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Analog Devices Inc. LT3991EMSE#TRPBF
- Part No.:
- LT3991EMSE#TRPBF
- Manufacturer:
- Analog Devices Inc.
- Package:
- 10-TFSOP, 10-MSOP (0.118", 3.00mm Width) Exposed Pad
- Datasheet:
-
LT3991EMSE#TRPBF.pdf
- Description:
- IC REG BUCK ADJ 1.2A 10MSOP
- Quantity:
- Payment:
- Shipping:
Inventory:6,187
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Product details
Overview
LT3991EMSE#TRPBF from Analog Devices (formerly Linear Technology) is a 55V, 1.2A monolithic step-down regulator with ultralow 2.8µA quiescent current in regulation and 700nA shutdown current. It features internal compensation, a 0.44Ω NPN switch, integrated boost Schottky diode driver, and power good flag. Designed for automotive battery regulation and portable power supplies where standby efficiency is critical.
For engineers reviewing the LT3991EMSE#TRPBF datasheet, LT3991EMSE#TRPBF pinout, LT3991EMSE#TRPBF application, or LT3991EMSE#TRPBF equivalent, key selection criteria include input voltage range (4.3V–55V), fixed 3.3V output, Burst Mode ripple performance (<15mVP-P), soft-start control via SS pin, and thermal management via exposed pad MSOP package.
Technical Context
The LT3991EMSE#TRPBF implements constant-frequency current-mode control with internal slope compensation and an active VC clamp for overcurrent protection. Its oscillator supports programmable switching frequency from 200kHz to 2MHz via RT pin resistor, and synchronizable operation between 250kHz–2MHz when driven externally.
Burst Mode operation enables ultralow quiescent current by disabling control circuitry between energy pulses, while maintaining output regulation and limiting ripple to <15mVP-P. The 1V enable threshold with 30mV hysteresis ensures reliable startup and shutdown across temperature, and the open-drain PG pin asserts when FB reaches 91% of target voltage.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Input Voltage Range | 4.3V to 55V - supports wide automotive and industrial supply rails without external 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 multi-year battery life in always-on sensor or telematics applications. |
| Switching Frequency | Adjustable 200kHz–2MHz - balances inductor size, efficiency, and EMI; RT pin sets exact value. |
| Shutdown Current | 700nA - reduces system leakage during deep sleep or fault conditions. |
| Power Good Threshold | 91% of regulated output - provides accurate sequencing signal for downstream logic or microcontrollers. |
Pinout & Package
LT3991EMSE#TRPBF is housed in a thermally enhanced 10-lead plastic MSOP package with exposed pad (Pin 11 = GND), offering θJA = 45°C/W and θJC = 10°C/W for high-power-density designs.
| 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. |
| BOOST (2) | Bootstrap Voltage Supply | Provides >VIN voltage to fully saturate internal NPN switch; requires external capacitor to SW. |
| SW (3) | Switch Node | Drives inductor and catch diode; high dv/dt node requiring careful PCB layout and snubbing. |
| VIN (4) | Main Input Supply | Supplies internal bias and switch current; must be locally bypassed with low-ESR ceramic capacitor. |
| EN (5) | Enable/UVLO Input | Hysteretic 1.01V rising / 0.975V falling threshold; disables regulator and reduces IQ to 700nA. |
| VOUT (6) | Fixed Output Voltage Terminal | Internally regulated 3.3V output; connects to load and output capacitor; also serves as FB reference point. |
| SS (7) | Soft-Start Control | Controls inrush current ramp rate via external RC; discharged only during EN low state. |
| RT (8) | Frequency Set Resistor | Ground-referenced resistor sets switching frequency from 200kHz to 2MHz per datasheet table. |
| PG (9) | Power Good Flag | Open-drain output asserting high when VOUT reaches 91% of 3.3V; requires external pull-up. |
| SYNC (10) | External Clock Input | Accepts 250kHz–2MHz clock; forces pulse-skipping mode if not grounded, increasing IQ to 1.5mA. |
Key Features
| Feature | Design Value |
|---|---|
| Ultralow Quiescent Current | 2.8µA regulating 12VIN to 3.3VOUT - extends battery runtime in always-on IoT nodes and automotive ECUs. |
| Low Ripple Burst Mode | Output ripple <15mVP-P at light loads - eliminates audible noise and avoids interference with sensitive analog circuits. |
| Integrated Boost Diode Driver | Internal Schottky driver on BOOST/BD pins - removes need for external bootstrap diode and simplifies layout. |
| Accurate Power Good Flag | PG asserts at 91% of 3.3V with 20mV hysteresis - enables precise power sequencing in multi-rail systems. |
| Thermally Optimized Package | 10-pin MSOP with exposed GND pad - achieves θJC = 10°C/W for direct heat transfer to PCB copper. |
Applications
| Automotive Battery Regulation | Portable Medical Sensors |
|---|---|
|
Use Scenario: Powering CAN transceivers and microcontrollers directly from 12V vehicle battery with cold-crank tolerance down to 4.3V. IC Role / Device Role / Timing Role: Primary buck regulator providing stable 3.3V rail with ultralow IQ to meet ISO 16750-2 quiescent current requirements. Use Value: Maintains system readiness during extended parking with <2.8µA draw, avoiding battery drain below 12.4V. |
Use Scenario: Long-life wearable ECG patch operating from coin cell or small Li-ion battery for multi-week monitoring. IC Role / Device Role / Timing Role: Main power converter enabling sleep-mode operation with sub-µA system leakage. Use Value: Delivers 3.3V at 1.2A peak while consuming only 2.8µA at no load, extending usable battery life by >3× vs. standard buck ICs. |
| Industrial Remote I/O Modules | Smart Meter Auxiliary Power |
|
Use Scenario: Field-deployed DIN-rail I/O module powered from 24V DC industrial bus with strict EMC and thermal constraints. IC Role / Device Role / Timing Role: Isolated auxiliary supply generating 3.3V for microcontroller and RS-485 transceivers. Use Value: Internal compensation and 55V rating eliminate need for external loop components and support brownout resilience. |
Use Scenario: AMI smart meter requiring continuous real-time clock and communication backup power during main AC failure. IC Role / Device Role / Timing Role: Backup buck regulator converting supercapacitor or LiFePO4 storage to 3.3V with minimal self-discharge. Use Value: 700nA shutdown current preserves stored energy for >30 days; PG flag triggers firmware safe-shutdown 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 |
|---|---|---|---|
| LT8609SISM#TRPBF | 42V max input, 2A output, 2.5µA IQ, Silent Switcher architecture reduces EMI. | Preferred for noise-sensitive applications (e.g., RF modules); requires external feedback resistors for 3.3V. | Select when EMI compliance (CISPR 25 Class 5) is mandatory and higher output current is needed. |
| TPS63020DSJR | Buck-boost topology, 1.8–5.5V input, 3.3V fixed output, 3.5µA IQ, no PG flag. | Suitable for single-cell Li-ion or NiMH inputs where input may drop below 3.3V; lacks power good signaling. | Choose for battery-powered systems with variable input voltage crossing VOUT; not suitable for automotive 12V+ rails. |
Compared with LT3991EMSE#TRPBF, LT8609SISM#TRPBF offers superior EMI performance and higher current but requires external feedback, while TPS63020DSJR supports buck-boost operation at lower input voltages but omits PG and has narrower VIN range.
Availability
LT3991EMSE#TRPBF is available at Aetrix Electronics and suitable for automotive battery regulation, portable medical sensors, and industrial remote I/O modules requiring stable component supply with long-term lifecycle assurance.
Supply support for LT3991EMSE#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 full product support, manufacturing, and qualification for all LT® parts including the LT3991 family.
The LT3991 product line delivers high-voltage, ultralow-IQ buck regulators optimized for automotive, industrial, and battery-powered systems where input voltage can exceed 40V and standby current must remain below 3µA.
FAQ
What is the output voltage of the LT3991EMSE#TRPBF?
The LT3991EMSE#TRPBF is the fixed 3.3V variant of the LT3991 family. It regulates its VOUT pin to 3.3V ±1.5% over temperature and line, using an internal 10MΩ feedback divider. No external resistors are required, simplifying design and improving accuracy versus adjustable versions that depend on external component tolerances.
Does the LT3991EMSE#TRPBF require an external Schottky diode?
Yes, the LT3991EMSE#TRPBF requires an external Schottky diode connected between BD (Pin 1) and VOUT. The IC integrates a boost Schottky driver on the BOOST pin but does not include the power diode itself. A low-leakage (<1µA), low-VF Schottky such as DFLS2100 is recommended to preserve ultralow quiescent current performance.
How does the LT3991EMSE#TRPBF achieve 2.8µA quiescent current?
The LT3991EMSE#TRPBF achieves 2.8µA quiescent current through low-ripple Burst Mode operation: it delivers discrete current pulses to the output capacitor and then enters deep sleep, powering down oscillator, error amplifier, and gate drivers. During sleep, only essential bias circuitry remains active, drawing just 1.7µA - the total 2.8µA includes minimal feedback divider current.
Can the LT3991EMSE#TRPBF operate with input voltage below 4.3V?
No, the LT3991EMSE#TRPBF has a minimum input voltage of 4.3V per Absolute Maximum Ratings and Electrical Characteristics. Below this, the internal regulator cannot maintain proper bias, EN threshold becomes inaccurate, and PG function is invalid. For sub-4.3V operation, consider buck-boost alternatives like TPS63020DSJR.
What is the purpose of the exposed pad on the LT3991EMSE#TRPBF MSOP package?
The exposed pad (Pin 11) on the LT3991EMSE#TRPBF MSOP package is electrically and thermally connected to GND. It must be soldered to a large PCB copper area to achieve θJC = 10°C/W and prevent thermal shutdown under 1.2A load. Failure to connect it degrades thermal performance by >30°C and risks reliability failure in sustained high-current operation.
LT3991EMSE#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
LT3991EMSE#TRPBF FAQ
1.How can I place an order for LT3991EMSE#TRPBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LT3991EMSE#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 LT3991EMSE#TRPBF reliable?
The price and inventory of LT3991EMSE#TRPBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LT3991EMSE#TRPBF is usually 5 days.
3.What payment methods are accepted for LT3991EMSE#TRPBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LT3991EMSE#TRPBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LT3991EMSE#TRPBF?
LT3991EMSE#TRPBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LT3991EMSE#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 LT3991EMSE#TRPBF?
For technical support, including LT3991EMSE#TRPBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LT3991EMSE#TRPBF requirements.
6.How does Aetrix verify that LT3991EMSE#TRPBF is sourced from the original manufacturer or authorized distributors?
All LT3991EMSE#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 LT3991EMSE#TRPBF meets industry standards.
7.What is the process for return or replacement of LT3991EMSE#TRPBF?
All LT3991EMSE#TRPBF units undergo pre-shipment inspection (PSI). If there is an issue with LT3991EMSE#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 LT3991EMSE#TRPBF part is unused and in its original packaging.
Return procedure for LT3991EMSE#TRPBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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