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Analog Devices Inc. LT3845AEFE#PBF
- Part No.:
- LT3845AEFE#PBF
- Manufacturer:
- Analog Devices Inc.
- Category:
- DC DC Switching Controllers
- Package:
- 16-TSSOP (0.173", 4.40mm Width) Exposed Pad
- Datasheet:
-
LT3845AEFE#PBF.pdf
- Description:
- IC REG CTRLR BUCK 16TSSOP
- Quantity:
- Payment:
- Shipping:
Inventory:832
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Product details
Overview
LT3845AEFE#PBF from Analog Devices (formerly Linear Technology) is a high-voltage, synchronous current-mode step-down DC/DC controller IC designed for medium-to-high-power industrial and automotive power supplies. It operates from 4V to 60V input, delivers up to 36V output, supports adjustable switching frequency from 100kHz to 500kHz, and features 1% output voltage regulation accuracy. It is used in 48V telecom and avionics power conversion systems requiring stable, high-efficiency regulation under wide load and temperature ranges.
For engineers reviewing the LT3845AEFE#PBF datasheet, LT3845AEFE#PBF pinout, LT3845AEFE#PBF application, or LT3845AEFE#PBF equivalent, key selection considerations include its 16-lead TSSOP thermal performance, reverse inductor current inhibit for light-load efficiency, programmable soft-start, Burst Mode® operation with 120µA no-load quiescent current, and adaptive nonoverlap gate drive timing to prevent shoot-through.
Technical Context
The LT3845AEFE#PBF implements a current-mode control architecture with an internal 1.231V reference and error amplifier transconductance of 270–410 µS. Its oscillator supports both internal resistor-programmed operation (via fSET pin) and external synchronization (100–600kHz), enabling noise-sensitive system integration.
It integrates dual N-channel MOSFET gate drivers (TG and BG) with adaptive nonoverlap circuitry (200ns TG→BG / 150ns BG→TG), reverse-current inhibit with 10mV sense offset, and precision undervoltage lockout on VIN (7.5V start-up, 3.8V falling threshold). The VCC regulator derives bias from VIN and provides 8V output with ~1V dropout.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Input Voltage Range | 4V to 60V - supports wide-input industrial, telecom, and 42V automotive systems without pre-regulation. |
| Output Voltage Max | 36V - enables direct generation of intermediate bus voltages like 24V or 36V from 48V input. |
| Switching Frequency | 100kHz to 500kHz (adjustable via fSET resistor) - balances size, efficiency, and EMI in high-power buck designs. |
| Quiescent Current | 120µA in Burst Mode - sustains >90% efficiency at milliamp loads in battery-backed or standby systems. |
| Regulation Accuracy | ±1% over line, load, and temperature - ensures tight output tolerance for sensitive downstream circuitry. |
| UVLO Threshold | 7.5V start-up, 3.8V hysteresis - prevents erratic startup during brownout and ensures clean power-on sequencing. |
| Gate Drive Capability | TG/BG drivers support large N-MOSFETs with typical 9.8V bootstrapped "ON" voltage - reduces conduction losses in high-current paths. |
Pinout & Package
LT3845AEFE#PBF is housed in a 16-lead thermally enhanced plastic TSSOP package with exposed pad (Pin 17) internally connected to SGND and required to be soldered to PCB ground for thermal and electrical integrity.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| VIN | Main input supply rail | Accepts 4–60V input; powers internal VCC regulator and UVLO detection. |
| SHDN | Enable/disable control | 1.35V rising threshold with 120mV hysteresis; pulls <10nA bias current. |
| CSS | Soft-start timing node | Charged by 2µA internal current source; controls output voltage slew rate during startup. |
| BURST_EN | Mode selection input | Enables/disables Burst Mode® and reverse-current inhibit based on voltage level (0.5V/2.5V thresholds). |
| VFB | Feedback reference input | Compares against internal 1.231V reference; sets output voltage via resistive divider. |
| VC | Error amplifier output | Drives current-sense comparator threshold; clamped to limit negative excursion in Burst Mode. |
| SYNC | External clock input | Accepts 100–600kHz sync signal; requires RSET set 10–25% below sync frequency. |
| fSET | Oscillator programming | Resistor-connected pin sets internal frequency; required even when SYNC is active. |
| BOOST | Bootstrap supply rail | Provides gate drive voltage for top MOSFET; referenced to SW, max 80V absolute rating. |
| TG | Top gate driver output | Drives N-channel high-side MOSFET gate; fast rise/fall (<50ns) with adaptive nonoverlap. |
| SW | Switch node | Connects to inductor and BOOST capacitor; handles high dv/dt; rated –2V transient. |
| VCC | Internal bias supply | 8V regulated output from VIN; powers most internal circuitry; can be externally driven to improve efficiency. |
| BG | Bottom gate driver output | Drives N-channel low-side MOSFET gate; complements TG with precise timing control. |
| PGND | Power ground return | High-current return path for VCC regulator and bottom driver; must connect directly to VCC decoupling cap. |
| SENSE+ | Current sense positive | Connects to inductor side of sense resistor; common-mode range up to 36V. |
| SENSE– | Current sense negative | Connects to output side of sense resistor; differential range ±1V with 100mV reverse inhibit offset. |
Key Features
| Feature | Design Value |
|---|---|
| Reverse Inductor Current Inhibit | Disables synchronous rectification when inductor current approaches zero, enabling discontinuous conduction mode and improving light-load efficiency. |
| Adaptive Nonoverlap Circuitry | Prevents shoot-through by enforcing 200ns delay between TG turn-off and BG turn-on, and 150ns between BG turn-off and TG turn-on. |
| Programmable Soft-Start | Controlled by external CSS capacitor charged at 2µA; eliminates output overshoot and limits inrush current during power-up. |
| Burst Mode® Operation | Reduces total input quiescent current to 120µA at no load while maintaining regulation, ideal for standby and battery-powered applications. |
| Synchronizable Oscillator | Supports external clock input from 100kHz to 600kHz, allowing coordinated switching across multiple converters to reduce EMI peaks. |
Applications
| 48V Telecom Power Supply | Automotive 12V/24V System |
|---|---|
Use Scenario: Converting 48V backplane voltage to 12V for base station radios and network interface cards. IC Role / Device Role / Timing Role: High-voltage synchronous buck controller managing peak currents >10A with precise current-mode loop stability. Use Value: Enables >94% efficiency at full load and >88% at 10% load using Burst Mode®, reducing thermal stress in dense telecom chassis. | Use Scenario: Regulating 42V battery-supplied power to 12V for engine control units and ADAS sensors in heavy-duty vehicles. IC Role / Device Role / Timing Role: Robust controller with 125°C junction-rated operation and reverse-current inhibit for cold-cranking compatibility. Use Value: Maintains regulation down to 4V input during cranking events and avoids reverse current flow into weak batteries. |
| Avionics Power Converter | Distributed Industrial Power |
Use Scenario: Generating 28V or 36V from 115VAC-derived 270VDC in aircraft auxiliary power units. IC Role / Device Role / Timing Role: High-reliability step-down controller with precision UVLO and shutdown current <10µA for fault-tolerant architectures. Use Value: Ensures safe startup only above 7.5V and enters ultra-low-power shutdown state during fault conditions. | Use Scenario: Local point-of-load regulation in factory automation PLCs where 48V DC bus powers multiple isolated modules. IC Role / Device Role / Timing Role: Synchronizable controller enabling phase-shifted operation across multiple rails to minimize input ripple current. Use Value: Reduces bulk capacitance requirements and improves system-level EMI compliance through deterministic switching alignment. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar high-voltage synchronous buck controller applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| LTC3891EFE#PBF | Wider input range (4.5V–60V), integrated LDO for gate drive, higher max frequency (850kHz), but no reverse-current inhibit. | Preferred for designs needing integrated bias regulation and faster transient response; less optimal for ultra-low-light-load efficiency. | Select LTC3891EFE#PBF when simplified layout and higher-frequency operation outweigh need for reverse-current suppression. |
| MP24894GQ-Z | Lower max input (40V), fixed 300kHz frequency, no SYNC or fSET, smaller QFN-16 package, lower cost. | Suitable for cost-sensitive 24V/36V industrial supplies where programmability and 60V headroom are unnecessary. | Choose MP24894GQ-Z for compact, fixed-frequency designs with ≤40V input and no requirement for Burst Mode® or external sync. |
Compared with LTC3891EFE#PBF and MP24894GQ-Z, the LT3845AEFE#PBF uniquely combines 60V input capability, reverse-current inhibit, and 120µA Burst Mode® quiescent current-making it optimal for high-reliability, wide-input, light-load-sensitive applications where efficiency across the full load range is critical.
Availability
LT3845AEFE#PBF is available at Aetrix Electronics and suitable for 48V telecom power supplies, 12V/24V automotive systems, and avionics power converters requiring stable component supply, long-term lifecycle support, and guaranteed lead-free compliance.
Supply support for LT3845AEFE#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. (acquired Linear Technology in 2017) is a global leader in high-performance analog, mixed-signal, and power management semiconductors.
The LT3845AEFE#PBF belongs to Linear's high-voltage DC/DC controller product line, engineered specifically for robust, high-efficiency step-down conversion in harsh environments including telecom infrastructure, transportation, and industrial automation.
FAQ
What is the operating temperature range for the LT3845AEFE#PBF?
The LT3845AEFE#PBF is rated for operation from –40°C to +125°C junction temperature. This extended range is validated per the LT3845AE grade specification and supports deployment in under-hood automotive, industrial enclosures, and telecom equipment without derating. The device includes overtemperature protection that activates above 125°C to safeguard against sustained thermal overload.
How does the reverse-current inhibit function work in the LT3845AEFE#PBF?
The LT3845AEFE#PBF detects near-zero inductor current via its SENSE+ and SENSE– inputs and disables the bottom gate driver (BG) before current reverses, preventing synchronous rectifier conduction in discontinuous mode. This is enabled by pulling BURST_EN ≤ 0.5V or = VFB, and uses a 10mV positive offset at the sense amplifier to avoid false triggering. The result is reduced conduction loss and improved light-load efficiency compared to forced continuous operation.
Can the LT3845AEFE#PBF be synchronized to an external clock, and what are the constraints?
Yes, the LT3845AEFE#PBF supports external synchronization via the SYNC pin across 100kHz–600kHz. To ensure reliable locking, the internal oscillator (set by fSET resistor) must run 10–25% below the external clock frequency. The SYNC input has 40kΩ internal resistance and 1.4–2.0V threshold; unused SYNC must be tied to SGND. This capability allows EMI reduction in multi-rail systems and deterministic timing in safety-critical applications.
What is the purpose of the exposed pad on the LT3845AEFE#PBF package, and how should it be handled?
The exposed pad (Pin 17) on the LT3845AEFE#PBF is electrically connected to SGND and serves dual thermal and electrical functions. It must be soldered to a dedicated PCB copper area tied to the low-noise signal ground plane to ensure optimal thermal dissipation (qJC = 10°C/W) and minimize noise coupling into the error amplifier and current sense circuitry. Leaving it unconnected degrades both thermal performance and regulation accuracy.
Does the LT3845AEFE#PBF require external components for basic operation, and which ones are mandatory?
Yes, the LT3845AEFE#PBF requires several external components for functional operation: a bootstrap capacitor (≥0.1µF ceramic) between BOOST and SW; input/output bulk capacitors; a current-sense resistor; feedback resistors for VFB; and an fSET resistor to set switching frequency. The CSS capacitor is optional but recommended for controlled startup. Gate drivers require short, wide PCB traces to TG and BG pins to minimize inductance and prevent oscillation.
LT3845AEFE#PBF Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc.
- Series:
- -
- Package/Case:
- 16-TSSOP (0.173", 4.40mm Width) Exposed Pad
- Packaging:
- Tube
- Product Status:
- Active
- Output Type:
- Transistor Driver
- Function:
- Step-Down
- Output Configuration:
- Positive
- Topology:
- Buck
- Number of Outputs:
- 1
- Output Phases:
- 1
- Voltage - Supply (Vcc/Vdd):
- 4V ~ 60V
- Frequency - Switching:
- 300kHz
- Duty Cycle (Max):
- -
- Synchronous Rectifier:
- Yes
- Clock Sync:
- Yes
- Serial Interfaces:
- -
- Control Features:
- Enable, Frequency Control, Soft Start
- Operating Temperature:
- -40°C ~ 125°C (TJ)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 16-TSSOP-EP
LT3845AEFE#PBF FAQ
1.How can I place an order for LT3845AEFE#PBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LT3845AEFE#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 LT3845AEFE#PBF reliable?
The price and inventory of LT3845AEFE#PBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LT3845AEFE#PBF is usually 5 days.
3.What payment methods are accepted for LT3845AEFE#PBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LT3845AEFE#PBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LT3845AEFE#PBF?
LT3845AEFE#PBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LT3845AEFE#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 LT3845AEFE#PBF?
For technical support, including LT3845AEFE#PBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LT3845AEFE#PBF requirements.
6.How does Aetrix verify that LT3845AEFE#PBF is sourced from the original manufacturer or authorized distributors?
All LT3845AEFE#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 LT3845AEFE#PBF meets industry standards.
7.What is the process for return or replacement of LT3845AEFE#PBF?
All LT3845AEFE#PBF units undergo pre-shipment inspection (PSI). If there is an issue with LT3845AEFE#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 LT3845AEFE#PBF part is unused and in its original packaging.
Return procedure for LT3845AEFE#PBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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