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Analog Devices Inc. LT3845EFE#TRPBF
- Part No.:
- LT3845EFE#TRPBF
- Manufacturer:
- Analog Devices Inc.
- Category:
- DC DC Switching Controllers
- Package:
- 16-TSSOP (0.173", 4.40mm Width) Exposed Pad
- Datasheet:
-
LT3845EFE#TRPBF.pdf
- Description:
- IC REG CTRLR BUCK 16TSSOP
- Quantity:
- Payment:
- Shipping:
Inventory:1,096
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Product details
Overview
LT3845EFE#TRPBF from Analog Devices (formerly Linear Technology) is a high-voltage, synchronous current-mode step-down controller IC designed 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 - enabling robust 48V-to-12V, 75W automotive and industrial power supplies.
For engineers reviewing the LT3845EFE#TRPBF datasheet, LT3845EFE#TRPBF pinout, LT3845EFE#TRPBF application, or LT3845EFE#TRPBF equivalent, key selection considerations include its 120μA no-load quiescent current in Burst Mode®, reverse inductor current inhibit for discontinuous operation, adaptive nonoverlap gate drive, programmable soft-start, and thermally enhanced 16-lead TSSOP package with exposed SGND pad.
Technical Context
The LT3845EFE#TRPBF implements a fixed-frequency current-mode control architecture with external N-channel MOSFETs, where peak inductor current is sensed differentially across SENSE+ and SENSE– with ±100mV threshold. Its oscillator frequency is set via fSET resistor or synchronized externally up to 600kHz, and its error amplifier (transconductance: 270–410 μS) drives VC to regulate output voltage referenced to 1.231V at VFB.
Burst Mode® operation reduces VIN supply current to 120μA at no load by disabling switching when VC drops 150mV below the 15% load threshold; reverse-current inhibit prevents negative inductor current using a 10mV sense offset and disables BG when current approaches zero - both functions are controlled via BURST_EN pin logic states.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Input Voltage Range | 4V to 60V - supports wide-range industrial, telecom, and automotive inputs including 48V systems. |
| Output Voltage Range | Up to 36V - enables high-VOUT buck configurations without post-regulation. |
| Switching Frequency | 100kHz–500kHz (adjustable), sync-capable up to 600kHz - balances efficiency, size, and EMI in noise-sensitive designs. |
| Quiescent Current | 120μA in Burst Mode®, 10μA in shutdown - extends battery life in standby and low-power modes. |
| Voltage Reference Accuracy | ±1% over temperature - ensures stable 12V/15V/24V rail regulation without trimming. |
| Current Sense Threshold | ±100mV differential - provides precise, duty-cycle-independent current limiting for reliable overcurrent protection. |
| Gate Drive Capability | TG/BG drivers support large N-MOSFETs with 9.8V typical "ON" voltage and 50ns rise/fall time - minimizes conduction losses in high-current stages. |
Pinout & Package
The LT3845EFE#TRPBF is housed in a 16-lead thermally enhanced plastic TSSOP package (FE grade) with an exposed lead-frame pad internally connected to SGND. The package requires soldering of the exposed pad to PCB ground for optimal thermal performance (θJC = 10°C/W) and electrical integrity.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| VIN | Main power input | Accepts 4V–60V input; powers internal VCC regulator; minimum start-up voltage is 7.5V. |
| SHDN | Enable/disable control | 1.35V rising threshold with 120mV hysteresis; pulls VIN current to ~9μA in shutdown. |
| CSS | Soft-start timing | Charged by 2μA internal current source; sets output voltage slew rate to limit inrush and overshoot. |
| BURST_EN | Mode selection | Controls Burst Mode® (≤0.5V) and reverse-current inhibit (0.5–2.5V); disables both at >2.5V. |
| VFB | Feedback input | Compares output voltage (via resistive divider) to 1.231V reference; regulates output with ±1% accuracy. |
| VC | Error amplifier output | Drives current-sense comparator threshold; clamped during Burst Mode® to limit ripple. |
| SYNC | External clock input | Accepts 100–600kHz sync signal; not available on PDIP variant; requires RSET set 10–25% below sync freq. |
| fSET | Oscillator programming | Resistor-connected pin sets nominal frequency; required even when SYNC is used. |
| BOOST | Bootstrap supply | Supplies TG driver; referenced to SW; max voltage = VIN + VCC; requires ≥0.1μF ceramic capacitor. |
| TG | Top gate driver | Bootstrapped N-MOSFET driver; fast 50ns edges; requires short/wide PCB trace to minimize inductance. |
| SW | Switch node | High-current return path for BOOST; withstands –2V transient (guaranteed design limit). |
| VCC | Internal bias supply | 8V regulated output from VIN; powers most circuitry; can be back-fed from VOUT to improve efficiency. |
| BG | Bottom gate driver | Direct-drive N-MOSFET driver; complements TG; nonoverlap timing prevents shoot-through. |
| PGND | Power ground | High-current return for VCC regulator and BG driver; must connect directly to VCC decoupling cap. |
| 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 sense range ±100mV. |
| SGND | Signal ground | Low-noise reference for VFB, VC, and error amp; must be isolated from PGND and tied to –VOUT caps. |
Key Features
| Feature | Design Value |
|---|---|
| Adaptive nonoverlap circuitry | Prevents simultaneous TG/BG conduction (200ns TG→BG, 150ns BG→TG), eliminating shoot-through losses and MOSFET failure risk. |
| Reverse inductor current inhibit | Disables BG when sensed current nears zero (10mV offset), enabling discontinuous mode and improving light-load efficiency by ~3–5%. |
| Programmable soft-start | 2μA CSS charging current allows precise control of output ramp rate - critical for sequencing in multi-rail systems. |
| Burst Mode® operation | Reduces total input current to 120μA at no load while maintaining regulation, extending battery runtime in always-on applications. |
| High-voltage input capability | 60V absolute max input (7.5V start-up) enables direct use in 48V telecom, 36V automotive, and industrial 24–60V bus systems. |
Applications
| Automotive 12V/24V Systems | 48V Telecom Power Supplies |
|---|---|
Use Scenario: Regulating 48V battery or distribution bus down to stable 12V for infotainment, ADAS sensors, and body control modules. IC Role / Device Role / Timing Role: High-voltage synchronous buck controller managing peak currents up to 15A with adaptive nonoverlap timing. Use Value: 120μA Burst Mode® quiescent current preserves vehicle battery during extended parking; 60V rating handles load-dump transients. | Use Scenario: Converting -48V telecom rectified supply to +12V or +5V for line cards and baseband processing units. IC Role / Device Role / Timing Role: Primary controller in isolated/non-isolated intermediate bus converters operating at 300kHz with external sync to avoid slot interference. Use Value: Adjustable 100–500kHz frequency allows optimization for magnetics size vs. EMI; ±100mV current sense enables accurate OCP across temperature. |
| Avionics Power Distribution | Industrial Motor Drives |
Use Scenario: Generating 28V or 270V-derived 15V rails for flight control computers and inertial measurement units in MIL-STD-704 environments. IC Role / Device Role / Timing Role: Robust step-down controller handling input surges up to 60V and cold-cranking dips to 4V with undervoltage lockout hysteresis. Use Value: 1% reference accuracy and –40°C to 125°C guaranteed operation ensure compliance with DO-160 Section 16 surge/temperature requirements. | Use Scenario: Providing auxiliary 24V/5V supplies for PLC I/O modules, servo amplifiers, and HMI panels powered from 40–60V DC link buses. IC Role / Device Role / Timing Role: Controller for high-efficiency, high-reliability buck stage driving SiC or GaN half-bridges with precise current limiting. Use Value: Reverse-current inhibit eliminates reverse conduction losses in intermittent loads; exposed TSSOP pad enables 2.5W continuous dissipation at 125°C ambient. |
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 | Higher integration: includes dual MOSFET drivers, 60V VIN, but fixed 300kHz/600kHz options (no 100–500kHz adjustment); lower 45μA Burst Mode® current. | Targeted at dual-output or polyphase designs; lacks fSET programmability and reverse-current inhibit disable flexibility. | Select LTC3891EFE#PBF when needing dual outputs or lowest possible quiescent current; retain LT3845EFE#TRPBF for full frequency tuning and discrete MOSFET optimization. |
| MP24894GQKT-Z | Monolithic 60V buck converter (integrated MOSFETs); 100kHz–2.5MHz range; no external sense resistor; 1.5% FB accuracy; no Burst Mode® or reverse-current inhibit. | Suitable for space-constrained, lower-current (<10A) applications where layout simplicity outweighs efficiency fine-tuning. | Choose MP24894GQKT-Z for compact, cost-sensitive designs under 8A; choose LT3845EFE#TRPBF when designing >10A, high-efficiency, or thermally demanding systems with discrete FETs. |
Compared with LTC3891EFE#PBF and MP24894GQKT-Z, the LT3845EFE#TRPBF offers unique adjustability in frequency (100–500kHz), explicit reverse-current inhibit control, and superior light-load efficiency via 120μA Burst Mode® - making it optimal for high-power, thermally constrained, and automotive-grade applications requiring field-programmable behavior.
Availability
LT3845EFE#TRPBF is available at Aetrix Electronics and suitable for automotive 12V/24V systems, 48V telecom power supplies, and avionics power distribution requiring stable component supply, long-term lifecycle assurance, and traceable sourcing.
Supply support for LT3845EFE#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 leader in high-performance analog, mixed-signal, and power management semiconductors, formed through the acquisition of Linear Technology in 2017.
The LT3845EFE#TRPBF belongs to ADI's high-voltage power controller product line, engineered specifically for rugged, high-efficiency DC/DC conversion in automotive, industrial, and telecom infrastructure where input transients, thermal stress, and light-load efficiency are critical.
FAQ
What is the minimum input voltage required for LT3845EFE#TRPBF to start up?
The LT3845EFE#TRPBF requires a minimum input voltage of 7.5V to initiate startup and enable its internal VCC regulator. However, once running, if VCC is externally supplied above 6.5V (e.g., from the output rail), the LT3845EFE#TRPBF can continue operating down to 4V input - enabling cold-cranking support in automotive applications. This dual-threshold behavior is explicitly specified in the Absolute Maximum Ratings and Applications Information sections of the official datasheet.
How does the BURST_EN pin control both Burst Mode® and reverse-current inhibit on the LT3845EFE#TRPBF?
The BURST_EN pin on the LT3845EFE#TRPBF uses three distinct voltage thresholds: ≤0.5V enables both Burst Mode® and reverse-current inhibit; 0.5–2.5V disables Burst Mode® but retains reverse-current inhibit; >2.5V disables both functions. This single-pin dual-control simplifies system-level power management - for example, tying BURST_EN to SGND activates full low-power operation, while connecting it to VFB maintains discontinuous mode without burst cycling. All states are validated in the Pin Functions and Applications Information sections.
Can the LT3845EFE#TRPBF synchronize to an external clock, and what are the constraints?
Yes, the LT3845EFE#TRPBF 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 pin is only available on the TSSOP package (LT3845EFE#TRPBF), not the PDIP variant, and exhibits 40kΩ input resistance with a 1.4–2.0V threshold. These parameters are confirmed in the Electrical Characteristics table and Applications Information section.
What is the purpose of the exposed pad on the LT3845EFE#TRPBF TSSOP package, and how must it be handled?
The exposed pad on the LT3845EFE#TRPBF's 16-lead TSSOP package is electrically connected to SGND and must be soldered to a PCB ground plane. It serves dual roles: lowering thermal resistance (θJC = 10°C/W) for improved power dissipation and providing a low-impedance, low-noise signal ground reference for sensitive analog circuits like the error amplifier and VFB node. Failure to solder the pad degrades thermal performance and may cause regulation instability - a requirement explicitly stated in the FE Package mechanical drawing and Applications Information.
Does the LT3845EFE#TRPBF support output voltages higher than the input voltage?
No, the LT3845EFE#TRPBF is strictly a step-down (buck) controller and cannot generate output voltages exceeding its input voltage. Its architecture relies on synchronous N-MOSFET switching between VIN and ground, with output derived from the duty-cycle-modulated SW node. The datasheet specifies "Output Voltages Up to 36V" - meaning VOUT ≤ 36V and always < VIN under normal operation. Any configuration attempting boost behavior would violate the device's functional design and is neither supported nor characterized.
LT3845EFE#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
LT3845EFE#TRPBF FAQ
1.How can I place an order for LT3845EFE#TRPBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LT3845EFE#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 LT3845EFE#TRPBF reliable?
The price and inventory of LT3845EFE#TRPBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LT3845EFE#TRPBF is usually 5 days.
3.What payment methods are accepted for LT3845EFE#TRPBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LT3845EFE#TRPBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LT3845EFE#TRPBF?
LT3845EFE#TRPBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LT3845EFE#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 LT3845EFE#TRPBF?
For technical support, including LT3845EFE#TRPBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LT3845EFE#TRPBF requirements.
6.How does Aetrix verify that LT3845EFE#TRPBF is sourced from the original manufacturer or authorized distributors?
All LT3845EFE#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 LT3845EFE#TRPBF meets industry standards.
7.What is the process for return or replacement of LT3845EFE#TRPBF?
All LT3845EFE#TRPBF units undergo pre-shipment inspection (PSI). If there is an issue with LT3845EFE#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 LT3845EFE#TRPBF part is unused and in its original packaging.
Return procedure for LT3845EFE#TRPBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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