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Analog Devices Inc. LT3431IFE#PBF
- Part No.:
- LT3431IFE#PBF
- Manufacturer:
- Analog Devices Inc.
- Package:
- 16-TSSOP (0.173", 4.40mm Width) Exposed Pad
- Datasheet:
-
LT3431IFE#PBF.pdf
- Description:
- IC REG BUCK ADJ 3A 16TSSOP
- Quantity:
- Payment:
- Shipping:
Inventory:381
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Product details
Overview
LT3431IFE#PBF from Analog Devices (formerly Linear Technology) is a high-voltage, current-mode synchronous buck switching regulator IC designed for industrial and automotive power supplies. It operates from 5.5V to 60V input, delivers up to 2A continuous output at 5V, features a fixed 500kHz switching frequency, integrated 0.1Ω NPN power switch, and 1.219V feedback reference voltage. It is used in 12V-input battery charger and distributed power systems requiring robust transient response.
For engineers reviewing the LT3431IFE#PBF datasheet, LT3431IFE#PBF pinout, LT3431IFE#PBF application, or LT3431IFE#PBF equivalent, key selection considerations include its –40°C to 125°C operating junction temperature range, BOOST-pin–enabled saturation drive, cycle-by-cycle current limiting, and external synchronization capability from 580kHz to 700kHz.
Technical Context
The LT3431IFE#PBF implements a constant-frequency current-mode control architecture with dual feedback loops: one regulating output voltage via the error amplifier (gm = 2200 µmho) and FB pin (1.219V reference), and another performing cycle-by-cycle peak switch current sensing. Its patented slope compensation cancellation maintains 3A peak switch current across full duty cycle range (up to 92%), eliminating typical current-limit roll-off above 50% duty.
Internal bias is derived either from VIN or externally via BIAS pin (≥3V), improving efficiency at high VIN/light load. The BOOST pin enables switch saturation using an external capacitor/diode, reducing conduction loss to ~0.1Ω. Shutdown (SHDN) provides two thresholds: 2.38V UVLO lockout and 0.4V micropower shutdown (30µA).
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Input Voltage Range | 5.5V to 60V - supports wide-range industrial inputs including 24V/48V rails and transient-tolerant 12V automotive systems |
| Output Current | 2A continuous - verified at VOUT = 5V, VIN = 12V, L = 15µH per typical application circuit |
| Switching Frequency | 500kHz (±40kHz) - fixed internal oscillator; synchronizable externally from 580kHz to 700kHz via SYNC pin |
| Feedback Reference | 1.219V (typ) - precise bandgap reference enabling accurate output voltage setting with standard resistor dividers |
| Peak Switch Current | 3.0A (min) at –40°C ≤ TJ ≤ 25°C - maintained over full duty cycle range due to patented slope compensation cancellation |
| Switch On Resistance | 0.1Ω (typ) - achieved via BOOST-pin–driven saturation, minimizing conduction loss at high current |
| Operating Temp Range | –40°C to 125°C - fully specified and guaranteed for industrial and automotive under-hood applications |
| Shutdown Current | 30µA (typ) - ultra-low quiescent draw during SHDN assertion, critical for battery-backed systems |
Pinout & Package
The LT3431IFE#PBF is housed in a thermally enhanced 16-lead plastic TSSOP package with exposed pad fused to GND pins (1, 8, 9, 16) for low θJC (10°C/W). The exposed pad must be soldered to a PCB ground plane for thermal and electrical integrity.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| GND (1, 8, 9, 16) | Power and signal reference ground | Four dedicated ground connections minimize ground bounce; exposed pad must be soldered to PCB ground plane for thermal management and noise reduction |
| SW (2, 5) | Switch emitter node | Drives inductor; swings from near-GND to VIN during on-time; clamped negative to –0.8V off-time by external catch diode |
| VIN (3, 4) | Power switch collector & primary supply | Supplies internal circuitry when BIAS pin is unconnected; high dI/dt path requires short trace to input bypass capacitor |
| BOOST (6) | Switch driver boost supply | Accepts voltage ≥VIN + 1.8V to saturate internal NPN; enables 0.1Ω RDS(on)-equivalent performance |
| NC (7, 13) | No connection | Not internally bonded; must remain unconnected and unstubbed on PCB |
| BIAS (10) | Efficiency-optimized bias supply | When tied to regulated output (≥3V), shifts internal bias current from VIN to VOUT, improving efficiency at high VIN/light load |
| VC (11) | Error amplifier output / current limit comparator input | Provides loop compensation node; also serves as current clamp point (0.9V light load → 2.1V full load); can override regulation |
| FB (12) | Feedback reference input | Senses 1.219V reference; enables output voltage setting, frequency foldback below 0.8V, and current limit foldback below 0.6V |
| SYNC (14) | External clock synchronization input | Logic-level compatible (1.5V–2.2V min amplitude); accepts 580kHz–700kHz external clock to eliminate beat frequencies |
| SHDN (15) | Enable/disable control | Two-threshold operation: 2.38V disables switching (UVLO), 0.4V forces micropower shutdown (30µA IQ) |
Key Features
| Feature | Design Value |
|---|---|
| Patented slope compensation cancellation | Maintains 3A peak switch current across full 0–92% duty cycle range-eliminates need for derating at high VIN/VOUT ratios |
| BOOST-pin–driven saturation | Reduces effective switch resistance to 0.1Ω (typ), cutting conduction loss vs. conventional bipolar or MOSFET-based buck regulators |
| Dual-threshold SHDN pin | Enables both precise undervoltage lockout (2.38V) and deep micropower shutdown (0.4V), supporting safe start-up and battery preservation |
| FB pin multifunctionality | Integrates output voltage regulation, frequency foldback (5:1 reduction below 0.8V), and current limit foldback (to <2A below 0.6V) for robust short-circuit protection |
| Thermally enhanced TSSOP-16 | Exposed pad + multiple GND pins achieve θJC = 10°C/W, enabling 2A operation without heatsink in compact industrial layouts |
| BIAS pin efficiency optimization | Redirects internal bias current from VIN to VOUT when BIAS ≥3V, increasing efficiency by ~1–2% at VIN = 36V, IOUT = 0.1A |
Applications
| Industrial Power Supply | Automotive Battery Charger |
|---|---|
Use Scenario: 24V rail conversion to 5V/2A for PLC I/O modules in factory automation cabinets with ambient temperatures up to 85°C. IC Role / Device Role / Timing Role: Primary buck regulator providing isolated, regulated 5V supply; operates continuously at 500kHz with no external clock required. Use Value: Guaranteed –40°C to 125°C operation ensures reliability in uncooled enclosures; 60V absolute max VIN withstands 48V system transients. | Use Scenario: 12V vehicle battery-powered 5V/2A USB-C charging port in infotainment head units, surviving cold-crank (4.6V) and load-dump (60V) events. IC Role / Device Role / Timing Role: Input-transient–tolerant buck controller managing charge delivery while maintaining stable 5V output during engine start-stop cycles. Use Value: Minimum 4.6V input start-up and 60V absolute max VIN enable direct connection to automotive battery; SHDN UVLO prevents erratic behavior during cranking. |
| Distributed Power System | Portable Computing Power |
Use Scenario: Point-of-load (POL) converter in telecom base station backplane delivering 5V/2A to FPGA I/O banks from a 48V intermediate bus. IC Role / Device Role / Timing Role: High-efficiency POL regulator synchronized to system clock via SYNC pin to suppress EMI in dense board layouts. Use Value: 580–700kHz synchronization eliminates beat frequencies with adjacent converters; BOOST-driven saturation minimizes heat generation in confined spaces. | Use Scenario: Compact 5V/2A power rail for embedded ARM-based tablets powered from 12V external adapters, requiring low profile and minimal thermal rise. IC Role / Device Role / Timing Role: Main system power supply operating in thermally constrained space; uses BIAS pin to improve light-load efficiency. Use Value: BIAS pin connection to 5V output reduces total input-referred quiescent current to 2.5mA (vs. 2.2mA IVIN alone), extending battery life during standby. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar buck regulator applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| LT3976IMSE#PBF | Higher 5A peak switch current, 3.2MHz switching, integrated MOSFETs; wider 4.2V–80V input range; no BOOST pin required | Better suited for higher-current (>2.5A) or higher-frequency (>1MHz) designs; lacks FB-foldback protection | Select LT3976IMSE#PBF only if >2.5A output or >1MHz operation is required; not drop-in due to different pinout and control architecture |
| LM5164QPWPRQ1 | 4.5V–65V input, 1A continuous, integrated FETs, 1MHz max frequency; AEC-Q100 qualified; no VC pin or BOOST function | Designed for automotive qualification; lower current rating limits use to sub-1.5A loads; no current foldback or frequency foldback | Choose LM5164QPWPRQ1 only for AEC-Q100–mandated automotive applications where 1A output suffices; not functionally equivalent for 2A industrial use |
Compared with LT3431IFE#PBF, LT3976IMSE#PBF offers higher current and frequency but removes the BOOST-driven saturation advantage and FB-foldback safety features, while LM5164QPWPRQ1 trades current capability and protection features for automotive qualification-neither matches the LT3431IFE#PBF's combination of 2A robustness, 60V tolerance, and integrated fault mitigation.
Availability
LT3431IFE#PBF is available at Aetrix Electronics and suitable for industrial power supplies, automotive battery chargers, and distributed power systems requiring stable component supply with guaranteed long-term availability and extended temperature support.
Supply support for LT3431IFE#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. (acquired Linear Technology in 2017) is a global leader in high-performance analog, mixed-signal, and power management semiconductors, serving industrial, automotive, communications, and healthcare markets.
The LT3431IFE#PBF belongs to Linear's high-voltage monolithic buck regulator product line, engineered specifically for rugged industrial and automotive power conversion where input transients, wide temperature operation, and reliable fault handling are critical design requirements.
FAQ
What is the minimum input voltage required for LT3431IFE#PBF to start regulation?
The LT3431IFE#PBF has a guaranteed minimum input voltage of 4.6V (over temperature) to initiate regulation. This value is defined by internal bias line regulation-not directly measured-and depends on output voltage and load. For example, with VOUT = 5V, the minimum VIN to sustain regulation rises to ~5.5V at full 2A load, as shown in Figure G11 of the datasheet. Below 4.6V, the device remains in UVLO state.
Can LT3431IFE#PBF operate without the BOOST capacitor and diode?
No. The LT3431IFE#PBF requires the external BOOST capacitor and diode to generate the elevated gate drive voltage needed to saturate the internal NPN power switch. Without it, switch conduction loss increases dramatically-voltage drop rises from ~0.1Ω-equivalent to ~1.5V-causing excessive power dissipation and potential thermal shutdown. The BOOST pin must be biased ≥VIN + 1.8V to guarantee full saturation per datasheet Note 4.
How does the FB pin provide short-circuit protection in LT3431IFE#PBF?
The FB pin in LT3431IFE#PBF enables dual-stage short-circuit protection: when FB voltage drops below 0.8V, switching frequency folds back ~5:1 (e.g., 500kHz → 100kHz) to reduce average power; when FB falls below 0.6V, peak switch current limit folds back from 3A to <2A. Both functions are implemented internally-no external components needed-and are disabled during normal operation to avoid interference.
Is LT3431IFE#PBF pin-compatible with LT3431EFE#PBF?
Yes. LT3431IFE#PBF and LT3431EFE#PBF share identical pinout, package (16-lead TSSOP), and electrical specifications. The only difference is temperature grade: LT3431IFE#PBF is guaranteed over –40°C to 125°C junction temperature, while LT3431EFE#PBF is specified for 0°C to 125°C. Both use the same FE marking and layout footprint.
What is the role of the BIAS pin in LT3431IFE#PBF, and when should it be used?
The BIAS pin in LT3431IFE#PBF allows internal bias circuitry to draw operating current from the regulated output (≥3V) instead of VIN, improving efficiency-especially when VIN ≫ VOUT (e.g., 36V → 5V). At light loads, this reduces total input-referred quiescent current by ~1mA. It must not be used for outputs <3V, and the BIAS pin voltage must never exceed 30V per absolute maximum ratings.
LT3431IFE#PBF Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc.
- Series:
- -
- Package/Case:
- 16-TSSOP (0.173", 4.40mm Width) Exposed Pad
- Packaging:
- Tube
- Product Status:
- Active
- Function:
- Step-Down
- Output Configuration:
- Positive
- Topology:
- Buck
- Output Type:
- Adjustable
- Number of Outputs:
- 1
- Voltage - Input (Min):
- 5.5V
- Voltage - Input (Max):
- 60V
- Voltage - Output (Min/Fixed):
- 1.219V
- Voltage - Output (Max):
- 55.2V
- Current - Output:
- 3A (Switch)
- Frequency - Switching:
- 500kHz
- Synchronous Rectifier:
- No
- Operating Temperature:
- -40°C ~ 125°C (TJ)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 16-TSSOP-EP
LT3431IFE#PBF FAQ
1.How can I place an order for LT3431IFE#PBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LT3431IFE#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 LT3431IFE#PBF reliable?
The price and inventory of LT3431IFE#PBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LT3431IFE#PBF is usually 5 days.
3.What payment methods are accepted for LT3431IFE#PBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LT3431IFE#PBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LT3431IFE#PBF?
LT3431IFE#PBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LT3431IFE#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 LT3431IFE#PBF?
For technical support, including LT3431IFE#PBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LT3431IFE#PBF requirements.
6.How does Aetrix verify that LT3431IFE#PBF is sourced from the original manufacturer or authorized distributors?
All LT3431IFE#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 LT3431IFE#PBF meets industry standards.
7.What is the process for return or replacement of LT3431IFE#PBF?
All LT3431IFE#PBF units undergo pre-shipment inspection (PSI). If there is an issue with LT3431IFE#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 LT3431IFE#PBF part is unused and in its original packaging.
Return procedure for LT3431IFE#PBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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