. The exposed pad must be soldered to PCB for thermal performance and electrical grounding.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| BD (1) | Boost Diode Anode Connection | Connects to cathode of external Schottky diode; forms charge pump path for BOOST pin |
| BOOST (2) | Switch Gate Drive Supply | Provides elevated voltage (>VIN) to fully saturate internal NPN switch; requires external boost capacitor |
| SW (3) | Switch Node | Drives inductor; connects to catch diode cathode and boost capacitor; carries high di/dt switching current |
| VIN (4) | Main Power Input | Supplies internal circuitry and switch; requires local 1µF ceramic bypass capacitor |
| EN (5) | Enable Control Input | Hysteretic 1.01V threshold; pulls device into 700nA shutdown when below 0.975V |
| VOUT (6) | Fixed Output Voltage Terminal | Regulated 3.3V output; connects to internal 10MΩ feedback divider; not FB pin |
| SS (7) | Soft-Start Control | Controls inrush current via external RC ramp; discharged only during EN low |
| RT (8) | Frequency Set Resistor | Ground-connected resistor sets switching frequency from 200kHz to 2MHz per datasheet table |
| PG (9) | Power Good Flag | Open-drain output active-high when VOUT ≥ 3.003V; requires external pull-up |
| SYNC (10) | External Clock Input | Ground for Burst Mode; accept 250kHz–2MHz square wave for synchronization |
Key Features
| Feature | Design Value |
|---|---|
| Ultralow Quiescent Current | 2.8µA regulating 12VIN to 3.3VOUT - extends battery runtime in always-on IoT sensors |
| Low-Ripple Burst Mode | Output ripple <15mVPP at light loads - maintains signal integrity without post-regulation LDO |
| Internal Compensation | No external compensation components needed - reduces BOM count and layout sensitivity |
| Saturating Switch Design | 0.44Ω on-resistance NPN switch - enables high efficiency at 1A load without external MOSFET driver |
| Accurate Enable Threshold | 1.01V EN rising threshold with 30mV hysteresis - ensures clean startup/shutdown across temperature |
| Soft-Start Programmability | RC-controlled SS pin - prevents inrush current damage to input capacitors and upstream converters |
Applications
| Automotive Battery Regulation | Portable Medical Sensors |
|---|---|
Use Scenario: Powering CAN transceiver and microcontroller from 12V vehicle battery with engine-off sleep mode. IC Role / Device Role / Timing Role: Primary 3.3V buck regulator delivering stable rail during cold-crank (4.3V min) and stop-start cycles. Use Value: 2.8µA quiescent current prevents parasitic battery drain over months of vehicle inactivity. |
Use Scenario: Long-life wearable ECG monitor powered by coin cell or small Li-ion battery. IC Role / Device Role / Timing Role: Main system regulator enabling multi-year operation without battery replacement. Use Value: Fixed 3.3V output eliminates need for external feedback resistors, reducing component count and leakage paths. |
| Industrial Remote I/O Modules | Smart Building Sensors |
Use Scenario: DIN-rail mounted sensor node operating from 24V DC industrial bus with strict EMC requirements. IC Role / Device Role / Timing Role: Isolated 3.3V supply for MCU and RS-485 transceiver in harsh EMI environments. Use Value: Burst Mode operation minimizes conducted noise during idle periods while maintaining regulation. |
Use Scenario: Wireless occupancy sensor using LoRaWAN, sleeping >99% of time between motion-triggered transmissions. IC Role / Device Role / Timing Role: Always-on 3.3V rail powering ultra-low-power MCU and RF front-end. Use Value: PG flag enables firmware to verify power stability before initiating radio transmission sequence. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar step-down regulator applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| LT8609SIV#TRPBF | 42V max input, 2.5A output, 2.5µA IQ, integrated MOSFETs (no external diode), 3mm × 4mm LQFN | Higher current capability but requires external boost capacitor; lacks BD pin for discrete diode option | Preferred for higher-current designs needing smaller footprint and lower EMI; not drop-in due to different pinout and diode integration |
| TPS63020DSJR | 18V max input, 2A output, 30µA IQ, buck-boost topology, 2mm × 2mm WSON | Supports input voltages below output (e.g., 2.5V–5.5V); higher IQ limits battery lifetime vs. LT3991IMSE#TRPBF | Only suitable where input may dip below 3.3V; inferior quiescent current makes it unsuitable for long-term battery operation |
Compared with LT8609SIV#TRPBF and TPS63020DSJR, the LT3991IMSE#TRPBF uniquely combines 55V input tolerance, sub-3µA quiescent current, and discrete boost diode flexibility-making it optimal for automotive and industrial 12V/24V systems demanding decades of maintenance-free operation.
Availability
LT3991IMSE#TRPBF is available at Aetrix Electronics and suitable for automotive battery regulation, portable medical sensors, industrial remote I/O modules, and smart building sensors requiring stable component supply across extended temperature ranges (–40°C to 125°C).
Supply support for LT3991IMSE#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 acquired Linear Technology in 2017 and maintains its precision analog and power management product lines with full technical documentation and long-term manufacturing commitment.
The LT3991 family was designed specifically for ultralow-quiescent-current step-down conversion in automotive, industrial, and battery-powered systems where input voltage can exceed 40V and standby power must be minimized.
FAQ
What is the guaranteed operating temperature range for LT3991IMSE#TRPBF?
The LT3991IMSE#TRPBF is specified for –40°C to 125°C junction temperature and is tested and guaranteed across this full range. This I-grade rating makes it suitable for under-hood automotive and industrial environments where ambient temperatures exceed 85°C. The MSOP package's exposed pad ensures reliable thermal dissipation at high load currents within this range.
Does LT3991IMSE#TRPBF require an external feedback resistor network?
No, the LT3991IMSE#TRPBF is the fixed 3.3V variant and contains an internal 10MΩ feedback divider connected to the VOUT pin (Pin 6). Unlike the adjustable LT3991 version, it does not use the FB pin and eliminates the need for external resistors - reducing BOM cost, board space, and potential leakage paths that degrade ultralow-IQ performance.
How does the LT3991IMSE#TRPBF achieve 2.8µA quiescent current?
The LT3991IMSE#TRPBF achieves 2.8µA quiescent current through low-ripple Burst Mode operation: during light loads, it delivers single energy pulses to the output capacitor followed by extended sleep intervals where most internal circuitry is disabled. This architecture minimizes average supply current while maintaining tight output regulation - confirmed at 12VIN/3.3VOUT with no load.
Can LT3991IMSE#TRPBF be synchronized to an external clock?
Yes, the LT3991IMSE#TRPBF supports external synchronization via the SYNC pin (Pin 10) over 250kHz–2MHz. However, doing so disables low-ripple Burst Mode and forces pulse-skipping operation, increasing quiescent current to 1.5mA. For ultralow-power applications, SYNC should be grounded; only use external sync when EMI reduction via frequency alignment is prioritized over standby current.
What is the function of the BD pin on LT3991IMSE#TRPBF?
The BD (Boost Diode) pin on LT3991IMSE#TRPBF connects to the anode of an external Schottky diode whose cathode ties to the BOOST pin. This forms a charge pump that generates a voltage ~1.8V above VIN on the BOOST pin, enabling full saturation of the internal bipolar NPN switch. The BD pin must be routed with low-inductance traces to minimize switching losses and EMI.
LT3991IMSE#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:
- Adjustable
- Number of Outputs:
- 1
- Voltage - Input (Min):
- 4.3V
- Voltage - Input (Max):
- 55V
- 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-MSOP-EP
LT3991IMSE#TRPBF FAQ
1.How can I place an order for LT3991IMSE#TRPBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LT3991IMSE#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#TRPBF reliable?
The price and inventory of LT3991IMSE#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#TRPBF is usually 5 days.
3.What payment methods are accepted for LT3991IMSE#TRPBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LT3991IMSE#TRPBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LT3991IMSE#TRPBF?
LT3991IMSE#TRPBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LT3991IMSE#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#TRPBF?
For technical support, including LT3991IMSE#TRPBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LT3991IMSE#TRPBF requirements.
6.How does Aetrix verify that LT3991IMSE#TRPBF is sourced from the original manufacturer or authorized distributors?
All LT3991IMSE#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#TRPBF meets industry standards.
7.What is the process for return or replacement of LT3991IMSE#TRPBF?
All LT3991IMSE#TRPBF units undergo pre-shipment inspection (PSI). If there is an issue with LT3991IMSE#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#TRPBF part is unused and in its original packaging.
Return procedure for LT3991IMSE#TRPBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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