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Analog Devices Inc. LT3651IUHE-8.4#PBF
- Part No.:
- LT3651IUHE-8.4#PBF
- Manufacturer:
- Analog Devices Inc.
- Category:
- Battery Chargers
- Package:
- 36-WFQFN Exposed Pad
- Datasheet:
-
LT3651IUHE-8.4#PBF.pdf
- Description:
- IC BATT CHG LI-ION 2CELL 36QFN
- Quantity:
- Payment:
- Shipping:
Inventory:3,595
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Product details
Overview
LT3651IUHE-8.4#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 8.4V, supports C/10 or programmable timer termination, and integrates NTC-based temperature monitoring for automotive cradle chargers and industrial handheld instruments.
For engineers reviewing the LT3651IUHE-8.4#PBF datasheet, LT3651IUHE-8.4#PBF pinout, LT3651IUHE-8.4#PBF application, or LT3651IUHE-8.4#PBF equivalent, key selection criteria include its 8.4V fixed float voltage, 36-lead QFN package with exposed SW/GND pads, ±7.5% charge current accuracy, dynamic input current limiting via ILIM, and auto-preconditioning below 5.8V battery voltage.
Technical Context
The LT3651IUHE-8.4#PBF implements an average current mode control loop using dual error amplifiers: V-EA regulates BAT voltage against an internal 8.4V reference, while C-EA compares scaled ITH (divided by 10) against SENSE–BAT voltage to enforce precise constant-current regulation. Its synchronous switcher uses bootstrapped high-side drive (BOOST pin) and MOSFET low-side switching to achieve >90% efficiency at 4A into 2-cell Li-Ion.
Charge termination is configurable: C/10 detection triggers when sensed current falls to ≤12.3mV across RSENSE, or timer-based termination uses a user-programmed capacitor on TIMER pin (e.g., 0.68µF = 3 hours). Fault handling includes bad battery detection (precondition timeout ≤22.5 min), thermal shutdown, and open-collector FAULT/CHRG status outputs with 10mA sink capability.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Float Voltage | 8.4V ±0.5% - precisely regulates 2-cell Li-Ion full-charge voltage with minimal thermal drift. |
| Max Charge Current | 4A - delivered via synchronous step-down with external RSENSE; accuracy ±7.5% ensures safe battery stress limits. |
| Input Voltage Range | 9V to 32V - supports 12V/24V automotive and industrial supplies; absolute max 40V prevents damage during transients. |
| C/10 Detection Threshold | 4.5mV to 12.3mV (SENSE–BAT) - enables reliable end-of-charge detection with low-noise sensing design. |
| Precondition Threshold | 5.80V - initiates 15% reduced charge current for deeply discharged batteries to prevent lithium plating. |
| Standby Supply Current | 85µA - minimizes parasitic drain when battery is fully charged and system is idle. |
| Oscillator Frequency | 1.1MHz typical (RT = 54.9kΩ) - enables compact magnetics and low output ripple in space-constrained designs. |
Pinout & Package
LT3651IUHE-8.4#PBF uses a 5mm × 6mm 36-lead plastic QFN package with two exposed thermal pads: Pin 37 (GND) and Pin 38 (SW), both requiring PCB soldering for thermal and electrical integrity.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| NTC (1) | Battery temperature monitor input | Sources 50µA into external 10kΩ NTC thermistor; halts charging if voltage falls outside 0.29V–1.36V range (0°C–40°C). |
| ACPR (2) | Open-collector AC present indicator | Sinks up to 10mA when VIN valid; enables system-level power-good signaling without additional logic. |
| BAT (3) | Kelvin battery voltage sense | Direct connection to battery anode; <0.1µA bias current post-charge minimizes self-discharge. |
| SENSE (4) | Charge current sense return | Completes current-sense path with BAT; 95mV full-scale corresponds to 4A max charge current. |
| BOOST (5) | High-side gate drive bootstrap supply | Requires ≥1µF capacitor to SW; sustains low RDS(on) for top switch under high-duty-cycle conditions. |
| GND (6,23,31,37) | Power and signal ground | Pins 37 (exposed pad) must be soldered to PCB plane for thermal management and noise immunity. |
| SW (7,11–18,22,38) | Synchronous switch node | Pins 38 (exposed pad) must be soldered to PCB; handles peak inductor current and high di/dt switching. |
| 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 status | Pulled low for NTC out-of-range, bad battery, or timer timeout; compatible with 3.3V/5V/24V pull-up rails. |
| 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 programmed input current limit. |
| VIN (32–34) | Main input power supply | Three parallel pins reduce trace resistance and thermal rise at up to 4A input current. |
| RNG/SS (35) | Charge current range and soft-start | 50µA sourced to RRNG/SS; 0–1V range scales max SENSE–BAT voltage from 0 to 95mV (0–4A). |
| RT (36) | Oscillator frequency set | Resistor to GND sets fSW: 54.9kΩ = 1.1MHz; enables optimization of efficiency vs. EMI trade-offs. |
Key Features
| Feature | Design Value |
|---|---|
| Auto-preconditioning below 5.8V | Reduces charge current to 15% of programmed value to safely recover deeply discharged 2-cell Li-Ion batteries. |
| Dynamic input current limiting | Maintains constant system input current by regulating battery charge current via CLP/CLN and ILIM feedback. |
| NTC-based thermal safety | Halts charging if battery temperature exceeds 0°C–40°C range, verified by 0.29V–1.36V voltage window on NTC pin. |
| Low-quiescent standby mode | Draws only 85µA from VIN after charge termination, extending host system runtime during battery-connected idle states. |
| Auto-recharge at 97.5% float voltage | Triggers new CC/CV cycle when BAT voltage drops 2.5% below 8.4V, ensuring battery remains at optimal state-of-charge. |
Applications
| Automotive Cradle Chargers | Industrial Handheld Instruments |
|---|---|
|
Use Scenario: Vehicle-mounted docking station for rugged tablets used in field service and logistics. IC Role / Device Role / Timing Role: Primary 2-cell Li-Ion charger managing 24V vehicle supply conversion, thermal monitoring, and automatic recharge cycles. Use Value: Enables hot-swap battery operation with zero downtime; NTC integration prevents thermal runaway during extended charging in high-ambient environments. |
Use Scenario: Portable gas analyzers and multimeters requiring long runtime and reliable field recharging. IC Role / Device Role / Timing Role: Monolithic charger IC providing precision 8.4V float regulation, C/10 termination, and input current limiting for shared 12V power rails. Use Value: Guarantees ±0.5% voltage accuracy over –40°C to 125°C junction temperature, ensuring battery longevity in uncontrolled environmental conditions. |
| Desktop Battery Cradles | Notebook Computer Docking Stations |
|
Use Scenario: Office desk cradle supporting simultaneous charging of multiple 2-cell Li-Ion packs for test equipment. IC Role / Device Role / Timing Role: High-efficiency (≥90%) synchronous charger with programmable 3-hour timer and bad-battery detection. Use Value: Detects failed cells within 22.5 minutes via precondition timeout, preventing overcharging and enabling automated maintenance alerts. |
Use Scenario: Docking station supplying power to notebook while concurrently charging its removable 2-cell battery pack. IC Role / Device Role / Timing Role: Dual-role power manager regulating both system load delivery (via CLP/CLN) and battery charge current (via SENSE/BAT). Use Value: Maintains stable 24V input current draw even as battery SoC changes, avoiding upstream supply brownouts during peak charging. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar 2-cell Li-Ion charger applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| LT3651EUHE-8.4#PBF | Same silicon, rated for 0°C to 85°C ambient (vs. –40°C to 125°C for LT3651IUHE-8.4#PBF); identical pinout and electrical specs. | Suitable for commercial-grade desktop cradles but not automotive or industrial environments with extended temperature requirements. | Select LT3651IUHE-8.4#PBF for designs requiring guaranteed operation across –40°C to 125°C junction temperature. |
| BQ24610RGER | TI 2-cell charger with 8.4V float; lacks integrated NTC monitoring, timer-based bad-battery detection, and input current limiting via CLP/CLN. | Requires external circuitry for thermal safety and system-level current control, increasing BOM count and layout complexity. | Choose LT3651IUHE-8.4#PBF when integrated safety features, minimal external components, and robust industrial qualification are mandatory. |
Compared with LT3651EUHE-8.4#PBF, the LT3651IUHE-8.4#PBF provides guaranteed performance over –40°C to 125°C, critical for automotive and heavy equipment. Against BQ24610RGER, it delivers complete thermal protection and system-level current regulation without added components-reducing design risk and time-to-market.
Availability
LT3651IUHE-8.4#PBF is available at Aetrix Electronics and suitable for automotive cradle chargers, industrial handheld instruments, desktop battery cradles, and notebook docking stations requiring stable component supply across extended temperature ranges.
Supply support for LT3651IUHE-8.4#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 reliability-critical applications.
The LT3651 product line delivers monolithic, high-voltage Li-Ion chargers for demanding 2-cell applications where wide input range, integrated safety, and thermal robustness are essential-targeting automotive, industrial, and portable instrumentation markets.
FAQ
What is the exact float voltage specification for LT3651IUHE-8.4#PBF?
The LT3651IUHE-8.4#PBF has a fixed nominal float voltage of 8.4V, specified with ±0.5% accuracy over the full –40°C to 125°C operating junction temperature range. This tolerance ensures precise termination for 2-cell Li-Ion batteries without external calibration, directly supporting JEITA-compliant charging profiles in industrial and automotive applications.
Does LT3651IUHE-8.4#PBF support both C/10 and timer-based charge termination?
Yes, the LT3651IUHE-8.4#PBF supports both termination methods. C/10 detection occurs when the SENSE–BAT voltage falls to 4.5–12.3mV; timer termination is set via a capacitor on the TIMER pin (e.g., 0.68µF = 3 hours). The device allows selection between modes-timer disabled by grounding TIMER, otherwise defaulting to timer-first behavior with C/10 as secondary check.
How does LT3651IUHE-8.4#PBF implement battery temperature monitoring?
The LT3651IUHE-8.4#PBF monitors battery temperature using a 10kΩ NTC thermistor connected between the NTC pin and GND. The IC sources 50µA, measuring resulting voltage: charging halts if voltage falls outside 0.29V–1.36V (corresponding to ~0°C–40°C). No external ADC or microcontroller is required-the function is fully autonomous and integrated.
What is the purpose of the CLP and CLN pins on LT3651IUHE-8.4#PBF?
The CLP and CLN pins enable system-level input current limiting. A sense resistor between CLP and CLN measures total input current (charger + system load). The LT3651IUHE-8.4#PBF dynamically reduces battery charge current to maintain the programmed input limit-ensuring stable operation from shared 12V/24V supplies without overloading upstream sources.
Can LT3651IUHE-8.4#PBF operate safely with a 32V input supply?
Yes, the LT3651IUHE-8.4#PBF is rated for continuous operation up to 32V input and has an absolute maximum rating of 40V. Its internal VIN OVLO threshold is 32V (with 1.1V hysteresis), providing robust protection against sustained overvoltage. This makes it suitable for 24V automotive and industrial systems where load-dump transients are managed externally.
LT3651IUHE-8.4#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:
- 8.4V
- Voltage - Supply (Max):
- 32V
- Interface:
- -
- Operating Temperature:
- -40°C ~ 125°C (TJ)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 36-QFN (5x6)
LT3651IUHE-8.4#PBF FAQ
1.How can I place an order for LT3651IUHE-8.4#PBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LT3651IUHE-8.4#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 LT3651IUHE-8.4#PBF reliable?
The price and inventory of LT3651IUHE-8.4#PBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LT3651IUHE-8.4#PBF is usually 5 days.
3.What payment methods are accepted for LT3651IUHE-8.4#PBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LT3651IUHE-8.4#PBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LT3651IUHE-8.4#PBF?
LT3651IUHE-8.4#PBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LT3651IUHE-8.4#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 LT3651IUHE-8.4#PBF?
For technical support, including LT3651IUHE-8.4#PBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LT3651IUHE-8.4#PBF requirements.
6.How does Aetrix verify that LT3651IUHE-8.4#PBF is sourced from the original manufacturer or authorized distributors?
All LT3651IUHE-8.4#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 LT3651IUHE-8.4#PBF meets industry standards.
7.What is the process for return or replacement of LT3651IUHE-8.4#PBF?
All LT3651IUHE-8.4#PBF units undergo pre-shipment inspection (PSI). If there is an issue with LT3651IUHE-8.4#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 LT3651IUHE-8.4#PBF part is unused and in its original packaging.
Return procedure for LT3651IUHE-8.4#PBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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