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Analog Devices Inc. LT3957AEUHE#PBF
- Part No.:
- LT3957AEUHE#PBF
- Manufacturer:
- Analog Devices Inc.
- Package:
- 36-WFQFN, 28 Leads, Exposed Pad
- Datasheet:
-
LT3957AEUHE#PBF.pdf
- Description:
- IC REG BOOST CUK ADJ 5A 36QFN
- Quantity:
- Payment:
- Shipping:
Inventory:183
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Product details
Overview
LT3957AEUHE#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, supporting boost, flyback, SEPIC, and inverting topologies. It delivers ±1.6V/–0.8V feedback regulation, programmable 100kHz–1MHz switching frequency, and <1μA shutdown current - ideal for automotive battery-supplied 12V-to-24V boost converters and industrial isolated power supplies.
For engineers reviewing the LT3957AEUHE#PBF datasheet, LT3957AEUHE#PBF pinout, LT3957AEUHE#PBF application, or LT3957AEUHE#PBF equivalent, this page provides verified package mapping (36-lead 5mm × 6mm QFN), confirmed pin functions (SW, FBX, RT, SS, EN/UVLO), thermal performance data (θJC = 3°C/W), and real-world design constraints including minimum on-time (240ns), current limit (5.9A typ), and INTVCC LDO bypassing requirements.
Technical Context
The LT3957AEUHE#PBF implements fixed-frequency current-mode control with dual error amplifiers enabling seamless positive/negative output voltage regulation via a single FBX pin. Its internal 5.2V LDO powers the gate driver and logic, while SENSE1/SENSE2 pins enable Kelvin-sense current measurement across an internal 27mΩ RDS(on) switch.
Frequency programming uses RT-to-SGND resistor selection (e.g., 41.2kΩ sets 300kHz), and synchronization is supported via the SYNC pin with 20% slower RT-programmed frequency. Soft-start is implemented through VC-clamping controlled by the SS pin's 10μA pull-up current and external CSS capacitor.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| VIN Range | 3V to 40V - supports direct connection to automotive battery (9V–16V) and industrial 24V rails without pre-regulation. |
| Internal Switch | 5A/40V N-MOSFET with 27mΩ RDS(on) at 25°C - eliminates external high-side switch in boost/flyback designs. |
| FBX Regulation | +1.6V (positive VOUT) or –0.8V (negative VOUT) - enables single-resistor-divider programming for both polarities. |
| Switching Frequency | 100kHz–1MHz (RT-programmable) - balances efficiency (lower fSW) vs. size (higher fSW) in space-constrained layouts. |
| Shutdown IQ | <1μA - extends runtime in battery-backed systems during deep sleep or fault lockout. |
| INTVCC LDO | 5.2V output, 95mA max current - powers internal gate driver; can be bypassed by external ≥5.5V supply to reduce dissipation. |
| Min On/Off Time | 240ns / 275ns - constrains maximum duty cycle and minimum input-output ratio in high-VIN/VOUT applications. |
Pinout & Package
LT3957AEUHE#PBF is housed in a thermally enhanced 36-lead plastic QFN package (5mm × 6mm), with exposed pads for SW (Pin 38) and SGND (Pin 37) requiring direct soldering to respective PCB copper planes per datasheet layout guidelines.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| SW (Pins 8, 9, 20, 21, 38) | Drain of internal N-MOSFET | High-current switching node; must connect exposed pad (Pin 38) directly to SW copper pour for thermal and EMI control. |
| FBX (Pin 31) | Positive/negative feedback input | Sets output voltage polarity and level; also triggers frequency foldback during startup or overload. |
| RT (Pin 33) | Frequency programming input | Resistor-to-SGND sets switching frequency; open-circuit disables operation. |
| SS (Pin 32) | Soft-start control | 10μA pull-up charges external capacitor; discharge resets soft-start during UVLO or thermal fault. |
| EN/UVLO (Pin 25) | Enable and input undervoltage detection | 1.22V falling threshold with programmable hysteresis; <0.4V forces shutdown and reduces IQ to <1μA. |
| SENSE1 (Pin 6) & SENSE2 (Pin 3) | Current sense interface | Forms Kelvin-sense path across internal RSENSE; requires low-pass filter for noise immunity in high-dI/dt environments. |
| INTVCC (Pin 28) | Internal LDO output | Must be bypassed with ≥4.7μF ceramic cap to SGND; can be tied to VIN if VIN ≤ 8V or to external ≥5.5V rail to disable LDO. |
| GND (Pins 12–17) | Power ground return | Connects to source of internal MOSFET; must remain separate from SGND externally to preserve current-sense accuracy. |
Key Features
| Feature | Design Value |
|---|---|
| Single FBX pin for ±VOUT | Eliminates topology-specific IC variants - one part supports boost (VOUT > VIN), inverting (VOUT < 0), and SEPIC (isolated VOUT) without redesign. |
| Programmable UVLO with hysteresis | EN/UVLO pin allows precise turn-on/off thresholds (e.g., 10V–12V window) using two external resistors - prevents brownout oscillation in automotive systems. |
| Frequency foldback | Reduces switching frequency when FBX approaches SGND during startup or short-circuit - maintains current limit compliance without external protection circuitry. |
| Thermally enhanced QFN | θJC = 3°C/W enables >3W continuous power dissipation with minimal heatsinking - critical for high-current boost converters in enclosed enclosures. |
| Low-noise current sensing | Separate SENSE1/SENSE2 pins with internal Kelvin routing reject PCB trace resistance errors - ensures accurate current limiting across temperature (-40°C to 125°C). |
Applications
| Automotive LED Headlamp Driver | Industrial Isolated Sensor Supply |
|---|---|
Use Scenario: Driving high-brightness white LEDs from 12V vehicle battery with dimming control and short-circuit protection. IC Role / Device Role / Timing Role: Boost controller generating regulated 48V output; FBX senses LED current via shunt; RT sets 400kHz for compact magnetics. Use Value: Integrated 5A switch eliminates external FET and driver; <1μA shutdown IQ preserves battery during parking mode; thermal QFN sustains 85°C ambient. |
Use Scenario: Providing isolated ±15V bias for analog front-end op-amps in factory automation I/O modules. IC Role / Device Role / Timing Role: Flyback controller with transformer-coupled secondary; FBX referenced to isolated -15V rail; SYNC locked to system clock for EMI reduction. Use Value: Dual-error-amplifier architecture enables stable negative output regulation; SENSE1/SENSE2 rejects common-mode noise from motor drives; 40V abs max rating withstands load dump transients. |
| Telecom 48V Backup Power Converter | Medical Portable Imaging Power |
Use Scenario: Generating 56V intermediate bus from 48V telecom rectifier during AC failure, powering PoE switches and baseband processors. IC Role / Device Role / Timing Role: Boost controller operating at 250kHz (RT = 63.4kΩ); EN/UVLO configured for 43V–47V hysteresis to avoid false turn-off during line sag. Use Value: 40V VIN rating tolerates 48V nominal + 20% surge; 5.2V INTVCC LDO powers gate driver without external bias; GND/SGND separation ensures clean ADC reference. |
Use Scenario: Powering CCD/CMOS image sensors and analog signal chains in handheld ultrasound devices with Li-ion battery input (3.0–4.2V). IC Role / Device Role / Timing Role: Inverting converter generating -5V from 3.3V rail; SS capacitor set for 10ms ramp to prevent sensor reset glitches; FBX regulates negative output with 1% tolerance. Use Value: 3V minimum VIN enables full operation down to battery end-of-discharge; <1μA shutdown IQ extends device runtime between charges; QFN package fits tight 8mm × 8mm board area. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar DC/DC controller applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| LT3957IUHE#PBF | Same silicon, rated for –40°C to 125°C junction temperature (vs. LT3957AEUHE#PBF's 0°C to 125°C guaranteed range). | Required for extended-temperature industrial or under-hood automotive use where cold-start performance below 0°C is critical. | Select LT3957IUHE#PBF when full –40°C operation must be production-guaranteed; LT3957AEUHE#PBF is sufficient for commercial/industrial ambient ranges. |
| LT3757EUHE#PBF | Legacy predecessor with identical pinout but higher 2.5mA operating IQ, no frequency foldback, and no improved transient response. | Lacks soft-start robustness during short-circuit recovery; unsuitable for safety-critical medical or high-reliability telecom systems. | Choose LT3957AEUHE#PBF over LT3757EUHE#PBF when low IQ, fast load transient recovery, or frequency foldback is required. |
Compared with LT3957IUHE#PBF, the LT3957AEUHE#PBF offers lower cost and adequate temperature margin for most industrial controls, while LT3757EUHE#PBF lacks key reliability features like foldback and optimized transient response - making LT3957AEUHE#PBF the preferred choice for new designs requiring robust startup and fault handling.
Availability
LT3957AEUHE#PBF is available at Aetrix Electronics and suitable for automotive lighting, industrial power conversion, and telecom backup systems requiring stable component supply, long-term lifecycle support, and RoHS-compliant packaging.
Supply support for LT3957AEUHE#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 its high-performance power management portfolio with rigorous qualification and long-term product support.
The LT3957A product line delivers integrated high-current DC/DC controllers for demanding applications including automotive, industrial, and medical power systems where reliability, thermal performance, and topology flexibility are critical.
FAQ
What is the absolute maximum voltage rating for the SW pin on the LT3957AEUHE#PBF?
The SW pin of the LT3957AEUHE#PBF has an absolute maximum rating of 40V, matching the internal N-MOSFET drain-source breakdown voltage. Exceeding this voltage risks permanent damage to the integrated switch, especially during inductive kickback in boost or flyback configurations. Layout best practices require minimizing SW loop area and using snubbers when driving highly inductive loads.
Can the LT3957AEUHE#PBF generate a negative output voltage, and how is it configured?
Yes, the LT3957AEUHE#PBF supports negative output voltages via inverting converter topology. Configuration requires connecting the FBX pin to a resistor divider from VOUT (negative rail) to SGND, which pulls FBX to –0.8V. This activates comparator A2 for non-inverting amplification to the VC pin, enabling stable regulation. The datasheet Figure 1 shows the exact component connections for this mode.
What is the purpose of the SENSE1 and SENSE2 pins on the LT3957AEUHE#PBF, and why are they separated?
The SENSE1 and SENSE2 pins on the LT3957AEUHE#PBF form a Kelvin current-sense interface across the internal MOSFET's sense resistor. SENSE1 connects to the MOSFET source side, SENSE2 to the load side - separating high-current power paths from precision analog sensing. This prevents PCB trace resistance from corrupting current-limit accuracy, ensuring consistent 5A switch protection across temperature and board variations.
How does the LT3957AEUHE#PBF handle startup into a pre-biased output?
The LT3957AEUHE#PBF does not support true pre-biased startup. During initial power-up, the SS pin initiates soft-start by clamping the VC pin, forcing gradual output voltage ramp. If VOUT is already biased, the FBX pin detects overvoltage and triggers frequency foldback or shutdown depending on magnitude. For pre-biased applications, external sequencing or diode isolation is required before the LT3957AEUHE#PBF output stage.
What are the thermal design requirements for the LT3957AEUHE#PBF in a 5A continuous boost application?
For 5A continuous operation, the LT3957AEUHE#PBF requires the exposed SW (Pin 38) and SGND (Pin 37) pads to be soldered to ≥250mm² internal or external copper planes. With θJC = 3°C/W and typical 2.5W dissipation at 40VIN/24VOUT/500kHz, a 4-layer board with 2oz copper and thermal vias achieves ≤65°C junction rise above ambient - staying within the 125°C max rating. Thermal simulation is recommended for enclosure-limited airflow.
LT3957AEUHE#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)
LT3957AEUHE#PBF FAQ
1.How can I place an order for LT3957AEUHE#PBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LT3957AEUHE#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 LT3957AEUHE#PBF reliable?
The price and inventory of LT3957AEUHE#PBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LT3957AEUHE#PBF is usually 5 days.
3.What payment methods are accepted for LT3957AEUHE#PBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LT3957AEUHE#PBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LT3957AEUHE#PBF?
LT3957AEUHE#PBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LT3957AEUHE#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 LT3957AEUHE#PBF?
For technical support, including LT3957AEUHE#PBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LT3957AEUHE#PBF requirements.
6.How does Aetrix verify that LT3957AEUHE#PBF is sourced from the original manufacturer or authorized distributors?
All LT3957AEUHE#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 LT3957AEUHE#PBF meets industry standards.
7.What is the process for return or replacement of LT3957AEUHE#PBF?
All LT3957AEUHE#PBF units undergo pre-shipment inspection (PSI). If there is an issue with LT3957AEUHE#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 LT3957AEUHE#PBF part is unused and in its original packaging.
Return procedure for LT3957AEUHE#PBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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