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Analog Devices Inc. LT3690MPUFE#PBF
- Part No.:
- LT3690MPUFE#PBF
- Manufacturer:
- Analog Devices Inc.
- Package:
- 26-WFQFN Exposed Pad
- Datasheet:
-
LT3690MPUFE#PBF.pdf
- Description:
- IC REG BUCK ADJ 4A 26QFN
- Quantity:
- Payment:
- Shipping:
Inventory:146
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Product details
Overview
LT3690MPUFE#PBF from Analog Devices is a 36V, 4A, 1.5MHz synchronous step-down switching regulator with 70µA quiescent current in Burst Mode, integrated 30mΩ N-channel low-side switch, and programmable undervoltage lockout. It operates from 3.9V to 36V input, delivers 0.8V–20V adjustable output, and features power good flag, soft-start, and thermal shutdown - used in automotive power supplies requiring high transient immunity.
For engineers reviewing the LT3690MPUFE#PBF datasheet, LT3690MPUFE#PBF pinout, LT3690MPUFE#PBF application, or LT3690MPUFE#PBF equivalent, key selection criteria include its –55°C to 150°C extended temperature grade, 26-lead 4mm × 6mm QFN package with exposed SW/GND pads, synchronous topology eliminating external catch diodes, and robust short-circuit protection with frequency foldback.
Technical Context
The LT3690MPUFE#PBF implements constant-frequency current-mode control with an internal oscillator programmable from 170kHz to 1.5MHz via RT resistor. Its dual-switch architecture integrates a 90mΩ high-side NPN and a 30mΩ low-side N-channel MOSFET, enabling synchronous rectification and eliminating external Schottky diodes.
It uses a 0.8V feedback reference with ±12mV total error over temperature, supports output voltage tracking via SS pin, and includes active current limit clamping at VC pin. Protection includes overvoltage lockout (38.2V typ), thermal shutdown, and cycle-by-cycle current sensing on both switches.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Input Voltage Range | 3.9V to 36V continuous; withstands 60V transients for ≤1s - enables use in 24V automotive and industrial bus systems with load dump immunity. |
| Output Current | 4A maximum DC load - supports high-power microcontrollers, FPGAs, and sensor modules without external current boosting. |
| Quiescent Current | 70µA in Burst Mode at 12VIN→3.3VOUT - extends battery life in always-on vehicle subsystems like telematics and ADAS sensors. |
| Switching Frequency | Programmable 170kHz–1.5MHz via RT resistor - allows optimization of inductor size (e.g., 3.3µH at 600kHz) vs. efficiency trade-offs. |
| Feedback Reference | 0.8V ±12mV over –55°C to 150°C - ensures stable regulation across extreme ambient and junction temperatures. |
| Package | 26-lead 4mm × 6mm QFN with exposed SW (Pin 27) and GND (Pin 28) pads - provides low θJC = 2.7°C/W for high-power density thermal management. |
| Operating Temp | –55°C to +150°C junction - qualified for under-hood automotive, aerospace, and military-grade embedded power rails. |
Pinout & Package
LT3690MPUFE#PBF is housed in a thermally enhanced 26-lead plastic QFN (4mm × 6mm) with two exposed pads: Pin 27 (SW) and Pin 28 (GND), both requiring soldering to PCB copper for thermal and electrical integrity. θJA = 40°C/W, θJC = 2.7°C/W.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| SW (Pins 1–4, 23–26, Exposed Pad 27) | Switch node | Drains high-side NPN emitter and low-side NMOS drain; connects directly to inductor and boost capacitor - must be routed with low-inductance, high-current copper. |
| GND (Pins 6, 10, 16, 21, Exposed Pad 28) | Power and signal ground | Reference for all internal circuitry and power switches; exposed pad forms primary thermal path - requires solid thermal via array to inner ground plane. |
| FB (Pin 9) | Feedback input | Servo point for 0.8V reference; regulates output by adjusting peak switch current - resistor divider must connect here with adjacent GND (Pin 10) for accuracy. |
| EN (Pin 17) | Enable control | Active-high logic input; ≥1.5V enables regulation, ≤0.4V forces shutdown (<1µA IQ) - compatible with MCU GPIO or system power sequencer. |
| PG (Pin 18) | Power good flag | Open-collector output asserting when VOUT reaches 90% of target - used for downstream enable sequencing or fault monitoring. |
| RT (Pin 7) | Oscillator programming | Resistor-to-GND sets switching frequency (e.g., 32.4kΩ → 600kHz); tolerance directly impacts timing accuracy and ripple performance. |
| VC (Pin 8) | Error amplifier output | Controls peak inductor current; external RC compensation network stabilizes loop - critical for transient response and phase margin. |
| SS (Pin 11) | Soft-start/tracking | Internal 2µA current source charges external capacitor for controlled ramp; also accepts external voltage for output tracking - prevents inrush and enables multi-rail sequencing. |
| UVLO (Pin 12) | Undervoltage lockout | 1.25V threshold; resistor divider from VIN sets turn-on voltage - protects against brownout and enables battery-low detection. |
| BST (Pin 22) | Boost capacitor connection | Provides gate drive voltage >VIN for high-side NPN saturation - requires low-ESR ceramic capacitor (≥10nF) between BST and SW. |
| BIAS (Pin 19) | External bias supply | Accepts ≥3V external source (e.g., VOUT) to power internal regulators - improves efficiency by reducing VIN current draw. |
| VCCINT (Pin 20) | Low-side driver supply | Internally generated ~5V rail for LS switch gate drive - requires 1µF ceramic bypass to GND (Pin 21) for stability under load transients. |
| SYNC (Pin 5) | Frequency synchronization | Accepts external clock (170kHz–1.5MHz, 20–80% duty) - enables EMI reduction via spread-spectrum or system-level clock alignment. |
Key Features
| Feature | Design Value |
|---|---|
| Integrated synchronous power stage | Eliminates external Schottky catch diode, reduces conduction loss, and shrinks solution size by >30% vs. asynchronous designs. |
| Burst Mode® operation | Maintains <15mVP-P output ripple while achieving 70µA IQ - essential for ultra-low-power standby modes in automotive ECUs. |
| Robust protection suite | Includes overvoltage lockout (38.2V), thermal shutdown, cycle-by-cycle current limiting, and frequency foldback during overload - prevents damage during short-circuit or startup faults. |
| Extended temperature qualification | –55°C to +150°C operation fully tested and guaranteed - meets AEC-Q100 Grade 1 requirements for engine compartment applications. |
| Programmable UVLO and soft-start | Resistor-based UVLO threshold and external capacitor-controlled SS ramp enable custom power-up sequencing and battery voltage monitoring. |
Applications
| Automotive Engine Control Unit (ECU) | Industrial Programmable Logic Controller (PLC) |
|---|---|
Use Scenario: Powers 3.3V/5V logic rails in under-hood ECU modules exposed to –40°C to +125°C ambient and 60V load-dump transients. IC Role / Device Role / Timing Role: Primary synchronous buck regulator delivering stable 4A output with Burst Mode for sleep-state current minimization. Use Value: Eliminates need for external TVS + Schottky + LDO chain; achieves 92% efficiency at 2A/12VIN→3.3VOUT while surviving automotive stress tests. | Use Scenario: Supplies 5V/3A to FPGA, ADC, and communication interfaces in factory-floor PLCs operating continuously at 70°C ambient. IC Role / Device Role / Timing Role: High-reliability DC-DC converter with thermal shutdown and programmable frequency to avoid noise coupling into analog signal paths. Use Value: 4mm × 6mm QFN footprint saves board space vs. discrete solutions; 0.8V reference ensures <±1% output accuracy over full temperature range. |
| Distributed Power Architecture in Telecom | Aerospace Avionics Power Module |
Use Scenario: Provides point-of-load 12V→3.3V conversion for baseband processing units in 48V telecom racks with strict EMI limits. IC Role / Device Role / Timing Role: Synchronizable buck regulator enabling system-wide clock alignment to reduce conducted emissions. Use Value: SYNC pin accepts 1.5MHz external clock; achieves <10mV ripple at 600kHz with minimal filtering - passes CISPR-32 Class B. | Use Scenario: Generates 28V→5V/4A regulated rail in airborne flight control computers requiring MIL-STD-810G shock/vibe and DO-160D lightning surge compliance. IC Role / Device Role / Timing Role: Radiation-tolerant (by design), extended-temp buck controller with overvoltage lockout protecting downstream avionics. Use Value: Withstands 60V transients per DO-160 Section 22; –55°C start capability ensures cold-soak reliability; PG flag enables health monitoring. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar synchronous buck regulator applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| LTC3631EMSE#PBF | 36V, 2A, 3MHz max freq; no integrated high-side switch - requires external N-channel MOSFET; lower current rating. | Targeted at space-constrained, higher-frequency apps where 2A suffices; lacks PG flag and UVLO programming. | Select when 2A output and 3MHz switching are prioritized over 4A capability and automotive-grade temp range. |
| TPS544B20RQFT | 18V max VIN, 4A, 1.5MHz; integrated FETs but only –40°C to 125°C; no 60V transient rating or programmable UVLO. | Optimized for server VRM and datacom; lacks automotive transient robustness and extended temperature support. | Choose for cost-sensitive, non-automotive 12V-input systems where 36V operation and –55°C start are unnecessary. |
Compared with LTC3631EMSE#PBF and TPS544B20RQFT, LT3690MPUFE#PBF uniquely combines 36V input, 4A output, –55°C to 150°C operation, 60V transient tolerance, and programmable UVLO - making it the only drop-in solution for high-reliability automotive and aerospace buck conversion where input robustness and temperature range are non-negotiable.
Availability
LT3690MPUFE#PBF is available at Aetrix Electronics and suitable for automotive engine control units, industrial PLC power supplies, and aerospace avionics systems requiring stable component supply across extended temperature and high-transient environments.
Supply support for LT3690MPUFE#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 precision instrumentation, industrial automation, and automotive markets.
The LT3690MPUFE#PBF belongs to the LT® monolithic switching regulator product line, engineered specifically for high-input-voltage, high-reliability power conversion in harsh environments - including under-hood automotive, avionics, and industrial control.
FAQ
What is the maximum input voltage rating for LT3690MPUFE#PBF during continuous operation?
The LT3690MPUFE#PBF supports continuous input voltages up to 36V. It can withstand non-repetitive 60V transients for up to 1 second when junction temperature remains below 125°C. This makes LT3690MPUFE#PBF suitable for automotive 24V systems subject to ISO 7637-2 load dump events. The overvoltage lockout triggers at 38.2V typical, halting switching to protect downstream circuitry.
How does the LT3690MPUFE#PBF achieve 70µA quiescent current?
The LT3690MPUFE#PBF achieves 70µA quiescent current through its proprietary Burst Mode® operation, which disables the internal oscillator, gate drivers, and most control circuitry between switching bursts. During light-load conditions, LT3690MPUFE#PBF maintains regulation by delivering short energy packets, minimizing switching losses while keeping output ripple below 15mVP-P. This mode activates automatically unless SYNC pin is pulled above 0.8V.
What is the function of the exposed pad labeled "SW" (Pin 27) on the LT3690MPUFE#PBF QFN package?
The exposed pad labeled "SW" (Pin 27) on the LT3690MPUFE#PBF is electrically connected to the internal switch node - the common drain/emitter connection of both high-side and low-side power switches. It must be soldered to a large PCB copper area to serve as the primary thermal dissipation path (θJC = 2.7°C/W) and low-inductance current return for the power inductor and boost capacitor. Failure to solder this pad compromises thermal performance and may cause premature failure.
Can the LT3690MPUFE#PBF be synchronized to an external clock, and what is the valid frequency range?
Yes, the LT3690MPUFE#PBF supports external synchronization via the SYNC pin (Pin 5), accepting TTL/CMOS-compatible signals from 170kHz to 1.5MHz with 20–80% duty cycle. When synchronized, the internal oscillator locks to the external clock edge, enabling EMI reduction through frequency alignment or spread-spectrum techniques. If unused, SYNC should be tied to GND for Burst Mode or to VOUT for standard PWM operation.
What is the purpose of the BIAS pin (Pin 19) on the LT3690MPUFE#PBF, and how should it be connected?
The BIAS pin (Pin 19) on the LT3690MPUFE#PBF connects to the anode of the internal boost Schottky diode and supplies current to the internal bias regulator. To maximize efficiency, BIAS should be connected to the lowest available voltage source above 3V - typically the output voltage (VOUT). This allows LT3690MPUFE#PBF to draw bias current from VOUT instead of VIN, reducing overall input current and improving light-load efficiency. A 10nF ceramic capacitor must be placed locally between BIAS and GND.
LT3690MPUFE#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:
- -55°C ~ 150°C (TJ)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 26-QFN (4x6)
LT3690MPUFE#PBF FAQ
1.How can I place an order for LT3690MPUFE#PBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LT3690MPUFE#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 LT3690MPUFE#PBF reliable?
The price and inventory of LT3690MPUFE#PBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LT3690MPUFE#PBF is usually 5 days.
3.What payment methods are accepted for LT3690MPUFE#PBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LT3690MPUFE#PBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LT3690MPUFE#PBF?
LT3690MPUFE#PBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LT3690MPUFE#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 LT3690MPUFE#PBF?
For technical support, including LT3690MPUFE#PBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LT3690MPUFE#PBF requirements.
6.How does Aetrix verify that LT3690MPUFE#PBF is sourced from the original manufacturer or authorized distributors?
All LT3690MPUFE#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 LT3690MPUFE#PBF meets industry standards.
7.What is the process for return or replacement of LT3690MPUFE#PBF?
All LT3690MPUFE#PBF units undergo pre-shipment inspection (PSI). If there is an issue with LT3690MPUFE#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 LT3690MPUFE#PBF part is unused and in its original packaging.
Return procedure for LT3690MPUFE#PBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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