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Analog Devices Inc. LT3689HMSE#TRPBF
- Part No.:
- LT3689HMSE#TRPBF
- Manufacturer:
- Analog Devices Inc.
- Package:
- 16-TFSOP (0.118", 3.00mm Width) Exposed Pad
- Datasheet:
-
LT3689HMSE#TRPBF.pdf
- Description:
- IC REG BUCK ADJ 700MA 16MSOP
- Quantity:
- Payment:
- Shipping:
Inventory:2,629
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Product details
Overview
LT3689HMSE#TRPBF from Analog Devices (formerly Linear Technology) is a 700mA monolithic step-down switching regulator with integrated power-on reset and pin-selectable watchdog timer. It operates from 3.6V to 36V input, withstands 60V transients, delivers adjustable output voltage with 0.800V feedback reference, and features programmable 350kHz–2.2MHz switching frequency. Used in automotive ECUs for reliable microprocessor supervision under harsh supply conditions.
For engineers reviewing the LT3689HMSE#TRPBF datasheet, LT3689HMSE#TRPBF pinout, LT3689HMSE#TRPBF application, or LT3689HMSE#TRPBF equivalent, key selection criteria include its 150°C guaranteed junction temperature rating, independent capacitor-programmable reset (tRST) and watchdog (tWDU/tWDL) timing, low-ripple Burst Mode® operation (<15mVP-P), and MSOP-16 exposed-pad thermal performance (θJC = 4.3°C/W).
Technical Context
The LT3689HMSE#TRPBF implements constant-frequency current-mode PWM control with slope compensation and frequency foldback during overload. Its internal bipolar NPN switch supports up to 1.55A typical current limit and integrates boost charge pump (BST/SW) for full saturation. The regulator uses an error amplifier servoing VC to maintain 0.800V at FB, with active clamp limiting peak inductor current.
Power-on reset and watchdog functions operate independently: RST asserts when VOUT drops below 90% of regulation and holds for CPOR-programmed delay; WDO asserts in timeout mode if no WDI transition occurs within tWDU, or in window mode if successive WDI falling edges violate tWDL/tWDU boundaries. Both outputs are open-collector with weak pull-up to VOUT.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Input Voltage Range | 3.6V to 36V continuous; survives 60V/1s nonrepetitive transients - enables direct battery connection in 24V automotive systems without external protection. |
| Output Current | 700mA DC load capability - sufficient for powering microcontrollers, CAN transceivers, and sensor interfaces in ECU subsystems. |
| Quiescent Current | 85µA in Burst Mode® at 12VIN→3.3VOUT - extends battery life in always-on vehicle modules. |
| Feedback Reference | 0.790V to 0.812V (min/max over temp) - ensures ±1.5% output accuracy with standard 1% resistors. |
| Switching Frequency | 350kHz to 2.2MHz, set by RT resistor - allows optimization of inductor size (e.g., 12µH @ 700kHz) vs. efficiency (peak >90% at 500mA). |
| Reset Threshold | VOUT dropout detection at 90% of programmed value - prevents system boot under marginal rail conditions. |
| Watchdog Modes | Pin-selectable timeout or window mode via W/T - supports both simple heartbeat and complex activity validation in safety-critical firmware. |
Pinout & Package
LT3689HMSE#TRPBF is housed in a 16-lead plastic MSOP package with exposed pad (pin 17 = GND), offering θJC = 4.3°C/W thermal resistance for high-power-density automotive layouts.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1 (WDO) | Watchdog output | Open-collector active-low signal indicating watchdog timeout or window violation; weak pull-up to VOUT enables direct MCU interrupt connection. |
| 2 (CWDT) | Watchdog timing capacitor | Connects to GND to set tWDU = 18.2·CWDT (ms) and tWDL = 0.588·CWDT (ms); defines fault response latency. |
| 3 (CPOR) | Reset timing capacitor | Connects to GND to set tRST = 2.3ms/nF; determines minimum reset pulse width after power-up or brownout recovery. |
| 4 (RT) | Oscillator frequency set | Resistor-to-GND sets switching frequency from 350kHz to 2.2MHz; enables layout-driven trade-off between inductor size and efficiency. |
| 5 (SYNC) | External clock input | Accepts logic-level signal ≥80ns pulse width; allows synchronization to system clock to reduce EMI in multi-regulator designs. |
| 6 (OUT) | Bias supply path | Provides bias current path to internal boost diode; reduces VIN quiescent current when VOUT > 3V - improves light-load efficiency. |
| 7 (BST) | Bootstrap drive | Charges external capacitor to drive internal NPN switch gate above VIN; enables low VCESAT (~450mV) and high efficiency. |
| 8 (VIN) | Main power input | Supplies internal circuitry and power switch; rated to 60V transient - eliminates need for upstream TVS in 24V rail applications. |
| 9 (RST) | Power-on reset output | Open-collector active-low signal asserting until VOUT reaches 90% and tRST expires - ensures deterministic MCU boot sequence. |
| 10 (WDI) | Watchdog input | Receives falling-edge-triggered pulses from MCU; validates processor activity in real time - critical for ASIL-B functional safety monitoring. |
| 11 (W/T) | Watchdog mode select | Logic-high selects timeout mode; logic-low selects window mode - configures fault detection logic without firmware change. |
| 12 (WDE) | Watchdog enable | Logic-high disables watchdog; allows safe MCU debug or bootloader operation without false resets. |
| 13 (FB) | Feedback input | Regulated to 0.800V; connects to resistor divider to set output voltage - supports adjustable or fixed 5V (LT3689-5 variant) configurations. |
| 14 (EN/UVLO) | Enable & undervoltage lockout | 1.26V threshold with hysteresis; resistor divider enables programmable startup voltage - prevents operation during cold-crank brownouts. |
| 15 (DA) | Catch diode anode sense | Monitors external Schottky diode current; disables switching if >1.2A - protects against short-circuit induced thermal runaway. |
| 16 (SW) | Switch node | Drives external inductor and catch diode; requires low-inductance layout to minimize EMI and switching losses. |
| 17 (GND) | Power & thermal ground | Exposed pad must be soldered to PCB ground plane - provides primary thermal path (θJC = 4.3°C/W) and low-impedance return. |
Key Features
| Feature | Design Value |
|---|---|
| Low-Ripple Burst Mode® | Maintains <15mVP-P output ripple at light loads while drawing only 85µA from VIN - eliminates need for post-regulation LDO in noise-sensitive analog sections. |
| Capacitor-Programmable Timing | Independent CPOR and CWDT pins allow precise, temperature-stable reset (tRST) and watchdog (tWDU/tWDL) periods without trimming resistors or firmware calibration. |
| 60V Transient Withstand | Operates continuously up to 36V and sustains 60V/1s transients on VIN - meets ISO 7637-2 Pulse 1/2/5a requirements for 24V commercial vehicles. |
| 150°C Junction Rating | Guaranteed operation from –40°C to +150°C - qualified for under-hood ECU placement without derating or forced cooling. |
| Integrated DA Current Limit | Monitors external catch diode current and disables switching above 1.2A - provides fast, hardware-based short-circuit protection independent of control loop response. |
Applications
| Automotive Engine Control Unit (ECU) | Industrial Programmable Logic Controller (PLC) |
|---|---|
Use Scenario: Powers 3.3V microcontroller, CAN transceiver, and analog sensor front-end in diesel engine ECU exposed to 24V battery with load-dump transients. IC Role / Device Role / Timing Role: Primary 700mA buck regulator with integrated POR and watchdog; CPOR sets 157ms reset hold time; CWDT configures 182ms/5.9ms watchdog window. Use Value: Eliminates discrete supervisor IC and reduces BOM count by integrating reset/watchdog with power conversion - improves system reliability and space efficiency. | Use Scenario: Supplies 5V rail to FPGA configuration memory and I/O banks in DIN-rail mounted PLC operating in factory ambient up to 70°C. IC Role / Device Role / Timing Role: Adjustable-output buck converter with EN/UVLO hysteresis set to 20V start/18V stop; RT resistor fixes fSW at 1MHz for compact 4.7µH inductor. Use Value: 85µA Burst Mode® IQ extends backup battery runtime during AC loss; 60V transient tolerance avoids external clamping diodes. |
| Railway Signaling Module | Medical Diagnostic Imaging Subsystem |
Use Scenario: Generates stable 3.3V supply for ARM-based controller in wayside signaling unit powered from 72V nominal traction supply. IC Role / Device Role / Timing Role: High-input-voltage buck regulator with SYNC pin synchronized to system clock to suppress conducted EMI in safety-critical comms interface. Use Value: 350kHz–2.2MHz frequency adjustability enables EMI filtering at fixed bands; 150°C rating supports convection-cooled enclosure design. | Use Scenario: Powers low-noise ADC and precision op-amp stage in portable ultrasound probe requiring ultra-low output ripple. IC Role / Device Role / Timing Role: Low-ripple Buck regulator in Burst Mode®; FB pin filtered with phase-lead capacitor to optimize transient response to pulsed imaging loads. Use Value: <15mVP-P ripple at 10mA load meets medical-grade analog signal integrity requirements without additional linear regulation. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar step-down regulator with supervisory functions applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| LTC3637EMSE#TRPBF | 40V max input, 500mA output, no integrated watchdog; uses external RC for reset timing. | Lacks pin-selectable watchdog modes and capacitor-programmable timing - requires external logic for window-mode supervision. | Select when only basic POR is needed and 500mA output suffices; not suitable for ASIL-B watchdog requirements. |
| TPS63060DSCR | 20V max input, 1.2A output, buck-boost topology, no reset/watchdog - requires external supervisor IC. | Supports input voltages below VOUT (buck-boost), but adds BOM cost and board area for discrete reset IC and timing capacitors. | Select for wide VIN range including sub-3.3V battery inputs; avoid when 36V+ automotive transients or integrated supervision are required. |
Compared with LTC3637EMSE#TRPBF and TPS63060DSCR, LT3689HMSE#TRPBF uniquely combines 36V operation, 700mA output, and fully integrated capacitor-programmable POR/watchdog in a single MSOP-16 package - reducing system complexity and qualification effort for automotive and industrial control applications.
Availability
LT3689HMSE#TRPBF is available at Aetrix Electronics and suitable for automotive electronic control units, industrial programmable logic controllers, railway signaling modules, and medical diagnostic imaging subsystems requiring stable component supply across extended temperature ranges.
Supply support for LT3689HMSE#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 its legacy of high-performance power management ICs for demanding applications.
The LT3689 product line was designed specifically for automotive and industrial systems requiring robust DC/DC conversion with integrated microprocessor supervision - combining regulation, reset, and watchdog in one thermally optimized package.
FAQ
What is the maximum junction temperature specification for LT3689HMSE#TRPBF?
The LT3689HMSE#TRPBF is guaranteed to operate over a junction temperature range of –40°C to +150°C. This H-grade rating is validated per manufacturer specifications and enables deployment in under-hood automotive locations where ambient temperatures exceed 105°C. Derating guidelines apply above 125°C to ensure long-term reliability.
How does the LT3689HMSE#TRPBF implement watchdog window mode?
The LT3689HMSE#TRPBF enters window mode when the W/T pin is held low. In this mode, it monitors WDI falling edges: WDO pulls low if two consecutive edges occur either too close together (violating tWDL) or too far apart (violating tWDU). The timing boundaries are set solely by the CWDT capacitor value, enabling hardware-defined fault detection without MCU intervention.
Can LT3689HMSE#TRPBF be synchronized to an external clock source?
Yes, LT3689HMSE#TRPBF supports external synchronization via the SYNC pin. A logic-level signal with ≥80ns positive and negative pulse widths can be applied to synchronize switching to a system clock. The internal RT resistor must be selected so the free-running frequency is at least 20% below the lowest sync frequency to ensure stable locking.
What is the purpose of the DA pin on LT3689HMSE#TRPBF?
The DA pin on LT3689HMSE#TRPBF senses current through the external catch Schottky diode. If DA current exceeds 1.2A (typical), the regulator disables switching until current falls below threshold. This hardware-based protection prevents thermal runaway during output short-circuits or high-VIN overload conditions - independent of the main control loop.
How is the power-on reset timeout period set for LT3689HMSE#TRPBF?
The power-on reset timeout period for LT3689HMSE#TRPBF is set by connecting a capacitor (CPOR) between the CPOR pin and GND. The relationship is linear: tRST = 2.3ms per nanofarad. For example, an 8.2nF capacitor yields a 157ms reset hold time, ensuring the microcontroller remains held in reset until the 3.3V rail stabilizes and remains valid.
LT3689HMSE#TRPBF Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc.
- Series:
- -
- Package/Case:
- 16-TFSOP (0.118", 3.00mm Width) Exposed Pad
- Packaging:
- Tape & Reel (TR)
- Product Status:
- Active
- Function:
- Step-Down
- Output Configuration:
- Positive
- Topology:
- Buck
- Output Type:
- Adjustable
- Number of Outputs:
- 1
- Voltage - Input (Min):
- 3.6V
- Voltage - Input (Max):
- 36V
- Voltage - Output (Min/Fixed):
- 0.8V
- Voltage - Output (Max):
- 36V
- Current - Output:
- 700mA
- Frequency - Switching:
- 500kHz ~ 2MHz
- Synchronous Rectifier:
- No
- Operating Temperature:
- -40°C ~ 150°C (TJ)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 16-MSOP-EP
LT3689HMSE#TRPBF FAQ
1.How can I place an order for LT3689HMSE#TRPBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LT3689HMSE#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 LT3689HMSE#TRPBF reliable?
The price and inventory of LT3689HMSE#TRPBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LT3689HMSE#TRPBF is usually 5 days.
3.What payment methods are accepted for LT3689HMSE#TRPBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LT3689HMSE#TRPBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LT3689HMSE#TRPBF?
LT3689HMSE#TRPBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LT3689HMSE#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 LT3689HMSE#TRPBF?
For technical support, including LT3689HMSE#TRPBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LT3689HMSE#TRPBF requirements.
6.How does Aetrix verify that LT3689HMSE#TRPBF is sourced from the original manufacturer or authorized distributors?
All LT3689HMSE#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 LT3689HMSE#TRPBF meets industry standards.
7.What is the process for return or replacement of LT3689HMSE#TRPBF?
All LT3689HMSE#TRPBF units undergo pre-shipment inspection (PSI). If there is an issue with LT3689HMSE#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 LT3689HMSE#TRPBF part is unused and in its original packaging.
Return procedure for LT3689HMSE#TRPBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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