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Analog Devices Inc. LTC3126EUFD#PBF
- Part No.:
- LTC3126EUFD#PBF
- Manufacturer:
- Analog Devices Inc.
- Package:
- 28-WFQFN Exposed Pad
- Datasheet:
-
LTC3126EUFD#PBF.pdf
- Description:
- IC REG BUCK ADJ 2.5A 28QFN
- Quantity:
- Payment:
- Shipping:
Inventory:6,415
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Product details
Overview
LTC3126EUFD#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. It enables automotive battery backup systems requiring automatic switchover without hold-up capacitors.
For engineers reviewing the LTC3126EUFD#PBF datasheet, LTC3126EUFD#PBF pinout, LTC3126EUFD#PBF application, or LTC3126EUFD#PBF equivalent, key selection criteria include dual-input transition behavior, 2µA Burst Mode quiescent current, 200kHz–2.2MHz programmable switching frequency, 60ns minimum on-time, and thermal performance in the 4mm × 5mm QFN package.
Technical Context
The LTC3126EUFD#PBF implements current-mode control with independent input validation comparators, internal VREF (1.000V ±1.8mV), and dual high-side/low-side MOSFET drivers (200mΩ/70mΩ RDS(on)). Its PowerPath architecture uses fast analog switchover (<50µs transition) between VIN1 and VIN2 without output rail disturbance.
It features programmable UVLO via VSET1/VSET2 pins (0–1V → 0–20V threshold), external synchronization capability on PWM/SYNC, and dedicated 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. |
| Output current | 2.5A continuous - sufficient for powering FPGA I/O banks, industrial sensors, or communication SoCs. |
| Burst Mode IQ | 2µA - enables multi-year operation from energy-harvesting or backup sources. |
| Switching frequency | 200kHz to 2.2MHz - adjustable via RT resistor; allows optimization of size vs. efficiency (e.g., 2MHz for compact 2.2µH inductors). |
| Min on-time | 46ns - supports high VIN-to-VOUT ratios (e.g., 24V→1.8V at 2MHz) without pulse skipping. |
| UVLO programming | VSET1/VSET2 = 0–1V → 0–20V threshold - enables precise input source handoff (e.g., 12V automotive main vs. 4.2V Li-ion backup). |
| PowerPath switchover | Automatic, no hold-up cap required - eliminates output droop during VIN1-to-VIN2 transition under 2.5A load. |
Pinout & Package
Package: 28-lead 4mm × 5mm plastic QFN (UFD) with exposed PGND pad (Pin 29) requiring PCB soldering for thermal and electrical integrity. θJA = 34°C/W.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| PGND (Pins 18,19,29) | Power ground return path | Mandatory low-impedance connection to PCB ground plane; exposed pad must be soldered for thermal dissipation and noise control. |
| VIN1 / PVIN1 (Pins 25,24) | Priority input Kelvin + power path | VIN1 is sense; PVIN1 supplies high-side gate driver and power stage - both require separate 0.1µF + 4.7µF ceramic bypassing. |
| VIN2 / PVIN2 (Pins 26,13) | Secondary input Kelvin + power path | Same dual-pin structure as VIN1; enables independent input impedance matching and transient suppression. |
| DIODE (Pin 23) | Mode select logic input | High = ideal diode-OR (auto-select highest valid input); Low = priority mode (VIN1 first, fallback to VIN2 only on UVLO). |
| PRIORITY (Pin 12) | Open-drain status output | Asserted low when buck is actively sourcing from VIN1 - used for system-level power path monitoring and sequencing. |
| VALID1 / VALID2 (Pins 1,28) | Open-drain input validity indicators | Low when respective input exceeds programmed UVLO - enables real-time health monitoring without external comparators. |
| RT (Pin 10) | Frequency programming node | Resistor to GND sets fSW: RT = 33.2MHz / fSW (e.g., 33.2kΩ → 1MHz); tolerance directly impacts regulation accuracy at light loads. |
| FB (Pin 9) | Feedback reference input | Regulates output to 818mV ±12mV; requires low-noise routing away from SW/BST nodes to avoid instability. |
Key Features
| Feature | Design Value |
|---|---|
| No-loss PowerPath™ switchover | Eliminates need for hold-up capacitors by enabling sub-50µs seamless transition between VIN1 and VIN2 under full 2.5A load. |
| Programmable dual-input UVLO | VSET1/VSET2 pins allow independent 2.34V–20V thresholds per input - critical for asymmetric sources (e.g., 24V automotive + 3.7V Li-ion). |
| 2µA Burst Mode quiescent current | Extends battery life in always-on backup systems; measured with VFB = 0.850V, not switching. |
| 60ns minimum on-time | Enables high step-down ratios (e.g., 36V→3.3V at 2MHz) without pulse-skipping artifacts or audible noise. |
| Integrated VREF (1.000V ±1.8mV) | Stable reference for UVLO dividers and external circuitry; 1mA max load ensures accuracy across temperature (-40°C to 125°C). |
| Thermally enhanced QFN | 4mm × 5mm footprint with exposed PGND pad delivers 34°C/W θJA - supports 2.5A continuous operation at 70°C ambient with minimal copper. |
Applications
| Automotive Battery Backup Systems | Industrial Uninterruptible Power Supplies |
|---|---|
Use Scenario: Maintaining 3.3V/2.5A power to CAN transceivers and microcontrollers during engine cranking (input dip to 6V) or alternator failure. IC Role / Device Role / Timing Role: Dual-input buck regulator with priority mode - VIN1 = 12V automotive bus, VIN2 = 3.7V Li-ion backup; switchover triggered by VIN1 UVLO. Use Value: Prevents system reset during 100ms–500ms brownouts; no hold-up capacitor reduces BOM cost and board area by >30%. | Use Scenario: Providing regulated 5V/2A to PLC I/O modules during AC mains loss, using supercapacitor bank as secondary source. IC Role / Device Role / Timing Role: Synchronous buck with ideal diode-OR mode - selects highest valid input between 24V DC supply and 15V supercap stack. Use Value: Achieves >95% efficiency at 1A (12V→5V), extends runtime by 2.3× vs. linear solution; 2µA IQ preserves supercap charge for >72 hours. |
| Portable Test Equipment Power | Redundant Telecom Power Interfaces |
Use Scenario: Powering handheld spectrum analyzers with dual inputs: USB-C PD (5–20V) and removable LiPo pack (3.0–4.2V). IC Role / Device Role / Timing Role: Input selector + regulator - VSET1/VSET2 configured for 4.5V/3.2V UVLO; DIODE pin set high for automatic OR-ing. Use Value: Enables hot-swap battery replacement without interrupting measurement; 46ns min on-time supports 20V→3.3V conversion at 2MHz. | Use Scenario: Supplying 12V/1.5A to baseband processors in 5G remote radio units with dual DC feeds (48V telecom + 24V PoE++). IC Role / Device Role / Timing Role: Priority-mode buck - VIN1 = 48V primary feed, VIN2 = 24V backup; PRIORITY pin signals active source to host controller. Use Value: Guarantees <50µs switchover during primary feed interruption; PGOOD/VALID outputs enable firmware-level fault logging and diagnostics. |
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 |
|---|---|---|---|
| LT8614EUDE#PBF | Single-input, 42V/4A, 2.5µA IQ, no PowerPath - lacks dual-input arbitration or VALID/PRIORITY status outputs. | Suitable only where backup source is managed externally (e.g., discrete OR-FET + separate supervisor IC). | Select when dual-input autonomy is unnecessary and higher peak current (4A) is required. |
| TPS63802DLAR | Single-input, 17V/2A, 1.5µA IQ, buck-boost topology - supports VOUT > VIN, but no input switchover or UVLO programming. | Applicable only for single-source systems needing wide VIN/VOUT ratio flexibility (e.g., 2.5V–15V input to 3.3V). | Choose when input voltage may fall below output (e.g., battery discharge), but dual-source redundancy is not needed. |
Compared with LT8614EUDE#PBF and TPS63802DLAR, the LTC3126EUFD#PBF uniquely integrates autonomous dual-input arbitration, programmable UVLO per channel, and dedicated status signaling - eliminating external comparators, FET drivers, and sequencing logic in backup power designs.
Availability
LTC3126EUFD#PBF is available at Aetrix Electronics and suitable for automotive battery backup, industrial uninterruptible power supplies, and portable test equipment requiring stable component supply across extended temperature ranges (–40°C to 125°C).
Supply support for LTC3126EUFD#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 precision analog and power management portfolio. The company specializes in high-performance signal conditioning and power conversion ICs for demanding industrial, automotive, and communications applications.
The LTC3126EUFD#PBF belongs to Linear's PowerPath™ regulator family, designed specifically for systems requiring seamless, capacitor-free switchover between two independent power sources while maintaining tight output regulation and low quiescent current.
FAQ
What is the maximum input voltage rating for LTC3126EUFD#PBF?
The LTC3126EUFD#PBF has an absolute maximum input voltage rating of 42V on PVIN1, PVIN2, VIN1, and VIN2 pins. This rating accommodates automotive load dump transients and industrial 36V bus systems. Operation above 42V risks permanent damage, and the device is guaranteed over 2.4V to 42V for normal functionality.
How does the LTC3126EUFD#PBF handle switchover between VIN1 and VIN2?
The LTC3126EUFD#PBF performs automatic, analog-controlled switchover in under 50µs with no output disturbance. In priority mode (DIODE = low), it sources from VIN1 until that input falls below its UVLO threshold, then transitions to VIN2. In ideal diode-OR mode (DIODE = high), it continuously selects the higher valid input - all without hold-up capacitors or external circuitry.
Can LTC3126EUFD#PBF operate with only one input source connected?
Yes, the LTC3126EUFD#PBF operates normally with only VIN1 or only VIN2 connected. When the unused input is left floating or grounded, its VALIDx output remains high (open-drain inactive), and the converter functions as a standard synchronous buck from the connected source. UVLO thresholds still apply, so grounding VSETx disables that input's programmable threshold.
What is the purpose of the EXTVCC pin on LTC3126EUFD#PBF?
The EXTVCC pin on LTC3126EUFD#PBF allows bootstrapping the internal VCC LDO from the output rail instead of the input sources. When driven ≥3.15V, EXTVCC powers the control circuitry, reducing quiescent current by up to 5× in high-VIN/low-VOUT applications (e.g., 36V→3.3V) and improving efficiency by bypassing the internal VIN-based LDO dropout.
Does LTC3126EUFD#PBF support external clock synchronization?
Yes, LTC3126EUFD#PBF supports external clock synchronization via the PWM/SYNC pin. Applying a 200kHz–2.2MHz CMOS clock forces fixed-frequency PWM operation and disables Burst Mode. This feature enables EMI reduction through frequency dithering or alignment with system clocks, and ensures deterministic timing in synchronized power domains.
LTC3126EUFD#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)
LTC3126EUFD#PBF FAQ
1.How can I place an order for LTC3126EUFD#PBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LTC3126EUFD#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 LTC3126EUFD#PBF reliable?
The price and inventory of LTC3126EUFD#PBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LTC3126EUFD#PBF is usually 5 days.
3.What payment methods are accepted for LTC3126EUFD#PBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LTC3126EUFD#PBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LTC3126EUFD#PBF?
LTC3126EUFD#PBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LTC3126EUFD#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 LTC3126EUFD#PBF?
For technical support, including LTC3126EUFD#PBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LTC3126EUFD#PBF requirements.
6.How does Aetrix verify that LTC3126EUFD#PBF is sourced from the original manufacturer or authorized distributors?
All LTC3126EUFD#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 LTC3126EUFD#PBF meets industry standards.
7.What is the process for return or replacement of LTC3126EUFD#PBF?
All LTC3126EUFD#PBF units undergo pre-shipment inspection (PSI). If there is an issue with LTC3126EUFD#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 LTC3126EUFD#PBF part is unused and in its original packaging.
Return procedure for LTC3126EUFD#PBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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