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Analog Devices Inc. LT3973EMSE-3.3#PBF
- Part No.:
- LT3973EMSE-3.3#PBF
- Manufacturer:
- Analog Devices Inc.
- Package:
- 10-TFSOP, 10-MSOP (0.118", 3.00mm Width) Exposed Pad
- Datasheet:
-
LT3973EMSE-3.3#PBF.pdf
- Description:
- IC REG BUCK 3.3V 750MA 10MSOP
- Quantity:
- Payment:
- Shipping:
Inventory:407
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Product details
Overview
LT3973EMSE-3.3#PBF from Analog Devices (formerly Linear Technology) is a fixed 3.3V, 42V-input, 750mA monolithic buck regulator with integrated boost and catch Schottky diodes, 2.5µA quiescent current, and low-ripple Burst Mode® operation. It delivers automotive-grade power regulation in cold-crank conditions with 530mV minimum dropout voltage and a power good flag for system sequencing.
For engineers reviewing the LT3973EMSE-3.3#PBF datasheet, LT3973EMSE-3.3#PBF pinout, LT3973EMSE-3.3#PBF application, or LT3973EMSE-3.3#PBF equivalent, key selection criteria include ultralow IQ at light load, fixed 3.3V output accuracy (±1.2% over –40°C to 125°C), integrated diode topology eliminating external components, and MSOP-10 thermal performance (θJA = 45°C/W).
Technical Context
The LT3973EMSE-3.3#PBF employs constant-frequency current-mode control with programmable switching frequency (200kHz–2.2MHz via RT pin) and automatic Burst Mode® entry below ~10mA load to maintain <10mVP-P output ripple while drawing only 1.8µA input current. Its bipolar NPN internal switch is driven by a charge-pump BOOST circuit enabling full saturation even during automotive dropout.
It integrates dual protection mechanisms: catch diode valley-current limiting (1.15A typical) for short-circuit fault containment and thermal shutdown. The EN/UVLO pin provides accurate, hysteresis-enabled (45mV) undervoltage lockout with 0.75µA shutdown current, and the PG pin asserts open-drain low until VOUT reaches 90% of 3.3V.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Output Voltage | Fixed 3.3V ±1.2% over –40°C to 125°C - ensures stable logic rail without external feedback resistors. |
| Input Voltage Range | 4.2V to 42V - supports 12V/24V automotive batteries including cold-crank transients down to 3.8V start-up. |
| Quiescent Current | 2.5µA at 12VIN/3.3VOUT - enables always-on systems with multi-year battery life in portable instrumentation. |
| Max Output Current | 750mA continuous - sufficient for powering microcontrollers, sensors, and interface ICs from a single compact regulator. |
| Switching Frequency | 200kHz to 2.2MHz (RT-programmable) - allows optimization of inductor size vs. EMI vs. efficiency across diverse PCB layouts. |
| Dropout Voltage | 530mV minimum - maintains regulation when input drops near output, critical for automotive brown-out resilience. |
| Output Ripple | <10mVP-P in Burst Mode - eliminates need for post-regulation LDOs in noise-sensitive analog signal chains. |
Pinout & Package
LT3973EMSE-3.3#PBF is housed in a thermally enhanced 10-lead plastic MSOP package (3mm × 3mm footprint, exposed pad) with θJA = 45°C/W. The exposed pad (Pin 11) must be soldered to PCB ground for thermal and electrical integrity.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| VOUT (Pin 1) | Fixed-output feedback reference | Internally regulated to 3.3V; connects to internal resistor divider - no external FB network required. |
| OUT (Pin 2) | Dropout regulation node | Tied to VOUT to enforce 530mV minimum dropout; supplies boost capacitor charging current during low-VIN operation. |
| EN/UVLO (Pin 3) | Enable and undervoltage lockout input | Active-high enable with 1.19V rising threshold and 45mV hysteresis; draws only 1nA bias current. |
| VIN (Pin 4) | Main power input | Accepts 4.2V–42V; powers internal circuitry and switch - requires local 4.7µF X7R ceramic bypass. |
| GND (Pin 5 & Exposed Pad) | Power and signal reference | Common return for all circuits; exposed pad is mandatory GND connection for thermal dissipation. |
| SW (Pin 6) | Switch node | Drives external inductor; connects to collector of internal bipolar NPN switch - requires careful layout to minimize EMI. |
| BOOST (Pin 7) | Charge-pump drive | Supplies >VIN voltage to switch base; requires 0.47µF ceramic capacitor to SW for proper saturation. |
| BD (Pin 8) | Bias diode anode | Accepts external bias ≥3.2V (e.g., from VOUT) to improve efficiency by powering internal regulator externally. |
| PG (Pin 9) | Power good flag | Open-drain output asserting high when VOUT ≥2.97V; sinks 350µA max - used for processor reset or sequencing. |
| RT (Pin 10) | Frequency set | Resistor-to-GND sets switching frequency; 215kΩ yields 600kHz - balances size, efficiency, and EMI. |
Key Features
| Feature | Design Value |
|---|---|
| Integrated boost and catch Schottky diodes | Eliminates 2 external diodes and associated layout area; reduces BOM count and improves reliability in space-constrained designs. |
| Low-ripple Burst Mode® operation | Maintains <10mVP-P output ripple at light loads while achieving 1.8µA no-load supply current - ideal for battery-powered IoT nodes. |
| Accurate programmable undervoltage lockout | EN/UVLO threshold tightly specified (1.16V–1.28V) with 45mV hysteresis - prevents erratic startup during slow-rising battery rails. |
| Thermal shutdown with current-limit protection | Combines catch diode valley-current limit (1.15A) and thermal shutdown - protects against sustained short-circuit faults without external circuitry. |
| Power good flag with 90% threshold | PG asserts valid only when VOUT ≥2.97V and VIN ≥4.2V - provides precise system-level power sequencing without external comparators. |
Applications
| Automotive Body Control Module (BCM) | Industrial Sensor Transmitter |
|---|---|
Use Scenario: Powering CAN transceiver, microcontroller, and analog front-end in under-hood modules exposed to 4.5V–42V battery transients and –40°C to 125°C ambient. IC Role / Device Role / Timing Role: Primary 3.3V system rail regulator with cold-crank support and power-good signaling for MCU reset coordination. Use Value: 530mV dropout and 2.5µA IQ ensure uninterrupted operation during engine start; integrated diodes reduce component count by two. |
Use Scenario: Providing stable 3.3V supply to 4–20mA loop-powered pressure/temperature sensors in hazardous-area field instruments. IC Role / Device Role / Timing Role: Isolated auxiliary rail generator with ultra-low standby current to extend loop-powered device battery life. Use Value: 1.8µA Burst Mode current enables multi-year operation on primary cell; 42V input withstands induced surges on long cable runs. |
| Portable Medical Diagnostic Device | Smart Building Controller |
Use Scenario: Powering low-noise ADCs, op-amps, and BLE radio in handheld ultrasound or glucose meters operating from single-cell Li-ion (3.0V–4.2V) or 9V alkaline. IC Role / Device Role / Timing Role: High-efficiency, low-ripple DC-DC converter delivering clean 3.3V rail for precision analog signal chain and digital subsystems. Use Value: <10mVP-P ripple avoids post-regulation filtering; 750mA output supports simultaneous sensor excitation and wireless transmission. |
Use Scenario: Regulating 3.3V for Zigbee/Thread SoCs, environmental sensors, and non-volatile memory in wall-mounted HVAC controllers powered from 24VAC rectified supply. IC Role / Device Role / Timing Role: Robust primary DC-DC stage converting unregulated 18V–36V DC to stable 3.3V with thermal fault protection. Use Value: Integrated current limiting and thermal shutdown prevent field failures due to capacitor aging or inductor saturation; MSOP-10 fits dense PCB layouts. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar buck regulator applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| LT8609SIV#PBF | 42V input, 3.3V fixed, 2A output, 2.5µA IQ, synchronous rectification, 3mm × 4mm LQFN | Higher output current and synchronous architecture improve efficiency above 500mA; lacks BD pin for external bias | Select when >750mA load or higher full-load efficiency is required; verify thermal design for LQFN package. |
| TPS54332DDAR | 28V input, 3.3V adjustable (external resistors), 3A output, 26µA IQ, SOIC-8 | Higher current but significantly higher quiescent current; no integrated catch diode - requires external Schottky | Select when cost sensitivity outweighs IQ and board area; accept added BOM and layout complexity for 3A capability. |
Compared with LT3973EMSE-3.3#PBF, LT8609SIV#PBF offers +1.25A output headroom and synchronous efficiency gains but trades off BD-pin flexibility, while TPS54332DDAR sacrifices ultralow IQ and integration for higher current and lower unit cost in non-battery-critical applications.
Availability
LT3973EMSE-3.3#PBF is available at Aetrix Electronics and suitable for automotive body electronics, industrial sensor transmitters, and portable medical diagnostics requiring stable component supply with guaranteed long-term manufacturability and extended temperature range support.
Supply support for LT3973EMSE-3.3#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. (ADI) is a global leader in high-performance analog, mixed-signal, and digital signal processing semiconductors, formed through the acquisition of Linear Technology in 2017.
The LT3973 family was designed by Linear Technology specifically for high-input-voltage, ultralow-quiescent-current step-down regulation in automotive, industrial, and portable applications where reliability, small size, and wide input range are critical.
FAQ
What is the guaranteed output voltage accuracy of the LT3973EMSE-3.3#PBF over temperature?
The LT3973EMSE-3.3#PBF guarantees a 3.3V output with ±1.2% tolerance over the full –40°C to 125°C junction temperature range, as confirmed by electrical characteristics tables specifying 3.26V to 3.34V min/max limits at temperature extremes. This accuracy is achieved via laser-trimmed internal feedback resistors and does not require external calibration.
Can the LT3973EMSE-3.3#PBF operate with input voltages below 4.2V?
Yes, the LT3973EMSE-3.3#PBF can begin switching at ~3V input, but regulation to 3.3V is not guaranteed below 4.2V. Below this threshold, the internal reference degrades and output voltage drops proportionally; the EN/UVLO pin also becomes inaccurate. For reliable 3.3V regulation, VIN must remain ≥4.2V, per Absolute Maximum Ratings and Electrical Characteristics specifications.
How does the BOOST pin function in the LT3973EMSE-3.3#PBF, and what capacitor value is required?
The BOOST pin in the LT3973EMSE-3.3#PBF supplies base drive voltage >VIN to fully saturate the internal bipolar NPN switch. A 0.47µF X7R ceramic capacitor must be placed between BOOST and SW pins. This capacitor is charged during switch-off time and discharged into the switch base during turn-on, ensuring low VCE(SAT) and high efficiency across the input range.
Does the LT3973EMSE-3.3#PBF require an external catch diode?
No, the LT3973EMSE-3.3#PBF integrates a catch Schottky diode on-die, eliminating the need for an external diode. This is explicitly stated in the product description ("integrated diodes") and confirmed in the Pin Functions section, where BD (Pin 8) is defined as the anode connection for the internal boost diode - not an external catch diode terminal.
What thermal derating applies to the LT3973EMSE-3.3#PBF in its MSOP package?
The LT3973EMSE-3.3#PBF in the 10-lead MSOP package has θJA = 45°C/W. At 125°C maximum junction temperature and 25°C ambient, maximum allowable power dissipation is (125–25)/45 ≈ 2.22W. With typical 85% efficiency at 750mA/3.3V (2.475W output), input power is ~2.91W, resulting in ~0.44W dissipation - well within thermal limits when the exposed pad is properly soldered to PCB copper.
LT3973EMSE-3.3#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):
- 4.2V
- Voltage - Input (Max):
- 42V
- Voltage - Output (Min/Fixed):
- 3.3V
- Voltage - Output (Max):
- -
- 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
LT3973EMSE-3.3#PBF FAQ
1.How can I place an order for LT3973EMSE-3.3#PBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LT3973EMSE-3.3#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 LT3973EMSE-3.3#PBF reliable?
The price and inventory of LT3973EMSE-3.3#PBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LT3973EMSE-3.3#PBF is usually 5 days.
3.What payment methods are accepted for LT3973EMSE-3.3#PBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LT3973EMSE-3.3#PBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LT3973EMSE-3.3#PBF?
LT3973EMSE-3.3#PBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LT3973EMSE-3.3#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 LT3973EMSE-3.3#PBF?
For technical support, including LT3973EMSE-3.3#PBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LT3973EMSE-3.3#PBF requirements.
6.How does Aetrix verify that LT3973EMSE-3.3#PBF is sourced from the original manufacturer or authorized distributors?
All LT3973EMSE-3.3#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 LT3973EMSE-3.3#PBF meets industry standards.
7.What is the process for return or replacement of LT3973EMSE-3.3#PBF?
All LT3973EMSE-3.3#PBF units undergo pre-shipment inspection (PSI). If there is an issue with LT3973EMSE-3.3#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 LT3973EMSE-3.3#PBF part is unused and in its original packaging.
Return procedure for LT3973EMSE-3.3#PBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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