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Analog Devices Inc. LT3973IMSE#PBF
- Part No.:
- LT3973IMSE#PBF
- Manufacturer:
- Analog Devices Inc.
- Package:
- 10-TFSOP, 10-MSOP (0.118", 3.00mm Width) Exposed Pad
- Datasheet:
-
LT3973IMSE#PBF.pdf
- Description:
- IC REG BUCK ADJ 750MA 10MSOP
- Quantity:
- Payment:
- Shipping:
Inventory:149
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Product details
Overview
LT3973IMSE#PBF from Analog Devices (formerly Linear Technology) is a 42V, 750mA monolithic step-down DC/DC regulator with integrated boost and catch diodes, 2.5µA quiescent current, and adjustable switching frequency (200kHz–2.2MHz). It delivers fixed 5V output in MSOP-10 package and is engineered for automotive cold-crank regulation where input may dip to 4.2V while maintaining 530mV dropout.
For engineers reviewing the LT3973IMSE#PBF datasheet, LT3973IMSE#PBF pinout, LT3973IMSE#PBF application, or LT3973IMSE#PBF equivalent, key selection criteria include ultralow IQ (2.5µA at 12VIN→5VOUT), low-ripple Burst Mode operation (<10mVP-P), programmable UVLO, power-good flag, and thermal shutdown - all critical for battery-powered and automotive subsystems.
Technical Context
The LT3973IMSE#PBF employs current-mode control for fast transient response and loop stability, with internal bipolar NPN switch driven via BOOST capacitor to ensure full saturation. Its minimum on-time (70ns) and maximum duty cycle (~97.5%) enable stable operation down to 4.2V input while sustaining 5V output under dropout conditions.
It integrates dual Schottky diodes (boost and catch), error amplifier, oscillator, and power-good comparator. The FB pin is internally tied to a 1.21V reference for adjustable versions; however, LT3973IMSE#PBF is the fixed 5V variant - VOUT pin replaces FB and is regulated directly to 4.94–5.06V across –40°C to 125°C.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Input Voltage Range | 4.2V to 42V - supports automotive battery transients including cold-crank (≥4.2V required for regulation) |
| Output Voltage | 5.0V ±1.2% (4.94V–5.06V) - factory-trimmed fixed output; no external feedback resistors needed |
| Max Output Current | 750mA - limited by switch peak current (1.65A typ.) and catch diode valley current (1.15A typ.) |
| Quiescent Current | 2.5µA at 12VIN → 5VOUT - enables always-on systems with multi-year battery life |
| Switching Frequency | 200kHz to 2.2MHz - set externally via RT resistor; higher frequencies allow smaller magnetics |
| Dropout Voltage | 530mV min - enforced by internal comparator; maintains regulation when VIN approaches VOUT |
| Power Good Threshold | 90% of VOUT (4.5V) - open-drain PG flag signals valid output within tolerance |
Pinout & Package
LT3973IMSE#PBF is housed in a thermally enhanced 10-lead plastic MSOP package (3mm × 3mm footprint, 0.85mm height) with exposed pad (Pin 11) soldered to PCB for thermal dissipation (θJA = 45°C/W).
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| VOUT (Pin 1) | Fixed-output voltage reference node | Internally regulated to 5V; connects to output capacitor and load - replaces FB pin in adjustable variants |
| OUT (Pin 2) | Dropout regulation sense & boost charge path | Tied to VOUT to enable minimum dropout mode; supplies current to charge BOOST capacitor during low-VIN operation |
| EN/UVLO (Pin 3) | Enable and undervoltage lockout input | Active-high enable; 1.19V threshold with 45mV hysteresis; shuts down device drawing only 0.75µA when low |
| VIN (Pin 4) | Main power input | Supplies internal circuitry and switch; must be locally bypassed with ≥4.7µF ceramic capacitor |
| GND (Pin 5 & Pin 11) | Signal and power ground | Pin 5 is signal GND; Pin 11 is exposed thermal pad - both must connect to PCB ground plane |
| SW (Pin 6) | Switch node | Connects to inductor; carries high di/dt switching current - requires tight layout and low-inductance path |
| BOOST (Pin 7) | Bootstrap drive voltage source | Drives internal NPN switch; requires external 0.47µF ceramic capacitor between BOOST and SW |
| BD (Pin 8) | Bias diode anode input | Accepts external bias >3.2V (e.g., from VOUT) to improve efficiency by powering internal regulator |
| PG (Pin 9) | Power good open-drain output | Sinks 350µA max when active; pulled high externally to indicate VOUT ≥4.5V and EN/UVLO high |
| RT (Pin 10) | Frequency programming input | Resistor to GND sets switching frequency; e.g., 215kΩ yields ~600kHz per datasheet Table 1 |
Key Features
| Feature | Design Value |
|---|---|
| Integrated boost and catch Schottky diodes | Eliminates 2 external diodes; reduces BOM count, board area, and EMI from discrete routing |
| Low-ripple Burst Mode operation | Maintains <10mVP-P output ripple at light loads while achieving 2.5µA IQ - critical for noise-sensitive analog rails |
| Accurate programmable UVLO | EN/UVLO threshold (1.19V) with 45mV hysteresis enables precise system-level brownout detection and sequencing |
| Internal catch diode current limit | Valley-current foldback limits output during short-circuit or overload - protects IC without external sensing |
| Thermal shutdown with auto-recovery | Shuts down above 165°C junction temperature; resumes operation after cooldown - prevents permanent damage |
Applications
| Automotive Body Control Module (BCM) | Industrial IoT Sensor Node |
|---|---|
Use Scenario: Powering microcontroller, CAN transceiver, and LIN interface in door module during cold-crank (VIN dips to 4.5V). IC Role / Device Role / Timing Role: Primary 5V buck regulator delivering stable rail despite wide input swing (4.2V–42V) and load transients. Use Value: 530mV dropout ensures uninterrupted operation below 6V input; 2.5µA IQ extends battery backup runtime during vehicle sleep mode. | Use Scenario: Long-life wireless sensor node powered by primary lithium battery (3.6V nominal) with energy-harvesting supplement. IC Role / Device Role / Timing Role: Efficient 5V conversion for MCU and radio, operating in Burst Mode during 99% idle time. Use Value: 2.5µA quiescent current enables >10-year battery life; integrated diodes reduce component count and leakage paths. |
| Portable Medical Diagnostic Device | Programmable Logic Controller (PLC) I/O Module |
Use Scenario: Battery-backed handheld ultrasound probe requiring clean, low-noise 5V supply for analog front-end and FPGA. IC Role / Device Role / Timing Role: Low-ripple 5V regulator feeding ADC reference and clock distribution circuits. Use Value: <10mVP-P ripple in Burst Mode avoids digitization artifacts; PG flag synchronizes system wake-up with rail readiness. | Use Scenario: DIN-rail mounted PLC module converting 24V industrial bus to isolated 5V logic rail for digital I/O drivers. IC Role / Device Role / Timing Role: Non-isolated 5V pre-regulator upstream of isolated DC/DC converters. Use Value: 42V absolute max input withstands 36V transients; thermal shutdown protects against enclosure overheating in confined spaces. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar step-down regulator applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| LT3973EMSE-5#PBF | Same electrical specs and pinout; rated for 0°C to 125°C (vs. –40°C to 125°C for LT3973IMSE#PBF) | Not qualified for extended industrial temperature range; unsuitable for automotive or outdoor deployments | Select LT3973IMSE#PBF for designs requiring guaranteed operation at –40°C ambient. |
| LM5164QDDARQ1 | 42V input, 500mA output, 1.5µA IQ; requires external high-side MOSFET and diode; no integrated catch diode | Lacks integrated diodes and PG flag; needs more external components and layout effort | Choose LM5164QDDARQ1 only if lower IQ outweighs added complexity and reduced reliability from discrete diodes. |
Compared with LT3973EMSE-5#PBF, LT3973IMSE#PBF guarantees full –40°C functionality; compared with LM5164QDDARQ1, it trades slightly higher IQ for integration, reduced EMI, and simplified design - making it optimal for space-constrained, reliability-critical 5V systems.
Availability
LT3973IMSE#PBF is available at Aetrix Electronics and suitable for automotive body electronics, industrial sensor nodes, portable medical devices, and PLC I/O modules requiring stable component supply with guaranteed –40°C to 125°C operation.
Supply support for LT3973IMSE#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 acquired Linear Technology in 2017 and maintains its precision power portfolio with rigorous automotive and industrial qualification standards.
The LT3973 product line delivers high-voltage, ultralow-IQ buck regulators for harsh-environment applications where input voltage extremes, thermal stress, and long-term reliability are critical - especially automotive infotainment, ADAS, and industrial control.
FAQ
What is the guaranteed operating temperature range for LT3973IMSE#PBF?
The LT3973IMSE#PBF is guaranteed to operate over –40°C to 125°C junction temperature. This rating is validated across process corners and environmental stress testing, distinguishing it from the E-grade LT3973EMSE-5#PBF (0°C to 125°C). The "I" grade designation confirms full industrial temperature compliance for LT3973IMSE#PBF.
Does LT3973IMSE#PBF require external feedback resistors to set the output voltage?
No. LT3973IMSE#PBF is the fixed 5V variant - it uses an internal resistor divider connected to the VOUT pin (Pin 1), eliminating external feedback components. This differs from the adjustable LT3973 version, which requires external R1/R2 on the FB pin. The 5V output is trimmed to 4.94V–5.06V across temperature and line conditions for LT3973IMSE#PBF.
How does the LT3973IMSE#PBF achieve ultralow quiescent current in Burst Mode?
LT3973IMSE#PBF reduces IQ to 2.5µA by disabling non-essential circuitry between switching bursts - including oscillator, gate drivers, and error amplifier - while retaining regulation via periodic sampling. During each burst, the internal switch delivers just enough energy to maintain VOUT within tolerance before returning to ultra-low-power sleep. This architecture is confirmed in the datasheet's Typical Performance Characteristics (Fig G08, G09).
Can LT3973IMSE#PBF operate with input voltage below 4.2V?
LT3973IMSE#PBF begins switching below 4.2V (down to ~3V), but regulation is not guaranteed. The 4.2V minimum is specified for accurate 5V output and proper UVLO function. Below this, FB reference accuracy degrades and PG flag becomes invalid. For reliable 5V regulation, maintain VIN ≥4.2V - a requirement explicitly stated in the Absolute Maximum Ratings and Electrical Characteristics tables for LT3973IMSE#PBF.
What is the role of the OUT pin (Pin 2) in LT3973IMSE#PBF?
In LT3973IMSE#PBF, the OUT pin serves two functions: (1) it senses dropout condition to enforce the 530mV minimum VIN–VOUT differential, and (2) it sources current to recharge the BOOST capacitor during low-input operation. Tying OUT to VOUT enables the extended-duty-cycle mode critical for cold-crank performance - a behavior confirmed in the Applications Information section and Pin Functions description for LT3973IMSE#PBF.
LT3973IMSE#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:
- Adjustable
- Number of Outputs:
- 1
- Voltage - Input (Min):
- 4.2V
- Voltage - Input (Max):
- 42V
- Voltage - Output (Min/Fixed):
- 1.21V
- Voltage - Output (Max):
- 24V
- Current - Output:
- 750mA
- Frequency - Switching:
- 195kHz ~ 2.15MHz
- Synchronous Rectifier:
- No
- Operating Temperature:
- -40°C ~ 125°C (TJ)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 10-MSOP-EP
LT3973IMSE#PBF FAQ
1.How can I place an order for LT3973IMSE#PBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LT3973IMSE#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 LT3973IMSE#PBF reliable?
The price and inventory of LT3973IMSE#PBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LT3973IMSE#PBF is usually 5 days.
3.What payment methods are accepted for LT3973IMSE#PBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LT3973IMSE#PBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LT3973IMSE#PBF?
LT3973IMSE#PBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LT3973IMSE#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 LT3973IMSE#PBF?
For technical support, including LT3973IMSE#PBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LT3973IMSE#PBF requirements.
6.How does Aetrix verify that LT3973IMSE#PBF is sourced from the original manufacturer or authorized distributors?
All LT3973IMSE#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 LT3973IMSE#PBF meets industry standards.
7.What is the process for return or replacement of LT3973IMSE#PBF?
All LT3973IMSE#PBF units undergo pre-shipment inspection (PSI). If there is an issue with LT3973IMSE#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 LT3973IMSE#PBF part is unused and in its original packaging.
Return procedure for LT3973IMSE#PBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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