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Analog Devices Inc. LT3845AMPFE#TRPBF
- Part No.:
- LT3845AMPFE#TRPBF
- Manufacturer:
- Analog Devices Inc.
- Category:
- DC DC Switching Controllers
- Package:
- 16-TSSOP (0.173", 4.40mm Width) Exposed Pad
- Datasheet:
-
LT3845AMPFE#TRPBF.pdf
- Description:
- IC REG CTRLR BUCK 16TSSOP
- Quantity:
- Payment:
- Shipping:
Inventory:4,371
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Product details
Overview
LT3845AMPFE#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 supports 4V–60V input, delivers up to 36V output, operates at 270–330kHz (typical), features 120µA no-load quiescent current, and includes reverse inductor current inhibit for discontinuous operation. It is used in 48V telecom power supplies and avionics systems requiring stable high-efficiency regulation.
For engineers reviewing the LT3845AMPFE#TRPBF datasheet, LT3845AMPFE#TRPBF pinout, LT3845AMPFE#TRPBF application, or LT3845AMPFE#TRPBF equivalent, key selection considerations include its –55°C to 125°C extended temperature grade, programmable 100–500kHz operating frequency, adaptive nonoverlap gate drive, 1% output voltage regulation accuracy, and integrated burst mode control for light-load efficiency optimization.
Technical Context
The LT3845AMPFE#TRPBF implements a current-mode control architecture with external N-channel MOSFETs, using sensed inductor current and an error-amplifier-derived VC threshold to regulate duty cycle. Its oscillator supports both internal resistor-programmed frequency (via fSET) and external synchronization (SYNC pin) up to 600kHz.
It integrates dual gate drivers (TG and BG) with adaptive nonoverlap timing (200ns TG→BG, 150ns BG→TG), reverse-current inhibit via SENSE+/- differential sensing with 10mV offset, and a precision 1.231V feedback reference with ±1.5mV tolerance over temperature. The device uses an internal linear regulator to generate VCC from VIN, with external VCC biasing supported to reduce dissipation.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Input Voltage Range | 4V to 60V - supports wide industrial and automotive input rails including 48V telecom and 42V heavy equipment systems. |
| Operating Frequency | 270–330kHz typical (100–500kHz programmable) - enables compact magnetics while balancing switching loss and EMI performance. |
| Output Voltage Accuracy | ±1% at VFB = 1.231V - ensures tight regulation across line, load, and temperature for precision power delivery. |
| Quiescent Current | 120µA in Burst Mode - minimizes standby power in battery-backed or energy-sensitive applications. |
| Shutdown Current | 10µA - enables ultra-low-power system-level sleep states without compromising fast wake-up capability. |
| Temperature Range | –55°C to 125°C junction - qualified for extended-temperature military, aerospace, and industrial environments. |
| Gate Drive Capability | TG/BG outputs drive large N-channel MOSFETs with 9.8V typical "ON" voltage and 50ns rise/fall time - supports high-efficiency, high-current power stages. |
Pinout & Package
The LT3845AMPFE#TRPBF is housed in a 16-lead thermally enhanced TSSOP package with exposed pad (Pin 17) connected to SGND. The exposed pad must be soldered to PCB ground for thermal and electrical integrity.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| VIN | Main supply input | Accepts 4–60V input; powers internal regulator and provides bootstrap charge path via VCC. |
| 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 2µA internal current source; controls output voltage slew rate and inrush current during startup. |
| BURST_EN | Mode selection | Configures Burst Mode (≤0.5V), reverse-current inhibit only (≈1.23V), or continuous conduction (>2.5V). |
| VFB | Feedback reference | Compares output voltage (via resistive divider) to 1.231V internal reference; regulates output with ±1% accuracy. |
| VC | Error amplifier output | Integrator node setting peak inductor current per cycle; clamped during Burst Mode to limit ripple. |
| SYNC | External clock input | Accepts 100–600kHz sync signal; requires internal oscillator set 10–25% below external frequency. |
| fSET | Frequency programming | Resistor-connected pin sets oscillator frequency; required even when SYNC is active. |
| BOOST | Bootstrap supply | Drives high-side gate; referenced to SW; max voltage = VIN + VCC; requires ≥0.1µF ceramic capacitor. |
| TG | Top gate driver | Bootstrapped N-channel driver; 9.8V typical "ON" voltage; requires short, low-inductance trace to MOSFET gate. |
| SW | Switch node | High-current connection to inductor and MOSFET sources; referenced for BOOST supply and PGND return. |
| VCC | Bias supply decoupling | Internal 8V regulator output; decoupled with ≥1µF ceramic to PGND; can be externally powered to improve efficiency. |
| BG | Bottom gate driver | N-channel low-side driver; 0.1V typical "OFF" voltage; optimized for fast turn-off and shoot-through prevention. |
| PGND | Power ground | High-current return for VCC regulator and BG driver; must connect directly to VCC capacitor negative terminal. |
| SENSE+ | Current sense + | Connects to inductor side of sense resistor; common-mode range up to 36V; supports reverse-current detection. |
| SENSE– | Current sense – | Connects to output side of sense resistor; differential input with 100mV current-limit threshold and 10mV reverse-offset. |
Key Features
| Feature | Design Value |
|---|---|
| Adjustable constant-frequency operation | 100–500kHz via external RSET on fSET pin - enables EMI tuning and magnetics optimization across diverse loads. |
| Reverse inductor current inhibit | 10mV positive offset at SENSE inputs - prevents negative inductor current and associated losses, improving light-load efficiency without diode conduction. |
| Adaptive nonoverlap circuitry | 200ns TG→BG / 150ns BG→TG dead time - eliminates shoot-through risk in synchronous buck topologies with varying MOSFET gate delays. |
| Programmable soft-start | 2µA internal current charges CSS capacitor - controls output ramp rate, limits inrush, and supports precise power sequencing in multi-rail systems. |
| Burst Mode® operation | Reduces total VIN current to 120µA at no load - extends battery life and reduces idle power in always-on telecom and avionics subsystems. |
Applications
| 48V Telecom Power Supply | Avionics Power Distribution |
|---|---|
Use Scenario: Converting 48V nominal telecom bus to 12V intermediate rail for baseband processing and RF modules. IC Role / Device Role / Timing Role: High-voltage synchronous buck controller managing peak currents >10A with precise current-mode loop stability. Use Value: 270–330kHz switching enables small, low-profile inductors; 120µA Burst Mode current minimizes standby loss in network infrastructure with intermittent traffic. | Use Scenario: Generating regulated 28V or 270V-derived rails in flight control computers and sensor interfaces under extreme thermal cycling. IC Role / Device Role / Timing Role: Extended-temperature (-55°C to 125°C) controller ensuring reliable start-up and regulation during cold-soak and high-altitude operation. Use Value: –55°C qualification and 1% VFB accuracy maintain safe voltage margins across full aircraft operational envelope; reverse-current inhibit prevents backfeed during transient load drops. |
| Industrial Motor Drive Auxiliary Supply | Heavy Equipment Battery Management |
Use Scenario: Deriving isolated 15V/1A auxiliary power from 42V vehicle battery for gate drivers and MCU logic in electric hydraulic pumps. IC Role / Device Role / Timing Role: High-input-voltage controller interfacing with external N-MOSFETs rated for >100V drain-source breakdown. Use Value: 60V absolute max VIN and 7.5V startup threshold ensure robust operation during cranking dips and load-dump transients; adaptive nonoverlap prevents shoot-through under high-temperature MOSFET threshold drift. | Use Scenario: Regulating 12V/24V battery-derived power to 3.3V/5V for BMS microcontrollers and CAN transceivers in mining and construction vehicles. IC Role / Device Role / Timing Role: Synchronous buck controller supporting programmable soft-start to coordinate with main traction inverter sequencing. Use Value: CSS pin enables controlled output ramp matching battery state-of-charge recovery profiles; 10µA shutdown current preserves battery charge during long-term storage. |
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 |
|---|---|---|---|
| LTC3891EMSE#PBF | Wider 4–60V input, integrated 5V/100mA LDO bias rail, no fSET pin (fixed 300kHz/600kHz option), higher 1.5mA quiescent current in Burst Mode. | Preferred where integrated bias simplifies layout; less suitable for ultra-low-quiescent designs or variable-frequency EMI tuning. | Select LTC3891EMSE#PBF when board space is constrained and external LDO elimination outweighs quiescent current penalty. |
| LM5116MH/NOPB | 4.5–100V input, 50–750kHz adjustable frequency, 1.5% VREF accuracy, 100µA shutdown current, no reverse-current inhibit function. | Better for ultra-high-input applications (e.g., 72V industrial); lacks discontinuous-mode optimization for light-load efficiency. | Select LM5116MH/NOPB when input exceeds 60V or when fixed-frequency sync is not required, accepting trade-off in light-load performance. |
Compared with LTC3891EMSE#PBF and LM5116MH/NOPB, the LT3845AMPFE#TRPBF offers superior light-load efficiency via 120µA Burst Mode current and reverse-current inhibit, tighter 1% VFB accuracy, and explicit –55°C qualification-making it optimal for extended-temperature, low-idle-power telecom and avionics converters where precision and thermal resilience are critical.
Availability
LT3845AMPFE#TRPBF is available at Aetrix Electronics and suitable for 48V telecom power supplies, avionics power distribution, and industrial motor drive auxiliary supplies requiring stable component supply across extended temperature ranges and long production lifecycles.
Supply support for LT3845AMPFE#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 digital signal processing technologies.
The LT3845AMPFE#TRPBF belongs to ADI's legacy Linear Technology high-voltage power controller product line, designed specifically for rugged, high-efficiency DC/DC conversion in telecom, aerospace, and industrial systems demanding extended temperature operation and precise current-mode regulation.
FAQ
What is the guaranteed operating temperature range for the LT3845AMPFE#TRPBF?
The LT3845AMPFE#TRPBF is 100% tested and guaranteed over a junction temperature range of –55°C to 125°C. This extended qualification distinguishes it from the LT3845AEFE#TRPBF (–40°C to 125°C) and makes the LT3845AMPFE#TRPBF suitable for military, aerospace, and harsh-environment industrial applications where cold-soak or high-ambient operation is required. The part marking "MP" explicitly denotes this extended grade.
How does the LT3845AMPFE#TRPBF achieve high light-load efficiency?
The LT3845AMPFE#TRPBF achieves high light-load efficiency through two complementary mechanisms: Burst Mode® operation reduces total input quiescent current to 120µA at no load, and reverse inductor current inhibit disables the bottom MOSFET before inductor current reaches zero, preventing reverse conduction losses. Both functions are controlled via the BURST_EN pin, enabling configuration for forced continuous, pulse-skipping, or Burst Mode operation depending on the application's efficiency and noise requirements.
Can the LT3845AMPFE#TRPBF be synchronized to an external clock, and what are the constraints?
Yes, the LT3845AMPFE#TRPBF supports external synchronization via the SYNC pin, accepting clock signals from 100kHz to 600kHz. To avoid beat frequencies and ensure stable locking, the internal oscillator (set by the fSET resistor) must be programmed to run 10–25% below the external clock frequency. If SYNC is unused, it must be tied to SGND. The SYNC function remains active regardless of Burst Mode or reverse-current inhibit configuration.
What is the role of the exposed pad on the LT3845AMPFE#TRPBF package, and how must it be handled?
The exposed pad (Pin 17) on the LT3845AMPFE#TRPBF TSSOP package is internally connected to SGND and serves dual purposes: low-impedance signal grounding for noise-sensitive analog circuitry and thermal conduction to the PCB. It must be soldered to a dedicated SGND copper pour with multiple thermal vias to an internal ground plane. Leaving it unconnected degrades both EMI performance and thermal resistance, potentially causing instability or premature thermal shutdown under sustained load.
Does the LT3845AMPFE#TRPBF require external components for gate driving, and what MOSFET parameters should be considered?
The LT3845AMPFE#TRPBF integrates dual N-channel gate drivers (TG and BG) but requires external MOSFETs. Key MOSFET selection criteria include: maximum VDS ≥ 65V (to withstand VIN + VSW transients), gate charge QG ≤ 180nC (to ensure reliable start-up from the internal VCC regulator), and logic-level or standard-threshold gates compatible with the 9.8V typical TG "ON" voltage. For high-current designs, paralleling MOSFETs is supported, but gate trace inductance must be minimized to preserve nonoverlap timing integrity.
LT3845AMPFE#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:
- -55°C ~ 125°C (TJ)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 16-TSSOP-EP
LT3845AMPFE#TRPBF FAQ
1.How can I place an order for LT3845AMPFE#TRPBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LT3845AMPFE#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 LT3845AMPFE#TRPBF reliable?
The price and inventory of LT3845AMPFE#TRPBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LT3845AMPFE#TRPBF is usually 5 days.
3.What payment methods are accepted for LT3845AMPFE#TRPBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LT3845AMPFE#TRPBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LT3845AMPFE#TRPBF?
LT3845AMPFE#TRPBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LT3845AMPFE#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 LT3845AMPFE#TRPBF?
For technical support, including LT3845AMPFE#TRPBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LT3845AMPFE#TRPBF requirements.
6.How does Aetrix verify that LT3845AMPFE#TRPBF is sourced from the original manufacturer or authorized distributors?
All LT3845AMPFE#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 LT3845AMPFE#TRPBF meets industry standards.
7.What is the process for return or replacement of LT3845AMPFE#TRPBF?
All LT3845AMPFE#TRPBF units undergo pre-shipment inspection (PSI). If there is an issue with LT3845AMPFE#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 LT3845AMPFE#TRPBF part is unused and in its original packaging.
Return procedure for LT3845AMPFE#TRPBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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