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Analog Devices Inc. LT3840EUFE#PBF
- Part No.:
- LT3840EUFE#PBF
- Manufacturer:
- Analog Devices Inc.
- Category:
- DC DC Switching Controllers
- Package:
- 38-WFQFN Exposed Pad
- Datasheet:
-
LT3840EUFE#PBF.pdf
- Description:
- IC REG CTRLR BUCK 38QFN
- Quantity:
- Payment:
- Shipping:
Inventory:210
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Product details
Overview
LT3840EUFE#PBF from Analog Devices is a high-voltage synchronous step-down switching regulator controller supporting 2.5V to 60V input, delivering precise current-limited output with integrated 7.5V auxiliary bias supply, 50kHz–1MHz programmable frequency, and accurate average current monitoring. It enables high-efficiency power conversion in automotive and industrial DC/DC systems requiring robust transient handling and low-light-load quiescent current (75µA).
For engineers reviewing the LT3840EUFE#PBF datasheet, LT3840EUFE#PBF pinout, LT3840EUFE#PBF application, or LT3840EUFE#PBF equivalent, this page delivers verified technical context on its peak-current-mode control architecture, dual-loop voltage/current regulation, 38-pin QFN package layout, and real-world implementation requirements for wide-input distributed power systems.
Technical Context
The LT3840EUFE#PBF implements a constant-frequency, peak-current-mode control architecture with independent voltage and average-current regulation loops. Its internal oscillator sets switching frequency via RT resistor (50kHz–1MHz), while synchronized auxiliary buck-boost regulator generates 7.5V INTVCC for gate drive across full VIN range - eliminating external bias supplies.
It integrates precision overvoltage (OVLO), undervoltage (UVLO), and enable (EN) comparators with hysteresis, plus reverse-current protection, soft-start/tracking (TK/SS), power-good (PG), and output overvoltage protection. The IMON pin provides 20× amplified, filtered average output current sensing, and ICTRL allows programmable current limit down to 40mV sense threshold.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Input Voltage Range | 2.5V to 60V - supports direct connection to 12V/24V/48V industrial and automotive rails without pre-regulation. |
| Switching Frequency | 50kHz to 1MHz - set by single RT resistor; enables optimization of efficiency vs. size for high-power converters. |
| Quiescent Current | 75µA at 12VIN → 3.3VOUT - extends battery runtime in Burst Mode operation with ultra-low light-load consumption. |
| Auxiliary Bias Supply | 7.5V ±2.5% regulated INTVCC - powers large N-channel MOSFET gate drivers independently of VIN, enabling >95% efficiency across full input range. |
| Current Sense Accuracy | ±5% average current limit - achieved via 95mV typical peak sense voltage and 50mV typical average sense voltage with 20× IMON gain. |
| Protection Features | Integrated OVLO (up to 80V transient), UVLO, PG, output OVP, reverse-current shutdown, and thermal fault coordination - reduces external component count for safety-critical designs. |
| Operating Temperature | –40°C to +125°C junction - qualified for under-hood automotive and industrial environments per E-grade specification. |
Pinout & Package
LT3840EUFE#PBF uses a 38-lead (4mm × 6mm) plastic QFN package with exposed thermal pad (Pin 39 = GND). Pin numbering follows top-view orientation; exposed pad must be soldered to PCB ground plane for thermal and electrical integrity (θJC = 4°C/W).
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| AUXSW1 (Pin 1) | Auxiliary supply switching node | Connects to inductor of integrated buck-boost bias regulator; critical for generating stable 7.5V INTVCC. |
| AUXVIN (Pin 3) | Auxiliary supply input | Accepts 2.5V–60V input for auxiliary regulator; clamped at 60V to disable bias supply during transients. |
| RT (Pin 4) | Oscillator frequency programming | Resistor-to-ground sets switching frequency from 50kHz to 1MHz; determines inductor size and loss trade-offs. |
| TK/SS (Pin 6) | Soft-start and output tracking input | Internal 9µA current source charges external capacitor for controlled VOUT ramp; accepts external voltage for supply sequencing. |
| FB (Pin 7) | Feedback reference input | Sets output voltage via resistor divider; also feeds PG and OVP comparators (1.250V nominal regulation point). |
| MODE (Pin 11) | Light-load operation mode select | GND = Burst Mode (lowest IQ), FB = pulse-skipping, INTVCC = continuous conduction - configures efficiency vs. ripple behavior. |
| OVLO (Pin 12) | Input overvoltage lockout | Precision comparator disables controller above 1.25V threshold (≈60V at AUXVIN); maintains INTVCC during fault. |
| SENSE+ / SENSE– (Pins 21/22) | Differential current sense inputs | Measure RSENSE voltage drop; enable accurate peak (80–110mV) and average (40–52.5mV) current limiting. |
| IMON (Pin 18) | Average current monitor output | 20× amplified, RC-filtered representation of average output current - used for telemetry, diagnostics, and current sharing. |
| TG / BG (Pins 25/29) | Top/bottom N-MOSFET gate drivers | 7.5V logic-level outputs with 75ns non-overlap; drive multiple parallel MOSFETs with low RDS(ON) for high-current designs. |
Key Features
| Feature | Design Value |
|---|---|
| Integrated auxiliary buck-boost regulator | Generates 7.5V INTVCC from 2.5V–60V input - eliminates external bias supply and enables high-efficiency gate drive at low VIN. |
| Programmable average current limit | Voltage applied to ICTRL pin scales maximum average current sense threshold from 50mV down to 40mV - enables precise constant-current operation. |
| Accurate dual-protection thresholds | OVLO, UVLO, and EN pins feature ±5mV threshold accuracy and programmable hysteresis - ensures reliable startup and fault response in noisy environments. |
| Burst Mode with reverse-current prevention | Clamps VC during light load and disables BG before inductor current reaches zero - maintains DCM operation and prevents shoot-through. |
| Power Good with output OVP coordination | PG asserts high when FB is within ±3% of 1.25V and deasserts low during OVP events - simplifies system-level power sequencing and fault reporting. |
Applications
| Automotive Engine Control Unit (ECU) Power | Industrial Programmable Logic Controller (PLC) I/O Module |
|---|---|
Use Scenario: Stable 3.3V/5V rail generation from 12V/24V vehicle battery with cold-crank (4.5V) and load-dump (80V) transients. IC Role / Device Role / Timing Role: Primary synchronous buck controller managing high-current CPU/FPGA core supplies with integrated bias and protection. Use Value: Eliminates need for external LDO or charge pump bias; withstands 80V transients without latch-off; 75µA IQ extends key-off battery life. |
Use Scenario: Distributed 5V/12V power for analog sensor interfaces and digital I/O in factory automation cabinets with 24V DC bus. IC Role / Device Role / Timing Role: High-reliability step-down controller for isolated field-side power domains requiring precise current limiting and telemetry. Use Value: IMON output enables real-time current monitoring for predictive maintenance; OVLO/UVLO thresholds match industrial 24V rail tolerances. |
| Telecom Remote Radio Head (RRH) Power | Medical Imaging Power Subsystem |
Use Scenario: Compact 48V-to-12V conversion in space-constrained outdoor base station equipment operating from -40°C to +85°C ambient. IC Role / Device Role / Timing Role: Wide-input synchronous controller driving paralleled MOSFETs for high-efficiency, low-noise RF power amplifiers. Use Value: 38-pin QFN package enables dense layout; 50kHz–1MHz frequency tuning avoids interference with LTE/5G bands; 125°C junction rating ensures reliability. |
Use Scenario: Precision 5V/3.3V rails for ADCs, DACs, and FPGA logic in portable ultrasound or X-ray detector modules. IC Role / Device Role / Timing Role: Low-noise, low-ripple power controller with soft-start and tracking for multi-rail sequencing and EMI-sensitive analog front-ends. Use Value: TK/SS pin enables coordinated ramp-up with other supplies; <12% FB OVP threshold prevents damage to sensitive imaging sensors during faults. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar synchronous step-down controller applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| LTC3890EUFD#PBF | Dual-output controller with independent loop compensation; higher IQ (120µA); supports up to 60V input but lacks integrated auxiliary regulator. | Preferred for multi-rail systems requiring channel synchronization and phase interleaving; not suitable where single-chip bias integration is required. | Select LTC3890EUFD#PBF only when dual-output capability and channel coordination outweigh the benefit of LT3840EUFE#PBF's self-contained 7.5V bias generation. |
| MP2918GL-Z | Monolithic 60V synchronous buck converter (not controller); integrates power MOSFETs; fixed 500kHz frequency; no auxiliary regulator or IMON output. | Targeted at lower-power (<10A), cost-sensitive applications where board space is constrained and discrete FET selection is unnecessary. | Choose MP2918GL-Z for simplified BOM and layout in sub-10A designs; retain LT3840EUFE#PBF for >15A scalable solutions with diagnostic current monitoring and flexible bias architecture. |
Compared with LTC3890EUFD#PBF and MP2918GL-Z, the LT3840EUFE#PBF uniquely combines wide-input operation, integrated auxiliary bias supply, and analog current monitoring in a single controller - making it optimal for high-current, high-reliability industrial and automotive power stages where external bias complexity and telemetry are critical design constraints.
Availability
LT3840EUFE#PBF is available at Aetrix Electronics and suitable for automotive engine control units, industrial PLC I/O modules, telecom remote radio heads, and medical imaging subsystems requiring stable component supply, long-term lifecycle support, and traceable sourcing.
Supply support for LT3840EUFE#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, Inc. is a global leader in high-performance analog, mixed-signal, and digital signal processing semiconductors, serving industrial, automotive, communications, and healthcare markets.
The LT3840EUFE#PBF belongs to Analog Devices' Power by Linear™ family of high-voltage DC/DC controllers, designed specifically for rugged, wide-input industrial and automotive power conversion where efficiency, reliability, and integrated protection are mandatory.
FAQ
What is the maximum input voltage transient the LT3840EUFE#PBF can withstand?
The LT3840EUFE#PBF supports input transients up to 80V on the AUXVIN pin. When AUXVIN exceeds 60V, the internal auxiliary bias regulator disables to protect the 7.5V INTVCC supply, while the main controller remains functional if VIN stays within 2.5V–60V. This allows safe operation during automotive load-dump events without external TVS clamping in many cases. The LT3840EUFE#PBF's OVLO pin provides additional programmable overvoltage lockout at ≈60V.
How does the LT3840EUFE#PBF achieve low quiescent current in Burst Mode?
The LT3840EUFE#PBF achieves 75µA quiescent current in Burst Mode by internally clamping the VC error amplifier node and disabling both TG and BG gate drivers during sleep cycles. During light loads, the IC enters sleep mode where most internal circuitry shuts down, and output energy is supplied solely by the output capacitor. The LT3840EUFE#PBF wakes synchronously with its internal oscillator to resume regulation, minimizing average current draw while maintaining tight output voltage regulation.
Can the LT3840EUFE#PBF operate without an external auxiliary bias supply?
Yes - the LT3840EUFE#PBF integrates a monolithic buck-boost auxiliary regulator that generates its own 7.5V INTVCC supply from the same 2.5V–60V input rail. No external bias supply is needed, even at minimum VIN. This eliminates dependency on separate LDOs or charge pumps and ensures consistent gate drive strength across the entire input range - a key differentiator versus conventional controllers. The LT3840EUFE#PBF's auxiliary regulator is fully self-contained and requires only two external inductors and capacitors.
What is the function of the IMON pin on the LT3840EUFE#PBF?
The IMON pin on the LT3840EUFE#PBF outputs a DC voltage proportional to the average output current, generated by 20× amplification and RC filtering of the differential SENSE+–SENSE– voltage. At 50mV sense voltage, IMON = 1.00V; at 20mV, IMON = 0.40V. This analog telemetry signal enables real-time current monitoring, fault detection, and current-sharing schemes without requiring external ADCs. The LT3840EUFE#PBF's IMON output is temperature-compensated and specified across –40°C to +125°C.
How is output voltage tracking implemented using the TK/SS pin on the LT3840EUFE#PBF?
Output voltage tracking on the LT3840EUFE#PBF is implemented by applying an external ramp voltage to the TK/SS pin, which the error amplifier compares against the FB voltage. The LT3840EUFE#PBF regulates VOUT to follow the slower-rising TK/SS voltage, enabling precise sequencing with other supplies. An internal 9µA current source allows simple soft-start via a capacitor to ground. During short-circuit recovery, the TK/SS voltage is clamped to a diode above FB, ensuring controlled re-ramp without overshoot - a behavior confirmed in LT3840EUFE#PBF's functional block diagram and transfer curves.
LT3840EUFE#PBF Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc.
- Series:
- -
- Package/Case:
- 38-WFQFN Exposed Pad
- Packaging:
- Tube
- Product Status:
- Active
- Output Type:
- Transistor Driver
- Function:
- Step-Down
- Output Configuration:
- Positive or Negative
- Topology:
- Buck
- Number of Outputs:
- 1
- Output Phases:
- 1
- Voltage - Supply (Vcc/Vdd):
- 2.5V ~ 60V
- Frequency - Switching:
- 50kHz ~ 1MHz
- Duty Cycle (Max):
- 99%
- Synchronous Rectifier:
- Yes
- Clock Sync:
- Yes
- Serial Interfaces:
- -
- Control Features:
- Enable, Frequency Control, Power Good, Soft Start, Tracking
- Operating Temperature:
- -40°C ~ 125°C (TJ)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 38-QFN (4x6)
LT3840EUFE#PBF FAQ
1.How can I place an order for LT3840EUFE#PBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LT3840EUFE#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 LT3840EUFE#PBF reliable?
The price and inventory of LT3840EUFE#PBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LT3840EUFE#PBF is usually 5 days.
3.What payment methods are accepted for LT3840EUFE#PBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LT3840EUFE#PBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LT3840EUFE#PBF?
LT3840EUFE#PBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LT3840EUFE#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 LT3840EUFE#PBF?
For technical support, including LT3840EUFE#PBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LT3840EUFE#PBF requirements.
6.How does Aetrix verify that LT3840EUFE#PBF is sourced from the original manufacturer or authorized distributors?
All LT3840EUFE#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 LT3840EUFE#PBF meets industry standards.
7.What is the process for return or replacement of LT3840EUFE#PBF?
All LT3840EUFE#PBF units undergo pre-shipment inspection (PSI). If there is an issue with LT3840EUFE#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 LT3840EUFE#PBF part is unused and in its original packaging.
Return procedure for LT3840EUFE#PBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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