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Analog Devices Inc. LT3957AIUHE#PBF
- Part No.:
- LT3957AIUHE#PBF
- Manufacturer:
- Analog Devices Inc.
- Package:
- 36-WFQFN, 28 Leads, Exposed Pad
- Datasheet:
-
LT3957AIUHE#PBF.pdf
- Description:
- IC REG BOOST CUK ADJ 5A 36QFN
- Quantity:
- Payment:
- Shipping:
Inventory:356
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Product details
Overview
LT3957AIUHE#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 operates from 3V to 40V input. Used in automotive LED drivers and industrial power supplies requiring high-side switch control and negative output capability.
For engineers reviewing the LT3957AIUHE#PBF datasheet, LT3957AIUHE#PBF pinout, LT3957AIUHE#PBF application, or LT3957AIUHE#PBF equivalent, key selection criteria include its dual-polarity feedback architecture, internal LDO for gate drive, 1μA shutdown current, thermal shutdown at 165°C, and QFN-36 (5mm × 6mm) package with exposed SW and SGND pads for enhanced thermal performance.
Technical Context
The LT3957AIUHE#PBF implements fixed-frequency current-mode control with slope compensation, enabling stable operation across wide VIN (3V–40V) and VOUT ranges. Its dual-comparator feedback architecture (A1 for positive, A2 for negative configurations) allows single-pin FBX to regulate either polarity output voltage with 1.569V/–0.816V reference thresholds.
It integrates a 5.2V LDO regulator (INTVCC) with 2.7V UVLO, programmable EN/UVLO hysteresis via external resistor divider, and frequency foldback triggered by low FBX voltage during startup or overload-preventing current runaway when minimum on-time limits duty cycle.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Input Voltage Range | 3V to 40V - supports 12V/24V automotive and industrial rails without pre-regulation. |
| Internal Switch Rating | 5A continuous, 40V drain-source - enables high-current boost/flyback designs without external FET. |
| Feedback Reference | +1.569V / –0.816V - precise dual-polarity regulation for positive or negative output configurations. |
| Switching Frequency | 100kHz to 1MHz (RT-programmable) - balances efficiency vs. size; 300kHz typical with 41.2kΩ RT. |
| Shutdown Current | <1μA - extends battery life in always-on systems with periodic wake-up. |
| Thermal Shutdown | 165°C with hysteresis - protects against sustained overload or poor PCB thermal design. |
| INTVCC Regulator | 5.2V LDO, 95mA max - powers internal gate driver; bypassed with ≥4.7μF ceramic to SGND. |
Pinout & Package
LT3957AIUHE#PBF uses a thermally enhanced 36-lead QFN package (5mm × 6mm) with two exposed pads: Pin 37 (SGND) and Pin 38 (SW), both requiring solder connection to respective PCB planes for thermal and electrical integrity.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| SENSE1 (6), SENSE2 (3) | Current sense interface | Forms Kelvin-sensed current path across internal RSENSE; SENSE1 is MOSFET source output, SENSE2 is comparator input - must be connected via RC filter for noise immunity. |
| SW (8,9,20,21,38) | Power switch drain | High-current output node tied to external inductor/diode; exposed pad (38) must connect directly to SW copper pour for thermal relief. |
| FBX (31) | Feedback and frequency modulation | Single pin accepts positive or negative feedback voltage; also modulates switching frequency during fault conditions via foldback. |
| EN/UVLO (25) | Enable and input undervoltage lockout | 1.22V falling threshold with user-programmable hysteresis; resets soft-start on undervoltage event. |
| SS (32) | Soft-start control | 10μA pull-up to 2.5V rail; external capacitor sets ramp time - prevents inrush current and inductor saturation at startup. |
| RT (33) | Frequency programming | Resistor to SGND sets operating frequency; 41.2kΩ yields ~300kHz - critical for EMI compliance and thermal management. |
| INTVCC (28) | Internal LDO output | 5.2V supply for gate driver and logic; requires ≥4.7μF ceramic cap to SGND; can be bypassed to external VOUT or VIN if needed. |
Key Features
| Feature | Design Value |
|---|---|
| Dual-polarity feedback architecture | Enables single-part support for both positive (boost/SEPIC) and negative (inverting) outputs using same FBX pin and reference voltages. |
| Programmable frequency foldback | Reduces switching frequency below 100kHz when FBX approaches SGND - prevents current runaway during short-circuit or low-VOUT startup. |
| Integrated 5.2V LDO with UVLO | Provides regulated gate drive independent of VIN; 2.7V INTVCC UVLO ensures sufficient gate voltage before enabling switch conduction. |
| Thermally optimized QFN-36 | Exposed SW and SGND pads enable direct thermal coupling to PCB copper - reduces θJA to 42°C/W for high-power operation. |
| Low shutdown IQ & precision EN/UVLO | <1μA shutdown current plus 20mV hysteresis on 1.22V threshold - enables robust brown-in/brown-out behavior in battery-powered systems. |
Applications
| Automotive LED Headlamp Driver | Industrial Negative Bias Supply |
|---|---|
Use Scenario: Driving high-brightness LEDs in vehicle headlamps with 12V–42V battery input range and EMI-sensitive environment. IC Role / Device Role / Timing Role: Controller IC implementing boost topology with constant-current regulation via SENSE1/SENSE2 current sensing and FBX feedback. Use Value: Integrated 5A/40V switch eliminates external FET; programmable frequency avoids AM radio band; 1μA shutdown preserves battery during ignition-off. |
Use Scenario: Generating –12V bias for op-amp rails or analog front-ends in factory automation PLCs with noisy 24V DC bus. IC Role / Device Role / Timing Role: Inverting converter controller using FBX to regulate negative output; INTVCC powered from VOUT via diode for efficiency. Use Value: Dual-reference feedback (–0.816V) enables accurate negative regulation; thermal shutdown protects against field wiring faults. |
| Telecom 48V Boost Converter | Medical Isolated Flyback Power |
Use Scenario: Stepping up 36V–57V telecom rectified input to 48V system rail in distributed power architecture. IC Role / Device Role / Timing Role: Boost controller with synchronous rectification support; RT pin set to 200kHz for optimal core loss vs. size tradeoff. Use Value: Wide 3V–40V input accommodates full telecom range; current-mode control ensures fast load transient response to burst-mode traffic loads. |
Use Scenario: Providing isolated ±15V auxiliary rails for analog signal conditioning in patient-connected diagnostic equipment. IC Role / Device Role / Timing Role: Flyback controller with optocoupler feedback referenced to secondary side; FBX configured for positive output with 1.569V reference. Use Value: Internal 40V switch withstands reflected flyback spikes; soft-start prevents transformer saturation during cold start; 125°C junction rating supports sealed enclosure operation. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar DC/DC controller applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| LTC3789EUF#PBF | Requires external high-side MOSFET; no integrated switch; supports 4V–36V input; dual-output capable. | Better suited for multi-rail systems needing independent voltage tracking; lacks negative output capability. | Select when higher efficiency >95% is required at >5A load or when layout flexibility justifies external FET. |
| LT8330EDD#PBF | Integrated 1.5A/140V switch; fixed 2MHz frequency; no frequency foldback; smaller 10-lead DFN package. | Optimized for compact isolated flyback or boost with high VIN; unsuitable for >3A loads or programmable frequency needs. | Select for space-constrained 12V–48V input applications where 1.5A output suffices and EMI filtering favors higher frequency. |
Compared with LT3957AIUHE#PBF, LTC3789EUF#PBF offers greater design flexibility but increases BOM count and layout complexity, while LT8330EDD#PBF trades current capability and configurability for size and high-frequency operation - making LT3957AIUHE#PBF optimal for mid-power, dual-polarity, thermally demanding applications.
Availability
LT3957AIUHE#PBF is available at Aetrix Electronics and suitable for automotive lighting, industrial power supplies, and telecom infrastructure requiring stable component supply, extended temperature operation (–40°C to 125°C), and long-term lifecycle continuity.
Supply support for LT3957AIUHE#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 legacy of high-performance analog and power management ICs with rigorous qualification and reliability testing.
The LT3957A product line was designed for high-efficiency, wide-input DC/DC conversion in harsh environments - targeting automotive, industrial, and telecom applications where integrated power switches, thermal resilience, and dual-polarity output capability are critical.
FAQ
What is the maximum output current achievable with LT3957AIUHE#PBF in boost configuration?
The LT3957AIUHE#PBF integrates a 5A/40V N-channel MOSFET with typical on-resistance of 27.6mΩ at 25°C. In boost topology, maximum continuous output current depends on input voltage, output voltage, efficiency, and thermal design. At VIN = 12V, VOUT = 24V, and 300kHz switching, practical output current is ~3A with proper heatsinking. The LT3957AIUHE#PBF current limit is 5.9A typical, but thermal derating applies above 85°C ambient.
Can LT3957AIUHE#PBF generate a negative output voltage?
Yes, the LT3957AIUHE#PBF supports negative output generation in inverting converter configuration. It uses the same FBX pin with a –0.816V internal reference voltage. A resistor divider from VOUT to SGND pulls FBX to –0.8V, activating comparator A2 for non-inverting amplification to VC. The LT3957AIUHE#PBF datasheet includes verified inverting application circuits with efficiency curves and startup waveforms.
How does the frequency foldback function operate in LT3957AIUHE#PBF?
When FBX voltage drops near SGND during startup or output short-circuit, the LT3957AIUHE#PBF automatically reduces switching frequency below the RT-set value - down to ~50kHz - to maintain peak switch current within the 5.9A limit. This occurs because minimum on-time prevents further duty-cycle reduction at high frequencies. Foldback disables SYNC input to avoid interference and resumes normal frequency once FBX recovers.
What is the recommended capacitor for the SS pin on LT3957AIUHE#PBF?
A ceramic capacitor from SS (Pin 32) to SGND sets soft-start duration per TSS = CSS × 1.25V / 10μA. For a 10ms soft-start, use 80nF (e.g., 100nF standard value). Larger values extend ramp time to limit inrush; smaller values risk overshoot. The LT3957AIUHE#PBF SS pin discharges fully during EN/UVLO undervoltage, INTVCC UVLO, or thermal lockout - ensuring repeatable startup behavior.
Is LT3957AIUHE#PBF pin-compatible with LT3957EUHE#PBF?
No, LT3957AIUHE#PBF is not pin-compatible with LT3957EUHE#PBF. Both share the same QFN-36 package and pinout, but the 'I' grade (LT3957AIUHE#PBF) is specified over –40°C to 125°C junction temperature with guaranteed performance, while the 'E' grade (LT3957EUHE#PBF) is characterized from 0°C to 125°C. Electrical parameters like FBX regulation voltage and current limit have tighter min/max bounds for the 'I' grade, and mixing grades may cause marginal operation in cold environments.
LT3957AIUHE#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)
LT3957AIUHE#PBF FAQ
1.How can I place an order for LT3957AIUHE#PBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LT3957AIUHE#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 LT3957AIUHE#PBF reliable?
The price and inventory of LT3957AIUHE#PBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LT3957AIUHE#PBF is usually 5 days.
3.What payment methods are accepted for LT3957AIUHE#PBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LT3957AIUHE#PBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LT3957AIUHE#PBF?
LT3957AIUHE#PBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LT3957AIUHE#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 LT3957AIUHE#PBF?
For technical support, including LT3957AIUHE#PBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LT3957AIUHE#PBF requirements.
6.How does Aetrix verify that LT3957AIUHE#PBF is sourced from the original manufacturer or authorized distributors?
All LT3957AIUHE#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 LT3957AIUHE#PBF meets industry standards.
7.What is the process for return or replacement of LT3957AIUHE#PBF?
All LT3957AIUHE#PBF units undergo pre-shipment inspection (PSI). If there is an issue with LT3957AIUHE#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 LT3957AIUHE#PBF part is unused and in its original packaging.
Return procedure for LT3957AIUHE#PBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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