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Analog Devices Inc. LT3845IFE#TRPBF
- Part No.:
- LT3845IFE#TRPBF
- Manufacturer:
- Analog Devices Inc.
- Category:
- DC DC Switching Controllers
- Package:
- 16-TSSOP (0.173", 4.40mm Width) Exposed Pad
- Datasheet:
-
LT3845IFE#TRPBF.pdf
- Description:
- IC REG CTRLR BUCK 16TSSOP
- Quantity:
- Payment:
- Shipping:
Inventory:1,062
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Product details
Overview
LT3845IFE#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 100kHz–500kHz adjustable switching frequency, and features reverse inductor current inhibit, 1% output regulation accuracy, and 120μA no-load quiescent current - used in 48V telecom power supplies and industrial control systems.
For engineers reviewing the LT3845IFE#TRPBF datasheet, LT3845IFE#TRPBF pinout, LT3845IFE#TRPBF application, or LT3845IFE#TRPBF equivalent, key selection considerations include its 60V max input rating, programmable fSET-based frequency tuning, Burst Mode® operation for light-load efficiency, adaptive nonoverlap gate drive, and thermal-enhanced 16-lead TSSOP package with exposed SGND pad.
Technical Context
The LT3845IFE#TRPBF implements a current-mode control architecture with an internal 1.231V reference, error amplifier transconductance of 270–410μS, and slope compensation derived from oscillator ramp. Its peak-current sensing uses ±100mV differential threshold across SENSE+ and SENSE–, with reverse-current detection offset at +10mV to prevent shoot-through during discontinuous conduction.
It integrates dual N-channel MOSFET gate drivers (TG and BG) with 9.8V typical bootstrapped "ON" voltage, 50ns rise/fall time (CL = 3300pF), and adaptive nonoverlap timing (150–200ns). The VCC regulator provides 8V bias from VIN with ~1V dropout, enabling external VCC sourcing to reduce dissipation at high input voltages.
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 - set via external resistive divider on VFB; regulated to ±1% accuracy over line/load/temperature. |
| Switching Frequency | 100kHz to 500kHz (adjustable via fSET resistor); synchronizable to 100–600kHz external clock for EMI control. |
| Quiescent Current | 120μA in Burst Mode®, 10μA in shutdown - enables battery-backed or energy-sensitive systems with low standby loss. |
| Current Sense Threshold | ±100mV across SENSE+ and SENSE– - sets peak inductor current limit independent of duty cycle. |
| Gate Drive Capability | TG/BG drivers support large N-MOSFETs; 9.8V bootstrapped gate voltage ensures strong turn-on under high-VGS requirements. |
| Thermal Rating | –40°C to +125°C junction temperature - qualified for automotive and industrial environments per I-grade specification. |
Pinout & Package
LT3845IFE#TRPBF is housed in a 16-lead thermally enhanced plastic TSSOP package with exposed lead-frame pad (Pin 17) internally connected to SGND. The exposed pad must be soldered to PCB ground for optimal thermal performance (θJA = 40°C/W).
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| VIN | Main input supply rail | Accepts 4–60V; powers internal VCC regulator; requires local 0.1μF ceramic decoupling to SGND. |
| SHDN | Enable/disable control input | 1.35V rising threshold with 120mV hysteresis; pulls IC into 10μA shutdown when below 0.7V. |
| CSS | Soft-start timing node | Charged by internal 2μA current source; controls output voltage slew rate and prevents inrush current. |
| BURST_EN | Mode selection control | Enables Burst Mode® (≤0.5V), maintains reverse-current inhibit only (0.5–2.5V), or disables both (>2.5V). |
| VFB | Feedback input | Compares output voltage (via resistor divider) to 1.231V internal reference; regulates output within ±1%. |
| VC | Error amplifier output | Drives current-sense comparator threshold; clamped during Burst Mode to limit negative excursion and reduce ripple. |
| SYNC | External clock input | Accepts 100–600kHz TTL-compatible signal; forces oscillator synchronization for noise-sensitive applications. |
| fSET | Oscillator frequency programming | Resistor-connected pin sets nominal frequency (100–500kHz); required even when SYNC is active. |
| BOOST | Bootstrap supply rail | Supplies TG driver; referenced to SW; max voltage = VIN + VCC; requires ≥0.1μF ceramic capacitor to SW. |
| TG | Top gate driver output | Bootstrapped N-MOSFET gate drive; fast 50ns edges; requires short/wide PCB trace to minimize inductance. |
| SW | Switch node | High dv/dt node connecting TG, BG, BOOST capacitor, and inductor; must be minimized in loop area. |
| VCC | Internal bias supply | 8V regulated output from VIN; powers most internal circuitry; can be externally driven to improve efficiency. |
| BG | Bottom gate driver output | Direct-drive N-MOSFET gate; low-impedance sink/source; connects to source of low-side FET. |
| PGND | Power ground return | High-current return path 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; forms ±100mV threshold window with SENSE–. |
| SENSE– | Current sense negative input | Connects to output side of sense resistor; common-mode range extends to 36V. |
| SGND | Signal ground reference | Low-noise analog ground; connects to output capacitor negative; must be isolated from PGND except at single point. |
Key Features
| Feature | Design Value |
|---|---|
| Adaptive nonoverlap gate drive | Prevents simultaneous TG/BG conduction (shoot-through) with 150–200ns dead-time, ensuring safe switching in high-power topologies. |
| Reverse inductor current inhibit | Disables BG when inductor current approaches zero, enabling discontinuous operation and improving light-load efficiency by eliminating reverse conduction loss. |
| Programmable soft-start | Controlled output voltage ramp via CSS capacitor; eliminates overshoot and limits inrush current during power-up or 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. |
| High-voltage input capability | Rated for continuous 60V input with 65V absolute maximum - suitable for 48V telecom, 12V/42V automotive, and industrial bus systems. |
Applications
| 48V Telecom Power Supply | Industrial Control System |
|---|---|
|
Use Scenario: Converting -48V or +48V telecom rectified bus to 12V/5V intermediate rails in base station power modules. IC Role / Device Role / Timing Role: Primary step-down controller managing high-efficiency, high-reliability DC/DC conversion with precise current limiting and thermal robustness. Use Value: 60V input rating accommodates transient surges on telecom lines; 1% regulation ensures stable downstream logic and RF subsystem operation. |
Use Scenario: Generating isolated or non-isolated 24V/15V rails for PLC I/O modules, motor drives, and sensor interfaces in factory automation. IC Role / Device Role / Timing Role: High-voltage synchronous buck controller delivering regulated output with programmable frequency to meet EMC requirements. Use Value: Adjustable 100–500kHz frequency allows optimization for size vs. efficiency; reverse-current inhibit improves partial-load efficiency in variable-speed drives. |
| Avionics Power Converter | Distributed Power Architecture |
|
Use Scenario: Converting 28V aircraft bus to 15V/5V for flight control computers, inertial measurement units, and cockpit displays. IC Role / Device Role / Timing Role: Ruggedized step-down controller operating across –40°C to +125°C with reliable UVLO and overcurrent protection. Use Value: I-grade qualification and 125°C max junction temperature ensure operation in high-ambient avionics bays; 10μA shutdown current preserves battery life during standby. |
Use Scenario: Local point-of-load (POL) conversion in server backplanes or telecom line cards where 48V intermediate bus feeds multiple sub-rails. IC Role / Device Role / Timing Role: Synchronous buck controller enabling compact, high-efficiency POL stages with minimal external components. Use Value: Integrated gate drivers eliminate need for external drivers; programmable fSET simplifies frequency coordination across multiple converters in a system. |
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 input range (4.5V–60V), integrated LDO for VCC, dual-output capability, but no reverse-current inhibit. | Preferred for dual-rail designs requiring independent output control; lacks discontinuous-mode optimization for ultra-light loads. | Select LTC3891EFE#PBF when dual outputs or integrated VCC LDO simplify design; retain LT3845IFE#TRPBF for cost-sensitive, single-output, high-light-load-efficiency needs. |
| MP24894GQZ-P | Lower max input (40V), fixed 300kHz frequency, no SYNC or fSET adjustment, but includes integrated MOSFETs. | Suitable for space-constrained, lower-power (<50W) applications where integration reduces BOM count; not rated for 48V telecom transients. | Choose MP24894GQZ-P for compact, integrated solutions under 40V; use LT3845IFE#TRPBF where 60V rating, frequency flexibility, and discrete FET control are mandatory. |
Compared with LTC3891EFE#PBF and MP24894GQZ-P, the LT3845IFE#TRPBF uniquely balances 60V input tolerance, programmable frequency, Burst Mode® efficiency, and reverse-current inhibit - making it optimal for high-reliability, single-output 48V-to-12V conversion where light-load performance and thermal margin are critical.
Availability
LT3845IFE#TRPBF is available at Aetrix Electronics and suitable for 48V telecom power supplies, industrial control systems, and avionics power converters requiring stable component supply, long-term lifecycle support, and guaranteed I-grade temperature performance.
Supply support for LT3845IFE#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) is a global leader in high-performance analog, mixed-signal, and power management semiconductors, serving precision instrumentation, industrial, automotive, and communications markets.
The LT3845IFE#TRPBF belongs to Linear's high-voltage DC/DC controller product line, designed specifically for robust, efficient step-down conversion in harsh-input environments such as telecom infrastructure, heavy equipment, and aerospace power systems.
FAQ
What is the maximum input voltage rating for the LT3845IFE#TRPBF?
The LT3845IFE#TRPBF has an absolute maximum input voltage rating of 65V on the VIN pin, with continuous operation supported up to 60V. Its 7.5V minimum start-up voltage requires external VCC bias if VIN drops below that threshold during operation. This 60V rating makes the LT3845IFE#TRPBF suitable for 48V telecom and 42V automotive applications with headroom for transients.
How does the LT3845IFE#TRPBF achieve high light-load efficiency?
The LT3845IFE#TRPBF achieves high light-load efficiency through two complementary features: Burst Mode® operation, which reduces total input quiescent current to 120μA by gating full-power switching cycles, and reverse inductor current inhibit, which disables the bottom gate driver near zero current to prevent reverse conduction losses. Both functions are controlled via the BURST_EN pin, allowing flexible configuration per application load profile.
Can the LT3845IFE#TRPBF be synchronized to an external clock?
Yes, the LT3845IFE#TRPBF supports external synchronization via its dedicated SYNC pin, accepting TTL-compatible clock signals from 100kHz to 600kHz. When using SYNC, the internal oscillator's fSET resistor must still be installed and configured to run ~10–25% below the external frequency to ensure reliable locking. The SYNC function is unavailable in PDIP packages but fully supported in the TSSOP package of the LT3845IFE#TRPBF.
What is the purpose of the exposed pad on the LT3845IFE#TRPBF package?
The exposed pad (Pin 17) on the LT3845IFE#TRPBF's 16-lead TSSOP package is internally connected to SGND and must be soldered to a PCB ground plane. It serves dual purposes: lowering thermal resistance (θJA = 40°C/W) for reliable operation at high ambient temperatures, and providing a low-impedance, low-noise analog ground reference for sensitive feedback and current-sense circuitry - critical for maintaining regulation accuracy and stability.
Does the LT3845IFE#TRPBF support programmable soft-start, and how is it implemented?
Yes, the LT3845IFE#TRPBF supports programmable soft-start via the CSS pin, which is charged by an internal 2μA current source. Connecting a capacitor from CSS to SGND sets the output voltage slew rate using the formula CSS = 2μA × tSS / 1.231V. This controlled ramp prevents output overshoot, limits input inrush current, and enables precise power sequencing - essential for systems with multiple regulated rails or sensitive downstream loads.
LT3845IFE#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
LT3845IFE#TRPBF FAQ
1.How can I place an order for LT3845IFE#TRPBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LT3845IFE#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 LT3845IFE#TRPBF reliable?
The price and inventory of LT3845IFE#TRPBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LT3845IFE#TRPBF is usually 5 days.
3.What payment methods are accepted for LT3845IFE#TRPBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LT3845IFE#TRPBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LT3845IFE#TRPBF?
LT3845IFE#TRPBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LT3845IFE#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 LT3845IFE#TRPBF?
For technical support, including LT3845IFE#TRPBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LT3845IFE#TRPBF requirements.
6.How does Aetrix verify that LT3845IFE#TRPBF is sourced from the original manufacturer or authorized distributors?
All LT3845IFE#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 LT3845IFE#TRPBF meets industry standards.
7.What is the process for return or replacement of LT3845IFE#TRPBF?
All LT3845IFE#TRPBF units undergo pre-shipment inspection (PSI). If there is an issue with LT3845IFE#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 LT3845IFE#TRPBF part is unused and in its original packaging.
Return procedure for LT3845IFE#TRPBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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