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Analog Devices Inc. LT3757IDD#PBF
- Part No.:
- LT3757IDD#PBF
- Manufacturer:
- Analog Devices Inc.
- Category:
- DC DC Switching Controllers
- Package:
- 10-WFDFN Exposed Pad
- Datasheet:
-
LT3757IDD#PBF.pdf
- Description:
- IC REG CTRLR MULT TOPOLOGY 10DFN
- Quantity:
- Payment:
- Shipping:
Inventory:633
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Product details
Overview
LT3757IDD#PBF from Analog Devices is a wide-input current-mode DC/DC controller supporting boost, flyback, SEPIC, and inverting topologies with single-feedback-pin polarity selection. It features 2.9V–40V input range, programmable 50kHz–1MHz switching frequency, internal 7.2V LDO, <1µA shutdown current, and AEC-Q100 qualification for automotive use.
For engineers reviewing the LT3757IDD#PBF datasheet, LT3757IDD#PBF pinout, LT3757IDD#PBF application, or LT3757IDD#PBF equivalent, this page delivers verified topology flexibility, precise UVLO hysteresis programming, soft-start timing control, and thermal-aware gate drive capability - all critical for battery-powered and automotive power supply design.
Technical Context
The LT3757IDD#PBF implements fixed-frequency current-mode control with slope compensation, enabling stable regulation across wide VIN and VOUT ranges. Its dual-reference feedback architecture (1.6V for positive outputs, –0.8V for negative) allows seamless configuration between boost/flyback/SEPIC and inverting modes using only the FBX pin and external resistor dividers.
It integrates a 7.2V low-dropout regulator (INTVCC) with 2.7V UVLO and 17.5V OVLO thresholds, programmable SHDN/UVLO with 1.22V nominal falling threshold and user-defined hysteresis, and frequency foldback during overcurrent to limit peak inductor current at startup and short-circuit conditions.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Input Voltage Range | 2.9V to 40V - supports direct connection to 12V/24V automotive rails and single-cell Li-ion up to 4S battery stacks. |
| Switching Frequency | 50kHz to 1MHz - set via RT resistor; enables optimization of efficiency vs. magnetics size and EMI profile. |
| Feedback Reference | +1.6V or –0.8V - selectable polarity on FBX pin eliminates need for separate positive/negative feedback networks. |
| Shutdown Current | <1µA - ensures minimal battery drain in always-on automotive modules or portable equipment standby. |
| SENSE Threshold | 110mV (typical) - defines accurate current-limit point for MOSFET protection and loop stability. |
| INTVCC Regulator | 7.2V ±0.2V - powers gate driver and internal circuitry; bypassed with ≥4.7µF ceramic capacitor near pin. |
| Operating Temp Range | –40°C to 125°C - qualified per AEC-Q100 Grade I, suitable for under-hood and industrial ambient environments. |
Pinout & Package
LT3757IDD#PBF is housed in a thermally enhanced 10-lead (3mm × 3mm) plastic DFN package with exposed pad (Pin 11) soldered to PCB ground for optimal thermal performance (θJA = 43°C/W).
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| VC (Pin 1) | Error amplifier compensation node | Accepts RC network to stabilize voltage loop; clamped during soft-start and fault conditions. |
| FBX (Pin 2) | Unified positive/negative feedback input | Detects output voltage via resistor divider; selects 1.6V or –0.8V reference based on polarity; triggers frequency foldback near GND. |
| SS (Pin 3) | Soft-start timing control | 10µA pull-up to 2.5V rail; external capacitor sets ramp time; reset by UV/OV/thermal events. |
| RT (Pin 4) | Frequency programming input | Resistor-to-GND sets oscillator frequency; must not be left floating. |
| SYNC (Pin 5) | External clock synchronization input | Accepts digital clock signal; requires RT setting 20% slower than SYNC frequency; ignored when FBX ≈ GND. |
| SENSE (Pin 6) | Current sense amplifier input | Kelvin-connected to high-side of sense resistor; monitors switch current for cycle-by-cycle limiting. |
| GATE (Pin 7) | N-channel MOSFET gate driver output | Sources/sinks to INTVCC/GND; forced low during shutdown, thermal lockout, or INTVCC UV/OV. |
| INTVCC (Pin 8) | Internal regulated supply output | 7.2V LDO output powering gate driver and logic; requires ≥4.7µF local ceramic bypass. |
| SHDN/UVLO (Pin 9) | Enable/disable and input undervoltage detection | 1.22V falling threshold with programmable hysteresis; resets soft-start on undervoltage; pulls VIN IQ below 1µA when ≤0.4V. |
| VIN (Pin 10) | Main input supply input | 2.9V–40V input; requires ≥0.22µF local ceramic bypass; powers internal LDO and bias circuits. |
| Exposed Pad (Pin 11) | Thermal ground and current sense return | Must be soldered to PCB ground plane; serves as SENSE resistor negative terminal and primary heat path. |
Key Features
| Feature | Design Value |
|---|---|
| Topology Flexibility | Single IC supports boost, flyback, SEPIC, and inverting configurations without external mode-select pins. |
| Programmable UVLO Hysteresis | Accurate 1.22V falling threshold with externally adjustable rising threshold via resistor divider - enables reliable brown-in/brown-out behavior. |
| Integrated Gate Driver | Capable of driving N-channel MOSFETs with fast rise/fall times (22ns/20ns @ 3.3nF); includes automatic disable during fault conditions. |
| Frequency Foldback | Reduces switching frequency during overload or short-circuit to limit peak inductor current and maintain control loop stability. |
| AEC-Q100 Qualified | Grade I (–40°C to +125°C) qualification confirms suitability for automotive power systems including ADAS and body electronics. |
Applications
| Automotive LED Headlamp Driver | Industrial Isolated Flyback PSU |
|---|---|
|
Use Scenario: High-brightness LED array powered from 12V vehicle battery with strict EMI and thermal constraints. IC Role / Device Role / Timing Role: Boost controller regulating constant current to LEDs; uses FBX for output voltage sensing and SENSE for current monitoring. Use Value: 2.9V minimum start-up enables operation during cranking; <1µA shutdown current preserves battery; AEC-Q100 compliance ensures reliability in harsh environments. |
Use Scenario: 24V industrial input converted to isolated 5V/12V outputs for PLC I/O modules requiring reinforced insulation. IC Role / Device Role / Timing Role: Flyback controller with optocoupler feedback; FBX referenced to secondary-side error amp; SYNC pin used to align switching with system clock. Use Value: Programmable frequency avoids noise-sensitive bands; 40V absolute max VIN withstands load-dump transients; INTVCC UVLO prevents erratic gate drive during brownout. |
| Portable Medical Instrument Power | Telecom DC-DC Intermediate Bus Converter |
|
Use Scenario: Battery-powered ultrasound device requiring clean, low-noise 3.3V and ±15V rails from single Li-ion cell. IC Role / Device Role / Timing Role: Inverting controller generating –15V from 3.3V intermediate rail; SS pin controls ramp rate to avoid inrush into capacitive loads. Use Value: Dual-reference FBX simplifies bipolar supply design; 110mV SENSE threshold enables precise current limiting on small sense resistors; DFN package saves board space. |
Use Scenario: Telecom shelf with 48V backplane supplying multiple point-of-load converters; requires efficient, compact 48V-to-12V intermediate bus. IC Role / Device Role / Timing Role: SEPIC controller delivering regulated 12V output; RT resistor sets 300kHz switching to balance efficiency and filter size; SYNC aligned to system master clock. Use Value: Wide 2.9V–40V input range accommodates 48V nominal with ripple and transients; 7.2V INTVCC ensures robust gate drive even at low duty cycles; thermal pad supports continuous 2A output. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar DC/DC controller applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| LT3757AIDD#PBF | Improved load transient response; identical pinout, specs, and package; higher production test coverage. | Better suited for dynamic load applications like CPU core supplies where fast line/load regulation is critical. | Select LT3757AIDD#PBF when tighter output voltage deviation under rapid load steps is required; otherwise LT3757IDD#PBF remains fully compatible. |
| LM5155RUMR | Lower 2.97V min VIN; no negative output support; integrated high-side MOSFET driver only; no FBX polarity auto-detection. | Limited to boost/SEPIC; lacks inverting/flyback capability; requires external high-side FET for flyback. | Choose LM5155RUMR only for cost-sensitive boost-only designs where negative output and topology flexibility are unnecessary. |
Compared with LT3757AIDD#PBF, the LT3757IDD#PBF offers identical functionality at lower test-cost premium, while LM5155RUMR trades topology versatility for integration and lower VIN start-up - making LT3757IDD#PBF the optimal choice for multi-topology, automotive-grade, or bipolar-output requirements.
Availability
LT3757IDD#PBF is available at Aetrix Electronics and suitable for automotive LED drivers, industrial flyback PSUs, portable medical instrument power, telecom intermediate bus converters, and battery-backed industrial controllers requiring stable component supply and long-term lifecycle support.
Supply support for LT3757IDD#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. is a global leader in high-performance analog, mixed-signal, and digital signal processing semiconductors, serving industrial, automotive, communications, and healthcare markets.
The LT3757 product line delivers highly flexible, high-voltage current-mode controllers designed specifically for demanding DC/DC conversion in automotive, industrial, and telecom power systems where reliability, topology adaptability, and thermal robustness are essential.
FAQ
What topologies does the LT3757IDD#PBF support?
The LT3757IDD#PBF supports boost, flyback, SEPIC, and inverting converter topologies using a single FBX pin for polarity selection. Its current-mode architecture with slope compensation ensures stable operation across all four configurations without external mode-select logic. The LT3757IDD#PBF achieves this through dual internal references (1.6V for positive outputs, –0.8V for negative), automatically selecting the active error amplifier based on FBX voltage polarity.
How is the switching frequency programmed on the LT3757IDD#PBF?
The LT3757IDD#PBF switching frequency is set using an external resistor from the RT pin to ground, covering 50kHz to 1MHz. Table 1 in the datasheet specifies exact RT values - e.g., 41.2kΩ yields 300kHz. The RT pin must never be left floating. For synchronization, the SYNC pin accepts an external clock; the RT resistor must then be selected for a frequency 20% slower than the SYNC signal to ensure reliable locking.
Can the LT3757IDD#PBF drive a P-channel MOSFET?
No, the LT3757IDD#PBF is designed exclusively to drive external N-channel MOSFETs via its GATE pin, which sources/sinks relative to INTVCC and GND. It lacks high-side gate drive capability or bootstrap circuitry required for P-channel or high-side N-channel configurations. The controller assumes low-side switch placement, as confirmed by the block diagram and typical application schematics showing the MOSFET source tied to ground.
What is the purpose of the exposed pad on the LT3757IDD#PBF DFN package?
The exposed pad (Pin 11) on the LT3757IDD#PBF serves two critical functions: it is the primary thermal conduction path to the PCB ground plane (reducing θJA to 43°C/W), and it acts as the Kelvin return for the SENSE resistor's negative terminal. Per the datasheet, this pad must be soldered directly to a solid copper ground plane - failure to do so compromises both thermal performance and current-sense accuracy.
Does the LT3757IDD#PBF include overvoltage protection?
Yes, the LT3757IDD#PBF includes dual overvoltage protection: FBX overvoltage comparators detect when the feedback voltage exceeds +1.6V by 8% (for positive outputs) or –0.8V by 11% (for negative outputs), triggering immediate MOSFET shutdown via the main RS latch. This protects downstream components during startup overshoot or output short-circuit recovery, independent of the main control loop.
LT3757IDD#PBF Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc.
- Series:
- -
- Package/Case:
- 10-WFDFN Exposed Pad
- Packaging:
- Tube
- Product Status:
- Active
- Output Type:
- Transistor Driver
- Function:
- Step-Up, Step-Up/Step-Down
- Output Configuration:
- Positive and Negative
- Topology:
- Boost, Flyback, SEPIC
- Number of Outputs:
- 1
- Output Phases:
- 1
- Voltage - Supply (Vcc/Vdd):
- 2.9V ~ 40V
- Frequency - Switching:
- 100kHz ~ 1MHz
- 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:
- 10-DFN (3x3)
LT3757IDD#PBF FAQ
1.How can I place an order for LT3757IDD#PBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LT3757IDD#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 LT3757IDD#PBF reliable?
The price and inventory of LT3757IDD#PBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LT3757IDD#PBF is usually 5 days.
3.What payment methods are accepted for LT3757IDD#PBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LT3757IDD#PBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LT3757IDD#PBF?
LT3757IDD#PBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LT3757IDD#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 LT3757IDD#PBF?
For technical support, including LT3757IDD#PBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LT3757IDD#PBF requirements.
6.How does Aetrix verify that LT3757IDD#PBF is sourced from the original manufacturer or authorized distributors?
All LT3757IDD#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 LT3757IDD#PBF meets industry standards.
7.What is the process for return or replacement of LT3757IDD#PBF?
All LT3757IDD#PBF units undergo pre-shipment inspection (PSI). If there is an issue with LT3757IDD#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 LT3757IDD#PBF part is unused and in its original packaging.
Return procedure for LT3757IDD#PBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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