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Analog Devices Inc. LT3957IUHE#PBF
- Part No.:
- LT3957IUHE#PBF
- Manufacturer:
- Analog Devices Inc.
- Package:
- 36-WFQFN, 28 Leads, Exposed Pad
- Datasheet:
-
LT3957IUHE#PBF.pdf
- Description:
- IC REG BOOST CUK ADJ 5A 36QFN
- Quantity:
- Payment:
- Shipping:
Inventory:2,817
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Product details
Overview
LT3957IUHE#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 regulated positive or negative output voltages via a single FBX pin, operates from 3V to 40V input, and features programmable 100kHz–1MHz switching frequency and <1μA shutdown current - ideal for automotive battery-powered 12V/24V systems requiring high-efficiency isolated or non-isolated conversion.
For engineers reviewing the LT3957IUHE#PBF datasheet, LT3957IUHE#PBF pinout, LT3957IUHE#PBF application, or LT3957IUHE#PBF equivalent, key selection considerations include its dual-polarity feedback capability (±0.8V/±1.6V reference), internal 5.2V LDO for gate drive, thermally enhanced 36-lead QFN (5mm × 6mm) package with exposed SW and SGND pads, and frequency foldback protection during startup or short-circuit conditions.
Technical Context
The LT3957IUHE#PBF implements fixed-frequency current-mode control using internal slope compensation and a PWM comparator that compares sensed switch current (via SENSE1/SENSE2) against a VC-set threshold. Its dual-comparator feedback architecture (A1/A2) enables seamless configuration for either positive-output (FBX referenced to +1.6V) or negative-output (FBX referenced to –0.8V) operation without external component changes.
It integrates a 5.2V low-dropout regulator (INTVCC) with 2.7V UVLO and 0.1V hysteresis, programmable EN/UVLO with 1.22V falling threshold and external hysteresis, soft-start via SS pin with 10μA pull-up, and SYNC pin for external clock synchronization - all coordinated through a single oscillator block that supports frequency foldback when FBX voltage drops near SGND during fault or startup.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Input Voltage Range | 3V to 40V - supports direct connection to automotive batteries (9V–16V nominal) and industrial 24V rails without pre-regulation. |
| Switch Rating | Internal 5A/40V N-MOSFET - eliminates need for external high-current switch in ≤5A peak applications. |
| Feedback Reference | +1.6V or –0.8V on FBX pin - enables single-pin polarity selection for boost/flyback (positive) or inverting (negative) outputs. |
| Switching Frequency | 100kHz to 1MHz (RT-programmable) - balances efficiency (lower fSW) vs. size (higher fSW); RT = 41.2kΩ sets 300kHz typical. |
| Shutdown Current | <1μA at EN/UVLO = 0V - extends battery life in always-on automotive modules and IoT edge nodes. |
| INTVCC Regulator | 5.2V LDO with 2.7V UVLO - powers internal gate driver and logic; bypass requires ≥4.7μF ceramic to SGND. |
| Operating Temp | –40°C to +125°C junction - qualified for under-hood automotive and industrial control environments. |
Pinout & Package
LT3957IUHE#PBF is housed in 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 planes for thermal and electrical integrity.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| SW (Pins 8, 9, 20, 21, 38) | Drain of internal N-MOSFET | High-current switching node; connects directly to inductor/diode; exposed pad (38) must be soldered to SW plane for thermal relief. |
| SENSE1 (Pin 6) & SENSE2 (Pin 3) | Current sense interface | Forms Kelvin-sense path across internal RSENSE; SENSE1 is MOSFET source output, SENSE2 is comparator input - requires RC filter for noise immunity. |
| FBX (Pin 31) | Feedback input / frequency modulation | Single pin accepts resistor-divider from VOUT; sets regulation point (+1.6V or –0.8V) and triggers frequency foldback if near SGND. |
| EN/UVLO (Pin 25) | Enable & input undervoltage detection | 1.22V falling threshold with programmable hysteresis; resets soft-start on undervoltage; pulls VIN IQ below 1μA when ≤0.4V. |
| SS (Pin 32) | Soft-start timing control | 10μA internal current source charges external capacitor; clamps VC to limit inrush current; discharged by faults (INTVCC UV, thermal lockout). |
| RT (Pin 33) | Frequency programming | Resistor to SGND sets switching frequency (100kHz–1MHz); open-circuit not allowed; 41.2kΩ = 300kHz typical. |
| SYNC (Pin 34) | External clock synchronization | Accepts digital clock input; forces operation at SYNC frequency if used; RT must be set 20% slower than SYNC for reliable locking. |
| INTVCC (Pin 28) | Internal 5.2V LDO output | Powers gate driver and logic; requires ≥4.7μF ceramic cap to SGND; can be bypassed to external supply >5.5V (but <8V) to reduce dissipation. |
| VC (Pin 30) | Error amplifier compensation | Connects to RC network (5kΩ–50kΩ + 470pF–22nF) to SGND; sets loop stability and transient response for chosen topology. |
| GND (Pins 12–17) | MOSFET source return | Connects to source terminal of internal switch; internally tied to SGND for Kelvin sensing - must not be externally shorted to SGND. |
| SGND (Pins 4, 23, 24, 37) | Signal ground reference | Reference for SENSE1/SENSE2, FBX, VC, SS, RT, SYNC; all small-signal components tie here; exposed pad (37) must be soldered to SGND plane. |
Key Features
| Feature | Design Value |
|---|---|
| Dual-polarity feedback architecture | Single FBX pin supports +1.6V (boost/flyback/SEPIC) or –0.8V (inverting) regulation without hardware change - reduces BOM count and layout variants. |
| Programmable frequency foldback | Automatically reduces switching frequency when FBX approaches SGND during startup or output short - prevents inductor saturation and overcurrent failure. |
| Integrated 5.2V LDO with UVLO | Supplies gate driver and internal logic; 2.7V UVLO ensures sufficient gate drive before enabling switch - avoids weak-turn-on and shoot-through risk. |
| Thermally optimized QFN package | 36-lead 5mm × 6mm QFN with dual exposed pads (SW and SGND) enables >3°C/W junction-to-board thermal resistance - sustains 5A switching at 125°C ambient. |
| Accurate programmable UVLO | EN/UVLO pin provides 1.22V ±20mV falling threshold with user-defined hysteresis via resistor divider - enables precise brown-in/brown-out control for battery systems. |
Applications
| Automotive LED Headlamp Driver | Industrial Isolated Bias Supply |
|---|---|
Use Scenario: Driving high-brightness LEDs from 12V vehicle battery with dimming control and short-circuit protection. IC Role / Device Role / Timing Role: LT3957IUHE#PBF configured as boost converter with constant-current regulation via SENSE2 feedback; FBX monitors LED string voltage. Use Value: Integrated 5A switch eliminates external FET; 3V–40V input range accommodates cold-crank (6V) and load-dump (40V); frequency foldback prevents LED current surge during dimming transients. | Use Scenario: Generating isolated ±15V bias rails for op-amps and ADCs in PLC analog I/O modules powered from 24V DC bus. IC Role / Device Role / Timing Role: LT3957IUHE#PBF configured as flyback converter with optocoupler feedback; INTVCC powered from auxiliary winding. Use Value: Single IC supports dual-polarity outputs; 125°C rating ensures reliability in sealed enclosures; programmable soft-start prevents transformer saturation at power-on. |
| Telecom DC-DC Intermediate Bus Converter | Medical Portable Equipment Power |
Use Scenario: Stepping up 48V telecom rack supply to 54V intermediate bus for downstream POL converters in base station RF cards. IC Role / Device Role / Timing Role: LT3957IUHE#PBF configured as boost converter; SYNC pin synchronized to system clock to minimize EMI peaks. Use Value: 1MHz max frequency enables compact magnetics; <1μA shutdown current preserves backup battery; robust 40V switch withstands 48V transient surges. | Use Scenario: Powering portable ultrasound or patient monitor subsystems from rechargeable Li-ion (3.0–4.2V) with regulated 3.3V and –5V outputs. IC Role / Device Role / Timing Role: LT3957IUHE#PBF configured as inverting converter for –5V rail; boost mode for 3.3V; shared FBX and soft-start control. Use Value: Wide 3V min input enables full battery discharge; dual-output capability reduces component count; 125°C rating supports sterilization temperature requirements. |
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 | 4-switch synchronous buck-boost controller; no integrated MOSFET; supports 4V–36V input; requires external FETs. | Better suited for high-efficiency, high-current (>10A) buck-boost applications where layout control and thermal management are critical. | Select LTC3789EUF#PBF when higher efficiency (>95%) and bidirectional power flow are required, and external FET selection is acceptable. |
| LM5122MH/NOPB | Current-mode boost/flyback/SEPIC controller; no integrated switch; 3V–65V input; 100kHz–2MHz programmable frequency. | Designed for higher input voltage (up to 65V) and wider frequency range; lacks negative-output capability and internal LDO. | Choose LM5122MH/NOPB for 48V telecom or industrial inputs exceeding 40V, or when external MOSFETs offer better thermal or cost optimization. |
Compared with LTC3789EUF#PBF and LM5122MH/NOPB, LT3957IUHE#PBF uniquely combines integrated 5A/40V switching, dual-polarity feedback, and frequency foldback in a single QFN package - simplifying design for mid-power (≤5A) automotive and industrial converters where board space and component count are constrained.
Availability
LT3957IUHE#PBF is available at Aetrix Electronics and suitable for automotive lighting, industrial power supplies, and telecom intermediate bus converters requiring stable component supply, extended temperature operation, and long-term production continuity.
Supply support for LT3957IUHE#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 LT3957IUHE#PBF belongs to ADI's Power by Linear™ portfolio of monolithic DC/DC converters, designed specifically for rugged, high-reliability power conversion in automotive, industrial, and communications infrastructure applications.
FAQ
What topology configurations does the LT3957IUHE#PBF support?
The LT3957IUHE#PBF supports boost, flyback, SEPIC, and inverting converter topologies. Its dual-reference feedback architecture (±1.6V/±0.8V on FBX) enables seamless configuration for either positive or negative output voltages without changing external components. The internal 5A/40V N-MOSFET eliminates the need for an external switch in most ≤5A applications, and the current-mode control ensures stable operation across all four topologies.
How does the LT3957IUHE#PBF handle input undervoltage conditions?
The LT3957IUHE#PBF uses the EN/UVLO pin to detect input undervoltage with a precise 1.22V falling threshold and user-programmable hysteresis. When VIN drops below this threshold, the device disables switching, resets soft-start, and reduces input quiescent current to <1μA. Hysteresis is set via an external resistor divider and an internal 2μA pull-down current, ensuring clean turn-on/turn-off behavior during battery brownout events.
Can the LT3957IUHE#PBF generate both positive and negative outputs simultaneously?
No, the LT3957IUHE#PBF generates either a positive or negative output per configuration - not both simultaneously. Its FBX pin selects polarity: a resistor divider pulling FBX toward +1.6V configures positive output (boost/flyback/SEPIC), while pulling toward –0.8V configures negative output (inverting). Dual-rail designs require two separate LT3957IUHE#PBF circuits or a different controller architecture.
What is the purpose of the frequency foldback function in the LT3957IUHE#PBF?
The frequency foldback function in the LT3957IUHE#PBF reduces switching frequency when the FBX voltage falls near SGND - such as during startup or output short-circuit. This prevents the minimum on-time limitation from forcing excessive duty cycle and uncontrolled inductor current rise. By lowering fSW, the controller maintains current limiting and avoids MOSFET overcurrent, enhancing reliability in fault-prone applications like automotive loads.
How should the INTVCC pin be bypassed for optimal performance of the LT3957IUHE#PBF?
The INTVCC pin of the LT3957IUHE#PBF must be bypassed to SGND with a minimum 4.7μF low-ESR ceramic capacitor placed immediately adjacent to the pin. This capacitor supplies high transient gate-drive currents and stabilizes the internal 5.2V LDO. If external power is available (5.5V–8V), INTVCC may be connected to it to disable the internal LDO and reduce power dissipation - but the 4.7μF capacitor remains mandatory regardless of supply source.
LT3957IUHE#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)
LT3957IUHE#PBF FAQ
1.How can I place an order for LT3957IUHE#PBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LT3957IUHE#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 LT3957IUHE#PBF reliable?
The price and inventory of LT3957IUHE#PBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LT3957IUHE#PBF is usually 5 days.
3.What payment methods are accepted for LT3957IUHE#PBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LT3957IUHE#PBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LT3957IUHE#PBF?
LT3957IUHE#PBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LT3957IUHE#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 LT3957IUHE#PBF?
For technical support, including LT3957IUHE#PBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LT3957IUHE#PBF requirements.
6.How does Aetrix verify that LT3957IUHE#PBF is sourced from the original manufacturer or authorized distributors?
All LT3957IUHE#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 LT3957IUHE#PBF meets industry standards.
7.What is the process for return or replacement of LT3957IUHE#PBF?
All LT3957IUHE#PBF units undergo pre-shipment inspection (PSI). If there is an issue with LT3957IUHE#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 LT3957IUHE#PBF part is unused and in its original packaging.
Return procedure for LT3957IUHE#PBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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