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Analog Devices Inc. LT3645IMSE#TRPBF
- Part No.:
- LT3645IMSE#TRPBF
- Manufacturer:
- Analog Devices Inc.
- Category:
- Voltage Regulators - Linear + Switching
- Package:
- 12-TSSOP (0.118", 3.00mm Width) Exposed Pad
- Datasheet:
-
LT3645IMSE#TRPBF.pdf
- Description:
- IC REG DL BUCK/LNR 750KHZ 12MSOP
- Quantity:
- Payment:
- Shipping:
Inventory:3,866
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Product details
Overview
LT3645IMSE#TRPBF from Analog Devices (formerly Linear Technology) is a dual-output DC/DC regulator integrating a 500mA synchronous step-down buck converter and a 200mA low-dropout linear regulator (LDO) in a single 12-lead MSE package. It operates from 3.6V to 36V input, delivers 3.3V/5V buck outputs and programmable LDO outputs (0.8V–8V), and features 750kHz switching frequency, <2μA shutdown current, and integrated overvoltage lockout up to 40V - enabling robust power management for automotive image sensor and microcontroller supply rails.
For engineers reviewing the LT3645IMSE#TRPBF datasheet, LT3645IMSE#TRPBF pinout, LT3645IMSE#TRPBF application, or LT3645IMSE#TRPBF equivalent, key selection criteria include its dual-regulator architecture with independent enable controls (EN/UVLO and EN2), thermally enhanced MSOP package with exposed pad, 310mV LDO dropout at 200mA, and precise 0.8V/0.797V feedback references for stable output regulation across industrial temperature range (–40°C to 125°C).
Technical Context
The LT3645IMSE#TRPBF implements a constant-frequency current-mode buck regulator with internal bipolar NPN switch and BOOST-driven gate drive, paired with a separate bipolar NPN-based LDO powered from VCC2. Its control loop uses dedicated error amplifiers with ramped soft-start (0.9ms buck / 0.6ms LDO) and cycle-by-cycle current limiting (1A typical switch limit).
Protection architecture includes undervoltage lockout (3.4V rising), overvoltage lockout (38.5V rising), thermal shutdown (~160°C), short-circuit robustness via DA-pin current sensing, and open-collector NPG flag asserting when both FB and FB2 exceed 720mV - confirming regulation of both outputs simultaneously.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Input Voltage Range | 3.6V to 36V continuous; withstands 55V nonrepetitive transients - supports 24V industrial and 12V automotive battery inputs. |
| Buck Output Current | 500mA maximum - sufficient for powering CMOS image sensors or MCU cores without external boost. |
| LDO Output Current | 200mA maximum with 310mV dropout at full load - enables clean post-regulation for noise-sensitive analog circuits. |
| Switching Frequency | 750kHz typical - allows use of compact 10–15μH inductors and reduces EMI compared to lower-frequency alternatives. |
| Feedback Reference Voltages | 0.800V (FB) and 0.797V (FB2) - high-precision references enable ±1% output voltage accuracy with standard resistor dividers. |
| Shutdown Current | <2μA - critical for always-on systems requiring ultra-low quiescent power during sleep modes. |
| Operating Temperature | –40°C to +125°C junction - qualified for under-hood automotive and industrial control environments. |
Pinout & Package
LT3645IMSE#TRPBF is housed in a thermally enhanced 12-lead plastic MSOP package (3mm × 4.1mm) with exposed pad (Pin 13) electrically connected to GND and required to be soldered to PCB for thermal performance (θJA = 40°C/W).
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| EN/UVLO (Pin 5) | Enable and undervoltage lockout input | 1.23V threshold enables precise input voltage monitoring; tie directly to VIN if UVLO not needed. |
| FB (Pin 6) | Buck feedback input | Regulated to 0.800V; sets buck output voltage via resistor divider (e.g., 3.3V = 10kΩ + 31.6kΩ). |
| GND (Pin 7, Exposed Pad Pin 13) | Power and signal ground reference | Must connect exposed pad to large PCB ground plane with thermal vias for thermal reliability. |
| DA (Pin 8) | Catch diode current sense | Detects external Schottky diode current; reduces switching frequency if >0.9A to prevent overload. |
| BOOST (Pin 10) | Internal switch gate drive supply | Charged via internal Schottky from VCC2; requires 0.1μF capacitor to SW for proper NPN saturation. |
| SW (Pin 9) | Buck switch node | Connects to inductor and cathode of external catch diode; carries high di/dt switching current. |
| VIN (Pin 11) | Main input power supply | Supplies buck switch, control circuitry, and LDO driver; requires ≥1μF local ceramic bypass. |
| VCC2 (Pin 14) | LDO input supply | Must be ≥2.5V to enable internal BOOST diode; powers LDO transistor Q2 and generates BOOST voltage. |
| OUT2 (Pin 15) | LDO regulated output | Delivers up to 200mA; requires ≥0.47μF output capacitor for stability and transient response. |
| FB2 (Pin 16) | LDO feedback input | Regulated to 0.797V; sets LDO output voltage (e.g., 1.8V = 10kΩ + 10kΩ). |
| EN2 (Pin 4) | LDO enable input | Pull >1.6V to enable LDO; pull <0.5V to disable independently of buck regulator. |
| NPG (Pin 3) | Open-collector power-good flag | Pulls low only when both FB ≥720mV and FB2 ≥720mV - confirms dual-output regulation status. |
Key Features
| Feature | Design Value |
|---|---|
| Integrated dual-regulator architecture | Combines 500mA buck and 200mA LDO in one IC - eliminates discrete LDO stage and saves board space in multi-rail systems. |
| Wide input voltage range with OVLO/UVO | 3.6V–36V operation plus 55V transient tolerance and 38.5V overvoltage lockout - protects against load dump and cold-crank conditions. |
| Independent enable and soft-start | Separate EN/UVLO (buck+LDO) and EN2 (LDO-only) pins with 0.9ms/0.6ms soft-start - prevents inrush and enables staggered power-up sequencing. |
| Thermally optimized MSOP package | 12-lead MSE with exposed GND pad (θJA = 40°C/W) - enables reliable 500mA operation without heatsink in compact layouts. |
| Precision dual feedback references | 0.800V (buck) and 0.797V (LDO) references with <±1% drift over temperature - ensures tight output voltage regulation without trimming. |
| Robust fault protection | Cycle-by-cycle current limit, DA-pin overload detection, thermal shutdown, and NPG flag - simplifies system-level safety design for automotive applications. |
Applications
| Automotive CMOS Image Sensors | Industrial/Automotive Micro-Controller Supply |
|---|---|
|
Use Scenario: Powering high-resolution camera modules in ADAS or rear-view systems where EMI-sensitive analog imaging paths coexist with digital logic. IC Role / Device Role / Timing Role: Provides clean, low-noise 1.2V/1.8V LDO rail for image sensor analog front-end while delivering 3.3V/5V buck power to digital interface and processor. Use Value: Dual-regulator integration eliminates cross-talk between switching and analog domains; NPG flag enables system-level power sequencing validation. |
Use Scenario: Supplying main MCU core (e.g., ARM Cortex-M7) and I/O peripherals in vehicle body control modules operating from 12V battery with wide voltage transients. IC Role / Device Role / Timing Role: Delivers 3.3V buck output for MCU core and 5V buck output for CAN transceivers, with independent EN2-controlled LDO for isolated sensor bias rails. Use Value: 36V input rating and 55V transient tolerance ensure uninterrupted operation during load dump; <2μA shutdown extends battery life in sleep mode. |
| Industrial PLC I/O Modules | Ruggedized Telematics Gateways |
|
Use Scenario: Powering isolated analog input channels and digital isolators in programmable logic controller backplanes exposed to 24V DC field wiring. IC Role / Device Role / Timing Role: Generates 5V buck rail for digital isolators and 3.3V LDO rail for precision ADC reference buffers using shared VCC2 supply. Use Value: 310mV LDO dropout at 200mA ensures stable 3.3V output even as 24V input sags to 18V during brownout events. |
Use Scenario: Supporting LTE/Wi-Fi modem, GPS receiver, and CAN/FlexRay interfaces in fleet management telematics units mounted in engine compartments. IC Role / Device Role / Timing Role: Supplies 3.3V buck output to modem baseband, 1.8V LDO output to RF front-end, and monitors dual-rail health via NPG flag for diagnostics. Use Value: –40°C to +125°C operation and thermal shutdown protect against under-hood thermal stress; 750kHz switching minimizes filter size in space-constrained enclosures. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar dual-output regulator applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| LT3641IMSE#TRPBF | Single-output 500mA buck only; no integrated LDO; same 3.6V–36V input and 750kHz frequency. | Suitable when only buck regulation is needed; requires external LDO for second rail. | Select when board space permits discrete LDO and cost optimization is prioritized over integration. |
| TPS63020DSJR | Buck-boost topology (2.5V–5.5V input); 3A output; no LDO; different control architecture (hysteretic vs current-mode). | Used in USB-powered or Li-ion battery systems where input may fall below output voltage. | Choose only for battery-fed applications needing buck-boost capability; not drop-in due to incompatible input range and lack of LDO. |
Compared with LT3645IMSE#TRPBF, LT3641IMSE#TRPBF reduces integration but lowers BOM count for single-rail designs, while TPS63020DSJR addresses fundamentally different input-voltage constraints and lacks the LDO functionality essential for noise-sensitive dual-rail systems.
Availability
LT3645IMSE#TRPBF is available at Aetrix Electronics and suitable for automotive CMOS image sensor power supplies, industrial PLC I/O modules, and ruggedized telematics gateway designs requiring stable component supply across extended temperature and high-reliability environments.
Supply support for LT3645IMSE#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, 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 LT3645 product line was designed specifically for dual-rail power management in harsh-environment applications - combining high-voltage buck conversion with precision low-noise LDO regulation in thermally efficient packages for automotive and industrial control systems.
FAQ
What is the maximum input voltage rating for LT3645IMSE#TRPBF during continuous operation?
The LT3645IMSE#TRPBF has a continuous maximum input voltage rating of 36V. It can withstand nonrepetitive 55V transients for up to one second, but will enter overvoltage lockout and cease regulation if VIN exceeds 38.5V. This makes LT3645IMSE#TRPBF suitable for 24V industrial systems and automotive applications with load-dump protection requirements.
How does the NPG pin on LT3645IMSE#TRPBF indicate power-good status?
The NPG pin on LT3645IMSE#TRPBF is an open-collector output that pulls low only when both FB voltage exceeds 720mV and FB2 voltage exceeds 720mV - confirming that both the buck and LDO outputs are within 90% of their target regulation. This dual-threshold behavior ensures system-level confidence in complete power rail readiness before enabling downstream logic.
Can LT3645IMSE#TRPBF operate with VCC2 supplied below 2.5V?
Yes, LT3645IMSE#TRPBF can operate with VCC2 below 2.5V, but requires an external Schottky diode (e.g., BAS70) connected from VCC2 (anode) to BOOST (cathode) to maintain proper gate drive for the internal NPN switch. Without this diode, the internal Schottky cannot generate sufficient BOOST voltage, risking reduced efficiency or instability in the buck regulator.
What is the minimum load requirement for reliable startup of LT3645IMSE#TRPBF?
LT3645IMSE#TRPBF has no mandatory minimum load for steady-state operation, but startup reliability depends on inductor energy transfer to charge the BOOST capacitor. For slow-ramping inputs or zero-load conditions at turn-on, a minimum load of ~10mA on the buck output helps ensure proper BOOST voltage establishment. Figure 4a/b in the datasheet shows typical minimum input voltage vs. output current for 3.3V and 5V configurations.
Does LT3645IMSE#TRPBF support independent enable control of its buck and LDO sections?
Yes, LT3645IMSE#TRPBF supports fully independent enable control: EN/UVLO (Pin 5) enables or disables both regulators simultaneously, while EN2 (Pin 4) provides dedicated control of the LDO only. Pulling EN2 below 0.5V disables the LDO without affecting buck operation - enabling flexible power sequencing and dynamic rail management in complex systems.
LT3645IMSE#TRPBF Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc.
- Series:
- -
- Package/Case:
- 12-TSSOP (0.118", 3.00mm Width) Exposed Pad
- Packaging:
- Tape & Reel (TR)
- Product Status:
- Active
- Topology:
- Step-Down (Buck) (1), Linear (LDO) (1)
- Number of Outputs:
- 2
- Frequency - Switching:
- 750kHz
- Voltage/Current - Output 1:
- 0.8V ~ 16V, 500mA
- Voltage/Current - Output 2:
- 0.8V ~ 8V, 200mA
- Voltage/Current - Output 3:
- -
- w/LED Driver:
- No
- w/Supervisor:
- No
- w/Sequencer:
- No
- Voltage - Supply:
- 3.6V ~ 36V
- Operating Temperature:
- -40°C ~ 125°C
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 12-MSOP-EP
LT3645IMSE#TRPBF FAQ
1.How can I place an order for LT3645IMSE#TRPBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LT3645IMSE#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 LT3645IMSE#TRPBF reliable?
The price and inventory of LT3645IMSE#TRPBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LT3645IMSE#TRPBF is usually 5 days.
3.What payment methods are accepted for LT3645IMSE#TRPBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LT3645IMSE#TRPBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LT3645IMSE#TRPBF?
LT3645IMSE#TRPBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LT3645IMSE#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 LT3645IMSE#TRPBF?
For technical support, including LT3645IMSE#TRPBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LT3645IMSE#TRPBF requirements.
6.How does Aetrix verify that LT3645IMSE#TRPBF is sourced from the original manufacturer or authorized distributors?
All LT3645IMSE#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 LT3645IMSE#TRPBF meets industry standards.
7.What is the process for return or replacement of LT3645IMSE#TRPBF?
All LT3645IMSE#TRPBF units undergo pre-shipment inspection (PSI). If there is an issue with LT3645IMSE#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 LT3645IMSE#TRPBF part is unused and in its original packaging.
Return procedure for LT3645IMSE#TRPBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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