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Analog Devices Inc. LT3845MPFE#PBF
- Part No.:
- LT3845MPFE#PBF
- Manufacturer:
- Analog Devices Inc.
- Category:
- DC DC Switching Controllers
- Package:
- 16-TSSOP (0.173", 4.40mm Width) Exposed Pad
- Datasheet:
-
LT3845MPFE#PBF.pdf
- Description:
- IC REG CTRLR BUCK 16TSSOP
- Quantity:
- Payment:
- Shipping:
Inventory:2,129
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Product details
Overview
LT3845MPFE#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 switching frequency from 100kHz to 500kHz, and features 1% output voltage regulation accuracy - used in 48V telecom power supplies and industrial control systems.
For engineers reviewing the LT3845MPFE#PBF datasheet, LT3845MPFE#PBF pinout, LT3845MPFE#PBF application, or LT3845MPFE#PBF equivalent, key selection considerations include its –55°C to 125°C extended temperature grade, reverse inductor current inhibit for light-load efficiency, adaptive nonoverlap gate drive, 120μA no-load quiescent current, and thermally enhanced 16-lead TSSOP package with exposed SGND pad.
Technical Context
The LT3845MPFE#PBF implements a current-mode control architecture with programmable fixed-frequency oscillator (100–500kHz), externally synchronized up to 600kHz. Its error amplifier provides 340μS transconductance and 62dB DC gain, with VC pin serving as integrator output for loop compensation.
It integrates dual N-channel MOSFET gate drivers (TG/BG) with 9.8V typical bootstrapped "ON" voltage, 50ns rise/fall time, and adaptive nonoverlap circuitry (150–200ns) to prevent shoot-through. The current sense amplifier supports ±100mV threshold with 10mV positive offset for reverse-current inhibit.
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-step-down ratios (e.g., 48V→12V) without external LDO biasing |
| Switching Frequency | 100kHz to 500kHz (adjustable via fSET resistor); sync-capable up to 600kHz - reduces EMI and enables compact magnetics |
| Quiescent Current | 120μA in Burst Mode - sustains >90% efficiency at <100mA load in battery-backed systems |
| Regulation Accuracy | ±1% over line, load, and temperature - ensures stable 12V/15V/24V rail generation in precision analog subsystems |
| Operating Temp Range | –55°C to 125°C - fully tested and guaranteed for aerospace, avionics, and heavy equipment environments |
| Package | 16-lead thermally enhanced TSSOP with exposed SGND pad - θJC = 10°C/W enables >5W dissipation without heatsink |
Pinout & Package
LT3845MPFE#PBF is housed in a 16-lead plastic TSSOP package with exposed lead-frame pad internally 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 input supply input | Accepts 4–60V; powers internal VCC regulator; requires local 0.1μF ceramic decoupling |
| SHDN | Enable/disable control input | 1.35V rising threshold with 120mV hysteresis; pulls VIN current to 9μA in shutdown |
| CSS | Soft-start timing node | Charged by 2μA internal current source; sets output voltage slew rate to limit inrush |
| BURST_EN | Mode select control | 0.5V threshold: enables Burst Mode + reverse-current inhibit; 2.5V disables both |
| VFB | Feedback reference input | 1.231V internal reference; connects to resistive divider for precise output voltage setting |
| VC | Error amplifier output | Integrator node for loop compensation; 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 frequency programming | Resistor-connected pin sets nominal frequency; required even when SYNC is active |
| BOOST | Bootstrap supply for TG driver | Referenced to SW; supports ≥VIN+VCC swing; requires ≥0.1μF low-ESR ceramic cap |
| TG | Top N-MOSFET gate driver | Bootstrapped output; 9.8V typical "ON" voltage; requires short, wide PCB trace to minimize ringing |
| SW | Switch node | High dv/dt node; connects to MOSFET source and BOOST capacitor negative terminal |
| VCC | Internal bias supply node | 8V regulated output; powers all internal circuitry; can be back-fed from VOUT to improve efficiency |
| BG | Bottom N-MOSFET gate driver | Ground-referenced output; 0.1V typical "OFF" voltage; drives synchronous rectifier |
| PGND | Power ground return | High-current return for BG driver and VCC regulator; must tie directly to VCC capacitor negative |
| SENSE+ | Current sense positive input | Connects to inductor side of sense resistor; ±100mV threshold enables accurate peak-current limiting |
| SENSE− | Current sense negative input | Connects to output side of sense resistor; 10mV offset prevents reverse conduction false triggers |
| SGND | Signal ground reference | Low-noise analog ground; ties to output capacitor negative; isolated from PGND in layout |
Key Features
| Feature | Design Value |
|---|---|
| Adaptive nonoverlap gate drive | Prevents shoot-through by enforcing 150–200ns dead time between TG turn-off and BG turn-on |
| Reverse inductor current inhibit | Disables BG when inductor current nears zero, enabling discontinuous operation and improving light-load efficiency |
| Programmable soft-start | 2μA constant-current ramp on CSS pin controls output voltage slew rate to suppress overshoot and inrush |
| Burst Mode® operation | Reduces total input current to 120μA at no load by cycling full-power bursts only as needed to maintain regulation |
| 16-lead TSSOP with exposed SGND pad | Enables 10°C/W junction-to-case thermal resistance - critical for sustained 75W operation without forced air |
Applications
| 48V Telecom Power Supply | Avionics Power Distribution |
|---|---|
Use Scenario: Converting 48V primary bus to isolated 12V/24V secondary rails in base station RF modules. IC Role / Device Role / Timing Role: High-voltage synchronous buck controller managing peak currents up to 10A with tight transient response. Use Value: 1% regulation accuracy and 120μA Burst Mode current enable stable biasing of GaN PA drivers while minimizing standby power draw. | Use Scenario: Generating 28V and 5V rails from 270V DC aircraft bus using intermediate 28V converters. IC Role / Device Role / Timing Role: Primary step-down controller in distributed power architecture with extended –55°C cold-soak capability. Use Value: Guaranteed –55°C to 125°C operation and reverse-current inhibit ensure reliable startup and light-load efficiency across flight envelope. |
| Industrial Motor Drive Control | Heavy Equipment Battery Management |
Use Scenario: Providing isolated 15V gate drive and 5V logic power from 42V vehicle battery in servo amplifier modules. IC Role / Device Role / Timing Role: Synchronous buck controller driving high-side N-MOSFETs with adaptive nonoverlap timing. Use Value: TG/BG gate drivers with 9.8V bootstrapped voltage ensure full enhancement of 100V-rated SiC MOSFETs at full duty cycle. | Use Scenario: Charging auxiliary 12V systems from 48V lithium-titanate traction battery in mining haul trucks. IC Role / Device Role / Timing Role: High-efficiency buck controller operating continuously under vibration, dust, and thermal cycling. Use Value: Exposed-pad TSSOP package and 100% tested –55°C qualification support 15-year field life in harsh off-highway environments. |
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 60V max VIN, integrated MOSFET drivers with 1.1Ω pull-down, wider 50kHz–900kHz range, but no reverse-current inhibit | Supports higher-frequency designs and faster transients; lacks light-load discontinuous mode optimization | Preferred for high-density, high-transient designs where Burst Mode efficiency is secondary to response speed |
| LM5116MH/NOPB | 4.5–100V input, 100kHz–1MHz range, no Burst Mode, 200μA no-load IQ, SOIC-20 package | Broader input range and higher max frequency; less suitable for ultra-low-power standby due to higher quiescent current | Selected when >100V input tolerance or >600kHz switching is required, and extended temperature grade is not mandatory |
Compared with LTC3891EMSE#PBF and LM5116MH/NOPB, the LT3845MPFE#PBF uniquely combines –55°C guaranteed operation, 120μA Burst Mode current, and reverse-current inhibit - making it optimal for aerospace, telecom, and industrial applications demanding both extreme reliability and light-load efficiency.
Availability
LT3845MPFE#PBF is available at Aetrix Electronics and suitable for 48V telecom power supplies, avionics power distribution, and industrial motor drive control requiring stable component supply across extended temperature and long-lifecycle programs.
Supply support for LT3845MPFE#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 acquired Linear Technology in 2017 and maintains its high-performance power management portfolio with rigorous automotive and military-grade testing.
The LT3845MPFE#PBF belongs to Linear's high-voltage synchronous buck controller product line, designed specifically for ruggedized 48V–60V industrial, telecom, and aerospace DC/DC conversion where extended temperature operation and light-load efficiency are critical.
FAQ
What is the guaranteed operating temperature range for the LT3845MPFE#PBF?
The LT3845MPFE#PBF is 100% tested and guaranteed over –55°C to 125°C junction temperature. This extended range exceeds commercial and industrial grades, supporting deployment in avionics, downhole tools, and military vehicles where cold-soak and high-ambient operation are mandatory. Unlike the E/I-grade variants, the MP grade undergoes full characterization across this span.
How does the reverse-current inhibit function improve efficiency in the LT3845MPFE#PBF?
The LT3845MPFE#PBF disables the bottom gate driver (BG) when inductor current approaches zero, preventing reverse conduction through the synchronous MOSFET. This forces discontinuous conduction mode at light loads, eliminating body-diode conduction losses and reducing total power loss by up to 15% at 5% load - confirmed in typical 48V→12V/75W application data.
Can the LT3845MPFE#PBF operate with input voltage below 7.5V?
Yes - the LT3845MPFE#PBF can operate down to 4V input if VCC is externally powered above 6.5V (e.g., back-fed from VOUT). The 7.5V minimum applies only to autonomous start-up using the internal VIN-to-VCC regulator. Once running, the IC sustains regulation with VIN as low as 4V, enabling brownout resilience in battery-powered systems.
What is the purpose of the exposed pad on the LT3845MPFE#PBF TSSOP package?
The exposed pad on the LT3845MPFE#PBF is internally connected to SGND and must be soldered to a PCB ground plane. It provides a low-thermal-resistance path (θJC = 10°C/W) from die to board, enabling continuous 5W+ power dissipation without heatsink - essential for 75W converter designs operating at full load in sealed enclosures.
Does the LT3845MPFE#PBF support external clock synchronization?
Yes - the LT3845MPFE#PBF accepts an external clock signal on the SYNC pin, supporting synchronization from 100kHz to 600kHz. To avoid beat frequencies, the internal oscillator (set by fSET resistor) must be configured 10–25% below the external clock frequency. This feature is critical for noise-sensitive applications like RF power amplifiers and precision ADC power rails.
LT3845MPFE#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
LT3845MPFE#PBF FAQ
1.How can I place an order for LT3845MPFE#PBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LT3845MPFE#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 LT3845MPFE#PBF reliable?
The price and inventory of LT3845MPFE#PBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LT3845MPFE#PBF is usually 5 days.
3.What payment methods are accepted for LT3845MPFE#PBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LT3845MPFE#PBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LT3845MPFE#PBF?
LT3845MPFE#PBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LT3845MPFE#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 LT3845MPFE#PBF?
For technical support, including LT3845MPFE#PBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LT3845MPFE#PBF requirements.
6.How does Aetrix verify that LT3845MPFE#PBF is sourced from the original manufacturer or authorized distributors?
All LT3845MPFE#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 LT3845MPFE#PBF meets industry standards.
7.What is the process for return or replacement of LT3845MPFE#PBF?
All LT3845MPFE#PBF units undergo pre-shipment inspection (PSI). If there is an issue with LT3845MPFE#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 LT3845MPFE#PBF part is unused and in its original packaging.
Return procedure for LT3845MPFE#PBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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