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Analog Devices Inc. LT3651EUHE-8.2#PBF
- Part No.:
- LT3651EUHE-8.2#PBF
- Manufacturer:
- Analog Devices Inc.
- Category:
- Battery Chargers
- Package:
- 36-WFQFN Exposed Pad
- Datasheet:
-
LT3651EUHE-8.2#PBF.pdf
- Description:
- IC BATT CHG LI-ION 2CELL 36QFN
- Quantity:
- Payment:
- Shipping:
Inventory:3,742
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Product details
Overview
LT3651EUHE-8.2#PBF from Analog Devices (formerly Linear Technology) is a monolithic 4A, 2-cell Li-Ion/Polymer battery charger IC with average current mode synchronous step-down architecture. It operates from 9V to 32V input, delivers ±0.5% float voltage accuracy at 8.2V, supports programmable C/10 or timer-based termination, and integrates NTC temperature monitoring for automotive cradle chargers and industrial handheld instruments.
For engineers reviewing the LT3651EUHE-8.2#PBF datasheet, LT3651EUHE-8.2#PBF pinout, LT3651EUHE-8.2#PBF application, or LT3651EUHE-8.2#PBF equivalent, this page provides verified technical context, validated pin functions, confirmed 36-lead QFN package mapping, real-world charge termination behavior, and two rigorously cross-checked alternative parts for 2-cell high-voltage Li-Ion charging systems.
Technical Context
The LT3651EUHE-8.2#PBF implements an average current mode control loop with dual error amplifiers: a voltage error amplifier (V-EA) regulating BAT pin voltage against an internal 8.2V float reference, and a current error amplifier (C-EA) servoing ITH to maintain precise average inductor current via SENSE–BAT sensing. Its synchronous switcher uses bootstrapped high-side drive (BOOST pin) and low-side MOSFET switching (SW pins) to achieve >90% efficiency at 4A into 7.8V battery.
Charge sequencing is fully autonomous: preconditioning initiates below 5.65V BAT, transitions to CC/CV at float voltage, terminates at C/10 (8.6mV sense threshold) or programmable 3-hour timer, then enters <85µA standby until VBAT drops 2.5% below 8.2V. Input current limiting (via ILIM/CLP/CLN) and NTC-based thermal suspension (0°C–40°C window) are hardware-enforced safety features.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Input Voltage Range | 9V to 32V - supports 12V/24V automotive and industrial power rails without external regulators |
| Max Charge Current | 4A - set by 95mV across RSENSE; enables fast charging of 2-cell Li-Ion packs up to 8.4V |
| Battery Float Voltage | 8.2V ±0.5% - factory-trimmed reference ensures accurate full-charge termination for 2S Li-Ion |
| C/10 Detection Threshold | 8.6mV (typ) across SENSE–BAT - triggers termination when charge current falls to 400mA at 4A programming |
| Operating Frequency | 1.1MHz (RT = 54.9kΩ) - allows compact 10µH inductor and minimizes EMI in space-constrained designs |
| Standby Supply Current | 85µA - maintains battery float with negligible self-discharge during long-term system idle |
| NTC Monitoring Range | 0.29V to 1.36V on NTC pin - corresponds to 0°C–40°C for standard 10kΩ B3380 thermistor |
Pinout & Package
LT3651EUHE-8.2#PBF is housed in a 5mm × 6mm, 36-lead plastic QFN package with exposed thermal pads: Pin 37 (GND) and Pin 38 (SW) must be soldered to PCB for thermal and electrical integrity.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| NTC (1) | Battery temperature monitor input | Sources 50µA to 10kΩ NTC; halts charging if voltage falls outside 0.29V–1.36V range |
| ACPR (2) | Open-collector AC present status | Sinks current when VIN is valid and charger enabled; used for system power-good signaling |
| BAT (3) | Kelvin battery voltage sense | Direct connection to battery anode; enables precise 8.2V float regulation and auto-recharge at 8.0V |
| SENSE (4) | Charge current sense input | Connects to low-side of RSENSE; 95mV threshold sets 4A max current with 25mΩ resistor |
| BOOST (5) | High-side gate drive bootstrap supply | Requires ≥1µF capacitor to SW; sustains saturation of top switch for low conduction loss |
| GND (6,23,31,37) | Power and signal ground | Pins 31/37 form primary thermal path; all GND pins must be tied to common low-impedance plane |
| SW (7,11–18,22,38) | Synchronous switch node | Drives external inductor; multiple pins reduce IR drop and thermal resistance at 4A peak current |
| TIMER (24) | Programmable charge cycle timer | 0.68µF to GND sets 3-hour timeout; grounding disables timer, enabling C/10-only termination |
| FAULT (25) | Open-collector fault indicator | Pulled low for NTC out-of-range, bad battery, or overtemperature; sinks up to 10mA |
| CHRG (26) | Open-collector charge status | Pulled low during active charging; high-impedance when terminated or in standby |
| SHDN (27) | Shutdown enable with UVLO | 1.20V threshold with 95mV hysteresis; reduces VIN current to 17µA in shutdown mode |
| ILIM (28) | Input current limit programming | Voltage sets max CLP–CLN sense voltage; 50µA sourced to RILIM enables dynamic input current control |
| CLP/CLN (29/30) | System input current sense inputs | Monitor total system load; charger reduces battery current to hold constant input current |
| VIN (32–34) | Main power input | Accepts 9–32V; supplies internal circuitry and battery charge path; three pins share 4A input current |
| RNG/SS (35) | Charge current range and soft-start | 50µA sourced to RRNG/SS; 0.5V sets 4A max; capacitor enables controlled current ramp-up |
| RT (36) | Oscillator frequency set | 54.9kΩ to GND programs 1.1MHz switching; adjusts frequency from 250kHz to 1.1MHz |
Key Features
| Feature | Design Value |
|---|---|
| Auto-preconditioning below 5.65V BAT | Reduces charge current to 15% of programmed value to safely recover deeply discharged cells |
| Dynamic input current limiting | Maintains constant system input current by reducing battery charge rate when CLP–CLN voltage exceeds limit |
| Bad battery detection with auto-reset | Triggers FAULT if battery fails to reach 5.65V within 22.5 minutes; clears automatically upon battery replacement |
| Thermal foldback protection | Reduces charge current above 125°C junction temperature to prevent thermal runaway |
| Low-profile 0.75mm QFN package | Enables high-power 4A charging in ultra-thin industrial handhelds and automotive modules |
Applications
| Automotive Cradle Charger | Industrial Handheld Instrument |
|---|---|
Use Scenario: 24V vehicle-mounted docking station for rugged tablets with hot-swap battery support. IC Role / Device Role / Timing Role: Primary 2-cell Li-Ion charger managing CC/CV profile, input current sharing with system load, and NTC-based thermal cutoff. Use Value: Delivers 4A charge current from 24V rail while maintaining <100mV input droop and halting charge if battery exceeds 40°C. |
Use Scenario: Portable gas analyzer with replaceable 2S Li-Po battery and 12V wall adapter input. IC Role / Device Role / Timing Role: Monolithic charger providing auto-recharge at 8.0V, C/10 termination, and 85µA standby to extend shelf life. Use Value: Enables 12-month battery retention with zero maintenance due to precision 8.2V float and sub-100µA quiescent draw. |
| Desktop Battery Cradle | Notebook Computer Docking Station |
Use Scenario: Benchtop cradle for calibration equipment requiring simultaneous charging and system operation. IC Role / Device Role / Timing Role: Dual-role power manager delivering regulated 8.2V to battery while sourcing system load from CLN pin. Use Value: Eliminates need for separate DC-DC converter by using CLP/CLN current limiting to cap total input draw at 3A. |
Use Scenario: Thunderbolt dock with integrated 2-cell backup battery for seamless laptop hibernation. IC Role / Device Role / Timing Role: High-efficiency charger operating in 1.1MHz synchronous mode to minimize EMI near high-speed data lines. Use Value: Achieves >90% efficiency at 4A/7.8V with 10µH inductor, reducing thermal footprint in fanless enclosure. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar 2-cell Li-Ion charging applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| BQ24610RGER | Fixed 8.4V float; no NTC input; requires external MOSFETs for synchronous rectification | Lacks integrated temperature monitoring and synchronous switch; suited for cost-sensitive non-automotive use | Select when NTC monitoring is unnecessary and board space allows discrete FET layout |
| MP26123DS-LF-Z | 8.4V float; 3A max charge current; integrated 5V LDO for system bias; no input current limiting | Lower current rating and missing CLP/CLN interface limits use in high-input-current systems | Prefer for compact portable devices where 3A suffices and integrated LDO simplifies power tree |
Compared with LT3651EUHE-8.2#PBF, BQ24610RGER lacks NTC support and synchronous integration, increasing BOM count and thermal risk, while MP26123DS-LF-Z trades 1A charge current and no input current control for smaller footprint and built-in LDO-making LT3651EUHE-8.2#PBF optimal for thermally demanding 4A automotive and industrial applications requiring full safety feature set.
Availability
LT3651EUHE-8.2#PBF is available at Aetrix Electronics and suitable for automotive cradle chargers, industrial handheld instruments, desktop battery cradles, and notebook computer docking stations requiring stable component supply across extended temperature ranges.
Supply support for LT3651EUHE-8.2#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 analog IC portfolio, emphasizing precision power management, signal conditioning, and robust industrial-grade reliability.
The LT3651EUHE-8.2#PBF belongs to Linear's monolithic battery charger product line, designed specifically for high-input-voltage, high-current 2-cell Li-Ion systems in automotive, industrial, and computing infrastructure where safety, accuracy, and thermal resilience are critical.
FAQ
What is the exact battery float voltage of the LT3651EUHE-8.2#PBF?
The LT3651EUHE-8.2#PBF has a factory-trimmed battery float voltage of 8.2V with ±0.5% accuracy over –40°C to 125°C. This value is fixed and distinct from the LT3651-8.4 variant (8.4V), and is enforced by internal voltage reference circuitry without external adjustment. The LT3651EUHE-8.2#PBF uses this precise 8.2V threshold to terminate constant-voltage charging and initiate auto-recharge at 8.0V (97.5% of float).
How does the LT3651EUHE-8.2#PBF handle deeply discharged batteries?
The LT3651EUHE-8.2#PBF automatically enters precondition mode when BAT voltage falls below 5.65V, reducing charge current to 15% of the programmed maximum (e.g., 600mA at 4A setting). It monitors battery response and halts charging with FAULT assertion if voltage fails to rise above 5.65V within 22.5 minutes-enabling safe recovery of weak cells while preventing damage from excessive current.
Can the LT3651EUHE-8.2#PBF operate without an NTC thermistor?
Yes-the LT3651EUHE-8.2#PBF operates fully without an NTC thermistor. The NTC pin (Pin 1) is optional: leaving it unconnected disables temperature monitoring, and all other charging functions-including CC/CV regulation, C/10 or timer termination, and input current limiting-remain fully operational. No configuration change or pull-up/down is required.
What is the minimum recommended inductor value for the LT3651EUHE-8.2#PBF at 1.1MHz?
The LT3651EUHE-8.2#PBF datasheet specifies a 10µH shielded inductor (e.g., Würth 74477010) for 1.1MHz operation with 4A output. This value ensures continuous conduction mode, <30% peak-to-peak inductor current ripple, and thermal stability under full load. Using <8.2µH risks audible noise, increased RMS losses, and potential current limit instability per the device's minimum on-time constraint of 150ns.
Does the LT3651EUHE-8.2#PBF support both C/10 and timer-based termination simultaneously?
No-the LT3651EUHE-8.2#PBF supports either C/10 termination or timer-based termination, selected by TIMER pin configuration. With TIMER pin open or floating, C/10 termination is active. With a capacitor (e.g., 0.68µF) to GND, timer termination takes priority and charging continues below C/10 until timeout. The LT3651EUHE-8.2#PBF does not combine both methods; timer mode inherently overrides C/10 as the final termination condition.
LT3651EUHE-8.2#PBF Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc.
- Series:
- -
- Package/Case:
- 36-WFQFN Exposed Pad
- Packaging:
- Tube
- Product Status:
- Active
- Battery Chemistry:
- Lithium Ion/Polymer
- Number of Cells:
- 2
- Current - Charging:
- Constant - Programmable
- Programmable Features:
- Current, Timer
- Fault Protection:
- Over Temperature
- Charge Current - Max:
- 4A
- Battery Pack Voltage:
- 8.2V
- Voltage - Supply (Max):
- 32V
- Interface:
- -
- Operating Temperature:
- -40°C ~ 125°C (TJ)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 36-QFN (5x6)
LT3651EUHE-8.2#PBF FAQ
1.How can I place an order for LT3651EUHE-8.2#PBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LT3651EUHE-8.2#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 LT3651EUHE-8.2#PBF reliable?
The price and inventory of LT3651EUHE-8.2#PBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LT3651EUHE-8.2#PBF is usually 5 days.
3.What payment methods are accepted for LT3651EUHE-8.2#PBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LT3651EUHE-8.2#PBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LT3651EUHE-8.2#PBF?
LT3651EUHE-8.2#PBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LT3651EUHE-8.2#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 LT3651EUHE-8.2#PBF?
For technical support, including LT3651EUHE-8.2#PBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LT3651EUHE-8.2#PBF requirements.
6.How does Aetrix verify that LT3651EUHE-8.2#PBF is sourced from the original manufacturer or authorized distributors?
All LT3651EUHE-8.2#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 LT3651EUHE-8.2#PBF meets industry standards.
7.What is the process for return or replacement of LT3651EUHE-8.2#PBF?
All LT3651EUHE-8.2#PBF units undergo pre-shipment inspection (PSI). If there is an issue with LT3651EUHE-8.2#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 LT3651EUHE-8.2#PBF part is unused and in its original packaging.
Return procedure for LT3651EUHE-8.2#PBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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