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Analog Devices Inc. LT3689IMSE#TRPBF
- Part No.:
- LT3689IMSE#TRPBF
- Manufacturer:
- Analog Devices Inc.
- Package:
- 16-TFSOP (0.118", 3.00mm Width) Exposed Pad
- Datasheet:
-
LT3689IMSE#TRPBF.pdf
- Description:
- IC REG BUCK ADJ 700MA 16MSOP
- Quantity:
- Payment:
- Shipping:
Inventory:3,331
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Product details
Overview
LT3689IMSE#TRPBF from Analog Devices (formerly Linear Technology) is a 700mA monolithic step-down switching regulator with integrated power-on reset (POR) and pin-selectable watchdog timer (window or timeout mode). It operates from 3.6V to 36V input, withstands 60V transients, delivers adjustable output voltage with 0.800V feedback reference, and maintains <15mVP-P output ripple in Burst Mode® at light load. It is used in automotive ECU power rails requiring fault-tolerant supervision.
For engineers reviewing the LT3689IMSE#TRPBF datasheet, LT3689IMSE#TRPBF pinout, LT3689IMSE#TRPBF application, or LT3689IMSE#TRPBF equivalent, key selection criteria include its 350kHz–2.2MHz programmable switching frequency, independent capacitor-programmable POR (tRST) and watchdog timing (tWDU/tWDL), 85µA quiescent current at 12VIN, and MSOP-16 exposed-pad thermal performance (θJA = 43°C/W).
Technical Context
The LT3689IMSE#TRPBF implements constant-frequency current-mode PWM control with slope compensation and frequency foldback during overload. Its internal bipolar NPN switch supports up to 700mA continuous output, with valley-current limiting via DA-pin monitoring and thermal shutdown protection.
Supervisory functions are fully decoupled: the POR comparator triggers RST low when VOUT drops below 90% of regulation, with delay set by CPOR; the watchdog uses WDI edge detection and W/T pin configuration to enforce either timeout or window-mode timing constraints, both programmable via CWDT capacitance.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Input Voltage Range | 3.6V to 36V continuous; withstands 60V nonrepetitive transients - enables direct connection to 24V industrial or 12V automotive battery rails without external TVS. |
| Output Current | 700mA continuous - sufficient for powering microcontrollers, CAN transceivers, and sensor interfaces in compact ECU designs. |
| Feedback Reference | 0.800V ±12mV - allows precise resistor-divider programming of any output voltage ≥1.2V while minimizing divider current error. |
| Quiescent Current | 85µA at 12VIN → 3.3VOUT in Burst Mode® - extends battery runtime in always-on vehicle modules. |
| Switching Frequency | 350kHz to 2.2MHz, RT-programmable - permits optimization of inductor size (e.g., 12µH @ 700kHz) vs. efficiency (peak >90% at 500mA). |
| Reset Threshold Accuracy | 90% of VFB (±2%) - ensures reliable µP release after stable regulation is achieved, avoiding false resets during brown-in. |
| Watchdog Timing Range | tWDU = 18.2 × CWDT (ms), tWDL = 0.588 × CWDT (ms); CWDT = 1nF–100nF - supports watchdog windows from ~18µs to ~1.8s for diverse firmware execution profiles. |
Pinout & Package
LT3689IMSE#TRPBF is housed in a 16-lead plastic MSOP package with exposed pad (θJA = 43°C/W, θJC = 4.3°C/W); the exposed pad (Pin 17) is GND and must be soldered to PCB for thermal and electrical integrity.
| 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. |
| 2 (CWDT) | Watchdog timing capacitor | Connects to GND to set tWDU and tWDL; timing accuracy depends on capacitor tolerance and temperature drift. |
| 3 (CPOR) | Reset delay capacitor | Connects to GND to set tRST = 2.3ms/nF; determines minimum hold time for RST assertion after power-up. |
| 4 (RT) | Oscillator frequency set | Resistor-to-GND sets fSW from 350kHz to 2.2MHz; value selected per Table 1 in datasheet. |
| 5 (SYNC) | External clock input | Accepts logic-level signal ≥80ns pulse width; forces LT3689IMSE#TRPBF to synchronize to external source if fSYNC > 1.2× fRT. |
| 6 (OUT) | Bias supply path | Provides bias current path from regulated output when VOUT > 3V, reducing VIN quiescent current and enabling efficient light-load operation. |
| 7 (BST) | Bootstrap drive | Charges external capacitor to drive internal NPN switch base above SW; requires Schottky diode and 10nF–100nF ceramic cap. |
| 8 (VIN) | Main power input | Supplies internal circuitry and switch; rated to 60V transient; local 10µF ceramic bypass required. |
| 9 (RST) | Power-on reset output | Open-collector active-low signal asserting until tRST expires after VOUT exceeds 90% of target. |
| 10 (WDI) | Watchdog input | Receives µP-generated edges; glitch-immune threshold (0.4–1.15V) prevents spurious timeouts. |
| 11 (W/T) | Watchdog mode select | Low = window mode (dual-edge timing), high = timeout mode (single-edge periodic reset). |
| 12 (WDE) | Watchdog enable | High (>1V) disables watchdog; WDO remains high regardless of WDI activity. |
| 13 (FB) | Feedback input | Regulated to 0.800V; connects to resistor divider tap; 800mV reference enables high-accuracy output setting. |
| 14 (EN/UVLO) | Enable & undervoltage lockout | 1.26V threshold with hysteresis; resistor divider enables programmable UVLO with 2.8–4.8µA hysteresis current. |
| 15 (DA) | Catch diode anode monitor | Current-sense input detecting external Schottky diode conduction; disables switching if IDA > 1.2A (short-circuit protection). |
| 16 (SW) | Switch node | Drives external inductor and catch diode; high dv/dt node requiring tight layout and ground plane stitching. |
Key Features
| Feature | Design Value |
|---|---|
| Low-ripple Burst Mode® operation | Maintains <15mVP-P output ripple at light load while drawing only 85µA from VIN - eliminates need for post-regulation LDO in noise-sensitive applications. |
| Independent POR and watchdog timing | CPOR and CWDT pins allow separate capacitor-based adjustment of reset delay (tRST) and watchdog boundaries (tWDU/tWDL) - enables coexistence with diverse µP boot sequences and watchdog requirements. |
| Programmable undervoltage lockout | EN/UVLO pin accepts resistor divider to set turn-on threshold with user-defined hysteresis - prevents erratic startup during battery sag in automotive environments. |
| Robust fault protection | Combines current limit (1.15–1.95A), frequency foldback, thermal shutdown, and DA-pin overcurrent latching - sustains operation under sustained overload without damage. |
| 60V transient survivability | Withstands 60V nonrepetitive transients on VIN while maintaining safe shutdown - eliminates need for upstream TVS in ISO 7637-2 compliant 12V/24V systems. |
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 under-hood ECU exposed to 12V battery transients and wide temperature swings. IC Role / Device Role / Timing Role: Primary 700mA buck regulator with integrated POR and watchdog; RST releases µP after stable 3.3V rail; WDO signals firmware hang to safety controller. Use Value: Eliminates discrete supervisor IC and reduces BOM count by integrating reset/watchdog with power conversion - critical for space-constrained ECU modules. | Use Scenario: Supplies 5V logic rails and 3.3V I/O for modular PLC backplane with hot-swap capability and field-wiring surge exposure. IC Role / Device Role / Timing Role: Adjustable-output buck converter with programmable UVLO (to ignore brief brownouts) and window-mode watchdog (to detect stuck firmware loops). Use Value: 36V max input and 60V transient rating enable direct connection to 24V DC field bus; CPOR/CWDT capacitors simplify timing calibration across production batches. |
| Railway Signaling Interface Module | Medical Diagnostic Sensor Hub |
Use Scenario: Powers isolated communication ICs and analog front-ends in EN 50155-compliant signaling equipment operating from 72V nominal DC traction supply. IC Role / Device Role / Timing Role: High-input-voltage step-down regulator (configured for 5V output) with POR ensuring clean µP boot after power restoration following line interruption. Use Value: 36V continuous input rating allows use of passive pre-regulator stage; 85µA quiescent current minimizes standby drain during track-side sleep modes. | Use Scenario: Supplies low-noise 1.8V and 3.3V rails to precision ADCs, MEMS sensors, and Bluetooth LE radio in portable diagnostic device with coin-cell backup. IC Role / Device Role / Timing Role: Dual-rail power source using FB divider and external resistors; Burst Mode® maintains ultra-low idle current while preserving <15mV ripple for ADC reference stability. Use Value: Integrated 0.800V reference and tight line/load regulation (0.005%/V) ensure consistent sensor biasing across battery discharge curve. |
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 |
|---|---|---|---|
| LTC3631EMSE#PBF | 40V max input, 500mA output, no integrated watchdog; includes power-good flag instead of RST/WDO. | Lacks programmable watchdog and POR - requires external supervisor for safety-critical µP reset. | Select when only basic regulation + PG is needed and watchdog is implemented separately. |
| MAX20004AATP+T | 42V max input, 600mA output, integrated watchdog and reset, but fixed 3.3V/5V outputs only (no adjustable FB). | Fixed-output variants only; no resistor-divider flexibility for custom voltages like 1.8V or 2.5V. | Select when standard 3.3V/5V rails suffice and board space favors single-chip solution without external resistors. |
Compared with LTC3631EMSE#PBF and MAX20004AATP+T, the LT3689IMSE#TRPBF uniquely combines adjustable output voltage, capacitor-programmable POR and watchdog timing, and 60V transient tolerance - making it optimal for automotive and industrial designs requiring flexible, robust, and integrated power supervision.
Availability
LT3689IMSE#TRPBF is available at Aetrix Electronics and suitable for automotive electronic control units, industrial programmable logic controllers, railway signaling interface modules, and medical diagnostic sensor hubs requiring stable component supply across extended temperature ranges (–40°C to 125°C).
Supply support for LT3689IMSE#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, datasheets, and application engineering for legacy Linear parts including the LT3689 series.
The LT3689 product line was designed specifically for automotive and industrial applications demanding high-voltage input capability, integrated power-supply supervision, and robust fault protection in compact MSOP/QFN packages.
FAQ
What is the maximum input voltage rating for LT3689IMSE#TRPBF during continuous operation?
The LT3689IMSE#TRPBF is rated for continuous operation up to 36V on the VIN pin. It can safely withstand nonrepetitive transients up to 60V for 1 second, as specified in Absolute Maximum Ratings. Operation above 38V (typical overvoltage lockout threshold) disables switching to protect downstream circuitry, allowing the device to survive load-dump events common in automotive 12V/24V systems without external clamping.
How does the LT3689IMSE#TRPBF implement watchdog window mode versus timeout mode?
The LT3689IMSE#TRPBF selects watchdog mode via the W/T pin: when pulled low, it enters window mode, requiring successive negative edges on WDI to occur within a defined time window (tWDL to tWDU); violation in either direction pulls WDO low. When W/T is high, it operates in timeout mode, pulling WDO low only if no WDI transition occurs within tWDU. Both modes are independently programmed using the same CWDT capacitor, and WDO remains asserted for tRST after triggering.
Can LT3689IMSE#TRPBF be synchronized to an external clock, and what are the timing requirements?
Yes, LT3689IMSE#TRPBF supports external synchronization via the SYNC pin. The external clock must have positive and negative pulse widths of at least 80ns. To ensure reliable locking, the RT resistor must be selected so that the free-running fSW is at least 20% lower than the lowest expected synchronization frequency. For example, with a 1MHz SYNC signal, RT should be chosen for ≤800kHz free-run operation.
What is the purpose of the DA pin on LT3689IMSE#TRPBF, and how does it affect system reliability?
The DA pin on LT3689IMSE#TRPBF monitors current through the external catch Schottky diode. If DA current exceeds 1.2A (typical), the regulator disables switching until current falls below threshold. This protects against sustained short-circuit faults by limiting inductor valley current, preventing thermal runaway and enabling safe auto-recovery. It eliminates need for external current-sense resistors or dedicated fault ICs in cost-sensitive designs.
Does LT3689IMSE#TRPBF require an external bootstrap diode, and what specifications apply?
Yes, LT3689IMSE#TRPBF requires an external Schottky diode connected between the OUT and BST pins. Diode forward voltage must be ≤0.5V at peak boost current (≥25mA), and reverse leakage must be ≤5µA at 12V (per datasheet specification). Recommended devices include Diodes Inc. B140HB or Vishay SS14 - low VF and fast recovery minimize bootstrap charge loss and ensure reliable NPN switch saturation across temperature.
LT3689IMSE#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 ~ 125°C (TJ)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 16-MSOP-EP
LT3689IMSE#TRPBF FAQ
1.How can I place an order for LT3689IMSE#TRPBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LT3689IMSE#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 LT3689IMSE#TRPBF reliable?
The price and inventory of LT3689IMSE#TRPBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LT3689IMSE#TRPBF is usually 5 days.
3.What payment methods are accepted for LT3689IMSE#TRPBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LT3689IMSE#TRPBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LT3689IMSE#TRPBF?
LT3689IMSE#TRPBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LT3689IMSE#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 LT3689IMSE#TRPBF?
For technical support, including LT3689IMSE#TRPBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LT3689IMSE#TRPBF requirements.
6.How does Aetrix verify that LT3689IMSE#TRPBF is sourced from the original manufacturer or authorized distributors?
All LT3689IMSE#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 LT3689IMSE#TRPBF meets industry standards.
7.What is the process for return or replacement of LT3689IMSE#TRPBF?
All LT3689IMSE#TRPBF units undergo pre-shipment inspection (PSI). If there is an issue with LT3689IMSE#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 LT3689IMSE#TRPBF part is unused and in its original packaging.
Return procedure for LT3689IMSE#TRPBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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