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Analog Devices Inc. LT3844EFE#PBF
- Part No.:
- LT3844EFE#PBF
- Manufacturer:
- Analog Devices Inc.
- Category:
- DC DC Switching Controllers
- Package:
- 16-TSSOP (0.173", 4.40mm Width) Exposed Pad
- Datasheet:
-
LT3844EFE#PBF.pdf
- Description:
- IC REG CTRLR MULT TOP 16TSSOP
- Quantity:
- Payment:
- Shipping:
Inventory:2,573
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Product details
Overview
LT3844EFE#PBF from Analog Devices (formerly Linear Technology) is a high-voltage, current-mode DC/DC controller IC for step-down, step-up, inverting, and SEPIC topologies. It supports 4V–60V input, delivers up to 36V output, operates at 100kHz–500kHz programmable frequency, and drives external N-channel MOSFETs - enabling 48V-to-12V, 50W industrial power supplies.
For engineers reviewing the LT3844EFE#PBF datasheet, LT3844EFE#PBF pinout, LT3844EFE#PBF application, or LT3844EFE#PBF equivalent, key selection criteria include its 60V max VIN rating, 100mV current sense threshold, ±1.3% reference accuracy, Burst Mode® operation (120µA IQ), and thermally enhanced 16-pin TSSOP package with exposed SGND pad.
Technical Context
The LT3844EFE#PBF implements fixed-frequency current-mode control with slope/antislope compensation to prevent subharmonic oscillation across duty cycles. Its error amplifier features 340µS transconductance and 62dB DC gain, with VC pin voltage directly setting peak inductor current per cycle.
It integrates a high-voltage bias regulator (VIN → VCC), bootstrapped gate driver (TG/BOOST/SW), and independent UVLO on VIN (7.5V start), VCC (6.25V), and BOOST (5V), all with hysteresis. Burst Mode® activation is controlled via BURST_EN pin, reducing quiescent current to 120µA while maintaining regulation at light loads.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Input Voltage Range | 4V to 60V - supports wide-range industrial and automotive inputs without pre-regulation |
| Operating Frequency | 100kHz to 500kHz (programmable via fSET resistor) - enables EMI optimization and magnetics sizing |
| Current Sense Threshold | 100mV (typical) - sets precise overcurrent protection independent of duty cycle |
| Reference Voltage Accuracy | ±1.3% over –40°C to 125°C - ensures stable output regulation across temperature |
| Quiescent Current (Burst) | 120µA - extends battery life in standby or low-load systems |
| Shutdown Current | 10µA - enables ultra-low-power system-level power gating |
| Gate Driver Output | TG pin drives N-MOSFET with 9.8V typical ON voltage and 40ns rise/fall - supports fast-switching, low-RDS(on) FETs |
Pinout & Package
LT3844EFE#PBF is housed in a 16-lead thermally enhanced TSSOP package with exposed pad (Pin 17), which must be soldered to PCB SGND for thermal and electrical integrity. The package supports 40°C/W junction-to-ambient thermal resistance.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| VIN (1) | Main power input | Accepts 4V–60V; powers internal regulator and provides energy for switching |
| SHDN (2) | Enable/disable control | 1.35V rising threshold with 120mV hysteresis - implements precision undervoltage lockout |
| CSS (3) | Soft-start timing | 2µA current source charges external capacitor to ramp output voltage and limit inrush |
| BURST_EN (4) | Burst Mode control | Ground to enable low-IQ operation; connect to VFB/VCC to disable |
| VFB (5) | Feedback reference node | 1.231V internal reference - compares against resistive divider to regulate output |
| VC (6) | Error amplifier output | Directly sets peak switch current; clamped during Burst Mode to limit ripple |
| SYNC (7) | External clock input | Accepts 100kHz–600kHz sync signal - enables noise-sensitive multi-converter synchronization |
| fSET (8) | Oscillator programming | Resistor sets nominal frequency; required even when SYNC is active |
| SGND (9,17) | Signal ground reference | Low-noise analog ground - must be isolated from PGND to avoid noise coupling |
| SENSE– (10) | Current sense negative | Connects to VOUT side of sense resistor - defines 100mV current limit threshold |
| SENSE+ (11) | Current sense positive | Connects to inductor side of sense resistor - completes differential current sensing |
| PGND (12) | Power ground return | High-current path for VCC regulator and internal low-side switch - requires direct capacitor connection |
| VCC (13) | Bias supply decoupling | Internal regulator output - decouple with ≥1µF ceramic to PGND; can be back-driven from VOUT |
| SW (14) | Switch node | Connects to MOSFET drain, Schottky cathode, and inductor - swings from VIN to ~–0.4V |
| TG (15) | Bootstrapped gate drive | Drives N-MOSFET gate with fast edges; requires short, low-inductance trace to MOSFET gate |
| BOOST (16) | Bootstrap supply | Charged via diode from SW; referenced to SW - powers TG driver during high-side conduction |
Key Features
| Feature | Design Value |
|---|---|
| Programmable constant frequency | 100kHz–500kHz via single resistor - simplifies EMI filtering and magnetics design |
| Burst Mode® operation | Reduces IQ to 120µA while maintaining regulation - critical for battery-backed or always-on systems |
| Antislope compensation | Maintains consistent 100mV current limit across all duty cycles - eliminates need for dynamic threshold adjustment |
| Integrated high-voltage bias regulator | Derives VCC from VIN up to 60V - eliminates external bias supply in most applications |
| Thermally enhanced TSSOP | 16-pin package with exposed SGND pad - achieves θJA = 40°C/W for medium-power density designs |
| Independent UVLO on VIN/VCC/BOOST | Prevents erratic startup or latch-up during brownout - each rail has dedicated hysteresis and threshold |
Applications
| Industrial Power Distribution | 12V/42V Automotive Systems |
|---|---|
Use Scenario: Distributed 48V-to-12V conversion in factory automation PLCs with wide input transients and thermal constraints. IC Role / Device Role / Timing Role: Primary PWM controller regulating buck converter with external N-MOSFET and Schottky diode. Use Value: 60V VIN rating withstands 48V bus surges; 120µA Burst Mode IQ minimizes standby loss in unpowered modules. | Use Scenario: On-board charger auxiliary supply in 42V heavy-duty vehicle systems requiring robust cold-crank operation. IC Role / Device Role / Timing Role: High-voltage step-down controller managing battery-fed 42V-to-12V conversion with programmable soft-start. Use Value: 7.5V VIN UVLO start threshold ensures reliable operation down to 8V cranking; 100mV current sense enables precise overload detection. |
| Avionics Power Supplies | Telecom Distributed Power |
Use Scenario: 28V-to-5V/3.3V intermediate bus converter in airborne communication equipment with strict EMI limits. IC Role / Device Role / Timing Role: Synchronizable current-mode controller enabling noise-free parallel operation with other converters. Use Value: SYNC pin accepts 100kHz–600kHz external clock - allows deterministic switching alignment to avoid beat frequencies. | Use Scenario: Hot-swap-capable 48V intermediate bus converter in telecom line cards requiring high efficiency at partial load. IC Role / Device Role / Timing Role: Fixed-frequency buck controller driving large N-MOSFETs with adaptive nonoverlap gate timing. Use Value: TG driver's 9.8V ON voltage and 40ns edges reduce MOSFET conduction losses; 10µA shutdown enables remote power cycling. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar high-voltage current-mode controller applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| LTC3891EFE#PBF | Includes integrated MOSFET drivers for synchronous rectification; higher 60V VIN rating; supports dual-output operation | Enables synchronous buck with higher efficiency (>95%) but requires additional external MOSFETs and layout complexity | Select LTC3891EFE#PBF when synchronous rectification and dual outputs are required; LT3844EFE#PBF remains optimal for cost-sensitive nonsynchronous designs |
| UCC28C44DR | Lower 28V VIN max; no integrated high-voltage bias regulator; 1mA typical startup current vs. LT3844EFE#PBF's 20µA | Suitable for 12V/24V systems only; lacks Burst Mode®, limiting light-load efficiency | Choose UCC28C44DR for legacy 24V industrial designs where cost is primary; LT3844EFE#PBF preferred for 48V+ or battery-backed applications |
Compared with LTC3891EFE#PBF, LT3844EFE#PBF offers lower BOM count and simpler layout for nonsynchronous buck, while UCC28C44DR trades off high-voltage capability and light-load efficiency for lower unit cost in constrained-input systems.
Availability
LT3844EFE#PBF is available at Aetrix Electronics and suitable for industrial power distribution, 12V/42V automotive systems, and avionics power supplies requiring stable component supply, long-term lifecycle support, and lead-free compliance.
Supply support for LT3844EFE#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 full product support, documentation, and manufacturing continuity for the LT® portfolio.
The LT3844EFE#PBF belongs to Linear's high-voltage DC/DC controller family, designed specifically for medium-power, transformerless switching supplies in harsh environments where input voltage exceeds 40V.
FAQ
What is the maximum input voltage rating for the LT3844EFE#PBF?
The LT3844EFE#PBF supports an absolute maximum input voltage of 65V on the VIN pin, with continuous operation rated up to 60V. Its 7.5V minimum start-up voltage and integrated high-voltage bias regulator allow direct operation from 48V and 60V industrial and automotive buses without external pre-regulation.
How does the LT3844EFE#PBF implement current limiting without duty-cycle dependence?
The LT3844EFE#PBF uses antislope compensation to maintain a fixed 100mV current sense threshold across all duty cycles. While standard slope compensation would reduce effective current limit as duty increases, the LT3844EFE#PBF adds a matching ramp to the current limit comparator threshold - preserving consistent overcurrent protection regardless of operating point.
Can the LT3844EFE#PBF be synchronized to an external clock, and what is the supported range?
Yes, the LT3844EFE#PBF supports external synchronization via the SYNC pin across 100kHz to 600kHz. The internal oscillator must be set 10%–25% below the external clock frequency using the fSET resistor. This enables deterministic switching alignment in multi-rail systems to suppress beat frequencies and simplify EMI filter design.
What is the purpose of the exposed pad (Pin 17) on the LT3844EFE#PBF package?
The exposed pad (Pin 17) on the LT3844EFE#PBF is internally connected to SGND and must be soldered to the PCB ground plane. It serves dual purposes: lowering thermal resistance (θJA = 40°C/W) for reliable operation at 125°C junction temperature, and providing a low-impedance, low-noise analog ground return path critical for current sense and feedback stability.
Does the LT3844EFE#PBF require an external bootstrap capacitor, and how is it sized?
Yes, the LT3844EFE#PBF requires an external ceramic bootstrap capacitor (CBOOST) connected between BOOST and SW pins. Its value should be at least 50× the total gate charge (QG) of the driven N-MOSFET; 0.1µF is sufficient for most applications. CBOOST supplies gate drive energy during high-side conduction and is recharged via the internal SW-pull-down switch during off-time.
LT3844EFE#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-Up, Step-Down, Step-Up/Step-Down
- Output Configuration:
- Positive or Negative
- Topology:
- Buck, Boost, SEPIC
- Number of Outputs:
- 1
- Output Phases:
- 1
- Voltage - Supply (Vcc/Vdd):
- 4V ~ 60V
- Frequency - Switching:
- 300kHz
- Duty Cycle (Max):
- -
- Synchronous Rectifier:
- No
- 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
LT3844EFE#PBF FAQ
1.How can I place an order for LT3844EFE#PBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LT3844EFE#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 LT3844EFE#PBF reliable?
The price and inventory of LT3844EFE#PBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LT3844EFE#PBF is usually 5 days.
3.What payment methods are accepted for LT3844EFE#PBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LT3844EFE#PBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LT3844EFE#PBF?
LT3844EFE#PBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LT3844EFE#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 LT3844EFE#PBF?
For technical support, including LT3844EFE#PBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LT3844EFE#PBF requirements.
6.How does Aetrix verify that LT3844EFE#PBF is sourced from the original manufacturer or authorized distributors?
All LT3844EFE#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 LT3844EFE#PBF meets industry standards.
7.What is the process for return or replacement of LT3844EFE#PBF?
All LT3844EFE#PBF units undergo pre-shipment inspection (PSI). If there is an issue with LT3844EFE#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 LT3844EFE#PBF part is unused and in its original packaging.
Return procedure for LT3844EFE#PBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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