My Inquiry
My Account
Analog Devices Inc. LT3991IMSE-5#PBF
- Part No.:
- LT3991IMSE-5#PBF
- Manufacturer:
- Analog Devices Inc.
- Package:
- 10-TFSOP, 10-MSOP (0.118", 3.00mm Width) Exposed Pad
- Datasheet:
-
LT3991IMSE-5#PBF.pdf
- Description:
- IC REG BUCK 5V 1.2A 10MSOP
- Quantity:
- Payment:
- Shipping:
Inventory:518
Please send an inquiry. Send us your inquiry, and we will respond immediately.
Product details
Overview
LT3991IMSE-5#PBF from Analog Devices (formerly Linear Technology) is a 55V input, 1.2A fixed-output buck regulator in thermally enhanced 10-pin MSOP package, featuring 2.8µA quiescent current, 5V output, and low-ripple Burst Mode operation. It integrates a 0.44Ω NPN switch, internal compensation, soft-start, and power-good flag - designed for automotive battery regulation and industrial supplies where ultra-low standby power is critical.
For engineers reviewing the LT3991IMSE-5#PBF datasheet, LT3991IMSE-5#PBF pinout, LT3991IMSE-5#PBF application, or LT3991IMSE-5#PBF equivalent, key selection criteria include its 5V fixed output, 4.3–55V input range, 700nA shutdown current, 1.2A load capability, and compatibility with external synchronization or Burst Mode operation via SYNC pin grounding.
Technical Context
The LT3991IMSE-5#PBF employs constant-frequency current-mode control with internal slope compensation and an actively clamped VC node for stable loop response. Its oscillator supports 200kHz–2MHz switching via RT resistor, and frequency foldback activates during startup or overload to limit peak inductor current.
Burst Mode operation reduces no-load input current to 2.8µA while maintaining <15mVP-P output ripple; it disables when SYNC is tied to an external clock, shifting to pulse-skipping with 1.5mA quiescent current. The 1V enable threshold with 30mV hysteresis ensures reliable UVLO behavior above 4.3V VIN.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Output Voltage | Fixed 5.00V ±1.4% over –40°C to 125°C junction temperature |
| Input Voltage Range | 4.3V to 55V - supports wide automotive and industrial supply rails |
| Maximum Output Current | 1.2A continuous - limited by thermal design and 2.3A typical switch current limit |
| Quiescent Current | 2.8µA at no load in Burst Mode - enables >10-year battery life in always-on systems |
| Shutdown Current | 700nA - achieved by pulling EN low, enabling deep sleep in energy-sensitive applications |
| Switch On/Off Time | 110ns / 150ns minimum - constrains practical max duty cycle and min input voltage at high fSW |
| Power Good Threshold | 91% of regulated output (4.55V) with 1.3% hysteresis - provides reliable rail validation |
Pinout & Package
LT3991IMSE-5#PBF is housed in a 10-lead plastic MSOP package with exposed pad (Pin 11 = GND), offering θJA = 45°C/W and θJC = 10°C/W for robust thermal performance in space-constrained layouts.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| BD (1) | Boost diode anode connection | Connects to cathode of external Schottky; forms charge pump path for BOOST drive |
| BOOST (2) | Internal switch driver supply | Provides >VIN voltage to saturate bipolar NPN switch; requires external capacitor to SW |
| SW (3) | Switch node | Drives inductor; connects to BOOST capacitor, catch diode cathode, and inductor |
| VIN (4) | Main power input | Supplies internal circuitry and switch; must be locally bypassed with low-ESR capacitor |
| EN (5) | Enable control | Hysteretic 1.01V rising / 0.975V falling threshold; pulls part into 700nA shutdown when low |
| VOUT (6) | Fixed 5V output sense | Internally regulated to 5V; connects to internal 10MΩ feedback divider - no external resistors needed |
| SS (7) | Soft-start ramp control | Controls inrush current via external RC; discharged only when EN is low |
| RT (8) | Frequency setting | Resistor to GND sets fSW from 200kHz to 2MHz; 255kΩ yields 200kHz, 11kΩ yields 2MHz |
| PG (9) | Open-drain power-good flag | Asserts high when VOUT reaches 91% of 5V; valid only if EN high and VIN > 4.3V |
| SYNC (10) | External clock input | Ground for Burst Mode; tie to external clock for synchronized pulse-skipping (1.5mA IQ) |
Key Features
| Feature | Design Value |
|---|---|
| Ultralow quiescent current | 2.8µA regulating 12VIN to 5VOUT - extends battery runtime in IoT sensors and telematics |
| Low-ripple Burst Mode | Output ripple <15mVP-P at light loads - eliminates audible noise and EMI concerns in sensitive analog circuits |
| Integrated power switch | 0.44Ω NPN switch with internal boost Schottky - eliminates external gate driver and bootstrap components |
| Accurate power-good signaling | PG asserts at 4.55V (91% of 5V) with 1.3% hysteresis - enables safe sequencing in multi-rail systems |
| Thermally enhanced package | 10-lead MSOP with exposed GND pad - achieves 10°C/W junction-to-case resistance for 1.2A operation without heatsink |
Applications
| Automotive Battery Regulation | Industrial Power Supplies |
|---|---|
|
Use Scenario: Regulating 12V/24V/48V vehicle battery to stable 5V for infotainment microcontrollers and CAN transceivers during engine cranking and stop-start cycles. IC Role / Device Role / Timing Role: Primary step-down regulator with UVLO hysteresis and wide input tolerance - maintains 5V output down to 4.3V input during cold-crank events. Use Value: 700nA shutdown current prevents battery drain during vehicle dormancy; 2.8µA operating IQ supports >10-year backup power for telematics modules. |
Use Scenario: Providing isolated 5V bias for PLC I/O modules, field transmitters, and HART communicators in 24V DC-powered factory automation equipment. IC Role / Device Role / Timing Role: Fixed-output buck converter with internal compensation - simplifies layout and eliminates external loop compensation components. Use Value: 55V absolute max input withstands 48V system transients; PG flag enables diagnostics and fault logging before downstream logic resets. |
| Portable Medical Devices | Smart Metering Systems |
|
Use Scenario: Powering low-power MCU, BLE radio, and sensor front-end in handheld glucose meters and portable ECG monitors powered by single Li-ion or AA cells. IC Role / Device Role / Timing Role: High-efficiency, low-noise regulator operating in Burst Mode - delivers clean 5V rail without interfering with analog signal chains. Use Value: <15mVP-P ripple avoids ADC reference contamination; soft-start prevents inrush-induced brownouts during wake-from-sleep transitions. |
Use Scenario: Generating 5V for metrology SoCs, RTCs, and secure elements in AMI smart meters requiring decade-long battery-backed operation and tamper detection. IC Role / Device Role / Timing Role: Always-on regulator with programmable frequency and precise PG flag - supports accurate timekeeping and secure boot sequencing. Use Value: 2.8µA IQ enables >15-year coin-cell lifetime; SYNC pin allows synchronization to meter's master clock to reduce conducted EMI during RF transmission bursts. |
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-5#PBF | 42V max input, 2.5A output, 2.5µA IQ, integrated inductor option available | Higher current, lower max input voltage; uses Silent Switcher architecture for lower EMI | Choose for space-constrained designs needing higher output current or stricter EMI compliance |
| TPS63020DSJR | 4.2–17V input, 3A buck-boost, 25µA IQ, adjustable output (not fixed 5V) | Supports buck-boost topology; lacks PG flag and Burst Mode ripple control | Choose only if input voltage may drop below 5V (e.g., single-cell Li-ion backup) |
Compared with LT3991IMSE-5#PBF, LT8609SIV-5#PBF offers higher current and lower EMI but sacrifices 55V input capability; TPS63020DSJR provides buck-boost flexibility at the cost of higher quiescent current and no fixed 5V option or PG flag - making LT3991IMSE-5#PBF optimal for high-input, ultra-low-IQ, fixed-rail industrial and automotive use cases.
Availability
LT3991IMSE-5#PBF is available at Aetrix Electronics and suitable for automotive battery regulation, industrial power supplies, portable medical devices, and smart metering systems requiring stable component supply across extended temperature ranges and long production lifecycles.
Supply support for LT3991IMSE-5#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 healthcare markets.
The LT3991 product line delivers ultralow-quiescent-current buck regulators for always-on systems - engineered specifically for automotive, industrial, and battery-powered applications demanding high efficiency across wide input voltage ranges and extreme temperature conditions.
FAQ
What is the output voltage tolerance of the LT3991IMSE-5#PBF over temperature?
The LT3991IMSE-5#PBF guarantees a 5V output with ±1.4% tolerance across its full –40°C to 125°C junction temperature range, based on internal 10MΩ feedback divider trimming and 1.19V reference stability. This corresponds to 4.93V to 5.07V at room temperature and 4.89V to 5.11V over full temperature range per Electrical Characteristics table.
Does the LT3991IMSE-5#PBF require external feedback resistors?
No - the LT3991IMSE-5#PBF integrates a precision 10MΩ internal feedback divider and phase-lead capacitor optimized for 5V regulation, eliminating the need for external resistors. Pin 6 is labeled VOUT (not FB), confirming fixed-output configuration; external resistors would disrupt regulation accuracy and void the specified 5V tolerance.
How does the SYNC pin affect quiescent current in the LT3991IMSE-5#PBF?
When SYNC is grounded, the LT3991IMSE-5#PBF operates in low-ripple Burst Mode with 2.8µA quiescent current at no load. When driven by an external clock, it switches to pulse-skipping mode and quiescent current rises to 1.5mA - a 535× increase - due to continuous oscillator and control circuit activity even at light loads.
What thermal derating applies to the LT3991IMSE-5#PBF at 125°C junction temperature?
At 125°C junction temperature, the LT3991IMSE-5#PBF maintains full 1.2A output current capability per datasheet specifications, supported by its 10°C/W junction-to-case thermal resistance and exposed-pad MSOP package. No current derating is required up to 125°C, though PCB copper area and airflow should be verified for sustained full-load operation.
Can the LT3991IMSE-5#PBF operate with input voltage below 4.3V?
No - the LT3991IMSE-5#PBF has a hard minimum input voltage of 4.3V, below which internal circuitry cannot sustain regulation or enable functionality. If VIN drops below 4.3V, the EN pin must be pulled low to force shutdown; tying EN to VIN is invalid in sub-4.3V scenarios and may cause undefined behavior or failure to regulate.
LT3991IMSE-5#PBF Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc.
- Series:
- -
- Package/Case:
- 10-TFSOP, 10-MSOP (0.118", 3.00mm Width) Exposed Pad
- Packaging:
- Tube
- 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):
- 5V
- 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-5#PBF FAQ
1.How can I place an order for LT3991IMSE-5#PBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LT3991IMSE-5#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 LT3991IMSE-5#PBF reliable?
The price and inventory of LT3991IMSE-5#PBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LT3991IMSE-5#PBF is usually 5 days.
3.What payment methods are accepted for LT3991IMSE-5#PBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LT3991IMSE-5#PBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LT3991IMSE-5#PBF?
LT3991IMSE-5#PBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LT3991IMSE-5#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 LT3991IMSE-5#PBF?
For technical support, including LT3991IMSE-5#PBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LT3991IMSE-5#PBF requirements.
6.How does Aetrix verify that LT3991IMSE-5#PBF is sourced from the original manufacturer or authorized distributors?
All LT3991IMSE-5#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 LT3991IMSE-5#PBF meets industry standards.
7.What is the process for return or replacement of LT3991IMSE-5#PBF?
All LT3991IMSE-5#PBF units undergo pre-shipment inspection (PSI). If there is an issue with LT3991IMSE-5#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 LT3991IMSE-5#PBF part is unused and in its original packaging.
Return procedure for LT3991IMSE-5#PBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
LT3991IMSE-5#PBF Tags
-
TPS562201DDCR
Texas Instruments
-
MC34063ABD-TR
STMicroelectronics
-
TPS561201DDCR
Texas Instruments
-
MC33063ADR
Texas Instruments
-
MC34063ADR
Texas Instruments
-
TPS560200DBVR
Texas Instruments
-
AP3012KTR-G1
Diodes Incorporated
-
TLV61048DBVR
Texas Instruments
-
AZ34063UMTR-G1
Diodes Incorporated
-
TPS562200DDCR
Texas Instruments
-
AP62300TWU-7
Diodes Incorporated
-
MC34063EBD-TR
STMicroelectronics
Tech Hub
A practical engineering guide to 3.3V and 5V logic compatibility, input thresholds, resistor dividers, translator ICs, MOSFET level shifting, I2C pull-ups, timing limits and power-sequencing risks.
The 74HC595 uses push-pull logic outputs, while the TPIC6B595 uses 50 V open-drain DMOS sinks for higher-power loads. This guide compares timing, current limits, 3.3 V interfacing, load wiring, thermal…
The 74HC595 converts serial data into eight stable parallel outputs. This guide covers pin functions, shift and storage timing, OE and MR behavior, drive-current limits, cascading, voltage compatibilit…
A technical comparison of level-sensitive latches and edge-triggered flip-flops, covering timing windows, setup and hold limits, master–slave operation, time borrowing, race-through, HDL inference and…
A D latch stores one bit while Enable controls when data can pass. This reference covers gate-level operation, truth tables, transparency, setup and hold timing, LE versus OE, common ICs and practical …
An SR latch stores one bit through cross-coupled feedback. This engineering reference covers NOR and NAND implementations, truth tables, forbidden-state recovery, gated operation, switch debouncing, fa…
Latch circuits retain one bit through feedback. This technical reference covers SR and D latches, truth tables, transparency, timing limits, latch-versus-flip-flop behavior, applications and common log…
An engineering guide to LED driver operation, constant-current and constant-voltage outputs, linear and switching topologies, dimming, IC selection, calculations, replacement compatibility, and fault c…
Operational amplifier guide covering op amp basics, feedback, ideal vs real op amps, common configurations, buffer circuits, offset, bias current, gain-bandwidth, slew rate, rail-to-rail limits and sel…
Jumper cables guide covering safe connection order, red and black clamp placement, final ground connection, cable gauge, length, clamp quality, copper vs CCA cables, jump starter comparison and battery…
