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Analog Devices Inc. LT3689EMSE#TRPBF
- Part No.:
- LT3689EMSE#TRPBF
- Manufacturer:
- Analog Devices Inc.
- Package:
- 16-TFSOP (0.118", 3.00mm Width) Exposed Pad
- Datasheet:
-
LT3689EMSE#TRPBF.pdf
- Description:
- IC REG BUCK ADJ 700MA 16MSOP
- Quantity:
- Payment:
- Shipping:
Inventory:4,693
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Product details
Overview
LT3689EMSE#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 via 0.800V feedback reference, and maintains <15mVP-P output ripple in Burst Mode® at 85µA quiescent current. It is used in automotive ECU power rails requiring fault-tolerant supervision.
For engineers reviewing the LT3689EMSE#TRPBF datasheet, LT3689EMSE#TRPBF pinout, LT3689EMSE#TRPBF application, or LT3689EMSE#TRPBF equivalent, key selection criteria include programmable POR delay (via CPOR), independently adjustable watchdog boundaries (via CWDT), EN/UVLO hysteresis programming, 350kHz–2.2MHz frequency synchronization capability, and MSOP-16 exposed-pad thermal performance for industrial and automotive environments.
Technical Context
The LT3689EMSE#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, while DA-pin monitoring enforces valley-current limiting during short-circuit faults.
Supervisory functions are hardware-decoupled: POR asserts RST low when VOUT drops below 90% of regulation and holds it for a capacitor-programmed tRST; the watchdog uses external CWDT to set tWDU (18.2·CWDT) and tWDL (0.588·CWDT), with W/T pin selecting window vs. timeout behavior - both independent of switching operation.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Input Voltage Range | 3.6V to 36V continuous; survives 60V/1s nonrepetitive transients - enables direct battery-input use in 24V automotive systems without external TVS. |
| Output Current | 700mA DC load capability with internal 1.55A typical switch current limit - supports mid-power microcontroller rails without external MOSFETs. |
| Quiescent Current | 85µA at 12VIN/3.3VOUT in Burst Mode® - extends battery life in always-on vehicle modules. |
| Feedback Reference | 0.800V ±12mV over temperature - allows precise resistor-divider programming of any output ≥0.8V with 1% resistors. |
| Switching Frequency | Adjustable 350kHz–2.2MHz via RT resistor; synchronizable to external clock - balances inductor size, EMI, and efficiency across 5V/3.3V/1.8V rails. |
| POR & Watchdog Timing | tRST = 2.3ms/nF on CPOR; tWDU = 18.2ms/nF, tWDL = 0.588ms/nF on CWDT - enables deterministic, capacitor-based timing without software dependency. |
| Package Thermal Resistance | θJA = 43°C/W, θJC = 4.3°C/W (MSOP-16 with exposed pad) - supports 125°C ambient operation with minimal PCB copper area. |
Pinout & Package
LT3689EMSE#TRPBF is housed in a 16-lead plastic MSOP package with exposed thermal pad (Pin 17 = GND), rated for –40°C to 125°C junction temperature. The exposed pad must be soldered to PCB ground plane for thermal and electrical integrity.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1 (SW) | Switch Node | Connects to inductor, catch diode cathode, and BST capacitor - carries high di/dt switching current; requires tight layout to minimize EMI. |
| 2 (I/O) | DA (Diode Anode Monitor) | Senses external Schottky diode anode current; disables switching if >1.2A - provides valley-current limiting during output short. |
| 3 (I/O) | RST (Reset Output) | Open-collector active-low output with weak VOUT pull-up; asserts after VOUT rises above 90% and holds for tRST programmed by CPOR. |
| 4 (I/O) | WDI (Watchdog Input) | Accepts falling-edge-triggered pulses from µP; monitored for timing compliance in window or timeout mode per W/T pin state. |
| 5 (I/O) | WDO (Watchdog Output) | Open-collector active-low output; pulled low on watchdog violation - drives µP reset or system fault latch. |
| 6 (I/O) | FB (Feedback) | Regulated to 0.800V; connects to resistor divider tap - sets output voltage; supports phase-lead capacitor for transient optimization. |
| 7 (I/O) | RT (Frequency Set) | Connects to GND via resistor to program fSW from 350kHz to 2.2MHz - enables EMI tuning and inductor size reduction. |
| 8 (I/O) | SYNC | Accepts external clock signal (≥80ns pulse width); forces LT3689EMSE#TRPBF to synchronize - eliminates beat frequencies in multi-regulator systems. |
| 9 (I/O) | BST (Bootstrap) | Drives internal NPN switch base above SW; requires 0.1µF ceramic capacitor to SW - enables full saturation and low VCE(SAT). |
| 10 (Power) | VIN | Main input supply (3.6V–36V); powers internal circuitry and switch - must be locally bypassed with low-ESR capacitor. |
| 11 (I/O) | EN/UVLO | Enable and programmable undervoltage lockout; threshold = 1.26V with 120mV hysteresis - prevents erratic startup during brownout. |
| 12 (I/O) | OUT | Internal bias rail; supplies current to control circuitry when >3V - reduces VIN quiescent current in regulated-output configurations. |
| 13 (I/O) | WDE (Watchdog Enable) | Disables watchdog when >1V - allows functional safety shutdown of supervision during test or safe states. |
| 14 (I/O) | W/T (Watchdog Type) | Selects window (low) or timeout (high) mode - defines whether WDI edges must fall within dual boundaries or only avoid missing one. |
| 15 (I/O) | CWDT | Capacitor connection for watchdog timing - sets tWDU and tWDL with 18.2×/0.588× scaling - enables field-adjustable fault response windows. |
| 16 (I/O) | CPOR | Capacitor connection for reset delay - sets tRST = 2.3ms/nF - ensures µP completes boot before releasing reset. |
| 17 (GND) | Exposed Pad | Thermal and electrical ground; must be soldered to PCB ground plane - accounts for >90% of heat dissipation and stabilizes noise immunity. |
Key Features
| Feature | Design Value |
|---|---|
| Low-Ripple Burst Mode® Operation | Maintains <15mVP-P output ripple at light loads while drawing only 85µA from VIN - eliminates audible noise and preserves efficiency in standby. |
| Programmable Undervoltage Lockout (UVLO) | EN/UVLO pin accepts resistor divider to set turn-on threshold with user-defined hysteresis - prevents cycling during marginal input conditions. |
| Independent POR and Watchdog Timing | CPOR and CWDT pins allow separate capacitor-based adjustment of reset delay and watchdog boundaries - decouples timing from µP firmware. |
| Robust Fault Protection | Includes current limit, frequency foldback, thermal shutdown, and DA-pin valley-current limiting - sustains operation during sustained overloads without latch-off. |
| 60V Transient Withstand | Operates up to 36V continuously and survives 60V/1s transients without external clamping - simplifies front-end protection in automotive 24V systems. |
| Synchronization Capability | SYNC pin accepts external clock to align switching edges - reduces conducted EMI in multi-rail power systems and avoids beat frequencies. |
Applications
| Automotive Engine Control Unit (ECU) | Industrial Programmable Logic Controller (PLC) |
|---|---|
Use Scenario: Powers 3.3V microcontroller and CAN transceiver in under-hood ECU exposed to 12V/24V battery fluctuations and load-dump transients. IC Role / Device Role / Timing Role: Primary 700mA buck regulator with integrated POR to hold µP in reset until stable 3.3V is established, and watchdog to detect firmware hangs during runtime. Use Value: Eliminates need for discrete supervisor IC and external reset generator - reduces BOM count and PCB area while meeting AEC-Q100 Grade 1 thermal requirements. |
Use Scenario: Supplies 5V logic rail for I/O modules in factory automation PLCs operating in wide-temperature industrial environments. IC Role / Device Role / Timing Role: Adjustable-output buck converter with programmable UVLO to prevent operation below 18V DC bus, and synchronized switching to meet CISPR-22 Class A EMI limits. Use Value: Enables single-component solution for both power conversion and supervisory timing - improves system reliability through hardware-enforced reset and watchdog timeouts. |
| Rail-Switching Power Supply for IoT Gateways | Medical Diagnostic Equipment Power Sequencing |
Use Scenario: Generates 1.8V core voltage for ARM Cortex-M7 SoC in battery-backed smart gateway with strict standby current budget. IC Role / Device Role / Timing Role: High-efficiency buck regulator using Burst Mode® to achieve 85µA IQ, with CPOR-set POR delay ensuring SoC boots only after LDOs stabilize. Use Value: Extends battery life in always-on edge devices by minimizing no-load consumption without sacrificing startup robustness. |
Use Scenario: Sequences 3.3V, 5V, and 12V rails in portable ultrasound device where power-up order and fault detection are safety-critical. IC Role / Device Role / Timing Role: One LT3689EMSE#TRPBF per rail provides independent POR and watchdog - enables per-rail reset assertion and coordinated fault reporting. Use Value: Meets IEC 62304 Class C software safety requirements via hardware-based supervision - avoids reliance on software-only watchdogs. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar step-down regulator with integrated supervision applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| LT3689IMSE#TRPBF | Same silicon, rated for –40°C to 125°C full-range guaranteed performance (vs. LT3689EMSE#TRPBF's assured-by-design spec over same range) | Required for production designs needing full temperature-grade validation per MIL-STD-883 or automotive PPAP | Select LT3689IMSE#TRPBF when full temperature-range parametric guarantees are contractually required. |
| LT3689HMSE#TRPBF | Same silicon, rated for –40°C to 150°C junction temperature - higher thermal limit enabled by enhanced process screening | Necessary for under-hood automotive modules exceeding 125°C ambient or high-power-density industrial enclosures | Choose LT3689HMSE#TRPBF for applications where junction temperature may exceed 125°C during sustained operation. |
Compared with LT3689EMSE#TRPBF, the IMSE and HMSE variants offer identical electrical functionality and pinout but differ in temperature-grade assurance level and maximum junction rating - enabling cost-optimized selection based on end-equipment thermal and qualification requirements.
Availability
LT3689EMSE#TRPBF is available at Aetrix Electronics and suitable for automotive electronic control units, industrial programmable logic controllers, and medical diagnostic equipment requiring stable component supply with long-term lifecycle support.
Supply support for LT3689EMSE#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 precision analog and power management product lines with full datasheet, SPICE model, and application support.
The LT3689 series belongs to Linear's monolithic DC/DC regulator family designed for harsh-environment applications requiring integrated supervision - specifically targeting automotive, industrial, and medical systems where reliability and deterministic timing are critical.
FAQ
What is the minimum input voltage required for LT3689EMSE#TRPBF to begin switching?
The LT3689EMSE#TRPBF requires VIN > 3.7V to initiate switching, as specified in the absolute maximum ratings table. Below this threshold, the internal bandgap and control circuitry remain inactive even if EN/UVLO is pulled high. This ensures clean startup without partial regulation or erratic behavior during brownout conditions. The LT3689EMSE#TRPBF will not deliver regulated output until both VIN exceeds 3.7V and EN/UVLO rises above 1.26V.
How does the DA pin protect the LT3689EMSE#TRPBF during output short-circuit events?
The DA pin monitors the anode of the external catch diode and disables switching if current exceeds 1.2A (typical), which occurs during output short-circuit with high input voltage. This action limits inductor valley current to ~1.2A, preventing thermal runaway and allowing safe current decay. Switching resumes only after DA current falls below the threshold. This protection is independent of the main current limit and applies specifically to fault conditions where diode conduction dominates.
Can LT3689EMSE#TRPBF operate with a fixed 5V output without external resistors?
No - the LT3689EMSE#TRPBF is the adjustable version and requires an external resistor divider from OUT to FB to set output voltage. For fixed 5V output, the pin-compatible LT3689EMSE-5#TRPBF variant must be used. That part integrates the feedback divider internally and ties FB to the midpoint, eliminating external resistors while maintaining identical supervision features and package.
What is the purpose of the OUT pin on LT3689EMSE#TRPBF beyond supplying bias current?
The OUT pin serves two critical roles: first, it sources bias current to internal circuitry when voltage exceeds 3V - reducing VIN quiescent current and improving light-load efficiency; second, it provides the charging path for the BST capacitor via an internal Schottky diode. This dual function enables efficient bootstrap operation and lowers overall system power consumption, especially in configurations where the regulated output powers the LT3689EMSE#TRPBF's own bias network.
How is watchdog window mode implemented on LT3689EMSE#TRPBF?
In window mode (W/T pin low), the LT3689EMSE#TRPBF requires successive negative edges on WDI to occur within a time window bounded by tWDL (lower) and tWDU (upper), both set by CWDT capacitance. If two edges arrive too close (
LT3689EMSE#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
LT3689EMSE#TRPBF FAQ
1.How can I place an order for LT3689EMSE#TRPBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LT3689EMSE#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 LT3689EMSE#TRPBF reliable?
The price and inventory of LT3689EMSE#TRPBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LT3689EMSE#TRPBF is usually 5 days.
3.What payment methods are accepted for LT3689EMSE#TRPBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LT3689EMSE#TRPBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LT3689EMSE#TRPBF?
LT3689EMSE#TRPBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LT3689EMSE#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 LT3689EMSE#TRPBF?
For technical support, including LT3689EMSE#TRPBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LT3689EMSE#TRPBF requirements.
6.How does Aetrix verify that LT3689EMSE#TRPBF is sourced from the original manufacturer or authorized distributors?
All LT3689EMSE#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 LT3689EMSE#TRPBF meets industry standards.
7.What is the process for return or replacement of LT3689EMSE#TRPBF?
All LT3689EMSE#TRPBF units undergo pre-shipment inspection (PSI). If there is an issue with LT3689EMSE#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 LT3689EMSE#TRPBF part is unused and in its original packaging.
Return procedure for LT3689EMSE#TRPBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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