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Analog Devices Inc. LT3844IFE#PBF
- Part No.:
- LT3844IFE#PBF
- Manufacturer:
- Analog Devices Inc.
- Category:
- DC DC Switching Controllers
- Package:
- 16-TSSOP (0.173", 4.40mm Width) Exposed Pad
- Datasheet:
-
LT3844IFE#PBF.pdf
- Description:
- IC REG CTRLR MULT TOP 16TSSOP
- Quantity:
- Payment:
- Shipping:
Inventory:112
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Product details
Overview
LT3844IFE#PBF from Analog Devices (formerly Linear Technology) is a high-voltage, current-mode DC/DC controller for step-down, step-up, inverting, and SEPIC topologies. It supports 4V–60V input, delivers up to 36V output, operates at 100kHz–500kHz (synchronizable to 600kHz), features Burst Mode® (120µA quiescent current), and drives external N-channel MOSFETs in industrial power distribution and 42V automotive systems.
For engineers reviewing the LT3844IFE#PBF datasheet, LT3844IFE#PBF pinout, LT3844IFE#PBF application, or LT3844IFE#PBF equivalent, key selection considerations include its programmable UVLO, ±1.3% reference accuracy, 100mV current sense threshold, thermal shutdown, and compatibility with high-side N-MOSFET gate drive in high-input-voltage buck configurations.
Technical Context
The LT3844IFE#PBF implements fixed-frequency current-mode control with slope/antislope compensation to prevent subharmonic oscillation across duty cycles. Its error amplifier (270–410 µS transconductance) regulates via VFB feedback against a 1.231V reference, while VC sets peak inductor current per cycle.
It integrates a high-voltage bias regulator (VIN → VCC), bootstrapped TG driver (9.8V typical ON voltage), and adaptive nonoverlap circuitry to prevent shoot-through between the external MOSFET and internal SW pull-down switch. Burst Mode® operation disables switching when VC drops 150mV below latched load level, reducing VIN supply current to 120µA.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Input Voltage Range | 4V to 60V - supports wide-range industrial and 42V automotive inputs without pre-regulation |
| Operating Frequency | 100kHz to 500kHz (programmable via fSET resistor) - enables EMI optimization and inductor size reduction |
| Reference Accuracy | ±1.3% over –40°C to 125°C - ensures stable output regulation across temperature extremes |
| Current Sense Threshold | 100mV (SENSE+ to SENSE–) - sets precise, duty-cycle-independent current limit for overcurrent protection |
| Burst Mode Quiescent Current | 120µA (VIN supply) - maintains high light-load efficiency in battery-backed or standby systems |
| Shutdown Current | 10µA - enables ultra-low-power system-level sleep modes |
| Gate Drive Capability | TG output drives large N-channel MOSFETs with 9.8V typical ON voltage and 40ns rise/fall time - reduces conduction and switching losses |
Pinout & Package
LT3844IFE#PBF is housed in a 16-lead thermally enhanced TSSOP package with exposed pad (Pin 17) soldered to SGND for optimal thermal performance and low-noise grounding.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| VIN (1) | Main input supply | Accepts 4V–60V; powers internal regulators and provides energy to BOOST capacitor via internal HV regulator |
| SHDN (2) | Enable/disable control | 1.35V rising threshold with 120mV hysteresis; pulls IC into 10µA shutdown when <0.7V |
| CSS (3) | Soft-start timing | 2µA current source charges external capacitor to ramp output voltage and limit inrush current |
| BURST_EN (4) | Burst Mode control | Ground to enable Burst Mode; connect to VFB or VCC to disable - selects low-IQ vs. continuous operation |
| VFB (5) | Feedback input | Compares output voltage (via resistive divider) to 1.231V reference; error signal drives VC loop |
| VC (6) | Error amplifier output | DC voltage sets peak inductor current per cycle; clamped during Burst Mode to limit negative excursion |
| SYNC (7) | External clock input | Accepts 100kHz–600kHz sync signal; requires RSET set 10–25% below sync frequency |
| fSET (8) | Oscillator programming | Resistor-to-ground sets nominal frequency; required even when SYNC is active |
| SGND (9,17) | Signal ground reference | Low-noise analog ground; connects to –VOUT side of output caps; exposed pad must be soldered |
| SENSE– (10) | Current sense negative | Connects to VOUT side of sense resistor; forms 100mV differential threshold with SENSE+ |
| SENSE+ (11) | Current sense positive | Connects to inductor side of sense resistor; enables accurate, high-side current sensing |
| PGND (12) | Power ground | High-current return path for VCC regulator and internal low-side switch; decouple VCC to this pin |
| VCC (13) | Bias supply node | Internally regulated ~8V output; powers most internal circuits; can be back-driven from VOUT for higher efficiency |
| SW (14) | Switch node | Connects to MOSFET drain, Schottky cathode, and inductor; swings from VIN to ~–0.4V during freewheeling |
| TG (15) | Bootstrapped gate driver | Drives N-MOSFET gate with fast edges; powered by BOOST capacitor referenced to SW |
| BOOST (16) | Bootstrap supply | Charged via external diode from VCC during SW off-time; max voltage = VIN + VCC (ground-referred) |
Key Features
| Feature | Design Value |
|---|---|
| Programmable UVLO with hysteresis | Enables robust start-up sequencing and brown-out recovery in 12V/42V automotive systems |
| Antislope compensation | Maintains constant 100mV current limit across all duty cycles - eliminates need for external compensation |
| Internal high-voltage VCC regulator | Eliminates external bias supply for VIN ≤60V applications - reduces BOM count and layout complexity |
| Thermally enhanced TSSOP-16 with exposed pad | θJA = 40°C/W - supports >50W operation without heatsink in properly laid-out PCBs |
| Adaptive nonoverlap timing | Prevents shoot-through between external MOSFET and internal SW pull-down switch - improves reliability in high-dV/dt environments |
Applications
| Industrial Power Distribution | 42V Automotive Systems |
|---|---|
Use Scenario: Centralized 48V-to-12V conversion in factory automation PLCs with strict EMI requirements. IC Role / Device Role / Timing Role: Primary controller for nonsynchronous buck converter driving 50W load with programmable 300kHz switching. Use Value: Programmable frequency allows EMI band avoidance; Burst Mode maintains >85% efficiency at 100mA load. | Use Scenario: High-voltage DC-DC supply for ADAS camera modules in commercial vehicles operating from 24V–42V battery rails. IC Role / Device Role / Timing Role: Step-down controller regulating 12V output with programmable UVLO (36V rising, 34.5V falling) for cold-crank resilience. Use Value: ±1.3% reference accuracy ensures camera sensor power stability; thermal shutdown protects under hood ambient up to 125°C. |
| Avionics Power Supplies | Telecom Distributed Power |
Use Scenario: 28V-to-5V conversion for flight control interface boards requiring low EMI and high reliability. IC Role / Device Role / Timing Role: Current-mode controller implementing synchronized 400kHz operation to avoid sensitive RF bands. Use Value: SYNC pin enables deterministic noise placement; antislope compensation ensures stable current limiting at 90% duty cycle. | Use Scenario: Intermediate bus converter in 48V telecom shelf supplying multiple point-of-load regulators. IC Role / Device Role / Timing Role: High-efficiency buck controller delivering 36V output with soft-start sequencing across redundant supplies. Use Value: CSS pin enables controlled 100ms output ramp; 10µA shutdown current minimizes standby loss in hot-swap modules. |
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 |
|---|---|---|---|
| LTC3890EFE#PBF | Dual-output, 60V input, integrated MOSFET drivers, no Burst Mode - higher integration but larger footprint | Suitable for dual-rail avionics supplies where channel interleaving reduces input ripple | Select LTC3890EFE#PBF when needing dual outputs or higher peak current capability (>20A); LT3844IFE#PBF remains optimal for single-output, cost-sensitive 50W designs |
| LM5116PWPR | 65V input, 100kHz–1MHz range, no integrated VCC regulator - requires external bias supply | Better suited for high-frequency telecom applications where 1MHz operation reduces magnetics size | Choose LM5116PWPR when board space is constrained and external VCC bias is acceptable; LT3844IFE#PBF simplifies design with internal HV bias and lower EMI at 300kHz |
Compared with LTC3890EFE#PBF and LM5116PWPR, LT3844IFE#PBF offers the best balance of integrated high-voltage bias, Burst Mode efficiency, and thermal performance in a compact TSSOP-16 - ideal for single-output industrial and automotive converters up to 50W.
Availability
LT3844IFE#PBF is available at Aetrix Electronics and suitable for industrial power distribution, 42V automotive systems, and avionics power supplies requiring stable component supply, long-term lifecycle support, and guaranteed lead-free compliance.
Supply support for LT3844IFE#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, datasheets, and application engineering for legacy Linear parts including the LT3844 series.
The LT3844IFE#PBF belongs to Linear's high-voltage DC/DC controller family, designed specifically for nonsynchronous buck, boost, inverting, and SEPIC converters in harsh environments where input voltages exceed 40V.
FAQ
What is the maximum input voltage rating for the LT3844IFE#PBF?
The LT3844IFE#PBF has an absolute maximum input voltage (VIN) rating of 65V. Its operational input range is 4V to 60V, with a minimum start-up voltage of 7.5V unless VCC is externally driven above 6.5V. This makes LT3844IFE#PBF suitable for 42V automotive and industrial 48V systems where transient spikes must be tolerated without damage.
How does the LT3844IFE#PBF implement current limiting without duty-cycle dependence?
The LT3844IFE#PBF uses antislope compensation to maintain a constant 100mV current sense threshold across all duty cycles. While standard slope compensation would reduce effective current limit as duty cycle increases, LT3844IFE#PBF adds a matching ramp to the current limit threshold - ensuring consistent overcurrent protection regardless of operating point.
Can the LT3844IFE#PBF drive a synchronous rectifier instead of a Schottky diode?
No - the LT3844IFE#PBF is designed exclusively for nonsynchronous operation with an external Schottky freewheeling diode. It lacks a second gate driver output required for synchronous rectification. For synchronous buck applications, consider the pin-compatible LTC3800 or LTC3890 families, which provide complementary high-side and low-side MOSFET drive signals.
What is the purpose of the exposed pad (Pin 17) on the LT3844IFE#PBF package?
The exposed pad (Pin 17) on the LT3844IFE#PBF is internally connected to SGND and must be soldered to the PCB ground plane. It serves two critical functions: (1) lowers thermal resistance (θJA = 40°C/W) to sustain >50W operation, and (2) provides a low-inductance, low-noise analog ground return path essential for stable current sensing and feedback accuracy in LT3844IFE#PBF designs.
How do I configure the LT3844IFE#PBF for Burst Mode operation?
To enable Burst Mode on the LT3844IFE#PBF, connect the BURST_EN pin (Pin 4) directly to SGND. To disable it, connect BURST_EN to either VFB (Pin 5) or VCC (Pin 13). When enabled, LT3844IFE#PBF reduces VIN supply current to 120µA at light loads by cycling the controller on/off based on VC pin voltage thresholds - improving efficiency below 10% load without adding external components.
LT3844IFE#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
LT3844IFE#PBF FAQ
1.How can I place an order for LT3844IFE#PBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LT3844IFE#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 LT3844IFE#PBF reliable?
The price and inventory of LT3844IFE#PBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LT3844IFE#PBF is usually 5 days.
3.What payment methods are accepted for LT3844IFE#PBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LT3844IFE#PBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LT3844IFE#PBF?
LT3844IFE#PBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LT3844IFE#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 LT3844IFE#PBF?
For technical support, including LT3844IFE#PBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LT3844IFE#PBF requirements.
6.How does Aetrix verify that LT3844IFE#PBF is sourced from the original manufacturer or authorized distributors?
All LT3844IFE#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 LT3844IFE#PBF meets industry standards.
7.What is the process for return or replacement of LT3844IFE#PBF?
All LT3844IFE#PBF units undergo pre-shipment inspection (PSI). If there is an issue with LT3844IFE#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 LT3844IFE#PBF part is unused and in its original packaging.
Return procedure for LT3844IFE#PBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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