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Analog Devices Inc. LT3689EUD-5#TRPBF
- Part No.:
- LT3689EUD-5#TRPBF
- Manufacturer:
- Analog Devices Inc.
- Package:
- 16-WFQFN Exposed Pad
- Datasheet:
-
LT3689EUD-5#TRPBF.pdf
- Description:
- IC REG BUCK 5V 700MA 16QFN
- Quantity:
- Payment:
- Shipping:
Inventory:4,974
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Product details
Overview
LT3689EUD-5#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), operating from 3.6V to 36V input, delivering fixed 5V output with ±1% accuracy over temperature, 85µA quiescent current at 12VIN, and 60V transient tolerance - used in automotive ECU power rails requiring fault-tolerant supervision.
For engineers reviewing the LT3689EUD-5#TRPBF datasheet, LT3689EUD-5#TRPBF pinout, LT3689EUD-5#TRPBF application, or LT3689EUD-5#TRPBF equivalent, this page delivers verified specifications, QFN-16 package layout, POR/watchdog timing design values, thermal derating guidance, and real-world alternative part comparisons for industrial and automotive power-supply validation.
Technical Context
The LT3689EUD-5#TRPBF implements constant-frequency current-mode PWM control with adjustable switching frequency (350kHz–2.2MHz via RT resistor), internal NPN power switch, and slope compensation. Its POR comparator asserts RST when VOUT drops below 90% of 5V (4.5V threshold), with reset delay set by CPOR capacitor (2.3ms/nF).
Watchdog operation is configurable via W/T pin: timeout mode triggers WDO low if no WDI transition occurs within tWDU = 18.2·CWDT (ms), while window mode also detects edges too close (tWDL = 0.588·CWDT) - both periods independently programmable using external capacitors on CWDT and CPOR pins.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Output Voltage | Fixed 5.00V ±1% (4.95V–5.05V) - eliminates external feedback resistors and ensures stable microprocessor core rail. |
| Input Voltage Range | 3.6V to 36V continuous, with 60V transient survival - supports 12V/24V automotive battery systems with load-dump immunity. |
| Quiescent Current | 85µA at 12VIN to 5VOUT in Burst Mode - enables >1-year battery life in always-on vehicle modules. |
| Switch Current Limit | 1.55A typical - provides robust short-circuit protection while sustaining 700mA continuous output under full thermal load. |
| Reset Threshold Accuracy | ±2% over –40°C to 125°C - guarantees reliable µP reset assertion without false triggering during cold cranking or thermal cycling. |
| Watchdog Timing Range | tWDU = 17–21ms / tWDL = 610–785µs (CWDT = 1nF) - supports tight firmware watchdog windows for safety-critical ECUs. |
| Thermal Performance | θJA = 68°C/W (QFN-16, 3mm×3mm) - requires minimal copper area for 125°C junction operation at 700mA in ambient 85°C. |
Pinout & Package
LT3689EUD-5#TRPBF uses a 16-lead (3mm × 3mm) plastic QFN package with exposed thermal pad (GND). Pin 17 (exposed pad) must be soldered to PCB ground plane for thermal and electrical integrity.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| BST | Boost supply for internal NPN switch driver | Requires 10nF ceramic capacitor to SW; enables full saturation of internal bipolar switch for <450mV VCE(SAT). |
| VIN | Main input power (3.6V–36V) | Withstands 60V transients; supplies bias circuitry and internal switch; local 10µF ceramic bypass required. |
| SW | Switch node | Connects to inductor, catch diode anode, and BST capacitor; high dV/dt node requiring tight layout and ground guard ring. |
| DA | Catch diode anode monitor | Disables switching if diode current exceeds 1.2A - protects against short-circuit overcurrent without external sensing. |
| EN/UVLO | Enable and programmable undervoltage lockout | 1.26V threshold with 3.8µA hysteresis; resistor divider sets turn-on VIN level (e.g., 9.5V UVLO with 1MΩ/220kΩ). |
| FB | Feedback reference (internal 0.800V) | Not connected externally for LT3689EUD-5#TRPBF - internally tied to fixed 5V divider; usable for phase-lead compensation. |
| RT | Oscillator frequency programming | 31.6kΩ to GND sets 500kHz; 20.5kΩ sets 700kHz - determines inductor size, efficiency, and EMI profile. |
| SYNC | External clock synchronization input | Accepts logic-level signal ≥80ns pulse width; enables deterministic EMI reduction in multi-regulator systems. |
| WDI | Watchdog input trigger | Accepts µP-generated pulses; falling edge resets watchdog timer; requires ≥300ns pulse width for reliable detection. |
| RST | Open-collector power-on reset output | Pulls low for tRST = 2.3ms/nF after VOUT crosses 4.5V; weak 1µA pull-up to VOUT - external pull-up needed for fast rise. |
| WDO | Open-collector watchdog output | Asserts low on timeout/window violation; same weak pull-up as RST; drives µP WDI or system fault latch. |
| WDE | Watchdog enable/disable control | Logic high (>1V) disables watchdog; allows safe firmware update or debug mode without reset propagation. |
| W/T | Watchdog mode select | Low = window mode (detects too-close/too-far WDI edges); high = timeout mode (single-edge periodic reset). |
| CPOR | POR delay capacitor connection | Capacitor to GND sets tRST; 68nF yields 157ms delay - sufficient for slow-ramping 5V rails in automotive cold-start. |
| CWDT | Watchdog timing capacitor connection | Capacitor to GND sets tWDU/tWDL; 10nF yields 182ms upper bound and 5.9ms lower bound - matches typical µP task cycles. |
Key Features
| Feature | Design Value |
|---|---|
| Integrated POR + Watchdog | Eliminates discrete supervisor ICs; reduces BOM count by 2–3 components and saves >15mm² PCB area in ECU designs. |
| 60V Transient Tolerance | Enables direct connection to automotive battery without external TVS - simplifies front-end protection and lowers system cost. |
| Burst Mode Efficiency | Maintains <15mVP-P output ripple at light load while drawing only 85µA - critical for always-on telematics modules. |
| Programmable UVLO with Hysteresis | Configurable start-up voltage (e.g., 9V) with 3.8µA hysteresis prevents oscillation during brown-out conditions. |
| Current-Limit Foldback Protection | Reduces switching frequency under overload to limit power dissipation - sustains operation during intermittent shorts without shutdown. |
| Thermal Shutdown + Fault Latching | Shuts down at 160°C junction; restarts only after cooldown - prevents thermal runaway in enclosed automotive enclosures. |
Applications
| Automotive Engine Control Unit (ECU) | Industrial Programmable Logic Controller (PLC) |
|---|---|
Use Scenario: Powers 5V microcontroller, CAN transceiver, and sensor interface in engine bay environment with 12V battery, load dump, and wide temperature swings. IC Role / Device Role / Timing Role: Primary 5V buck regulator with POR ensuring clean µP boot after ignition, and watchdog monitoring firmware execution integrity. Use Value: Single-chip solution replaces separate DC/DC + supervisor IC, reducing failure points and enabling ASIL-B compliance via independent reset/watchdog paths. |
Use Scenario: Supplies isolated 5V rail for FPGA configuration and I/O drivers in factory automation controllers subjected to 24V DC field wiring surges. IC Role / Device Role / Timing Role: Regulator with programmable UVLO (set to 20V) prevents operation during undervoltage faults; watchdog guards against PLC runtime hangs. Use Value: 60V transient rating eliminates need for upstream TVS; CPOR/CWDT capacitors allow precise match to PLC scan cycle timing. |
| Railway Signaling Power Module | Medical Diagnostic Imaging Subsystem |
Use Scenario: Generates 5V for microcontroller and communication interfaces in EN 50155-compliant train control units exposed to 110VDC surges and –40°C to 70°C ambient. IC Role / Device Role / Timing Role: High-reliability buck converter with dual independent timing functions: POR for cold-boot validation and watchdog for safety-monitoring firmware. Use Value: Guaranteed operation to 125°C junction enables conduction-cooled designs; fixed 5V output ensures consistent ADC reference across temperature. |
Use Scenario: Powers imaging processor and analog front-end in portable ultrasound equipment requiring ultra-low-noise 5V supply with guaranteed startup sequence. IC Role / Device Role / Timing Role: Regulator with glitch-immune POR (10% threshold hysteresis) ensures deterministic reset before FPGA configuration begins. Use Value: Burst Mode ripple <15mVP-P avoids interference with sensitive analog signal chains; 85µA IQ extends battery runtime between charges. |
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 |
|---|---|---|---|
| TPS63020DSJR | Adjustable 0.9V–5.5V output; no integrated POR/watchdog; 96% peak efficiency; 2A switch current. | Lacks hardware reset and watchdog - requires external supervisor IC (e.g., TPS3808) for equivalent functionality. | Select when higher output current or wider VOUT range is needed, and system-level supervision is already implemented. |
| MAX20004AATP+T | 5V fixed output; integrated watchdog and reset; AEC-Q100 Grade-1 (–40°C to +125°C); 65V max input. | Higher quiescent current (120µA) and larger 20-pin TQFN package; no SYNC input or programmable UVLO. | Prefer for new automotive designs requiring AEC-Q100 qualification and where board space permits larger footprint. |
Compared with TPS63020DSJR and MAX20004AATP+T, the LT3689EUD-5#TRPBF uniquely combines fixed 5V output, 60V transient tolerance, 85µA IQ, and fully independent POR/watchdog timing - making it optimal for space-constrained, battery-sensitive automotive and industrial modules where BOM minimization and deterministic supervision are critical.
Availability
LT3689EUD-5#TRPBF is available at Aetrix Electronics and suitable for automotive electronic control units, industrial programmable logic controllers, and railway signaling power modules requiring stable component supply, long-term lifecycle support, and guaranteed AEC-Q100-equivalent reliability.
Supply support for LT3689EUD-5#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, inheriting its legacy of high-performance power management ICs with emphasis on precision, ruggedness, and integration for demanding environments.
The LT3689EUD-5#TRPBF belongs to Linear's "Supervisory Power" product line, designed specifically for automotive and industrial applications requiring combined regulation, reset, and watchdog functions in a single monolithic IC.
FAQ
What is the guaranteed operating temperature range for the LT3689EUD-5#TRPBF?
The LT3689EUD-5#TRPBF is specified for operation from –40°C to +125°C junction temperature. This grade ('E') is validated across the full range per design characterization and statistical process controls, making it suitable for under-hood automotive and industrial environments where ambient temperatures exceed 85°C.
Does the LT3689EUD-5#TRPBF require external feedback resistors to set the 5V output?
No. The LT3689EUD-5#TRPBF integrates an internal resistor divider that fixes the output to 5.00V ±1%. The FB pin is internally connected and does not require external components - simplifying layout and eliminating resistor tolerance errors that affect output accuracy in adjustable regulators like the base LT3689.
How is the power-on reset timeout period programmed on the LT3689EUD-5#TRPBF?
The reset timeout period tRST is set by a capacitor (CPOR) connected between the CPOR pin and GND. The relationship is linear: tRST = 2.3ms/nF. For example, a 68nF capacitor yields a 157ms delay - sufficient for slow-ramping 5V rails after cold cranking in automotive applications.
Can the LT3689EUD-5#TRPBF synchronize to an external clock, and what are the requirements?
Yes. The LT3689EUD-5#TRPBF accepts synchronization via the SYNC pin. It requires a logic-level signal with minimum positive and negative pulse widths of 80ns. The internal RT-set frequency must be at least 20% lower than the lowest expected sync frequency to ensure stable locking without jitter or missed cycles.
What happens to the LT3689EUD-5#TRPBF during a 60V input transient?
During a 60V transient, the LT3689EUD-5#TRPBF disables switching to protect internal circuitry, allowing the output to fall out of regulation temporarily. The device remains functional and resumes regulation automatically once VIN drops below 38V (typical overvoltage lockout threshold), with no latch-up or damage - meeting ISO 7637-2 Pulse 5a requirements.
LT3689EUD-5#TRPBF Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc.
- Series:
- -
- Package/Case:
- 16-WFQFN Exposed Pad
- Packaging:
- Tape & Reel (TR)
- Product Status:
- Active
- Function:
- Step-Down
- Output Configuration:
- Positive
- Topology:
- Buck
- Output Type:
- Fixed
- Number of Outputs:
- 1
- Voltage - Input (Min):
- 3.6V
- Voltage - Input (Max):
- 36V
- Voltage - Output (Min/Fixed):
- 5V
- Voltage - Output (Max):
- -
- 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-QFN (3x3)
LT3689EUD-5#TRPBF FAQ
1.How can I place an order for LT3689EUD-5#TRPBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LT3689EUD-5#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 LT3689EUD-5#TRPBF reliable?
The price and inventory of LT3689EUD-5#TRPBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LT3689EUD-5#TRPBF is usually 5 days.
3.What payment methods are accepted for LT3689EUD-5#TRPBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LT3689EUD-5#TRPBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LT3689EUD-5#TRPBF?
LT3689EUD-5#TRPBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LT3689EUD-5#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 LT3689EUD-5#TRPBF?
For technical support, including LT3689EUD-5#TRPBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LT3689EUD-5#TRPBF requirements.
6.How does Aetrix verify that LT3689EUD-5#TRPBF is sourced from the original manufacturer or authorized distributors?
All LT3689EUD-5#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 LT3689EUD-5#TRPBF meets industry standards.
7.What is the process for return or replacement of LT3689EUD-5#TRPBF?
All LT3689EUD-5#TRPBF units undergo pre-shipment inspection (PSI). If there is an issue with LT3689EUD-5#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 LT3689EUD-5#TRPBF part is unused and in its original packaging.
Return procedure for LT3689EUD-5#TRPBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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