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Analog Devices Inc. LT3845AMPFE#PBF
- Part No.:
- LT3845AMPFE#PBF
- Manufacturer:
- Analog Devices Inc.
- Category:
- DC DC Switching Controllers
- Package:
- 16-TSSOP (0.173", 4.40mm Width) Exposed Pad
- Datasheet:
-
LT3845AMPFE#PBF.pdf
- Description:
- IC REG CTRLR BUCK 16TSSOP
- Quantity:
- Payment:
- Shipping:
Inventory:319
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Product details
Overview
LT3845AMPFE#PBF 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, programmable soft-start, and 1% output regulation accuracy - deployed in 48V telecom power supplies and avionics systems.
For engineers reviewing the LT3845AMPFE#PBF datasheet, LT3845AMPFE#PBF pinout, LT3845AMPFE#PBF application, or LT3845AMPFE#PBF equivalent, key selection considerations include its –55°C to 125°C extended temperature rating, 16-lead thermally enhanced TSSOP package with exposed SGND pad, burst mode quiescent current of 120µA, and gate drivers optimized for N-channel MOSFETs in high-efficiency synchronous buck topologies.
Technical Context
The LT3845AMPFE#PBF implements a current-mode control architecture with internal slope compensation, adaptive nonoverlap circuitry to prevent shoot-through, and a precision 1.231V error amplifier reference. Its oscillator supports both internal resistor-programmed operation (via fSET pin) and external synchronization (SYNC pin) up to 600kHz.
It integrates dual N-channel MOSFET gate drivers (TG and BG), a bootstrap supply regulator (BOOST), and a dedicated current-sense amplifier with ±100mV reverse-current inhibit offset. The controller uses VCC as its internal bias rail - derived either from VIN via an onboard linear regulator (with ~1V dropout) or externally from VOUT to improve efficiency.
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 12V/42V vehicle systems. |
| Operating Frequency | 100kHz to 500kHz (adjustable via fSET resistor) - enables optimization of size vs. efficiency; sync-capable up to 600kHz for EMI-sensitive designs. |
| Output Voltage Accuracy | ±1% at VFB = 1.231V - ensures tight regulation across line, load, and temperature for stable downstream power domains. |
| Quiescent Current | 120µA in Burst Mode - maintains high light-load efficiency without requiring auxiliary bias supplies. |
| Shutdown Current | 10µA - enables ultra-low-power system standby states compliant with energy standards. |
| Temperature Range | –55°C to 125°C junction - qualified for harsh-environment applications including military, aerospace, and heavy equipment. |
| Package | 16-lead thermally enhanced TSSOP with exposed SGND pad - provides low thermal resistance (θJA = 40°C/W) for high-power density layouts. |
Pinout & Package
The LT3845AMPFE#PBF is housed in a 16-lead plastic TSSOP package with an exposed leadframe pad internally connected to SGND. Soldering this pad to PCB ground is mandatory for thermal performance and noise integrity.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| VIN | Main input supply input | Accepts 4V–60V; powers internal VCC regulator and UVLO circuitry; requires local 0.1µF+ ceramic decoupling. |
| SHDN | Enable/disable control input | 1.35V rising threshold with 120mV hysteresis; pulls IC into 10µA shutdown when <0.7V. |
| CSS | Soft-start timing node | Charged by internal 2µA current source; controls output voltage slew rate and inrush current during startup. |
| BURST_EN | Burst Mode & reverse-current inhibit control | 0.5V threshold: enables both functions; 2.5V disables reverse-current inhibit; ties to VFB for light-load discontinuous operation. |
| VFB | Feedback input | Compares against 1.231V internal reference; sets output voltage via external resistive divider. |
| VC | Error amplifier output | Drives current-sense comparator threshold; clamped at 100mV below burst threshold to limit ripple in Burst Mode. |
| SYNC | External clock input | Accepts 100kHz–600kHz square wave; requires RSET set 10–25% below sync frequency for stable locking. |
| fSET | Oscillator frequency programming | Connects to ground via resistor (e.g., 49.9kΩ → 300kHz); required even when SYNC is active. |
| BOOST | Bootstrap supply for TG driver | Supplies bootstrapped gate drive; referenced to SW; max voltage = VIN + VCC; requires ≥0.1µF ceramic capacitor to SW. |
| TG | Top N-MOSFET gate driver output | Drives high-side switch; fast rise/fall (<50ns) with 9.8V typical "ON" voltage under dynamic bootstrapping. |
| SW | Switch node connection | High-current return path for BOOST supply; connects to inductor and source of bottom MOSFET. |
| VCC | Internal bias supply node | 8V regulated output (from VIN); powers all internal circuitry; can be back-fed from VOUT to reduce dissipation. |
| BG | Bottom N-MOSFET gate driver output | Drives synchronous rectifier; fast switching with adaptive nonoverlap to prevent shoot-through. |
| PGND | Power ground reference | High-current return for BG driver and VCC regulator; must connect directly to VCC capacitor negative terminal. |
| SENSE+ | Current sense positive input | Connects to inductor side of sense resistor; common-mode range up to 36V; supports bidirectional sensing. |
| SENSE− | Current sense negative input | Connects to output side of sense resistor; differential range ±1V; reverse-current inhibit offset = –100mV. |
Key Features
| Feature | Design Value |
|---|---|
| Adaptive nonoverlap circuitry | Prevents simultaneous conduction of TG and BG drivers (200ns TG→BG, 150ns BG→TG), eliminating shoot-through losses and MOSFET failure risk. |
| Reverse inductor current inhibit | Disables BG driver when sensed current approaches zero (–100mV offset), enabling discontinuous conduction mode and improving light-load efficiency. |
| Programmable soft-start | Controls output voltage ramp rate via CSS capacitor; prevents inrush current and output overshoot during startup and fault recovery. |
| Burst Mode operation | Reduces total input quiescent current to 120µA at no load by cycling full-power bursts only as needed to maintain regulation. |
| Extended temperature grade | 100% tested over –55°C to 125°C junction range - suitable for aerospace, defense, and downhole industrial applications. |
Applications
| 48V Telecom Power Supply | Avionics Power Distribution |
|---|---|
Use Scenario: Converting 48V nominal telecom rack voltage to 12V intermediate bus for digital signal processors and FPGAs. 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 75W output while maintaining low EMI via synchronized 300kHz operation and reverse-current inhibit at standby loads. | Use Scenario: Regulating 28V aircraft bus to 5V/3.3V for flight control computers and sensor interfaces in certified avionics modules. IC Role / Device Role / Timing Role: Radiation-tolerant, extended-temperature controller providing robust start-up and undervoltage lockout under cold-soak and transient conditions. Use Value: Delivers guaranteed operation from –55°C with 1% output accuracy and 10µA shutdown current to meet DO-160E environmental compliance. |
| Industrial Motor Drive Auxiliary Supply | Heavy Equipment Battery Management |
Use Scenario: Generating isolated 15V gate drive and 5V logic supplies from 42V battery in electric hydraulic pump controllers. IC Role / Device Role / Timing Role: Primary controller for non-isolated buck stage feeding downstream isolated DC/DC converters; handles wide input transients (up to 60V). Use Value: Survives load-dump events up to 65V VIN and maintains regulation during 4V brownouts using external VCC bias - critical for functional safety. | Use Scenario: Powering BMS microcontrollers and CAN transceivers from 12V–36V lead-acid or LiFePO₄ battery banks in mining vehicles and agricultural machinery. IC Role / Device Role / Timing Role: High-reliability step-down controller supporting cold-cranking (4V start) and reverse-polarity protection via SENSE−/SENSE+ differential architecture. Use Value: Achieves 120µA no-load quiescent current in Burst Mode - extends battery runtime during long idle periods without compromising wake-up responsiveness. |
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 | Higher integration: includes integrated MOSFET drivers, 60V VIN, but fixed 300kHz/600kHz options; no fSET programmability. | Targets space-constrained designs where board area is premium; lacks reverse-current inhibit and Burst Mode flexibility. | Select LTC3891EMSE#PBF when simplified layout and reduced external component count outweigh need for frequency tuning and light-load optimization. |
| MPQ4332GJ-AEC1-P | Automotive-grade (AEC-Q100 Grade 1), 40V max VIN, integrated power stage (4A), fixed 500kHz; no BOOST/TG/BG separation. | Designed for ASIL-B automotive subsystems; not rated for >40V or –55°C operation; unsuitable for telecom or avionics. | Choose MPQ4332GJ-AEC1-P only for automotive infotainment or ADAS domain controllers requiring AEC-Q100 qualification and integrated power stage. |
Compared with LTC3891EMSE#PBF and MPQ4332GJ-AEC1-P, the LT3845AMPFE#PBF uniquely combines extended temperature validation (–55°C), fully programmable frequency (100–500kHz), discrete gate drivers for scalable power stages, and dual-mode light-load optimization - making it optimal for ruggedized, high-reliability, and thermally demanding applications where design flexibility is essential.
Availability
LT3845AMPFE#PBF 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 and long product lifecycles.
Supply support for LT3845AMPFE#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. (ADI) is a global leader in high-performance analog, mixed-signal, and digital signal processing semiconductors, formed through the acquisition of Linear Technology in 2017.
The LT3845AMPFE#PBF belongs to ADI's high-voltage power management controller family, designed specifically for robust, efficient, and flexible DC/DC conversion in demanding industrial, aerospace, and telecom infrastructure applications.
FAQ
What is the minimum input voltage required to start up the LT3845AMPFE#PBF?
The LT3845AMPFE#PBF requires a minimum VIN of 7.5V to initiate start-up, ensuring sufficient headroom for its internal VCC regulator to reach its 8V output and enable internal circuitry. However, once running, if VCC is externally powered above 6.5V, the LT3845AMPFE#PBF can sustain operation down to 4V VIN - a key feature for cold-cranking and brownout resilience in automotive and industrial systems.
How does the LT3845AMPFE#PBF achieve high efficiency at light loads?
The LT3845AMPFE#PBF achieves high light-load efficiency through two complementary mechanisms: Burst Mode operation reduces total input quiescent current to 120µA by disabling switching until output droop triggers reactivation, and reverse inductor current inhibit disables the bottom MOSFET when current approaches zero, enabling discontinuous conduction mode and eliminating synchronous rectifier conduction losses - both features are controlled independently via the BURST_EN pin.
Can the LT3845AMPFE#PBF be synchronized to an external clock, and what are the requirements?
Yes, the LT3845AMPFE#PBF supports external synchronization via the SYNC pin across 100kHz–600kHz. To ensure reliable locking, the internal oscillator frequency (set by fSET resistor) must be programmed 10%–25% lower than the external clock frequency. The SYNC input has 40kΩ internal resistance and a 1.4V–2V threshold; unused SYNC pins must be tied to SGND to avoid floating inputs and unintended behavior.
What is the purpose of the exposed pad on the LT3845AMPFE#PBF package, and how must it be handled?
The exposed pad on the LT3845AMPFE#PBF is internally connected to SGND and serves dual roles: electrical noise reference for the error amplifier and primary thermal path. It must be soldered to a dedicated PCB copper pour tied to SGND - not PGND - with multiple thermal vias to inner ground planes. Failure to solder this pad degrades thermal performance (θJA increases significantly) and risks instability due to ground noise coupling into sensitive analog nodes like VFB and VC.
Does the LT3845AMPFE#PBF support reverse-current protection, and how is it implemented?
Yes, the LT3845AMPFE#PBF implements reverse-current protection via its reverse inductor current inhibit function. When the differential voltage across SENSE+ and SENSE− falls to –100mV (indicating approaching-zero or negative inductor current), the BG driver is disabled for the remainder of the cycle. This prevents reverse conduction through the synchronous MOSFET, avoids inductive kick at SW, and improves light-load efficiency - all without requiring external diodes or complex control logic.
LT3845AMPFE#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:
- -55°C ~ 125°C (TJ)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 16-TSSOP-EP
LT3845AMPFE#PBF FAQ
1.How can I place an order for LT3845AMPFE#PBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LT3845AMPFE#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 LT3845AMPFE#PBF reliable?
The price and inventory of LT3845AMPFE#PBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LT3845AMPFE#PBF is usually 5 days.
3.What payment methods are accepted for LT3845AMPFE#PBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LT3845AMPFE#PBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LT3845AMPFE#PBF?
LT3845AMPFE#PBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LT3845AMPFE#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 LT3845AMPFE#PBF?
For technical support, including LT3845AMPFE#PBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LT3845AMPFE#PBF requirements.
6.How does Aetrix verify that LT3845AMPFE#PBF is sourced from the original manufacturer or authorized distributors?
All LT3845AMPFE#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 LT3845AMPFE#PBF meets industry standards.
7.What is the process for return or replacement of LT3845AMPFE#PBF?
All LT3845AMPFE#PBF units undergo pre-shipment inspection (PSI). If there is an issue with LT3845AMPFE#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 LT3845AMPFE#PBF part is unused and in its original packaging.
Return procedure for LT3845AMPFE#PBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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