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Analog Devices Inc. LT3690EUFE#PBF
- Part No.:
- LT3690EUFE#PBF
- Manufacturer:
- Analog Devices Inc.
- Package:
- 26-WFQFN Exposed Pad
- Datasheet:
-
LT3690EUFE#PBF.pdf
- Description:
- IC REG BUCK ADJ 4A 26QFN
- Quantity:
- Payment:
- Shipping:
Inventory:556
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Product details
Overview
LT3690EUFE#PBF from Analog Devices is a 36V, 4A synchronous step-down DC/DC regulator with 1.5MHz programmable switching frequency, 70µA quiescent current in Burst Mode, and integrated 30mΩ low-side N-channel MOSFET. It delivers regulated 3.3V/5V outputs for industrial power rails and automotive subsystems requiring high input voltage tolerance and thermal robustness.
For engineers reviewing the LT3690EUFE#PBF datasheet, LT3690EUFE#PBF pinout, LT3690EUFE#PBF application, or LT3690EUFE#PBF equivalent, key selection criteria include its 3.9–36V input range, 0.8V feedback reference, programmable UVLO via resistor divider, power good flag, and thermal shutdown with 125°C junction rating in the 4mm × 6mm QFN package.
Technical Context
The LT3690EUFE#PBF employs current-mode control with slope compensation for fast transient response and stable loop behavior across wide duty cycles. Its internal architecture integrates a bipolar NPN high-side switch and synchronous N-channel low-side switch, eliminating external catch diodes while enabling >90% efficiency at full load.
Operation includes frequency foldback during startup/overload, soft-start via SS pin with 2µA internal current source, and selectable Burst Mode (SYNC = GND) or forced PWM (SYNC = VOUT). The VC pin provides direct access to error amplifier output for loop compensation, and the PG open-collector flag asserts when FB reaches 90% of regulation.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Input Voltage Range | 3.9V to 36V continuous; withstands 60V transients without damage |
| Output Current | Up to 4A DC; current limit threshold 5.5–8A depending on temperature and duty cycle |
| Switching Frequency | Programmable 170kHz–1.5MHz via RT resistor; supports external synchronization |
| Quiescent Current | 70µA typical in Burst Mode at 12VIN→3.3VOUT; <1µA in shutdown |
| Feedback Reference | 0.792–0.814V over temperature; enables precise output regulation from 0.8V to 20V |
| Thermal Rating | –40°C to +125°C junction; θJC = 2.7°C/W via exposed SW/GND pads |
| Protection Features | UVLO with programmable threshold, OVLO at 38.2V typ, thermal shutdown, short-circuit robustness |
Pinout & Package
The LT3690EUFE#PBF is housed in a thermally enhanced 26-lead 4mm × 6mm plastic QFN package with two exposed pads: Pin 27 (SW) and Pin 28 (GND), both requiring soldering to PCB copper for optimal thermal performance (θJA = 40°C/W).
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| SW (Pins 1–4, 23–26, Exposed Pad 27) | Switch node | Drain of LS MOSFET and emitter of HS BJT; connects to inductor and BST capacitor; carries full switching current |
| FB (Pin 9) | Feedback input | Servo point for 0.8V reference; regulates output by adjusting peak inductor current via VC pin |
| PG (Pin 18) | Power good flag | Open-collector output asserting high when FB ≥ 90% of target; valid only if EN high, UVLO high, VIN > 3.9V |
| RT (Pin 7) | Oscillator programming | Resistor-to-GND sets switching frequency from 170kHz to 1.5MHz per Table 1 in datasheet |
| SS (Pin 11) | Soft-start/tracking | 2µA internal current source charges external capacitor for controlled ramp; also supports output voltage tracking |
| UVLO (Pin 12) | Undervoltage lockout | 1.25V internal threshold; external resistor divider programs wake-up voltage and hysteresis |
| BST (Pin 22) | Bootstrap supply | Drives HS BJT gate above VIN via external capacitor; requires ≥1.6V boost voltage above SW |
| BIAS (Pin 19) | Internal regulator input | Connects to VOUT (≥3V) to improve efficiency by powering bias circuitry from output instead of VIN |
| VCCINT (Pin 20) | LS driver supply | Internally generated ~5V rail for low-side MOSFET gate drive; requires 1µF bypass to GND (Pin 21) |
| EN (Pin 17) | Enable control | Active-high logic input; <0.4V disables regulator and reduces VIN current to <1µA |
Key Features
| Feature | Design Value |
|---|---|
| Synchronous rectification | Integrated 30mΩ N-channel LS switch eliminates Schottky diode, reducing conduction loss and board area |
| Burst Mode operation | Maintains <15mVP-P output ripple at light loads while achieving 70µA IQ, extending battery life in standby |
| Programmable UVLO | Resistor divider on UVLO pin sets custom start-up voltage with hysteresis, preventing brownout oscillation |
| Robust protection suite | Includes frequency foldback during overload, thermal shutdown, OVLO (38.2V), and current-limit clamping |
| Thermally optimized package | Exposed SW and GND pads enable low-thermal-resistance PCB layout for 4A continuous operation at 125°C |
Applications
| Industrial Power Supply | Automotive Infotainment |
|---|---|
Use Scenario: Distributed 5V/3.3V rails in PLC I/O modules powered from 24V factory bus. IC Role / Device Role / Timing Role: Primary buck regulator delivering stable 5V @ 3A to microcontroller, CAN transceivers, and analog front-ends. Use Value: 36V max input and 60V transient tolerance ensure reliable operation during 24V bus surges; 70µA Burst Mode extends uptime in low-power sleep states. | Use Scenario: Powering head unit display controller and audio DSP from vehicle battery (9–16V nominal, up to 36V during load dump). IC Role / Device Role / Timing Role: Synchronous step-down converter generating 3.3V @ 4A for SoC core and memory subsystems. Use Value: Programmable UVLO prevents startup until battery stabilizes post-cranking; PG flag synchronizes firmware boot sequence with power rail readiness. |
| Distributed Telecom Supply | Test & Measurement Equipment |
Use Scenario: Point-of-load regulation for FPGA I/O banks in 48V-powered base station cards. IC Role / Device Role / Timing Role: High-efficiency buck stage converting 48V intermediate bus to 1.8V/3.3V for digital logic and ADCs. Use Value: 1.5MHz switching allows compact 2.2µH inductors and 10µF ceramic output caps; SYNC pin enables system-wide clock alignment to reduce EMI. | Use Scenario: Precision analog supply in portable oscilloscope front-end, requiring ultra-low noise and tight regulation. IC Role / Device Role / Timing Role: Low-ripple 3.3V source for op-amps, references, and SAR ADCs with minimal PSRR impact. Use Value: <15mVP-P ripple in Burst Mode ensures clean analog rails; 0.8V reference and 0.01%/V line regulation minimize output drift across input variations. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar synchronous buck regulator applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| LM5164QPWPRQ1 | 4.5–65V input, 0.5A max, integrated FETs, 100kHz–2.2MHz freq, no PG flag | Lower current rating; suited for lower-power automotive sensors vs. 4A industrial loads | Select LM5164QPWPRQ1 only for <1A applications where extended input range (65V) outweighs missing PG and thermal performance |
| MP2451DT-LF-Z | 4.5–36V input, 0.6A max, no programmable UVLO, fixed 2MHz freq, no SYNC or SS pins | Limited feature set; targets cost-sensitive consumer power supplies, not industrial control | Choose MP2451DT-LF-Z only for simple 0.6A rails where footprint and BOM count are prioritized over configurability and protection |
Compared with LM5164QPWPRQ1 and MP2451DT-LF-Z, the LT3690EUFE#PBF delivers higher output current (4A), comprehensive protection (PG, UVLO, OVLO, thermal), and design flexibility (programmable freq, soft-start, tracking), making it suitable for demanding industrial and automotive power systems where reliability and configurability are critical.
Availability
LT3690EUFE#PBF is available at Aetrix Electronics and suitable for industrial power supplies, automotive infotainment systems, and distributed telecom regulation requiring stable component supply, long-term lifecycle support, and guaranteed thermal performance up to 125°C junction temperature.
Supply support for LT3690EUFE#PBF 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 is a global leader in high-performance analog, mixed-signal, and digital signal processing semiconductors, serving industrial, automotive, communications, and healthcare markets.
The LT3690EUFE#PBF belongs to Analog Devices' Power by Linear™ family of monolithic DC/DC regulators, designed specifically for high-input-voltage, high-current industrial and automotive power conversion with emphasis on thermal robustness, protection integrity, and design flexibility.
FAQ
What is the maximum continuous output current supported by the LT3690EUFE#PBF?
The LT3690EUFE#PBF supports up to 4A of continuous output current under typical thermal conditions (θJA = 40°C/W, ambient ≤ 85°C). Its current limit threshold is specified from 5.5A to 8A depending on junction temperature and duty cycle, with built-in slope compensation to maintain stability at high duty ratios. Derating is required above 125°C junction temperature per datasheet Note 3.
How does the LT3690EUFE#PBF achieve low quiescent current in light-load conditions?
The LT3690EUFE#PBF achieves 70µA typical quiescent current using low-ripple Burst Mode® operation, where the controller shuts down all non-essential circuitry between switching bursts while maintaining output regulation. This mode activates automatically below ~100mA load and keeps output ripple below 15mVP-P. Pulling the SYNC pin to GND enables Burst Mode; tying SYNC to VOUT forces continuous PWM.
Can the LT3690EUFE#PBF be synchronized to an external clock, and what is the valid frequency range?
Yes, the LT3690EUFE#PBF supports external synchronization via the SYNC pin (Pin 5), accepting logic-level signals with 20–80% duty cycle across a 170kHz to 1.5MHz range. When synchronized, the internal oscillator locks to the external clock edge, enabling EMI reduction through frequency alignment in multi-rail systems. If unused, SYNC must be tied to GND or VOUT to select operating mode.
What thermal management features does the LT3690EUFE#PBF include, and how should the exposed pads be handled?
The LT3690EUFE#PBF includes thermal shutdown protection and is packaged in a 4mm × 6mm QFN with two exposed thermal pads: Pin 27 (SW) and Pin 28 (GND). Both must be soldered to large PCB copper areas to achieve θJC = 2.7°C/W. The SW pad connects internally to switching nodes 1–4 and 23–26, requiring careful isolation from other nets; the GND pad ties to all ground pins (6, 10, 16, 21) for optimal heat dissipation.
Does the LT3690EUFE#PBF support output voltage tracking, and how is it implemented?
Yes, the LT3690EUFE#PBF supports output voltage tracking via the SS (soft-start) pin (Pin 11). Instead of connecting an external capacitor for soft-start, a resistor divider from a master supply voltage to GND is connected to SS. The FB pin then servo-controls to match the SS voltage until it exceeds 0.8V, enabling coordinated ramp-up of multiple rails. Tracking offset is specified as ±15mV, ensuring tight sequencing accuracy.
LT3690EUFE#PBF Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc.
- Series:
- -
- Package/Case:
- 26-WFQFN Exposed Pad
- Packaging:
- Tube
- Product Status:
- Active
- Function:
- Step-Down
- Output Configuration:
- Positive
- Topology:
- Buck
- Output Type:
- Adjustable
- Number of Outputs:
- 1
- Voltage - Input (Min):
- 3.9V
- Voltage - Input (Max):
- 36V
- Voltage - Output (Min/Fixed):
- 0.8V
- Voltage - Output (Max):
- 20V
- Current - Output:
- 4A
- Frequency - Switching:
- 138kHz ~ 1.5MHz
- Synchronous Rectifier:
- No
- Operating Temperature:
- -40°C ~ 125°C (TJ)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 26-QFN (4x6)
LT3690EUFE#PBF FAQ
1.How can I place an order for LT3690EUFE#PBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LT3690EUFE#PBF 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 LT3690EUFE#PBF reliable?
The price and inventory of LT3690EUFE#PBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LT3690EUFE#PBF is usually 5 days.
3.What payment methods are accepted for LT3690EUFE#PBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LT3690EUFE#PBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LT3690EUFE#PBF?
LT3690EUFE#PBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LT3690EUFE#PBF 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 LT3690EUFE#PBF?
For technical support, including LT3690EUFE#PBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LT3690EUFE#PBF requirements.
6.How does Aetrix verify that LT3690EUFE#PBF is sourced from the original manufacturer or authorized distributors?
All LT3690EUFE#PBF 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 LT3690EUFE#PBF meets industry standards.
7.What is the process for return or replacement of LT3690EUFE#PBF?
All LT3690EUFE#PBF units undergo pre-shipment inspection (PSI). If there is an issue with LT3690EUFE#PBF, 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 LT3690EUFE#PBF part is unused and in its original packaging.
Return procedure for LT3690EUFE#PBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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