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Analog Devices Inc. LT3845MPFE#TRPBF
- Part No.:
- LT3845MPFE#TRPBF
- Manufacturer:
- Analog Devices Inc.
- Category:
- DC DC Switching Controllers
- Package:
- 16-TSSOP (0.173", 4.40mm Width) Exposed Pad
- Datasheet:
-
LT3845MPFE#TRPBF.pdf
- Description:
- IC REG CTRLR BUCK 16TSSOP
- Quantity:
- Payment:
- Shipping:
Inventory:4,009
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Product details
Overview
LT3845MPFE#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, programmable soft-start, and 1% output voltage regulation accuracy - used in 48V telecom power supplies and industrial control systems.
For engineers reviewing the LT3845MPFE#TRPBF datasheet, LT3845MPFE#TRPBF pinout, LT3845MPFE#TRPBF application, or LT3845MPFE#TRPBF equivalent, key selection considerations include its –55°C to 125°C extended temperature rating, 120μA no-load quiescent current in Burst Mode®, adaptive nonoverlap gate drive, and compatibility with standard N-channel MOSFETs in high-efficiency synchronous buck topologies.
Technical Context
The LT3845MPFE#TRPBF implements a current-mode control architecture with external N-channel MOSFETs, using sensed inductor current (±100mV across SENSE+ and SENSE–) to regulate peak switch current per cycle. Its oscillator frequency is set via an external resistor on fSET or synchronized externally up to 600kHz.
Burst Mode® operation reduces total 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 via 10mV sense offset and disables BG during light loads to enable discontinuous conduction mode.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Input Voltage Range | 4V to 60V - supports wide-range industrial and telecom inputs; minimum start-up at 7.5V |
| Output Voltage Range | Up to 36V - enables high-VOUT step-down without post-regulation |
| Switching Frequency | 100kHz to 500kHz (adjustable), sync-capable up to 600kHz - allows EMI optimization and noise-sensitive system integration |
| Quiescent Current | 120μA in Burst Mode®, 10μA in shutdown - extends battery life in standby and low-power states |
| Regulation Accuracy | ±1% over line, load, and temperature - ensures stable output under varying conditions |
| Current Sense Threshold | ±100mV - sets precise peak current limit independent of duty cycle |
| Operating Temperature | –55°C to 125°C - qualified for harsh environments including avionics and heavy equipment |
Pinout & Package
LT3845MPFE#TRPBF is housed in a 16-lead thermally enhanced TSSOP package with exposed pad (SGND) soldered to PCB for optimal thermal performance and low-inductance grounding.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| VIN | Main input supply rail | Accepts 4V–60V; powers internal VCC regulator; requires local 0.1μF decoupling to SGND |
| 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 source; controls output voltage slew rate to limit inrush and overshoot |
| BURST_EN | Mode selection control | Enables Burst Mode® (≤0.5V) and/or reverse-current inhibit (≤2.5V); determines light-load behavior |
| VFB | Feedback reference input | Compares against 1.231V internal reference; sets output voltage via resistive divider |
| VC | Error amplifier output | Drives current-sense comparator threshold; clamped during Burst Mode® to limit ripple |
| SYNC | External clock input | Accepts 100kHz–600kHz sync signal; not available on PDIP variant |
| fSET | Oscillator frequency 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 cap to SW |
| TG | Top gate driver output | Bootstrapped N-channel driver; fast rise/fall (<50ns) with nonoverlap protection |
| SW | Switch node | High-current return path for BOOST; withstands –2V transient (guaranteed design) |
| VCC | Internal bias supply node | 8V regulated output; powers internal circuitry; can be back-fed from VOUT to improve efficiency |
| BG | Bottom gate driver output | Direct-drive N-channel driver; fast switching with adaptive nonoverlap vs TG |
| PGND | Power ground reference | High-current return for VCC regulator and BG driver; must connect directly to VCC capacitor negative |
| SENSE+ | Current sense positive input | Connects to inductor side of sense resistor; ±100mV threshold defines current limit |
| SENSE– | Current sense negative input | Connects to VOUT side of sense resistor; differential input with 10mV reverse-offset for inhibit |
| SGND | Signal ground reference | Low-noise analog ground; connects to output capacitor negative; exposed pad tied to SGND |
Key Features
| Feature | Design Value |
|---|---|
| Adaptive nonoverlap gate drive | Prevents shoot-through by enforcing 150–200ns dead time between TG off/BG on and BG off/TG on transitions |
| Reverse inductor current inhibit | Disables BG when sensed current approaches zero, enabling discontinuous mode and improving light-load efficiency |
| Programmable soft-start | 2μA constant-current ramp on CSS pin controls output voltage slew rate, minimizing inrush and overshoot |
| Burst Mode® operation | Reduces total VIN current to 120μA at no load by cycling full-power bursts only as needed to maintain regulation |
| Wide-input, high-output capability | Supports 4V–60V input and up to 36V output with external N-MOSFETs - suitable for 48V telecom and industrial bus architectures |
Applications
| 48V Telecom Power Supply | Industrial Control System |
|---|---|
Use Scenario: Converting 48V distributed bus to 12V/75W for base station RF modules and backplane logic. IC Role / Device Role / Timing Role: High-voltage synchronous buck controller regulating output with current-mode feedback and external Si7370DP MOSFETs. Use Value: 120μA Burst Mode® quiescent current minimizes standby loss; 1% regulation maintains stable voltage under dynamic RF load transients. | Use Scenario: Powering PLC I/O modules and sensor interfaces from 24V or 48V field wiring in factory automation cabinets. IC Role / Device Role / Timing Role: Step-down controller driving N-channel MOSFETs in forced continuous or pulse-skipping mode based on load demand. Use Value: –55°C to 125°C operating range ensures reliability in uncontrolled cabinet environments; reverse-current inhibit improves efficiency at partial loads. |
| Avionics Power Converter | Distributed Power Architecture |
Use Scenario: Generating 28V or 12V from aircraft 270V DC bus for flight control electronics and cockpit displays. IC Role / Device Role / Timing Role: High-input-voltage synchronous buck controller with external gate drivers and precision UVLO thresholds. Use Value: 60V absolute max input rating and robust 120mV SHDN hysteresis support MIL-STD-704 transient immunity requirements. | Use Scenario: Local point-of-load conversion in server racks where 48V intermediate bus feeds multiple isolated DC/DC stages. IC Role / Device Role / Timing Role: Primary controller managing high-efficiency buck stage before downstream isolated converters. Use Value: Adjustable 100–500kHz frequency enables EMI filtering coordination across multiple converters; SYNC input allows deterministic phase alignment. |
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#TRPBF | Higher 60V max input, integrated MOSFET drivers with higher current (1.2A peak), supports dual-phase operation | Targeted at higher-current (>20A), multi-phase designs requiring tighter current sharing | Select LTC3891EMSE#TRPBF when needing integrated high-current drivers and multi-phase capability; LT3845MPFE#TRPBF remains optimal for discrete MOSFET flexibility and cost-sensitive single-phase 75W designs |
| LM5116MH/NOPB | 4.5V–100V input, no integrated VCC regulator, requires external bias supply, lower 105°C max junction temp | Suited for ultra-high-input applications (e.g., 72V battery systems) where external bias is acceptable | Choose LM5116MH/NOPB for >60V input rails; LT3845MPFE#TRPBF offers simpler biasing (VIN-powered VCC) and extended –55°C rating for aerospace-grade cold-start operation |
Compared with LTC3891EMSE#TRPBF and LM5116MH/NOPB, the LT3845MPFE#TRPBF provides the best balance of wide input range, integrated bias regulation, extended temperature qualification, and discrete MOSFET control - making it ideal for ruggedized 48V telecom and industrial power supplies where layout simplicity and thermal robustness are critical.
Availability
LT3845MPFE#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 extended temperature performance.
Supply support for LT3845MPFE#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. (acquired Linear Technology in 2017) is a global leader in high-performance analog, mixed-signal, and power management semiconductors.
The LT3845MPFE#TRPBF belongs to Linear's high-voltage DC/DC controller product line, designed specifically for efficient, reliable, and thermally robust step-down conversion in demanding industrial, telecom, and aerospace applications.
FAQ
What is the operating temperature range of the LT3845MPFE#TRPBF?
The LT3845MPFE#TRPBF is rated for –55°C to 125°C junction temperature and is 100% tested across this full range. This extended specification makes it suitable for aerospace, military, and heavy industrial applications where extreme ambient temperatures or cold-start reliability are critical - unlike commercial-grade variants (e.g., LT3845EFE#TRPBF) limited to –40°C.
How does the LT3845MPFE#TRPBF achieve high light-load efficiency?
The LT3845MPFE#TRPBF achieves high light-load efficiency through two complementary mechanisms: Burst Mode® operation reduces total VIN supply current to 120μA by disabling switching until output droop triggers resumption, and reverse inductor current inhibit disables the bottom gate driver (BG) near zero current to prevent negative inductor flow - both features are controlled via the BURST_EN pin and supported by the 10mV sense offset.
Can the LT3845MPFE#TRPBF be synchronized to an external clock?
Yes, the LT3845MPFE#TRPBF supports external synchronization via the SYNC pin, accepting clock signals from 100kHz to 600kHz. When using SYNC, the internal oscillator (set by fSET resistor) must run 10–25% below the external frequency to ensure reliable locking. The SYNC function is available only on TSSOP packages like the LT3845MPFE#TRPBF - not on the PDIP variant.
What is the purpose of the exposed pad on the LT3845MPFE#TRPBF package?
The exposed pad on the LT3845MPFE#TRPBF's 16-lead TSSOP package is internally connected to SGND and must be soldered to the PCB ground plane. It serves dual purposes: providing low-inductance signal grounding for sensitive analog circuits (VFB, VC, SENSE) and enhancing thermal dissipation - reducing θJA from 40°C/W to ~30°C/W when properly implemented, critical for sustained high-power operation.
Does the LT3845MPFE#TRPBF require external MOSFETs?
Yes, the LT3845MPFE#TRPBF is a controller-only IC and requires external N-channel MOSFETs for both high-side (driven by TG) and low-side (driven by BG) switching. It does not integrate power switches. This architecture allows designers to select MOSFETs optimized for voltage, RDS(on), gate charge, and thermal performance - essential for achieving >95% efficiency in 48V-to-12V/75W applications using devices like Si7370DP.
LT3845MPFE#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
LT3845MPFE#TRPBF FAQ
1.How can I place an order for LT3845MPFE#TRPBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LT3845MPFE#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 LT3845MPFE#TRPBF reliable?
The price and inventory of LT3845MPFE#TRPBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LT3845MPFE#TRPBF is usually 5 days.
3.What payment methods are accepted for LT3845MPFE#TRPBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LT3845MPFE#TRPBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LT3845MPFE#TRPBF?
LT3845MPFE#TRPBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LT3845MPFE#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 LT3845MPFE#TRPBF?
For technical support, including LT3845MPFE#TRPBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LT3845MPFE#TRPBF requirements.
6.How does Aetrix verify that LT3845MPFE#TRPBF is sourced from the original manufacturer or authorized distributors?
All LT3845MPFE#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 LT3845MPFE#TRPBF meets industry standards.
7.What is the process for return or replacement of LT3845MPFE#TRPBF?
All LT3845MPFE#TRPBF units undergo pre-shipment inspection (PSI). If there is an issue with LT3845MPFE#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 LT3845MPFE#TRPBF part is unused and in its original packaging.
Return procedure for LT3845MPFE#TRPBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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