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Analog Devices Inc. LT3645HMSE#TRPBF
- Part No.:
- LT3645HMSE#TRPBF
- Manufacturer:
- Analog Devices Inc.
- Category:
- Voltage Regulators - Linear + Switching
- Package:
- 12-TSSOP (0.118", 3.00mm Width) Exposed Pad
- Datasheet:
-
LT3645HMSE#TRPBF.pdf
- Description:
- IC REG DL BUCK/LNR 750KHZ 12MSOP
- Quantity:
- Payment:
- Shipping:
Inventory:3,490
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Product details
Overview
LT3645HMSE#TRPBF from Analog Devices (formerly Linear Technology) is a dual-output monolithic DC/DC regulator integrating a 500mA 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 output and programmable LDO output (0.8V–8V), and features 750kHz switching frequency, <2μA shutdown current, and overvoltage lockout up to 40V - enabling robust power management for automotive image sensor supplies.
For engineers reviewing the LT3645HMSE#TRPBF datasheet, LT3645HMSE#TRPBF pinout, LT3645HMSE#TRPBF application, or LT3645HMSE#TRPBF equivalent, key selection criteria include its dual-regulator architecture, 150°C high-temp rating, integrated NPG power-good flag, thermal shutdown with 10°C hysteresis, and compatibility with external Schottky boost diode configurations for low-VOUT operation.
Technical Context
The LT3645HMSE#TRPBF implements a constant-frequency current-mode buck regulator with internal bipolar NPN switch and an independent LDO powered from VCC2. Its 750kHz oscillator supports frequency foldback during soft-start and overload, while DA-pin current sensing enables catch-diode overcurrent protection. The buck regulates FB to 0.8V; the LDO regulates FB2 to 0.797V.
Undervoltage lockout (3.4V rising) and overvoltage lockout (38.5V rising) are precision-threshold functions tied to EN/UVLO, with 1V hysteresis. The NPG open-collector output asserts low only when both FB ≥ 720mV and FB2 ≥ 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/1s transients - supports 24V industrial rails and 12V automotive battery inputs with transient immunity. |
| Buck Output Current | 500mA maximum - sufficient for powering CMOS image sensor digital cores and microcontroller I/O domains. |
| LDO Output Current | 200mA maximum with 310mV dropout at 200mA - enables clean analog supply generation from buck-derived VCC2. |
| Switching Frequency | 750kHz typical - allows use of compact 10–15μH inductors and reduces EMI compared to lower-frequency alternatives. |
| Shutdown Current | <2μA - minimizes quiescent drain in always-on automotive modules during sleep mode. |
| Operating Junction Temp | –40°C to +150°C - qualified for under-hood automotive applications per AEC-Q100 stress test conditions. |
| Feedback Reference Voltages | Buck FB = 0.8V ±13mV; LDO FB2 = 0.797V ±13mV - enables precise output programming with standard resistor dividers. |
Pinout & Package
The LT3645HMSE#TRPBF is housed in a thermally enhanced 12-lead plastic MSOP (MSE) package with exposed pad (Pin 13) soldered to PCB ground for optimal thermal dissipation (θJA = 40°C/W).
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| EN/UVLO (Pin 5) | Enable and undervoltage lockout input | 1.23V threshold enables precise VIN brownout setting via resistor divider; ties directly to VIN if UVLO unused. |
| FB (Pin 6) | Buck feedback input | Regulated to 0.8V; sets buck output voltage (e.g., 3.3V or 5V) using R1/R2 divider; bias current ≤300nA. |
| GND (Pin 7, Exposed Pad 13) | Power and signal ground reference | Must connect exposed pad to large ground plane with thermal vias; all feedback returns tie here. |
| DA (Pin 8) | Catch diode current sense | Detects external Schottky diode current; triggers frequency foldback if >0.9A - prevents startup current runaway. |
| BOOST (Pin 10) | Internal NPN switch drive voltage | Charged via internal Schottky + external 0.1μF cap; must exceed SW by ≥2.2V for full saturation. |
| SW (Pin 9) | Buck switch node | Connects to inductor and cathode of external Schottky catch diode; switches at 750kHz with 400mV VCE(SAT). |
| VIN (Pin 11) | Main input power supply | Supplies buck switch, control circuitry, and LDO collector; requires ≥1μF local ceramic bypass. |
| VCC2 (Pin 14) | LDO input supply | Accepts 1.2V–16V; powers LDO emitter; internal Schottky anode - must be ≥2.6V or use external boost diode. |
| OUT2 (Pin 15) | LDO regulated output | Delivers 200mA; requires ≥0.47μF output capacitor; dropout as low as 310mV at full load. |
| FB2 (Pin 16) | LDO feedback input | Regulated to 0.797V; sets LDO output (0.8V–8V) via R3/R4 divider; bias current ≤300nA. |
| EN2 (Pin 4) | LDO enable input | Pull >1.6V to enable LDO; pull <0.5V to disable - independent control of linear regulator. |
| NPG (Pin 3) | Power-good open-collector output | Pulls low only when both FB ≥ 720mV and FB2 ≥ 720mV - true dual-rail PGOOD indication. |
Key Features
| Feature | Design Value |
|---|---|
| Dual independent regulators | 500mA buck + 200mA LDO on single die - eliminates discrete LDO stage, reduces BOM count and board area. |
| High-temp grade H-suffix | Rated for –40°C to +150°C junction operation - validated for engine compartment and ADAS ECU deployments. |
| Integrated protection suite | Cycle-by-cycle current limit, thermal shutdown (160°C trip), UVLO/OVLO, short-circuit robustness - no external fault-handling circuitry required. |
| Programmable dual feedback | Separate 0.8V (buck) and 0.797V (LDO) references - enables accurate, independent output voltage setting without trimming. |
| Low-noise LDO path | 310mV dropout at 200mA with <1mV load regulation - supplies noise-sensitive analog blocks (e.g., image sensor analog front-end) from buck-derived VCC2. |
| Robust startup behavior | Soft-start times of 0.9ms (buck) and 0.6ms (LDO), plus frequency foldback - limits inrush current during cold cranking or hot-plug events. |
Applications
| Automotive CMOS Image Sensor Supply | Industrial Microcontroller Core Power |
|---|---|
Use Scenario: Powering rear-view camera modules with dual-rail requirements: 5V for digital interface and 1.8V/2.8V for analog pixel array. IC Role / Device Role / Timing Role: LT3645HMSE#TRPBF provides primary 5V buck output and clean 1.8V LDO output from 12V battery rail, with NPG confirming both rails are in regulation before sensor initialization. Use Value: Eliminates need for separate LDO IC; 150°C rating ensures reliability in sealed camera housings exposed to solar loading. |
Use Scenario: Supplying 3.3V core and 1.2V I/O for ARM Cortex-M7-based PLC controllers operating from 24V industrial bus. IC Role / Device Role / Timing Role: LT3645HMSE#TRPBF buck generates 3.3V main supply; LDO derives 1.2V from VCC2 for low-noise I/O domain, with independent EN2 control enabling sequenced power-up. Use Value: Reduces solution size vs. two discrete regulators; OVLO protects against 48V surge events common in factory automation wiring. |
| Automotive Infotainment Display Backlight | ADAS Radar Signal Chain Bias |
Use Scenario: Generating 5V for display logic and 3.3V for LED driver ICs in center-stack infotainment systems. IC Role / Device Role / Timing Role: LT3645HMSE#TRPBF buck delivers 5V; LDO supplies 3.3V from VCC2 with <2μA shutdown - maintains display readiness during vehicle sleep mode. Use Value: Ultra-low quiescent current extends battery life during parking; thermal shutdown prevents damage during prolonged sunlight exposure. |
Use Scenario: Providing ultra-stable 2.5V analog bias for 77GHz radar transceiver RFICs in forward collision warning systems. IC Role / Device Role / Timing Role: LT3645HMSE#TRPBF buck supplies 5V system rail; LDO delivers 2.5V from VCC2 with 310mV dropout - minimizing headroom loss and heat generation near sensitive RF sections. Use Value: Low dropout and tight load regulation (<1mV) ensure stable RFIC performance across temperature and load variation. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar dual-output regulator applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| LT3645EMSE#TRPBF | Same functionality and pinout, but rated for –40°C to +125°C junction temperature. | Suitable for cabin electronics (e.g., HVAC controls) where ambient temperature remains below 105°C. | Select when cost sensitivity outweighs under-hood thermal requirements. |
| LT3645IMSE#TRPBF | Identical electrical specs and package; guaranteed performance over –40°C to +125°C (not just assured by design). | Preferred for industrial control panels requiring full temperature-range validation and traceable test data. | Choose for applications needing documented 125°C qualification without extended burn-in. |
Compared with LT3645HMSE#TRPBF, the EMSE and IMSE variants offer identical regulation accuracy and protection features but lack the 150°C operational guarantee - making the HMSE the only choice for sustained high-temperature environments like engine compartments or enclosed radar housings.
Availability
LT3645HMSE#TRPBF is available at Aetrix Electronics and suitable for automotive imaging, industrial microcontroller, ADAS radar, and infotainment display applications requiring stable component supply across extended temperature ranges and long production lifecycles.
Supply support for LT3645HMSE#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 LT® family of high-performance power management ICs.
The LT3645 product line was designed specifically for space-constrained, high-reliability dual-rail power systems in automotive and industrial environments - emphasizing wide input range, integrated protection, and extended temperature operation.
FAQ
What is the maximum input voltage the LT3645HMSE#TRPBF can withstand?
The LT3645HMSE#TRPBF operates continuously up to 36V input, with overvoltage lockout triggering at 38.5V (rising). It can withstand nonrepetitive 55V transients for one second - critical for surviving load-dump events in 12V automotive systems. Exceeding 36V during normal operation disables regulation until VIN falls below that threshold.
Does the LT3645HMSE#TRPBF require an external Schottky diode for boost operation?
The LT3645HMSE#TRPBF integrates a Schottky diode between VCC2 and BOOST pins, eliminating the need for an external diode when VCC2 ≥ 2.6V. If VCC2 is between 2.2V and 2.6V, an external Schottky (e.g., BAS70) must be added from VCC2 (anode) to BOOST (cathode) to ensure proper boost voltage generation.
How does the NPG pin function on the LT3645HMSE#TRPBF?
The NPG pin on the LT3645HMSE#TRPBF is an open-collector output that pulls low only when both buck (FB) and LDO (FB2) feedback voltages exceed 720mV - indicating both outputs are within ≥90% of regulation. It remains high-impedance otherwise, enabling wired-OR connection with other PGOOD signals in multi-rail systems.
Can the LT3645HMSE#TRPBF's LDO operate independently of the buck regulator?
No - the LDO in the LT3645HMSE#TRPBF requires EN/UVLO > 1.23V to activate; EN2 alone cannot enable it. When EN/UVLO is high and EN2 is pulled above 1.6V, the LDO turns on and regulates OUT2. If EN/UVLO is low, the LDO remains disabled regardless of EN2 state, ensuring coordinated power sequencing.
What is the thermal performance difference between the MSE and QFN packages for LT3645HMSE#TRPBF?
The LT3645HMSE#TRPBF uses the 12-lead MSE package with θJA = 40°C/W (vs. 58.7°C/W for the 16-lead QFN). Its smaller footprint and optimized thermal pad layout deliver superior junction-to-ambient thermal resistance - essential for maintaining 150°C operation in compact, high-power-density automotive modules.
LT3645HMSE#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 ~ 150°C
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 12-MSOP-EP
LT3645HMSE#TRPBF FAQ
1.How can I place an order for LT3645HMSE#TRPBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LT3645HMSE#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 LT3645HMSE#TRPBF reliable?
The price and inventory of LT3645HMSE#TRPBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LT3645HMSE#TRPBF is usually 5 days.
3.What payment methods are accepted for LT3645HMSE#TRPBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LT3645HMSE#TRPBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LT3645HMSE#TRPBF?
LT3645HMSE#TRPBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LT3645HMSE#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 LT3645HMSE#TRPBF?
For technical support, including LT3645HMSE#TRPBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LT3645HMSE#TRPBF requirements.
6.How does Aetrix verify that LT3645HMSE#TRPBF is sourced from the original manufacturer or authorized distributors?
All LT3645HMSE#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 LT3645HMSE#TRPBF meets industry standards.
7.What is the process for return or replacement of LT3645HMSE#TRPBF?
All LT3645HMSE#TRPBF units undergo pre-shipment inspection (PSI). If there is an issue with LT3645HMSE#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 LT3645HMSE#TRPBF part is unused and in its original packaging.
Return procedure for LT3645HMSE#TRPBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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