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Analog Devices Inc. LT3957EUHE#PBF
- Part No.:
- LT3957EUHE#PBF
- Manufacturer:
- Analog Devices Inc.
- Package:
- 36-WFQFN, 28 Leads, Exposed Pad
- Datasheet:
-
LT3957EUHE#PBF.pdf
- Description:
- IC REG BOOST CUK ADJ 5A 36QFN
- Quantity:
- Payment:
- Shipping:
Inventory:470
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Product details
Overview
LT3957EUHE#PBF from Analog Devices (formerly Linear Technology) is a wide-input, current-mode DC/DC controller IC with an integrated 5A/40V N-channel power MOSFET. It supports boost, flyback, SEPIC, and inverting topologies, delivers ±1.6V/–0.8V feedback reference accuracy, operates from 3V to 40V input, and features programmable 100kHz–1MHz switching frequency. It is used in automotive infotainment power supplies requiring high efficiency and negative rail generation.
For engineers reviewing the LT3957EUHE#PBF datasheet, LT3957EUHE#PBF pinout, LT3957EUHE#PBF application, or LT3957EUHE#PBF equivalent, key selection considerations include its dual-polarity feedback capability, internal 5.2V LDO for gate drive, 5A switch current limit, thermal shutdown at 165°C, and QFN-36 (5mm × 6mm) package with exposed SW and SGND pads for enhanced thermal performance.
Technical Context
The LT3957EUHE#PBF implements fixed-frequency current-mode control with slope compensation, enabling stable operation across wide VIN (3V–40V) and VOUT ranges. Its dual-reference FBX pin (1.6V for positive outputs, –0.8V for negative outputs) allows single-pin configuration of both polarity modes without external logic.
It integrates a 5.2V LDO regulator for internal gate drive and logic, with UVLO (2.7V) and programmable EN/UVLO hysteresis. Frequency is set via RT-to-SGND resistor or synchronized externally via SYNC pin, with foldback activated when FBX approaches SGND during startup or overload.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Input Voltage Range | 3V to 40V - supports 12V automotive battery systems with cold-crank margin and industrial 24V rails. |
| Internal Power Switch | 5A/40V N-channel MOSFET - eliminates external high-side switch in SEPIC/flyback designs; RDS(on) ~27mΩ at 25°C. |
| Feedback Reference | +1.6V / –0.8V - enables precise regulation of both positive and negative output voltages using one FBX pin. |
| Switching Frequency | 100kHz to 1MHz - adjustable via RT resistor; allows trade-off between efficiency (lower fSW) and component size (higher fSW). |
| Shutdown Current | <1μA - enables ultra-low-power sleep mode in battery-backed telecom or portable systems. |
| Thermal Protection | 165°C junction lockout - prevents damage during sustained overload or poor PCB thermal design. |
| Package | 36-lead QFN (5mm × 6mm) with exposed SW and SGND pads - provides low θJA = 42°C/W for high-current operation. |
Pinout & Package
LT3957EUHE#PBF uses a thermally enhanced 36-lead plastic QFN package (5mm × 6mm) with two exposed pads: Pin 37 (SGND) and Pin 38 (SW), both requiring solder connection to respective PCB copper planes.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| SENSE1 (Pin 6) | Current sense output | Connects directly to SENSE2 to close internal current-sense loop; Kelvin-connected to GND via internal sense resistor. |
| SENSE2 (Pin 3) | Current sense input | Receives filtered current-sense voltage; triggers 48mV overcurrent shutdown if exceeded. |
| FBX (Pin 31) | Feedback input | Dual-reference pin: regulates to +1.6V for positive outputs, –0.8V for negative outputs; also modulates frequency during fault conditions. |
| RT (Pin 33) | Frequency programming | Resistor to SGND sets switching frequency (e.g., 41.2kΩ → 300kHz); must not be left floating. |
| SYNC (Pin 34) | External clock input | Accepts digital clock signal; requires RT setting 20% slower than SYNC frequency to avoid jitter or loss of sync. |
| SS (Pin 32) | Soft-start control | 10μA pull-up to 2.5V rail; capacitor to SGND sets soft-start time; discharged during UVLO/thermal faults to reinitiate ramp. |
| EN/UVLO (Pin 25) | Enable & undervoltage detection | 1.22V falling threshold with programmable hysteresis; resets soft-start on undervoltage; <0.4V disables IC and reduces IQ to <1μA. |
| INTVCC (Pin 28) | Internal LDO output | 5.2V regulated supply for gate driver and logic; bypassed with ≥4.7μF ceramic cap to SGND; can be tied to VIN if VIN < 8V. |
| SW (Pins 8,9,20,21,38) | Power switch drain | High-current drain node of internal 5A MOSFET; exposed pad (Pin 38) must be soldered to SW plane for thermal and electrical integrity. |
| GND (Pins 12–17) | Power ground | Source terminal connection for internal MOSFET; internally connected to SGND for Kelvin sensing-do not tie externally to SGND. |
| SGND (Pins 4,23,24,37) | Signal ground | Reference for all small-signal pins (FBX, VC, SS, RT); exposed pad (Pin 37) must be soldered to SGND plane; isolated from GND externally. |
Key Features
| Feature | Design Value |
|---|---|
| Single FBX pin for ±VOUT regulation | Eliminates need for external polarity-select logic or dual-error amplifiers in bipolar power supplies. |
| Programmable EN/UVLO with hysteresis | Enables precise brown-in/brown-out thresholds (e.g., 9V turn-on / 7.5V turn-off) using two external resistors. |
| Frequency foldback during low FBX | Reduces switching frequency automatically during startup or short-circuit to prevent current runaway and inductor saturation. |
| Internal 5.2V LDO with bypass option | Reduces external BOM count; INTVCC can be powered from VOUT (via diode) or VIN to improve efficiency in high-frequency/high-VIN applications. |
| Thermally enhanced QFN with dual exposed pads | Enables >3W continuous power dissipation in compact layout; SW and SGND pads support independent thermal management paths. |
Applications
| Automotive Infotainment Supply | Industrial Isolated Bias Rail |
|---|---|
Use Scenario: Generating ±12V rails from 12V vehicle battery for audio amplifiers and ADC/DAC interfaces under cold-crank (4.5V) and load-dump (40V) conditions. IC Role / Device Role / Timing Role: Configured as inverting converter for –12V and boost for +12V; FBX pin switches polarity via resistor divider; current-mode control ensures fast transient response to speaker load steps. Use Value: Single IC replaces dual controllers; 5A switch handles peak amplifier currents; 1μA shutdown extends battery life during vehicle sleep mode. | Use Scenario: Providing isolated ±5V bias for RS-485 transceivers and isolated gate drivers in factory automation PLC modules. IC Role / Device Role / Timing Role: Operated as flyback converter with optocoupler feedback; FBX referenced to secondary-side SGND; SYNC pin synchronized to system clock to reduce EMI in noise-sensitive environments. Use Value: Eliminates need for external MOSFET and gate driver; programmable UVLO prevents false triggering during line sags; thermal shutdown protects against enclosure overheating. |
| Telecom DC-DC Intermediate Bus | Medical Imaging Sensor Bias |
Use Scenario: Stepping up 3.3V or 5V intermediate bus to 24V for optical transceiver lasers in access network equipment. IC Role / Device Role / Timing Role: Boost topology with 500kHz switching (RT = 24.3kΩ); soft-start limits inrush into large laser bias capacitors; frequency foldback prevents current overshoot during laser turn-on transients. Use Value: High efficiency (>92% at 600mA) minimizes heat in sealed chassis; 3V minimum input supports deep discharge backup batteries. | Use Scenario: Generating low-noise –3.3V bias for CMOS image sensor analog front-ends in portable ultrasound devices. IC Role / Device Role / Timing Role: Inverting converter with LC filtering on output; FBX referenced to sensor ground; VC compensation optimized for low-output-impedance and <10μVRMS ripple. Use Value: Dual-reference precision (±0.5% FBX tolerance) ensures stable sensor bias; 125°C max junction rating supports operation inside thermally constrained handheld enclosures. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar DC/DC controller applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| LT3757EUHE#PBF | Same pinout and topology support, but lacks internal 5A switch - requires external MOSFET; higher IQ (2.5mA vs 1.7mA typical). | Suitable for higher-voltage (>40V) or higher-current (>5A) designs where external FET selection is needed. | Choose LT3757EUHE#PBF only when internal switch limitations (voltage, current, or RDS(on)) are insufficient for the target application. |
| TPS40210DRCT | Fixed 1.25V FB reference only; no negative output support; no integrated switch; 40V max VIN; 2.5A max external FET drive. | Designed for cost-sensitive boost-only applications without polarity flexibility or integrated power stage. | Select TPS40210DRCT when budget constraints outweigh need for dual-polarity output or integrated switch robustness. |
Compared with LT3957EUHE#PBF, LT3757EUHE#PBF offers greater voltage/current scalability at the cost of added BOM and layout complexity, while TPS40210DRCT provides lower system cost in single-rail boost applications but lacks the LT3957EUHE#PBF's polarity flexibility, integrated switch, and automotive-grade thermal performance.
Availability
LT3957EUHE#PBF is available at Aetrix Electronics and suitable for automotive infotainment power supplies, industrial isolated bias rails, and telecom intermediate bus converters requiring stable component supply, long-term lifecycle assurance, and AEC-Q200-aligned reliability.
Supply support for LT3957EUHE#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 leader in high-performance analog, mixed-signal, and digital signal processing semiconductors, formed through the acquisition of Linear Technology in 2017.
The LT3957EUHE#PBF belongs to ADI's Power by Linear™ portfolio of high-efficiency DC/DC controllers, designed specifically for demanding industrial, automotive, and telecom power conversion applications requiring wide input range, high integration, and robust protection features.
FAQ
What is the maximum recommended output current for LT3957EUHE#PBF in boost configuration?
The LT3957EUHE#PBF internal 5A/40V MOSFET supports peak switch currents up to 5.9A (typical) and 6.8A (max). For reliable continuous operation in boost topology, design peak inductor current to remain ≤4.5A - allowing 10% margin below the 5A minimum current limit. Output current depends on topology, duty cycle, and efficiency; at 12V input to 24V output with 90% efficiency, LT3957EUHE#PBF supports ~2.2A continuous output current.
Can LT3957EUHE#PBF generate a negative output voltage without additional op-amps or level shifters?
Yes. The LT3957EUHE#PBF natively supports negative output generation using its dual-reference FBX pin. When configured as an inverting converter, the FBX pin regulates to –0.8V (not +1.6V), enabling direct feedback from the negative rail via a standard resistor divider to SGND. No external op-amps, level shifters, or polarity-reversal circuitry are required - the LT3957EUHE#PBF handles both polarities internally.
How does the LT3957EUHE#PBF handle thermal overload, and what happens to the output during shutdown?
The LT3957EUHE#PBF incorporates a thermal lockout circuit that disables switching when junction temperature exceeds 165°C. During thermal shutdown, the internal MOSFET turns off, FBX is released, and the SS pin is discharged to SGND - halting all regulation. Once temperature falls below ~155°C (10°C hysteresis), the LT3957EUHE#PBF automatically initiates soft-start. Output voltage drops to zero during shutdown and ramps up cleanly upon recovery.
Is the LT3957EUHE#PBF compatible with lead-free PCB assembly processes?
Yes. The LT3957EUHE#PBF carries the #PBF suffix, indicating it is lead-free and RoHS-compliant. It is qualified for standard Pb-free reflow profiles (J-STD-020D), with a maximum peak temperature of 260°C. The 36-lead QFN package uses matte tin plating and is rated for MSL-3 moisture sensitivity, requiring bake-out only if exposed to ambient >30°C/60% RH for >168 hours.
What is the purpose of the dual exposed pads (Pin 37 SGND and Pin 38 SW) on the LT3957EUHE#PBF package?
Pin 37 (SGND) and Pin 38 (SW) are thermally and electrically critical exposed pads on the LT3957EUHE#PBF QFN package. Pin 37 must be soldered to the PCB's signal ground plane to ensure low-impedance return for all small-signal pins (FBX, VC, SS, RT). Pin 38 must be soldered to the high-current SW net - typically a dedicated copper pour - to conduct the 5A switch current and dissipate heat. Separating these pads prevents ground bounce and improves thermal resistance (θJC = 3°C/W).
LT3957EUHE#PBF Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc.
- Series:
- -
- Package/Case:
- 36-WFQFN, 28 Leads, Exposed Pad
- Packaging:
- Tube
- Product Status:
- Active
- Function:
- Step-Up, Step-Up/Step-Down
- Output Configuration:
- Positive or Negative
- Topology:
- Boost, Cuk, Flyback, SEPIC
- Output Type:
- Adjustable
- Number of Outputs:
- 1
- Voltage - Input (Min):
- 3V
- Voltage - Input (Max):
- 40V
- Voltage - Output (Min/Fixed):
- 1.6V
- Voltage - Output (Max):
- 40V (Switch)
- Current - Output:
- 5A (Switch)
- Frequency - Switching:
- 100kHz ~ 1MHz
- Synchronous Rectifier:
- No
- Operating Temperature:
- -40°C ~ 125°C (TJ)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 36-QFN (5x6)
LT3957EUHE#PBF FAQ
1.How can I place an order for LT3957EUHE#PBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LT3957EUHE#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 LT3957EUHE#PBF reliable?
The price and inventory of LT3957EUHE#PBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LT3957EUHE#PBF is usually 5 days.
3.What payment methods are accepted for LT3957EUHE#PBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LT3957EUHE#PBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LT3957EUHE#PBF?
LT3957EUHE#PBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LT3957EUHE#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 LT3957EUHE#PBF?
For technical support, including LT3957EUHE#PBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LT3957EUHE#PBF requirements.
6.How does Aetrix verify that LT3957EUHE#PBF is sourced from the original manufacturer or authorized distributors?
All LT3957EUHE#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 LT3957EUHE#PBF meets industry standards.
7.What is the process for return or replacement of LT3957EUHE#PBF?
All LT3957EUHE#PBF units undergo pre-shipment inspection (PSI). If there is an issue with LT3957EUHE#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 LT3957EUHE#PBF part is unused and in its original packaging.
Return procedure for LT3957EUHE#PBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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