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Analog Devices Inc. LTC3126IUFD#PBF
- Part No.:
- LTC3126IUFD#PBF
- Manufacturer:
- Analog Devices Inc.
- Package:
- 28-WFQFN Exposed Pad
- Datasheet:
-
LTC3126IUFD#PBF.pdf
- Description:
- IC REG BUCK ADJ 2.5A 28QFN
- Quantity:
- Payment:
- Shipping:
Inventory:4,694
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Product details
Overview
LTC3126IUFD#PBF from Analog Devices (formerly Linear Technology) is a 42V, 2.5A synchronous step-down regulator with integrated no-loss PowerPath™ for seamless dual-input power source management. It supports pin-selectable ideal diode-OR or priority input mode, programmable UVLO thresholds (2.34V–20V), and operates from 2.4V to 42V input while delivering 0.818V to VIN output. Used in automotive battery backup systems where transient robustness and automatic switchover are critical.
For engineers reviewing the LTC3126IUFD#PBF datasheet, LTC3126IUFD#PBF pinout, LTC3126IUFD#PBF application, or LTC3126IUFD#PBF equivalent, key selection considerations include dual-input UVLO programming, 2µA Burst Mode quiescent current, 200kHz–2.2MHz programmable switching frequency, and thermal performance in the 4mm × 5mm QFN package with exposed PGND pad.
Technical Context
The LTC3126IUFD#PBF implements current-mode control with 60ns minimum on-time and integrates two independent input validation comparators with user-programmable thresholds via VSET1/VSET2 pins. Its PowerPath architecture uses internal MOSFETs to enable zero-downtime transition between VIN1 (priority) and VIN2 (backup), eliminating hold-up capacitors.
It features dual charge-pump gate drivers (BST1/COM1 and BST2/COM2) supporting high-side switch operation, an internal 1.000V precision VREF for UVLO divider biasing, and open-drain status outputs (VALID1, VALID2, PRIORITY, PGOOD) with 70Ω pull-down strength and 5.5V absolute max rating.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Input Voltage Range | 2.4V to 42V - supports automotive transients (42V), supercapacitor discharge, and multicell battery stacks without external protection. |
| Output Current | 2.5A continuous - sufficient for powering FPGA I/O banks, microcontroller cores, or industrial sensors directly. |
| Burst Mode IQ | 2µA - enables >10-year battery life in always-on backup systems with low-duty-cycle wakeups. |
| Switching Frequency | 200kHz to 2.2MHz - adjustable via RT resistor; higher frequencies allow smaller inductors (e.g., 2.2µH at 2MHz) for space-constrained designs. |
| UVLO Threshold Range | 2.34V to 20V per input - set independently via VSET1/VSET2 resistive dividers from 1.000V VREF for precise source handoff. |
| PowerPath Transition Time | <50µs - verified in load-step testing; prevents brownout during automotive ignition-off to battery switchover. |
| Thermal Performance | θJA = 34°C/W - enabled by exposed PGND pad soldered to PCB; supports 2.5A continuous operation at TA ≤ 85°C ambient. |
Pinout & Package
Package: 28-lead 4mm × 5mm plastic QFN with exposed thermal pad (Pin 29 = PGND). Requires soldering of exposed pad to PCB ground plane for thermal and electrical integrity.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| VIN1 / VIN2 | Kelvin sense inputs | Low-impedance sensing path for UVLO comparators; must be routed separately from PVIN1/PVIN2 power paths to avoid noise coupling. |
| PVIN1 / PVIN2 | Main power inputs | High-current paths rated to 42V; require ≥4.7µF ceramic bypass each to suppress ripple and support fast load steps. |
| SW | Power switch node | Connects to buck inductor; high dv/dt node requiring tight layout and minimal trace length to reduce EMI and switching losses. |
| BST1 / BST2 | High-side gate drive rails | Each requires 0.1µF ceramic capacitor to COM1/COM2; critical for reliable 200mΩ high-side FET turn-on under all load conditions. |
| VSET1 / VSET2 | UVLO programming inputs | Analog inputs referenced to 1.000V VREF; set rising/falling UVLO thresholds with 11% hysteresis for stable input handoff. |
| VALID1 / VALID2 | Open-drain status outputs | Indicate real-time validity of respective inputs; pulled low when VINx > programmed UVLO; float when ENA = low. |
| PRIORITY | Priority channel indicator | Asserted low only when operating from VIN1 in priority mode; used for system-level power sequencing or fault logging. |
| PGOOD | Output regulation monitor | Asserted low if VOUT deviates >8.7% below or >9.8% above FB-set point; includes 200µs delay to reject transient disturbances. |
Key Features
| Feature | Design Value |
|---|---|
| No-loss PowerPath™ | Eliminates series diode voltage drop and heat generation; enables >95% efficiency at 1A (12V→5V) without external OR-ing FETs. |
| Pin-selectable operation modes | DIODE pin selects between ideal-diode-OR (auto-select highest valid input) and priority mode (VIN1 primary, VIN2 backup) - no firmware or external logic required. |
| Programmable UVLO with hysteresis | VSET1/VSET2 allow independent, temperature-stable UVLO thresholds (2.34V–20V) with 11% hysteresis to prevent oscillation near threshold. |
| 2µA Burst Mode quiescent current | Extends runtime in energy-harvesting or battery-backed applications where load current is typically <1mA. |
| 200kHz–2.2MHz synchronization | RT resistor sets base frequency; PWM/SYNC pin accepts external clock up to 2.2MHz for EMI reduction or multi-rail coherence. |
| Integrated VREF and soft-start | 1.000V ±1.8mV VREF powers UVLO dividers and serves as system reference; 7.5ms internal soft-start prevents inrush current into large output caps. |
Applications
| Automotive Battery Backup | Industrial Uninterruptible Supply |
|---|---|
Use Scenario: Maintaining 3.3V rail during engine cranking when battery dips to 6V while alternator is offline. IC Role / Device Role / Timing Role: Dual-input buck controller managing seamless transition from 12V automotive bus to isolated LiFePO₄ backup cell. Use Value: 50µs switchover prevents MCU reset; 42V transient tolerance eliminates need for external TVS clamping. | Use Scenario: Providing clean 5V/2.5A to PLC I/O module during AC mains failure. IC Role / Device Role / Timing Role: Primary DC-DC converter powered from supercapacitor bank, backed by 24V industrial supply. Use Value: 2.4V start-up enables full utilization of supercapacitor discharge curve; 2µA IQ extends hold-up time by >30%. |
| Portable Test Equipment | Communications Base Station |
Use Scenario: Field-deployable spectrum analyzer powered from USB-C PD (9–20V) or internal Li-ion pack (3.0–4.2V). IC Role / Device Role / Timing Role: Input-agnostic power manager selecting optimal source based on voltage and validity status. Use Value: Pin-selectable priority mode ensures USB-C remains primary unless disconnected; VALID1/VALID2 signals enable host OS power-aware scheduling. | Use Scenario: Remote radio unit requiring 12V/2A from either PoE++ (57V) or local 24V DC plant. IC Role / Device Role / Timing Role: High-voltage buck converter with no-loss PowerPath enabling hot-swap capability between redundant supplies. Use Value: 42V absolute max rating withstands PoE++ surge events; PRIORITY signal triggers upstream supply failover logic. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar dual-input buck regulator applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| LTC3122IUFD#PBF | Lower 36V max input, 1.5A output, no programmable UVLO - fixed 2.5V threshold per input. | Suitable for cost-sensitive 12V/24V systems without wide UVLO tuning needs. | Select when input range ≤36V and UVLO flexibility is not required; saves BOM cost but lacks LTC3126's 42V/2.5A capability. |
| MAX20406AATG+T | 42V input, 3A output, I²C-configurable UVLO and fault reporting - no discrete VSET pins. | Preferred for systems requiring digital supervision, telemetry, or dynamic reconfiguration. | Choose when firmware-controlled power policy (e.g., adaptive UVLO, event logging) is needed; adds software overhead vs. LTC3126's pin-strapped simplicity. |
Compared with LTC3122IUFD#PBF and MAX20406AATG+T, the LTC3126IUFD#PBF uniquely balances analog configurability (VSET-based UVLO), high-voltage resilience (42V), and ultra-low quiescent current (2µA) in a pin-compatible QFN footprint - making it optimal for deterministic, maintenance-free dual-source systems.
Availability
LTC3126IUFD#PBF is available at Aetrix Electronics and suitable for automotive battery backup, industrial uninterruptible power, and portable test equipment requiring stable component supply across extended temperature ranges.
Supply support for LTC3126IUFD#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 LTC3126IUFD#PBF belongs to Linear's PowerPath™ buck regulator family, designed specifically for mission-critical dual-input power systems where reliability, transient immunity, and autonomous source handoff are mandatory.
FAQ
What is the maximum input voltage rating for the LTC3126IUFD#PBF?
The LTC3126IUFD#PBF has an absolute maximum input voltage rating of 42V on PVIN1, PVIN2, VIN1, and VIN2 pins. This allows direct connection to automotive batteries subject to load-dump transients without external clamping. Operation above 42V risks permanent damage per Absolute Maximum Ratings.
How does the LTC3126IUFD#PBF handle switchover between VIN1 and VIN2?
The LTC3126IUFD#PBF performs sub-50µs automatic switchover using internal PowerPath™ MOSFETs and comparator-based validation. In priority mode (DIODE = low), it operates from VIN1 until voltage falls below the VSET1-programmed UVLO threshold, then transitions to VIN2. No hold-up capacitors are needed due to zero-downtime architecture.
Can the LTC3126IUFD#PBF operate with only one input source connected?
Yes - the LTC3126IUFD#PBF functions normally with only VIN1 or only VIN2 present. If the active input drops below its UVLO threshold, the buck converter disables output. When only one input is valid, the device behaves as a standard synchronous buck regulator with full 2.5A capability and Burst Mode efficiency.
What is the purpose of the VSET1 and VSET2 pins on the LTC3126IUFD#PBF?
VSET1 and VSET2 pins program the rising/falling UVLO thresholds for VIN1 and VIN2 respectively. A resistive divider from the 1.000V VREF pin sets thresholds from 2.34V up to 20V with 11% hysteresis. Grounding VSET1/VSET2 enables the internal 2.34V threshold, allowing operation down to 2.4V input.
Does the LTC3126IUFD#PBF require external bootstrap capacitors?
Yes - the LTC3126IUFD#PBF requires two 0.1µF ceramic capacitors: one between BST1 and COM1, and another between BST2 and COM2. These are essential for high-side gate drive; omitting them causes immediate failure of the internal power switches and loss of regulation.
LTC3126IUFD#PBF Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc.
- Series:
- -
- Package/Case:
- 28-WFQFN 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):
- 2.4V
- Voltage - Input (Max):
- 42V
- Voltage - Output (Min/Fixed):
- 0.818V
- Voltage - Output (Max):
- 42V
- Current - Output:
- 2.5A
- Frequency - Switching:
- 200kHz ~ 2.2MHz
- Synchronous Rectifier:
- Yes
- Operating Temperature:
- -40°C ~ 125°C (TA)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 28-QFN (4x5)
LTC3126IUFD#PBF FAQ
1.How can I place an order for LTC3126IUFD#PBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LTC3126IUFD#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 LTC3126IUFD#PBF reliable?
The price and inventory of LTC3126IUFD#PBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LTC3126IUFD#PBF is usually 5 days.
3.What payment methods are accepted for LTC3126IUFD#PBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LTC3126IUFD#PBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LTC3126IUFD#PBF?
LTC3126IUFD#PBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LTC3126IUFD#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 LTC3126IUFD#PBF?
For technical support, including LTC3126IUFD#PBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LTC3126IUFD#PBF requirements.
6.How does Aetrix verify that LTC3126IUFD#PBF is sourced from the original manufacturer or authorized distributors?
All LTC3126IUFD#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 LTC3126IUFD#PBF meets industry standards.
7.What is the process for return or replacement of LTC3126IUFD#PBF?
All LTC3126IUFD#PBF units undergo pre-shipment inspection (PSI). If there is an issue with LTC3126IUFD#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 LTC3126IUFD#PBF part is unused and in its original packaging.
Return procedure for LTC3126IUFD#PBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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