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Analog Devices Inc. LT3845AEFE#TRPBF
- Part No.:
- LT3845AEFE#TRPBF
- Manufacturer:
- Analog Devices Inc.
- Category:
- DC DC Switching Controllers
- Package:
- 16-TSSOP (0.173", 4.40mm Width) Exposed Pad
- Datasheet:
-
LT3845AEFE#TRPBF.pdf
- Description:
- IC REG CTRLR BUCK 16TSSOP
- Quantity:
- Payment:
- Shipping:
Inventory:1,398
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Product details
Overview
LT3845AEFE#TRPBF from Analog Devices (formerly Linear Technology) is a high-voltage, synchronous current-mode step-down controller for medium-to-high-power DC/DC conversion. 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-used in 48V telecom power supplies and industrial control systems.
For engineers reviewing the LT3845AEFE#TRPBF datasheet, LT3845AEFE#TRPBF pinout, LT3845AEFE#TRPBF application, or LT3845AEFE#TRPBF equivalent, key selection considerations include its 120µA no-load quiescent current, reverse inductor current inhibit for discontinuous operation, programmable soft-start, adaptive nonoverlap circuitry, and thermally enhanced 16-lead TSSOP package with exposed SGND pad.
Technical Context
The LT3845AEFE#TRPBF implements a current-mode control architecture with an internal 1.231V reference and error amplifier transconductance of 270–410µS. Its oscillator supports both internal resistor-programmed operation (via fSET pin) and external synchronization (SYNC pin, 100–600kHz), enabling noise-sensitive system integration.
It integrates dual N-channel MOSFET gate drivers (TG and BG) with adaptive nonoverlap timing (200ns TG→BG, 150ns BG→TG) and reverse-current inhibit logic that disables the bottom switch when sensed inductor current approaches zero-preventing shoot-through and improving light-load efficiency via discontinuous conduction mode.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Input Voltage Range | 4V to 60V - supports wide-range industrial and telecom inputs; minimum 7.5V required for startup without external VCC bias |
| Output Voltage Range | Up to 36V - enables high-side buck conversion for intermediate bus architectures |
| Switching Frequency | 100kHz to 500kHz (adjustable) - set by external RSET on fSET pin; synchronized externally up to 600kHz |
| Quiescent Current | 120µA in Burst Mode - maintains high efficiency at light loads without auxiliary bias supply |
| Regulation Accuracy | ±1% over line, load, and temperature - ensures stable output under dynamic conditions |
| Shutdown Current | 10µA - enables ultra-low-power standby in battery-backed or energy-conscious systems |
| Current Sense Threshold | 100mV (typical) - sets peak inductor current limit; includes 10mV positive offset for reverse-current detection |
Pinout & Package
LT3845AEFE#TRPBF is housed in a 16-lead thermally enhanced plastic TSSOP package (FE grade) with exposed leadframe connected to SGND. The exposed pad must be soldered to PCB ground for thermal performance and low-noise grounding.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| VIN | Main input supply | Accepts 4V–60V; powers internal regulator; requires ≥0.1µF local ceramic decoupling to SGND |
| SHDN | Enable/disable control | 1.35V rising threshold with 120mV hysteresis; pulls IC into 10µA shutdown when <0.7V |
| CSS | Soft-start timing | Charged by internal 2µA current source; controls output voltage slew rate during startup |
| BURST_EN | Mode selection | Enables Burst Mode (≤0.5V), disables it but retains reverse-current inhibit (≈VFB), or disables both (≥2.5V) |
| VFB | Feedback input | Connects to resistive divider; regulated to 1.231V; serves as error amp inverting input |
| VC | Error amplifier output | Drives current sense comparator threshold; clamped internally during Burst Mode to limit negative excursion |
| SYNC | External clock input | Accepts 100–600kHz square wave; requires RSET set 10–25% below sync frequency |
| fSET | Oscillator programming | Resistor-connected pin sets nominal frequency; required even when SYNC is active |
| BOOST | Bootstrap supply | Drives top MOSFET gate; referenced to SW; max voltage = VIN + VCC (ground-referenced) |
| TG | Top gate driver | Bootstrapped N-channel driver; fast rise/fall (<50ns); requires short, wide trace to minimize inductance |
| SW | Switch node | High dv/dt node; connects to boost capacitor and inductor; absolute max −2V transient |
| VCC | Internal bias rail | 8V regulated output; powers most internal circuitry; can be back-fed from VOUT to improve efficiency |
| BG | Bottom gate driver | Direct-drive N-channel driver; complements TG; same timing constraints and layout rules |
| PGND | Power ground | High-current return for BG driver and VCC regulator; connect directly to VCC capacitor negative terminal |
| SENSE+ | Current sense + | Connects to inductor side of sense resistor; common-mode range up to 36V |
| SENSE− | Current sense − | Connects to output side of sense resistor; differential input with 100mV threshold and reverse-current offset |
Key Features
| Feature | Design Value |
|---|---|
| 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 |
| Reverse inductor current inhibit | Disables BG when sensed current nears zero, enabling discontinuous operation and reducing light-load conduction losses |
| Programmable soft-start | Controlled by external CSS capacitor; prevents 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 and fast transient response |
| Thermally enhanced TSSOP | 16-lead package with exposed SGND pad; θJA = 40°C/W; requires PCB copper area for heat dissipation |
Applications
| 48V Telecom Power Supply | Industrial Control System |
|---|---|
Use Scenario: Converting 48V distributed bus to 12V/5V intermediate rails in base station power modules. IC Role / Device Role / Timing Role: High-voltage synchronous buck controller managing peak currents >10A with precise cycle-by-cycle current limiting. Use Value: 60V absolute max input rating withstands telecom surge transients; 1% regulation ensures stable downstream logic and RF bias rails. | Use Scenario: Powering PLC I/O modules and sensor interfaces in factory automation cabinets with 24V/48V field wiring. IC Role / Device Role / Timing Role: Primary step-down controller delivering isolated or non-isolated 5V/3.3V rails with robust UVLO and fault protection. Use Value: −40°C to 125°C operating junction range meets industrial temperature requirements; reverse-current inhibit extends efficiency down to µA-level loads. |
| Avionics Power Converter | Distributed Power Architecture |
Use Scenario: Generating 28V or 12V from 270V DC aircraft bus using multi-stage conversion with pre-regulation. IC Role / Device Role / Timing Role: High-input-voltage buck controller stage operating at 300kHz to minimize EMI and filter size in weight-constrained enclosures. Use Value: SYNC pin allows clock alignment across multiple converters to avoid beat frequencies; low 120µA Burst Mode current reduces parasitic drain on backup batteries. | Use Scenario: Local point-of-load (POL) regulation in server motherboards or network switches where 12V or 48V backplanes feed multiple DC/DC stages. IC Role / Device Role / Timing Role: Synchronous buck controller driving discrete SiC or GaN MOSFETs for high-efficiency, high-density POL conversion. Use Value: Adjustable 100–500kHz frequency enables optimization for efficiency vs. size trade-offs; TG/BG drivers support >180nC total gate charge without external buffers. |
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 |
|---|---|---|---|
| LTC3890EFE#PBF | Dual-output, 60V input, integrated MOSFET drivers with phase-lock loop; higher pin count and complexity | Designed for dual-rail or interleaved designs; lacks reverse-current inhibit and Burst Mode | Select when needing dual outputs or channel synchronization; not drop-in for single-rail LT3845AEFE#TRPBF designs |
| LM5116PWPR | 60V input, external MOSFET controller with 50–750kHz range; no Burst Mode; 1.5% regulation accuracy | Lower cost, lower integration; requires external bootstrap diode; no reverse-current inhibit | Choose for cost-sensitive industrial applications where 120µA light-load current is not required |
Compared with LTC3890EFE#PBF and LM5116PWPR, the LT3845AEFE#TRPBF uniquely combines 120µA Burst Mode, reverse-current inhibit, and 1% regulation in a compact 16-pin TSSOP-making it optimal for space-constrained, efficiency-critical 48V telecom and avionics supplies where light-load behavior and thermal management are prioritized.
Availability
LT3845AEFE#TRPBF is available at Aetrix Electronics and suitable for 48V telecom power supplies, industrial control systems, avionics power converters, and distributed power architectures requiring stable component supply, long-term lifecycle support, and guaranteed temperature-grade performance.
Supply support for LT3845AEFE#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 and maintains full product support, documentation, and manufacturing continuity for legacy Linear parts including the LT3845A family.
The LT3845A product line was designed specifically for high-efficiency, high-input-voltage synchronous buck conversion in demanding environments-emphasizing light-load efficiency, thermal robustness, and noise-immune clock synchronization.
FAQ
What is the maximum input voltage rating for the LT3845AEFE#TRPBF?
The LT3845AEFE#TRPBF has an absolute maximum input voltage (VIN) rating of 65V, with continuous operation supported from 4V to 60V. Startup requires a minimum of 7.5V on VIN unless VCC is externally biased above 6.5V-enabling operation down to 4V after startup in systems with auxiliary bias.
How does the reverse-current inhibit function work in the LT3845AEFE#TRPBF?
The LT3845AEFE#TRPBF detects near-zero inductor current via its SENSE+ and SENSE− pins and disables the bottom gate driver (BG) before current reverses. This is enabled by pulling BURST_EN ≤0.5V (Burst Mode) or ≈VFB (reverse-current only). A built-in 10mV positive offset prevents false triggering, allowing true discontinuous conduction mode and improved light-load efficiency.
Can the LT3845AEFE#TRPBF be synchronized to an external clock, and what is the valid frequency range?
Yes, the LT3845AEFE#TRPBF supports external synchronization via the SYNC pin across 100kHz to 600kHz. To ensure reliable locking, the internal oscillator (set by fSET resistor) must run 10–25% below the external clock frequency. Unused SYNC pins must be tied to SGND to prevent noise coupling.
What is the purpose of the exposed pad on the LT3845AEFE#TRPBF package?
The exposed pad on the LT3845AEFE#TRPBF is electrically connected to SGND and serves dual purposes: it provides a low-inductance, low-resistance path for sensitive analog ground return and significantly improves thermal dissipation. Per datasheet guidelines, it must be soldered to a dedicated PCB copper area tied to SGND for both electrical integrity and thermal performance.
Does the LT3845AEFE#TRPBF support programmable soft-start, and how is it implemented?
Yes, the LT3845AEFE#TRPBF implements programmable soft-start via the CSS pin, which is charged by an internal 2µA current source. Connecting an external capacitor from CSS to SGND sets the output voltage ramp rate using the formula CSS = 2µA × tSS/1.231V. The soft-start circuit discharges automatically during UVLO or shutdown events, ensuring repeatable startup behavior.
LT3845AEFE#TRPBF Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc.
- Series:
- -
- Package/Case:
- 16-TSSOP (0.173", 4.40mm Width) Exposed Pad
- Packaging:
- Tape & Reel (TR)
- 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#TRPBF FAQ
1.How can I place an order for LT3845AEFE#TRPBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LT3845AEFE#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 LT3845AEFE#TRPBF reliable?
The price and inventory of LT3845AEFE#TRPBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LT3845AEFE#TRPBF is usually 5 days.
3.What payment methods are accepted for LT3845AEFE#TRPBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LT3845AEFE#TRPBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LT3845AEFE#TRPBF?
LT3845AEFE#TRPBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LT3845AEFE#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 LT3845AEFE#TRPBF?
For technical support, including LT3845AEFE#TRPBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LT3845AEFE#TRPBF requirements.
6.How does Aetrix verify that LT3845AEFE#TRPBF is sourced from the original manufacturer or authorized distributors?
All LT3845AEFE#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 LT3845AEFE#TRPBF meets industry standards.
7.What is the process for return or replacement of LT3845AEFE#TRPBF?
All LT3845AEFE#TRPBF units undergo pre-shipment inspection (PSI). If there is an issue with LT3845AEFE#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 LT3845AEFE#TRPBF part is unused and in its original packaging.
Return procedure for LT3845AEFE#TRPBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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