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Analog Devices Inc. LT3651EUHE-8.4#PBF
- Part No.:
- LT3651EUHE-8.4#PBF
- Manufacturer:
- Analog Devices Inc.
- Category:
- Battery Chargers
- Package:
- 36-WFQFN Exposed Pad
- Datasheet:
-
LT3651EUHE-8.4#PBF.pdf
- Description:
- IC BATT CHG LI-ION 2CELL 36QFN
- Quantity:
- Payment:
- Shipping:
Inventory:418
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Product details
Overview
LT3651EUHE-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 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-8.4#PBF datasheet, LT3651EUHE-8.4#PBF pinout, LT3651EUHE-8.4#PBF application, or LT3651EUHE-8.4#PBF equivalent, key selection considerations include its 36-lead QFN package, 8.4V fixed float voltage, ±7.5% charge current accuracy, dynamic input current limiting via ILIM, and auto-preconditioning below 5.8V battery voltage.
Technical Context
The LT3651EUHE-8.4#PBF implements an average current mode control loop using dual error amplifiers: a voltage error amplifier (V-EA) sets ITH based on BAT-to-8.4V reference deviation, while a current error amplifier (C-EA) compares scaled ITH against SENSE–BAT voltage to regulate inductor current. Its synchronous switcher uses bootstrapped high-side drive (BOOST pin) and MOSFET low-side switching for efficiency up to 91% at 24VIN/7.8VBAT/4A.
Charge sequencing is fully autonomous: preconditioning activates below 5.8V with 15% reduced current; CV mode engages near 8.4V; C/10 termination triggers when SENSE–BAT falls to 8.6mV (typ); timer termination uses external capacitor on TIMER pin for 3-hour default cycle. Fault handling includes open-collector FAULT/CHRG outputs, thermal foldback above 125°C, and bad-battery detection after 22.5 minutes in precondition.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Float Voltage | 8.4V ±0.5% - precisely regulates 2-cell Li-ion full-charge voltage; enables compliance with JEITA battery safety standards. |
| Max Charge Current | 4A - set by external sense resistor; corresponds to 95mV across RSENSE; supports fast charging of high-capacity packs. |
| Input Voltage Range | 9V to 32V - accommodates 12V/24V automotive and industrial supplies; 40V absolute max prevents damage during load dump. |
| C/10 Detection Accuracy | ±4% - ensures reliable termination at ~0.4A for 4A programmed current; minimizes overcharge risk in CV phase. |
| NTC Monitoring Range | 0.29V to 1.36V - supports standard 10kΩ B3380 thermistor; halts charging outside 0°C–40°C safe zone. |
| Standby Current | 85µA - maintains battery float with negligible self-discharge; enables long-term connection in desktop cradles. |
| Oscillator Frequency | 1.1MHz (RT = 54.9kΩ) - allows compact 10µH inductor; reduces EMI vs lower-frequency alternatives. |
Pinout & Package
LT3651EUHE-8.4#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 management and electrical integrity.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| NTC (1) | Battery temperature monitor input | Sources 50µA to 10kΩ NTC; voltage threshold (0.29V–1.36V) defines safe charging window. |
| ACPR (2) | Open-collector AC present indicator | Sinks current when VIN valid; signals system controller that input power is stable and charger is active. |
| BAT (3) | Kelvin battery voltage sense | Directly monitors cell stack voltage; enables accurate 8.4V regulation and 2.5% auto-recharge hysteresis. |
| SENSE (4) | Charge current sense input | Measures voltage drop across RSENSE; sets average charge current with ±7.5% accuracy up to 4A. |
| BOOST (5) | High-side gate drive bootstrap supply | Charges 1µF capacitor to SW+4V; ensures low RDS(on) for top switch, improving efficiency >90%. |
| GND (6,23,31,37) | Power and signal ground | Pins 31/37 are thermal pads requiring PCB soldering; low-impedance return path critical for current sensing stability. |
| SW (7,11–18,22,38) | Synchronous switch node | Drives external inductor; Pin 38 is exposed pad-must be soldered to minimize thermal resistance and EMI. |
| TIMER (24) | Programmable charge cycle timer | 0.68µF to GND sets 3-hour timeout; enables top-off charging beyond C/10 and bad-battery fault detection. |
| FAULT (25) | Open-collector fault status output | Pulled low for NTC out-of-range, bad battery, or thermal shutdown; drives LED or microcontroller interrupt. |
| CHRG (26) | Open-collector charge status output | Pulled low during active charging; high-impedance when terminated-indicates ready-for-use battery state. |
| SHDN (27) | Shutdown enable with precision UVLO | 1.20V threshold with 95mV hysteresis; reduces VIN current to 17µA in shutdown-ideal for battery-backed systems. |
| ILIM (28) | Input current limit programming | Voltage sets max input current via CLP/CLN sense resistor; enables dynamic load sharing with system loads. |
| CLP/CLN (29/30) | System input current sense inputs | Monitor total input current; allow charger to throttle battery current to maintain constant 12V/24V rail loading. |
| RNG/SS (35) | Charge current range and soft-start | 0–1V input scales max charge current; capacitor to GND provides controlled ramp-up, reducing inrush stress. |
| RT (36) | Oscillator frequency set | 54.9kΩ to GND sets 1.1MHz switching; higher frequency enables smaller magnetics and faster transient response. |
Key Features
| Feature | Design Value |
|---|---|
| Auto-preconditioning below 5.8V | Reduces charge current to 15% of programmed value-prevents lithium plating on deeply discharged cells. |
| Dynamic input current limiting | Regulates battery charge current in real time to hold total system input current constant-enables shared 12V/24V rails. |
| Thermal foldback protection | Reduces charge current above 125°C junction temperature-prevents thermal runaway without hard shutdown. |
| Bad battery detection | Triggers FAULT if battery fails to reach 5.8V within 22.5 minutes-avoids indefinite charging of shorted or open cells. |
| Low-quiescent standby mode | Draws only 85µA after charge termination-minimizes parasitic drain in always-connected cradle applications. |
Applications
| Automotive Battery Cradle Charger | Industrial Handheld Instrument |
|---|---|
|
Use Scenario: 24V vehicle electrical system powers a portable diagnostic tool cradle that charges internal 2S Li-ion packs. IC Role / Device Role / Timing Role: LT3651EUHE-8.4#PBF acts as primary CC/CV charger with input current limiting to avoid overloading alternator or fuse. Use Value: Maintains constant 24V input draw while delivering 4A to battery; NTC monitoring ensures safe charging in hot engine bays. |
Use Scenario: Ruggedized field meter with replaceable 2S Li-ion battery pack requires reliable charging from 12V wall adapter. IC Role / Device Role / Timing Role: LT3651EUHE-8.4#PBF provides autonomous charge management including precondition, CV regulation, and auto-restart. Use Value: ±0.5% float voltage accuracy extends battery cycle life; 85µA standby current prevents pack discharge during storage. |
| Notebook Computer Docking Station | Desktop USB-C PD Power Bank |
|
Use Scenario: Docking station accepts 20V USB-C PD input and charges both host laptop and peripheral devices. IC Role / Device Role / Timing Role: LT3651EUHE-8.4#PBF manages high-current 2S battery charging while sharing input power with USB ports. Use Value: Input current limiting via ILIM/CLP/CLN prevents exceeding 3A PD contract; timer termination enables top-off for full capacity. |
Use Scenario: High-capacity portable power bank uses 24V DC input to rapidly recharge 2S Li-ion cells for mobile device support. IC Role / Device Role / Timing Role: LT3651EUHE-8.4#PBF serves as main charging controller with BOOST-driven synchronous switcher for >90% efficiency. Use Value: 1.1MHz operation allows 10µH inductor-reducing solution size by 40% vs 500kHz alternatives; QFN package aids thermal design. |
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 |
|---|---|---|---|
| BQ24610RGER | Fixed 8.4V float; no NTC input; uses external MOSFETs; 3A max charge current | Lacks integrated synchronous switches and temperature monitoring-requires additional FETs and thermistor circuitry | Select when cost-sensitive designs can accept discrete power stage and omit battery thermal safety. |
| MP2617GR-Z | 8.4V float; 3.5A max; integrated NTC; 2.5V–36V input; no input current limiting | Supports wider VIN but lacks CLP/CLN-based system current regulation-unsuitable for shared-rail applications | Choose for simpler 2S charging where input current coordination with system loads is not required. |
Compared with BQ24610RGER and MP2617GR-Z, the LT3651EUHE-8.4#PBF uniquely combines 4A synchronous switching, precise 8.4V regulation, NTC monitoring, and dynamic input current limiting in a single QFN-making it optimal for space-constrained, safety-critical 24V-powered battery systems.
Availability
LT3651EUHE-8.4#PBF is available at Aetrix Electronics and suitable for automotive cradle chargers, industrial handheld instruments, notebook docking stations, and desktop power banks requiring stable component supply and long-term lifecycle support.
Supply support for LT3651EUHE-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) is a global leader in high-performance analog, mixed-signal, and power management semiconductors.
The LT3651EUHE-8.4#PBF belongs to Linear's high-voltage battery charger product line, designed specifically for robust, high-current charging of 2-cell Li-ion/polymer batteries in automotive, industrial, and computing applications.
FAQ
What is the exact float voltage setpoint of the LT3651EUHE-8.4#PBF?
The LT3651EUHE-8.4#PBF has a factory-trimmed float voltage of 8.4V with ±0.5% accuracy over –40°C to 125°C. This fixed value is specific to the "-8.4" variant and differs from the LT3651-8.2's 8.2V setting. The voltage is internally referenced and does not require external resistive programming.
Does the LT3651EUHE-8.4#PBF support both C/10 and timer-based charge termination?
Yes, the LT3651EUHE-8.4#PBF supports both methods. C/10 termination occurs when sensed current drops to 10% of the programmed maximum (e.g., 0.4A for 4A setting). Timer termination is enabled by connecting a capacitor to the TIMER pin-0.68µF yields a 3-hour cycle. The two modes are mutually exclusive and selected at design time.
How does the LT3651EUHE-8.4#PBF implement input current limiting?
The LT3651EUHE-8.4#PBF uses the CLP and CLN pins to monitor system input current via an external sense resistor. The ILIM pin sets the target voltage across that resistor. When actual input current exceeds the limit, the charger dynamically reduces battery charge current to maintain constant total input draw-critical for shared 12V/24V rails.
What is the role of the RNG/SS pin on the LT3651EUHE-8.4#PBF?
The RNG/SS pin on the LT3651EUHE-8.4#PBF sets the maximum charge current by scaling the internal current sense threshold. A 0–1V input corresponds to 0–100% of full-scale current (e.g., 0.5V = 2A for 4A max). Adding a capacitor to ground provides soft-start, preventing inrush current into the battery during initial connection.
Can the LT3651EUHE-8.4#PBF operate safely without an NTC thermistor?
Yes-the NTC pin (Pin 1) is optional. If left unconnected, temperature monitoring is disabled and the LT3651EUHE-8.4#PBF proceeds with charging normally. However, this removes JEITA-compliant thermal safety; for automotive or medical applications, Analog Devices recommends retaining the NTC circuit.
LT3651EUHE-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)
LT3651EUHE-8.4#PBF FAQ
1.How can I place an order for LT3651EUHE-8.4#PBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LT3651EUHE-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 LT3651EUHE-8.4#PBF reliable?
The price and inventory of LT3651EUHE-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 LT3651EUHE-8.4#PBF is usually 5 days.
3.What payment methods are accepted for LT3651EUHE-8.4#PBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LT3651EUHE-8.4#PBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LT3651EUHE-8.4#PBF?
LT3651EUHE-8.4#PBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LT3651EUHE-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 LT3651EUHE-8.4#PBF?
For technical support, including LT3651EUHE-8.4#PBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LT3651EUHE-8.4#PBF requirements.
6.How does Aetrix verify that LT3651EUHE-8.4#PBF is sourced from the original manufacturer or authorized distributors?
All LT3651EUHE-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 LT3651EUHE-8.4#PBF meets industry standards.
7.What is the process for return or replacement of LT3651EUHE-8.4#PBF?
All LT3651EUHE-8.4#PBF units undergo pre-shipment inspection (PSI). If there is an issue with LT3651EUHE-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 LT3651EUHE-8.4#PBF part is unused and in its original packaging.
Return procedure for LT3651EUHE-8.4#PBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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