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Analog Devices Inc. LT3845EN#PBF
- Part No.:
- LT3845EN#PBF
- Manufacturer:
- Analog Devices Inc.
- Category:
- DC DC Switching Controllers
- Package:
- 16-DIP (0.300", 7.62mm)
- Datasheet:
-
LT3845EN#PBF.pdf
- Description:
- IC REG CTRLR BUCK 16DIP
- Quantity:
- Payment:
- Shipping:
Inventory:1,307
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Product details
Overview
LT3845EN#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 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 LT3845EN#PBF datasheet, LT3845EN#PBF pinout, LT3845EN#PBF application, or LT3845EN#PBF equivalent, key selection considerations include its 16-pin PDIP package, 7.5V minimum start-up voltage, programmable soft-start, Burst Mode® operation for light-load efficiency, and dual gate drivers for external N-channel MOSFETs.
Technical Context
The LT3845EN#PBF implements a current-mode control architecture with an internal oscillator whose frequency is set by an external resistor on the fSET pin or synchronized via the SYNC pin (100–600kHz). Its error amplifier (transconductance: 270–410 μS) compares VFB against a 1.231V reference and drives the VC pin to modulate peak inductor current per cycle.
It integrates adaptive nonoverlap circuitry between TG and BG outputs to prevent shoot-through, uses differential SENSE+ and SENSE– inputs for ±100mV current limit detection, and includes reverse-current inhibit with 10mV offset to enable discontinuous conduction mode - all while maintaining 1% output voltage regulation accuracy across line, load, and temperature.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Input Voltage Range | 4V to 60V - supports wide-range industrial and telecom inputs; 7.5V min start-up requires external VCC bias below that threshold. |
| Output Voltage Range | Up to 36V - set externally via resistive divider on VFB; regulated to ±1% over full operating conditions. |
| Switching Frequency | 100kHz to 500kHz (adjustable), sync-capable up to 600kHz - enables noise-sensitive layout optimization and EMI compliance. |
| Quiescent Current | 120μA in Burst Mode®, 10μA in shutdown - extends battery life in standby and low-power states. |
| Current Sense Threshold | ±100mV across SENSE+ and SENSE– - provides accurate, duty-cycle-independent current limiting for robust overload protection. |
| Gate Drive Outputs | TG and BG drivers support standard N-channel MOSFETs - TG is bootstrapped; BG is referenced to PGND; nonoverlap timing prevents cross-conduction. |
| Soft-Start Control | Programmable via CSS pin with 2μA internal current source - controls output voltage slew rate to limit inrush and enable sequencing. |
Pinout & Package
The LT3845EN#PBF is housed in a 16-lead PDIP (Plastic Dual In-line Package) with through-hole mounting, rated for –40°C to 125°C junction temperature and θJA = 70°C/W.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| VFB | Feedback input | Connects to resistive divider from VOUT; regulates output to 1.231V reference with 1% accuracy. |
| VC | Error amplifier output | Drives current sense comparator threshold; integrator network (RC to SGND) sets loop compensation. |
| fSET | Oscillator programming | Resistor to SGND sets nominal frequency (100–500kHz); required even when SYNC is used. |
| SGND | Signal ground reference | Low-noise analog ground; connect to –VOUT side of output capacitors; separate from PGND. |
| SENSE– | Current sense negative input | Connected to VOUT side of sense resistor; forms ±100mV differential window with SENSE+. |
| SENSE+ | Current sense positive input | Connected to inductor side of sense resistor; enables accurate peak-current-mode control. |
| PGND | Power ground return | High-current return for BG driver and VCC regulator; tie directly to VCC decoupling capacitor negative terminal. |
| BG | Bottom gate driver output | Drives gate of low-side N-MOSFET; fast rise/fall (50ns) and 0.1V logic-low ensure clean turn-off. |
| BURST_EN | Mode control input | 0.5V threshold: enables Burst Mode® and reverse-current inhibit; 2.5V disables both functions. |
| CSS | Soft-start capacitor node | Charged by 2μA current source; overrides error amp reference during startup to control VOUT ramp rate. |
| SHDN | Enable/disable input | 1.35V rising threshold with 120mV hysteresis; pulls VIN supply current to ~9μA in shutdown. |
| VIN | Main power input | Supplies internal VCC regulator (4V–60V range); 7.5V min for autonomous start-up. |
| BOOST | Bootstrap supply | Provides gate drive voltage for TG; referenced to SW; max voltage = VIN + VCC (≤80V). |
| TG | Top gate driver output | Bootstrapped driver for high-side N-MOSFET; 9.8V typical "ON" voltage under switching conditions. |
| SW | Switch node | Connection point between TG, BG, inductor, and BOOST capacitor; transient rating down to –2V. |
| VCC | Internal bias supply | 8V regulated output from VIN; powers most internal circuitry; can be back-fed from VOUT to improve efficiency. |
Key Features
| Feature | Design Value |
|---|---|
| Adaptive nonoverlap timing | 200ns (TG↓→BG↑) and 150ns (BG↓→TG↑) prevents shoot-through and reduces MOSFET stress. |
| Reverse inductor current inhibit | 10mV positive offset at sense inputs detects near-zero current and disables BG to enable DCM, improving light-load efficiency. |
| Programmable soft-start | 2μA constant-current source charges external CSS capacitor, enabling precise control of output voltage ramp rate and inrush current. |
| Burst Mode® operation | Reduces total input quiescent current to 120μA at no load by cycling full-power bursts only as needed to maintain regulation. |
| Precision undervoltage lockout | VIN UVLO threshold = 3.8V (falling), 4.42V (rising) with 670mV hysteresis - ensures reliable start-up and brownout recovery. |
Applications
| 48V Telecom Power Supplies | Industrial Control Systems |
|---|---|
Use Scenario: Converting -48V or +48V telecom rack supply to 12V/24V intermediate bus for base station radios and line cards. IC Role / Device Role / Timing Role: High-voltage synchronous buck controller managing peak-current-mode regulation, thermal-aware gate drive, and EMI-controlled synchronization. Use Value: Enables >92% efficiency at 75W (48V→12V) with minimal external components and no external bias supply required above 7.5V VIN. | Use Scenario: Powering PLC I/O modules, motor drives, and sensor interfaces in factory automation equipment with wide-input industrial rails. IC Role / Device Role / Timing Role: Primary step-down controller supporting 12V/15V/24V outputs from unregulated 24–60V DC distribution buses. Use Value: Delivers stable 1% output regulation across –40°C to 125°C ambient, with reverse-current inhibit extending efficiency down to 10mA loads. |
| Avionics Power Conversion | Distributed Power Architectures |
Use Scenario: Generating 28V or 270V-derived 5V/15V rails in airborne systems where input transients exceed 60V and reliability is critical. IC Role / Device Role / Timing Role: Robust high-voltage controller with 65V absolute max VIN rating, overtemperature protection, and latch-off fault response. Use Value: Supports MIL-STD-704F input surges via 65V absolute max rating and maintains regulation during 10ms 80V transients on VIN or BOOST pins. | Use Scenario: Local point-of-load (POL) conversion in server backplanes or modular instrumentation where multiple isolated outputs are derived from a common 48V bus. IC Role / Device Role / Timing Role: Synchronizable controller allowing phase-shifted operation across multiple LT3845EN#PBF units to reduce input ripple current. Use Value: SYNC pin accepts 100–600kHz external clock, enabling interleaved operation without additional timing ICs or complex PLL design. |
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 |
|---|---|---|---|
| LTC3890EMSE#PBF | Higher integration: dual-output, integrated MOSFET drivers, wider 4.5V–60V input, but requires external VREF for tracking. | Supports dual-output POL designs; lacks reverse-current inhibit; higher pin count (28-MSOP). | Choose LTC3890EMSE#PBF when dual outputs or tighter input UVLO (4.5V) are required; not drop-in compatible. |
| LM5116MH/NOPB | Lower max input (100V), no Burst Mode®, fixed 100kHz–1MHz freq range, no reverse-current inhibit, 1.5% regulation accuracy. | Designed for high-VIN industrial converters; requires external soft-start circuit; higher quiescent current (2.5mA). | Choose LM5116MH/NOPB for cost-sensitive 100V-input applications where light-load efficiency is secondary. |
Compared with LTC3890EMSE#PBF and LM5116MH/NOPB, the LT3845EN#PBF offers superior light-load efficiency via Burst Mode® and reverse-current inhibit, tighter 1% regulation, and simpler single-output implementation - making it optimal for 48V telecom and industrial step-down where precision and standby power matter.
Availability
LT3845EN#PBF is available at Aetrix Electronics and suitable for 48V telecom power supplies, industrial control systems, avionics power conversion, and distributed power architectures requiring stable component supply, long-term lifecycle support, and RoHS-compliant through-hole packaging.
Supply support for LT3845EN#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 semiconductor leader specializing in high-performance analog, mixed-signal, and power management ICs - formed through the acquisition of Linear Technology in 2017.
The LT3845EN#PBF belongs to ADI's high-voltage DC/DC controller product line, designed specifically for efficient, robust, and thermally resilient step-down conversion in harsh industrial, telecom, and transportation environments.
FAQ
What is the minimum input voltage required for the LT3845EN#PBF to start up autonomously?
The LT3845EN#PBF requires a minimum VIN of 7.5V to initiate autonomous start-up, as this ensures sufficient headroom for the internal VCC regulator to reach its 6.5V UVLO threshold. If VCC is externally biased above 6.5V, the LT3845EN#PBF can operate down to 4V VIN - confirmed in the Absolute Maximum Ratings table and Applications Information section.
Does the LT3845EN#PBF support synchronization to an external clock signal?
Yes, the LT3845EN#PBF supports external clock synchronization via the SYNC pin, which accepts frequencies from 100kHz to 600kHz. The internal oscillator must be programmed 10–25% below the external clock frequency using the fSET resistor. Note: the SYNC pin is not available on the PDIP package - this applies only to TSSOP variants, so LT3845EN#PBF (PDIP) does not support SYNC functionality.
How does the reverse-current inhibit feature function in the LT3845EN#PBF?
The LT3845EN#PBF implements reverse-current inhibit by detecting inductor current approaching zero via its SENSE+ and SENSE– inputs, then disabling the BG driver to prevent negative current flow. A 10mV positive offset at the sense amplifier ensures early detection. This feature is enabled when BURST_EN ≤ 0.5V or = VFB, and improves light-load efficiency by enabling discontinuous conduction mode.
What is the purpose of the exposed pad on the LT3845EN#PBF package?
The LT3845EN#PBF uses a 16-pin PDIP package, which does not include an exposed thermal pad. Exposed pad (SGND) is present only on the TSSOP variants (e.g., LT3845EFE#PBF). Therefore, the LT3845EN#PBF has no exposed pad - thermal performance relies on standard through-hole PCB copper pour and θJA = 70°C/W as specified in the Order Information table.
Can the LT3845EN#PBF be used with external N-channel MOSFETs only, or does it support P-channel high-side switches?
The LT3845EN#PBF is designed exclusively for external N-channel MOSFETs: TG drives the high-side N-MOSFET via bootstrap circuitry, and BG drives the low-side N-MOSFET referenced to PGND. It does not support P-channel high-side configurations - the gate drive architecture, voltage levels (e.g., 9.8V TG "ON" voltage), and bootstrap requirements are optimized for N-channel devices only, as confirmed in the Pin Functions and Applications Information sections.
LT3845EN#PBF Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc.
- Series:
- -
- Package/Case:
- 16-DIP (0.300", 7.62mm)
- 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:
- -40°C ~ 125°C (TJ)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Through Hole
- Supplier Device Package:
- 16-PDIP
LT3845EN#PBF FAQ
1.How can I place an order for LT3845EN#PBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LT3845EN#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 LT3845EN#PBF reliable?
The price and inventory of LT3845EN#PBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LT3845EN#PBF is usually 5 days.
3.What payment methods are accepted for LT3845EN#PBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LT3845EN#PBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LT3845EN#PBF?
LT3845EN#PBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LT3845EN#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 LT3845EN#PBF?
For technical support, including LT3845EN#PBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LT3845EN#PBF requirements.
6.How does Aetrix verify that LT3845EN#PBF is sourced from the original manufacturer or authorized distributors?
All LT3845EN#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 LT3845EN#PBF meets industry standards.
7.What is the process for return or replacement of LT3845EN#PBF?
All LT3845EN#PBF units undergo pre-shipment inspection (PSI). If there is an issue with LT3845EN#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 LT3845EN#PBF part is unused and in its original packaging.
Return procedure for LT3845EN#PBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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