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Analog Devices Inc. LT3845AIFE#TRPBF
- Part No.:
- LT3845AIFE#TRPBF
- Manufacturer:
- Analog Devices Inc.
- Category:
- DC DC Switching Controllers
- Package:
- 16-TSSOP (0.173", 4.40mm Width) Exposed Pad
- Datasheet:
-
LT3845AIFE#TRPBF.pdf
- Description:
- IC REG CTRLR BUCK 16TSSOP
- Quantity:
- Payment:
- Shipping:
Inventory:2,965
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Product details
Overview
LT3845AIFE#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 100kHz–500kHz switching frequency, and features reverse inductor current inhibit, 1% VFB regulation accuracy, and 120µA no-load quiescent current - used in 48V telecom power supplies and industrial control systems.
For engineers reviewing the LT3845AIFE#TRPBF datasheet, LT3845AIFE#TRPBF pinout, LT3845AIFE#TRPBF application, or LT3845AIFE#TRPBF equivalent, key selection considerations include its 16-lead TSSOP package with exposed thermal pad, programmable soft-start via CSS pin, Burst Mode® operation enabling ultra-low-light-load efficiency, and dual gate drivers (TG/BG) optimized for N-channel MOSFETs in high-side/low-side configurations.
Technical Context
The LT3845AIFE#TRPBF implements a fixed-frequency current-mode control architecture with external oscillator programming via fSET resistor and optional synchronization via SYNC pin (100–600kHz). Its error amplifier (VC pin) integrates feedback to generate peak-current threshold per cycle, while adaptive nonoverlap circuitry prevents shoot-through by enforcing minimum dead time (150–200ns) between TG and BG transitions.
Burst Mode® operation is triggered when VC drops 150mV below the 15% load threshold, disabling switching and reducing total VIN supply current to 120µA; reverse-current inhibit engages at ~10mV differential sense voltage to disable BG before inductor current reverses, supporting discontinuous conduction mode without external diode.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Input Voltage Range | 4V to 60V - supports wide-range industrial and telecom inputs; 7.5V min start-up requires internal VCC regulator enable. |
| Output Voltage Max | 36V - enables direct regulation of intermediate bus rails without post-regulation. |
| Switching Frequency | 100kHz to 500kHz (adjustable via fSET); sync-capable up to 600kHz - balances EMI control and magnetics size. |
| VFB Regulation Accuracy | ±1% at 1.231V - ensures tight output voltage tolerance across line/load/temperature. |
| No-Load Quiescent Current | 120µA in Burst Mode - extends battery life in standby or low-duty-cycle applications. |
| Shutdown Current | 10µA - enables deep sleep states in automotive or remote sensing systems. |
| Gate Drive Capability | TG/BG drivers support large N-channel MOSFETs; typical 9.8V bootstrapped "ON" voltage ensures full enhancement. |
Pinout & Package
LT3845AIFE#TRPBF is housed in a 16-lead thermally enhanced plastic TSSOP package (FE) with exposed SGND pad (Pin 17) requiring PCB soldering for thermal and electrical performance.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| VIN | Main input supply rail | Accepts 4–60V; powers internal VCC regulator; requires ≥0.1µF local ceramic decoupling. |
| SHDN | Enable/disable control | 1.35V rising threshold with 120mV hysteresis; pulls IC into 10µA shutdown when <0.7V. |
| CSS | Soft-start timing node | Charged by 2µA internal current source; controls output voltage slew rate to limit inrush. |
| BURST_EN | Mode selection | 0.5V threshold enables Burst Mode + reverse-current inhibit; >2.5V disables both. |
| VFB | Feedback reference input | Compares against 1.231V internal reference; sets output voltage via resistive divider. |
| VC | Error amplifier output | Integrates feedback error; sets peak inductor current threshold per cycle; clamped during Burst Mode. |
| 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 rail | Drives TG gate; referenced to SW; max voltage = VIN + VCC; requires ≥0.1µF ceramic capacitor. |
| TG | Top N-MOSFET gate driver | Bootstrapped high-side driver; fast rise/fall (<50ns) minimizes switching losses. |
| SW | Switch node | Connects to inductor and BOOST capacitor; transient rating down to –2V (non-repetitive). |
| VCC | Internal bias supply | 8V regulated output from VIN; can be back-fed from VOUT to improve efficiency. |
| BG | Bottom N-MOSFET gate driver | Low-side driver with fast edge rates; referenced to PGND. |
| PGND | Power ground return | High-current return path for BG driver and VCC regulator; must tie directly to VCC capacitor negative. |
| SENSE+ | Current sense positive input | Connected to inductor side of sense resistor; common-mode range up to 36V. |
| SENSE– | Current sense negative input | Connected to VOUT side of sense resistor; supports reverse-current detection with 10mV offset. |
Key Features
| Feature | Design Value |
|---|---|
| Adjustable constant-frequency operation | 100–500kHz via fSET resistor - enables optimization of efficiency vs. size vs. EMI in custom designs. |
| Reverse inductor current inhibit | 10mV sense offset disables BG before current reversal - eliminates body-diode conduction loss in light-load DCM. |
| Adaptive nonoverlap circuitry | 150–200ns guaranteed dead time - prevents simultaneous TG/BG conduction and MOSFET shoot-through. |
| Programmable soft-start | 2µA CSS charging current - allows precise control of output ramp time without external timers or logic. |
| Precision undervoltage lockout | 7.5V VIN start threshold with 670mV hysteresis - ensures reliable startup and brownout recovery in noisy environments. |
Applications
| 48V Telecom Power Supply | Industrial Control System |
|---|---|
Use Scenario: Converting -48V or +48V telecom rectified input to stable 12V/24V intermediate bus for shelf management and interface cards. IC Role / Device Role / Timing Role: Primary synchronous buck controller regulating output with current-mode stability and fast transient response. Use Value: 60V absolute max input rating accommodates 48V system transients; 1% VFB accuracy maintains tight bus tolerance under varying load profiles. | Use Scenario: Providing isolated 15V/24V rails for PLC I/O modules, motor drives, and sensor signal conditioning in factory automation. IC Role / Device Role / Timing Role: High-efficiency step-down controller managing distributed power with programmable frequency to avoid noise coupling into analog circuits. Use Value: SYNC pin enables clock alignment with system master clock; Burst Mode reduces standby power in idle states without compromising regulation. |
| Avionics Power Converter | Heavy Equipment Onboard Power |
Use Scenario: Generating 28V DC from 270V DC aircraft distribution bus for flight control computers and navigation subsystems. IC Role / Device Role / Timing Role: High-input-voltage synchronous controller with robust UVLO and thermal protection for safety-critical power stages. Use Value: –40°C to 125°C operating junction temperature range meets DO-160 environmental requirements; exposed pad enhances thermal reliability. | Use Scenario: Regulating 42V starter-battery input to 12V/5V rails for telematics, displays, and CAN controllers in construction and agricultural vehicles. IC Role / Device Role / Timing Role: Automotive-grade buck controller with reverse-current inhibit to maintain efficiency during engine cranking and load dump events. Use Value: Reverse-current inhibit prevents backfeed into battery during coast-down; 10µA shutdown current preserves battery charge during long vehicle idle periods. |
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 4.5V–60V input; integrated LDO for bias; higher 10A gate drive; no Burst Mode | Preferred where integrated bias simplifies layout; less suitable for ultra-low-IQ battery backup | Select LTC3891EFE#PBF when board space is constrained and external VCC generation is undesirable. |
| MP24894GQKT-LF-Z | Lower 4.5V–60V input; fixed 300kHz freq; no SYNC or fSET; 2.5A gate drive; lower cost | Targeted at cost-sensitive industrial supplies without EMI synchronization needs | Choose MP24894GQKT-LF-Z for fixed-frequency, non-synchronized applications where design simplicity outweighs programmability. |
Compared with LTC3891EFE#PBF, LT3845AIFE#TRPBF offers superior light-load efficiency via Burst Mode but requires external VCC management; versus MP24894GQKT-LF-Z, it provides full frequency adjustability and synchronization - critical for noise-sensitive avionics and telecom systems.
Availability
LT3845AIFE#TRPBF is available at Aetrix Electronics and suitable for 48V telecom power supplies, industrial control systems, avionics converters, and heavy equipment onboard power requiring stable component supply across extended temperature ranges.
Supply support for LT3845AIFE#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, Inc. (ADI) is a global semiconductor leader specializing in high-performance analog, mixed-signal, and power management ICs, acquired Linear Technology in 2017 to expand its precision power portfolio.
The LT3845AIFE#TRPBF belongs to ADI's high-voltage DC/DC controller product line, designed specifically for robust, efficient, and noise-aware power conversion in telecom infrastructure, industrial automation, and transportation systems.
FAQ
What is the maximum input voltage rating for the LT3845AIFE#TRPBF?
The LT3845AIFE#TRPBF has an absolute maximum input voltage (VIN) rating of 65V, with continuous operation supported from 4V to 60V. The device starts reliably at 7.5V due to internal VCC regulator requirements, and operation below that threshold is only possible if VCC is externally powered above 6.5V - a key design consideration for low-VIN hold-up scenarios in the LT3845AIFE#TRPBF.
How does the reverse-current inhibit function work in the LT3845AIFE#TRPBF?
The LT3845AIFE#TRPBF detects approaching zero inductor current using a 10mV positive offset on the SENSE+ and SENSE– inputs. When reverse current is imminent, the bottom gate driver (BG) is disabled mid-cycle to prevent body-diode conduction, enabling discontinuous operation and improving light-load efficiency. This function is enabled by pulling BURST_EN to ground or VFB - a core energy-saving feature unique to the LT3845AIFE#TRPBF.
Can the LT3845AIFE#TRPBF be synchronized to an external clock, and what are the limits?
Yes, the LT3845AIFE#TRPBF supports external synchronization via the SYNC pin over 100kHz to 600kHz. To ensure stable locking, the internal oscillator (set by fSET) 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 makes the LT3845AIFE#TRPBF suitable for noise-sensitive multi-rail systems where clock harmonics must be aligned.
What is the purpose of the exposed pad on the LT3845AIFE#TRPBF package?
The exposed pad on the LT3845AIFE#TRPBF's 16-lead TSSOP package is electrically connected to SGND and must be soldered to the PCB ground plane. It serves dual purposes: lowering thermal resistance (θJA = 40°C/W) to sustain 125°C junction temperature operation, and providing a low-inductance, low-noise ground return for sensitive analog circuitry like the error amplifier and current sense comparator - essential for stable regulation in the LT3845AIFE#TRPBF.
Does the LT3845AIFE#TRPBF support programmable soft-start, and how is it implemented?
Yes, the LT3845AIFE#TRPBF implements programmable soft-start via the CSS pin, which is charged by an internal 2µA current source. A capacitor from CSS to SGND sets the output voltage ramp time using the formula CSS = 2µA × (tSS / 1.231V). During startup, the CSS voltage overrides the error amplifier reference to limit inrush current - a critical feature for reliable power sequencing in systems using the LT3845AIFE#TRPBF.
LT3845AIFE#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
LT3845AIFE#TRPBF FAQ
1.How can I place an order for LT3845AIFE#TRPBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LT3845AIFE#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 LT3845AIFE#TRPBF reliable?
The price and inventory of LT3845AIFE#TRPBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LT3845AIFE#TRPBF is usually 5 days.
3.What payment methods are accepted for LT3845AIFE#TRPBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LT3845AIFE#TRPBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LT3845AIFE#TRPBF?
LT3845AIFE#TRPBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LT3845AIFE#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 LT3845AIFE#TRPBF?
For technical support, including LT3845AIFE#TRPBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LT3845AIFE#TRPBF requirements.
6.How does Aetrix verify that LT3845AIFE#TRPBF is sourced from the original manufacturer or authorized distributors?
All LT3845AIFE#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 LT3845AIFE#TRPBF meets industry standards.
7.What is the process for return or replacement of LT3845AIFE#TRPBF?
All LT3845AIFE#TRPBF units undergo pre-shipment inspection (PSI). If there is an issue with LT3845AIFE#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 LT3845AIFE#TRPBF part is unused and in its original packaging.
Return procedure for LT3845AIFE#TRPBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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