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Analog Devices Inc. LT3991EMSE-3.3#TRPBF
- Part No.:
- LT3991EMSE-3.3#TRPBF
- Manufacturer:
- Analog Devices Inc.
- Package:
- 10-TFSOP, 10-MSOP (0.118", 3.00mm Width) Exposed Pad
- Datasheet:
-
LT3991EMSE-3.3#TRPBF.pdf
- Description:
- IC REG BUCK 3.3V 1.2A 10MSOP
- Quantity:
- Payment:
- Shipping:
Inventory:7,498
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Product details
Overview
LT3991EMSE-3.3#TRPBF from Analog Devices (formerly Linear Technology) is a fixed-output 3.3V, 1.2A monolithic step-down switching regulator with ultralow 2.8µA quiescent current, 4.3V–55V input range, and integrated 0.44Ω NPN switch. It delivers regulated power in automotive battery systems, portable electronics, and industrial supplies where low standby power and wide VIN tolerance are critical.
For engineers reviewing the LT3991EMSE-3.3#TRPBF datasheet, LT3991EMSE-3.3#TRPBF pinout, LT3991EMSE-3.3#TRPBF application, or LT3991EMSE-3.3#TRPBF equivalent, key selection criteria include its guaranteed 3.3V ±1.5% output accuracy over –40°C to 125°C, 700nA shutdown current, power good flag, soft-start control via SS pin, and compatibility with low-leakage Schottky catch diodes to preserve ultralow IQ performance.
Technical Context
The LT3991EMSE-3.3#TRPBF implements constant-frequency current-mode control with internal compensation and a saturating bipolar NPN power switch. Its feedback loop regulates the VOUT pin directly to 3.3V using an internal 10MΩ resistor divider and 1.19V reference - eliminating external FB resistors while maintaining 1.175V–1.205V reference accuracy.
Burst Mode® operation reduces no-load input current to 2.8µA while holding output ripple below 15mVP-P; frequency foldback during startup and overload protects against excessive peak inductor current. The device supports synchronization (250kHz–2MHz) or autonomous operation via RT pin, and features an accurate 1.01V EN threshold with 30mV hysteresis for reliable enable/disable control.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Output Voltage | Fixed 3.3V ±1.5% over full temperature and line/load range - eliminates need for external feedback network. |
| Input Voltage Range | 4.3V to 55V - supports 12V/24V/36V/48V automotive and industrial bus rails without pre-regulation. |
| Quiescent Current | 2.8µA at no load - enables >10-year battery life in always-on IoT sensors and telematics modules. |
| Max Output Current | 1.2A continuous - sufficient for powering microcontrollers, CAN transceivers, and low-power FPGAs. |
| Switch On-Resistance | 0.44Ω - minimizes conduction loss at high duty cycles and improves efficiency above 100mA load. |
| Power Good Threshold | VOUT ≥ 91% of 3.3V (≥3.003V) - provides reliable system reset and sequencing signal with 20mV hysteresis. |
| Shutdown Current | 700nA - ensures negligible battery drain when disabled in sleep modes. |
Pinout & Package
LT3991EMSE-3.3#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 charge pump path for BOOST pin voltage generation. |
| BOOST (2) | Internal Switch Drive Supply | Provides >VIN voltage to fully saturate internal NPN switch; requires external boost capacitor between BOOST and SW. |
| SW (3) | Switch Node | Drives inductor and connects to boost capacitor; carries high dI/dt switching current - requires tight layout and ground plane. |
| VIN (4) | Main Power Input | Supplies internal circuitry and switch; must be locally bypassed with low-ESR ceramic capacitor near pin. |
| EN (5) | Enable Control Input | Hysteretic 1.01V rising threshold enables regulation; <0.95V disables device and reduces IQ to 700nA. |
| VOUT (6) | Regulated Output Sense | Internally connected to fixed 3.3V feedback divider; serves as output voltage monitor and PG reference point. |
| SS (7) | Soft-Start Control | Controls ramp rate of peak current limit during startup; capacitor-to-ground sets inrush current profile. |
| RT (8) | Frequency Set Input | Resistor-to-ground programs switching frequency from 200kHz to 2MHz; enables optimization of size vs. efficiency. |
| PG (9) | Power Good Flag | Open-drain output signals VOUT ≥3.003V; requires external pull-up for system monitoring and sequencing. |
| SYNC (10) | External Clock Input | Accepts 250kHz–2MHz clock for synchronization; grounding enables low-ripple Burst Mode operation. |
Key Features
| Feature | Design Value |
|---|---|
| Ultralow Quiescent Current | 2.8µA IQ at no load enables multi-year operation from coin cells or energy-harvesting sources. |
| Fixed 3.3V Output | Factory-trimmed internal 10MΩ feedback divider eliminates external resistors and associated leakage paths. |
| Low Ripple Burst Mode® | Maintains <15mVP-P output ripple at light loads while sustaining >85% efficiency down to 100µA output current. |
| Integrated Boost Schottky | On-die Schottky diode reduces component count and PCB area; supports efficient high-side NPN switch drive. |
| Thermally Enhanced MSOP | Exposed pad soldered to PCB provides low thermal resistance (θJC = 10°C/W) for reliable 1.2A operation at 125°C ambient. |
Applications
| Automotive Battery Regulation | Portable Medical Sensors |
|---|---|
Use Scenario: Powering infotainment head units and ADAS camera modules from 12V vehicle battery with cold-crank immunity. IC Role / Device Role / Timing Role: Primary DC/DC converter delivering stable 3.3V to MCU, memory, and interface ICs under 4.3V–55V input transients. Use Value: 2.8µA quiescent current prevents battery drain during extended parking; 55V absolute max rating withstands load dump spikes. | Use Scenario: Long-life wearable ECG monitors powered by CR2032 coin cell with multi-month runtime. IC Role / Device Role / Timing Role: Main power supply regulating 3.3V for ultra-low-power ARM Cortex-M0+ MCU and analog front-end. Use Value: 700nA shutdown current extends shelf life; fixed 3.3V output eliminates resistor network errors and leakage. |
| Industrial IoT Gateways | Railway Signaling Modules |
Use Scenario: Remote edge node converting 24V/48V PoE or rail supply to 3.3V for wireless SoCs and sensor interfaces. IC Role / Device Role / Timing Role: High-reliability buck regulator operating continuously across –40°C to 125°C junction temperature range. Use Value: Guaranteed 3.3V ±1.5% accuracy over full temp range ensures ADC reference stability and communication integrity. | Use Scenario: Safety-critical signaling controller requiring fail-safe power with brown-out detection and reset coordination. IC Role / Device Role / Timing Role: Regulated 3.3V source feeding FPGA configuration logic and watchdog circuits with PG flag for system health monitoring. Use Value: Open-drain PG output provides precise 91% VOUT threshold for deterministic reset timing and fault isolation. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar step-down regulator applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| LT3991IMSE-3.3#TRPBF | Same electrical specs and pinout; rated for –40°C to 125°C industrial temp grade (vs. LT3991EMSE-3.3#TRPBF's E-grade –40°C to 125°C with 0°C to 125°C guaranteed performance). | Required for designs needing full-spec performance across entire –40°C to 125°C range without derating. | Select LT3991IMSE-3.3#TRPBF when full temperature-range characterization and guaranteed parametrics are mandatory. |
| LT8609SIV#TRPBF | 42V max input, 3.3V fixed output, 2.5A capability, 2.5µA IQ, but uses synchronous rectification and different pinout (no BD/BOOST pins). | Suitable for space-constrained designs needing higher current or lower EMI; not drop-in due to different topology and pin assignment. | Choose LT8609SIV#TRPBF when synchronous operation, smaller solution size, or higher output current is prioritized over bipolar switch ruggedness. |
Compared with LT3991IMSE-3.3#TRPBF, the LT3991EMSE-3.3#TRPBF offers identical functionality at lower cost for commercial-extended temperature applications, while LT8609SIV#TRPBF provides synchronous efficiency and higher current at the expense of architectural compatibility and bipolar switch robustness.
Availability
LT3991EMSE-3.3#TRPBF is available at Aetrix Electronics and suitable for automotive battery regulation, portable medical sensors, and industrial IoT gateways requiring stable component supply with long-term lifecycle support.
Supply support for LT3991EMSE-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 acquired Linear Technology in 2017 and maintains full product support, documentation, and manufacturing continuity for the LT3991 family.
The LT3991 product line targets high-input-voltage, ultralow-quiescent-current DC/DC conversion in automotive, industrial, and battery-powered systems where reliability across extreme temperatures and input transients is essential.
FAQ
What is the guaranteed output voltage accuracy of the LT3991EMSE-3.3#TRPBF over temperature?
The LT3991EMSE-3.3#TRPBF guarantees 3.3V output within ±1.5% (3.25V to 3.35V) over the full –40°C to 125°C operating junction temperature range, based on internal 10MΩ feedback divider trimming and 1.19V reference stability. This specification is assured by design and correlation with statistical process controls, with full performance guaranteed from 0°C to 125°C.
Does the LT3991EMSE-3.3#TRPBF require external feedback resistors?
No, the LT3991EMSE-3.3#TRPBF does not require external feedback resistors. It integrates a precision 10MΩ internal resistor divider and 1.19V reference to regulate the VOUT pin directly to 3.3V. Pin 6 is labeled VOUT (not FB), confirming fixed-output configuration - eliminating resistor network errors, leakage paths, and board space.
How does the LT3991EMSE-3.3#TRPBF achieve 2.8µA quiescent current?
The LT3991EMSE-3.3#TRPBF achieves 2.8µA quiescent current through low-ripple Burst Mode® operation: it delivers discrete current pulses to the output capacitor followed by extended sleep periods where most internal circuitry is disabled. During sleep, only essential bias currents remain active, reducing total input current to 2.8µA while maintaining regulation - verified at 12VIN to 3.3VOUT.
What is the function of the BD pin on the LT3991EMSE-3.3#TRPBF?
The BD (Boost Diode) pin on the LT3991EMSE-3.3#TRPBF connects to the anode of an external Schottky diode whose cathode ties to VOUT. This forms a charge pump that generates a voltage on the BOOST pin higher than VIN, enabling full saturation of the internal bipolar NPN power switch for optimal conduction efficiency and thermal performance.
Can the LT3991EMSE-3.3#TRPBF be synchronized to an external clock?
Yes, the LT3991EMSE-3.3#TRPBF supports external clock synchronization via the SYNC pin (Pin 10), accepting input frequencies from 250kHz to 2MHz. When synchronized, the device operates in pulse-skipping mode at light loads - increasing quiescent current to 1.5mA but enabling EMI reduction through fixed-frequency operation. Grounding SYNC enables native low-ripple Burst Mode®.
LT3991EMSE-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
LT3991EMSE-3.3#TRPBF FAQ
1.How can I place an order for LT3991EMSE-3.3#TRPBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LT3991EMSE-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 LT3991EMSE-3.3#TRPBF reliable?
The price and inventory of LT3991EMSE-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 LT3991EMSE-3.3#TRPBF is usually 5 days.
3.What payment methods are accepted for LT3991EMSE-3.3#TRPBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LT3991EMSE-3.3#TRPBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LT3991EMSE-3.3#TRPBF?
LT3991EMSE-3.3#TRPBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LT3991EMSE-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 LT3991EMSE-3.3#TRPBF?
For technical support, including LT3991EMSE-3.3#TRPBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LT3991EMSE-3.3#TRPBF requirements.
6.How does Aetrix verify that LT3991EMSE-3.3#TRPBF is sourced from the original manufacturer or authorized distributors?
All LT3991EMSE-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 LT3991EMSE-3.3#TRPBF meets industry standards.
7.What is the process for return or replacement of LT3991EMSE-3.3#TRPBF?
All LT3991EMSE-3.3#TRPBF units undergo pre-shipment inspection (PSI). If there is an issue with LT3991EMSE-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 LT3991EMSE-3.3#TRPBF part is unused and in its original packaging.
Return procedure for LT3991EMSE-3.3#TRPBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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