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Analog Devices Inc. LTC4121IUD#PBF
- Part No.:
- LTC4121IUD#PBF
- Manufacturer:
- Analog Devices Inc.
- Category:
- Battery Chargers
- Package:
- 16-WFQFN Exposed Pad
- Datasheet:
-
LTC4121IUD#PBF.pdf
- Description:
- IC BATT CHG MULTI-CHEM 16QFN
- Quantity:
- Payment:
- Shipping:
Inventory:205
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Product details
Overview
LTC4121IUD#PBF from Analog Devices (formerly Linear Technology) is a 400mA synchronous step-down battery charger IC with MPPT input regulation, ±1% feedback voltage accuracy, and programmable float voltage (3.5V–18V). It operates across 4.4V–40V input and supports Li-ion/polymer charging with NTC temperature qualification, timer termination, and auto-recharge-ideal for solar-powered industrial sensors.
For engineers reviewing the LTC4121IUD#PBF datasheet, LTC4121IUD#PBF pinout, LTC4121IUD#PBF application, or LTC4121IUD#PBF equivalent, key selection criteria include its 16-lead 3mm×3mm QFN package, 750kHz/1.5MHz selectable switching frequency, 2.400V feedback regulation voltage, 400mA max charge current, and MPPT-enabled operation with solar panel compatibility.
Technical Context
The LTC4121IUD#PBF implements a synchronous buck topology with integrated high-side and low-side MOSFETs (RDSON = 0.8Ω / 0.5Ω), internal INTVCC LDO, and precision analog control loops for CC/CV charging. Its MPPT algorithm samples open-circuit input voltage every ~28 seconds, stores it via DAC, and regulates input voltage to a user-defined percentage using a resistive divider on the MPPT pin.
It features dual-mode battery sensing: programmable FB/FBG feedback for adjustable float voltage (LTC4121 variant), or fixed 4.2V BATSNS sensing (LTC4121-4.2 variant); this part is the standard LTC4121 version, not the -4.2 variant, confirmed by part number suffix and absence of "-4.2" in marking.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Input Voltage Range | 4.4V to 40V - supports wide-range unregulated sources including solar panels and industrial power rails. |
| Max Charge Current | 400mA - set by external PROG resistor (e.g., 3.01kΩ), enabling precise current scaling from 50mA to 400mA. |
| Float Voltage Range | 3.5V to 18V - programmable via FB/FBG resistive divider, suitable for Li-ion, LiFePO₄, and other chemistries. |
| Feedback Voltage Accuracy | ±1% at 2.400V - ensures tight battery voltage regulation critical for cycle life and safety compliance. |
| Switching Frequency | 750kHz or 1.5MHz - selected via FREQ pin, balancing efficiency, inductor size, and EMI performance. |
| MPPT Regulation | Programmable % of VOC - maintains maximum power transfer from high-impedance sources like solar cells without external controllers. |
| Operating Temp Range | –40°C to 125°C - qualified for industrial and automotive under-hood environments with full parameter guarantees. |
Pinout & Package
Package: 16-lead (3mm × 3mm) plastic QFN with exposed thermal pad (Pin 17 = GND), thermally enhanced, 0.75mm profile.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| INTVCC (1) | Internal LDO output | Powers gate drivers and low-battery linear charge; must be decoupled with 2.2µF, no external load beyond NTC bias. |
| BOOST (2) | Bootstrap supply | Connects 22nF capacitor to SW to enable high-side MOSFET drive; critical for efficient synchronous operation. |
| IN (3) | Main power input | Accepts 4.4V–40V; requires ≥10µF low-ESR ceramic decoupling; forms RC network with MPPT sampling. |
| SW (4) | Switch node | Drives external inductor; connects to CHGSNS; carries pulsed current up to 1.25A peak. |
| GND (5, 17) | Power and thermal ground | Exposed pad (Pin 17) must be soldered to PCB ground plane for θJA = 54°C/W and reliable thermal performance. |
| MPPT (6) | MPPT reference input | Compares against stored VOC fraction; requires low-parasitic resistive divider to set regulation point (e.g., 90% VOC). |
| FREQ (7) | Frequency select | Logic-level input: GND = 750kHz, INTVCC = 1.5MHz - sets switching speed and inductor sizing requirements. |
| CHGSNS (8) | Current sense input | Monitors charge current via internal 300mΩ sense resistor between CHGSNS and BAT; enables accurate CC mode. |
| BAT (9) | Battery output | Delivers regulated charge current; includes low-battery preconditioning (6–16mA linear charge below 2.21V). |
| FB (10) | Voltage feedback | Sets float voltage via resistive divider (BAT→FB→FBG); 25nA bias current compensated by 588kΩ Thevenin resistance. |
| FBG (11) | Feedback ground | Switches low-Z to GND during active sensing; high-Z in shutdown - isolates divider from battery leakage. |
| NTC (12) | Temperature monitor | Interfaces with NTC thermistor to pause charging outside safe temp range; requires INTVCC-to-NTC bias resistor. |
| PROG (13) | Charge current programming | 1.227V servo voltage; ICHG = 988 × VPROG / RPROG - enables real-time current monitoring and precise setting. |
| CHRG (14) | Charge status flag | Open-drain output pulled low during active charge; high-impedance at end-of-charge (EoC) or fault. |
| FAULT (15) | Fault indicator | Open-drain output pulled low on NTC fault or bad battery detection; remains high-Z otherwise. |
| RUN (16) | Enable control | 2.45V threshold with 200mV hysteresis; ties to VIN divider to set turn-on voltage and prevent brownout oscillation. |
Key Features
| Feature | Design Value |
|---|---|
| MPPT Input Regulation | Maintains input voltage at user-defined % of open-circuit voltage (e.g., 85% VOC) to maximize power harvest from solar panels without external MCU. |
| Programmable Float Voltage | 3.5V–18V range via FB/FBG divider - supports multi-chemistry battery systems (Li-ion, LiFePO₄, lead-acid) with single IC design. |
| Thermal & Safety Protection | NTC-based hot/cold fault detection, 2-hour safety timer, bad battery timeout (30 min), and auto-recharge at 2.2% voltage drop. |
| Low-Power Sleep Mode | 60–110µA quiescent current after EoC - extends system runtime in battery-backed applications with infrequent recharge cycles. |
| High-Efficiency Synchronous Buck | Up to 95% efficiency at 200mA/8.4V - enabled by integrated 0.8Ω/0.5Ω MOSFETs and Burst Mode™ operation at light loads. |
Applications
| Solar-Powered Remote Sensors | Industrial Handheld Instruments |
|---|---|
Use Scenario: Battery-charged environmental sensor node deployed in off-grid locations with intermittent solar irradiance. IC Role / Device Role / Timing Role: Primary battery charger managing energy harvesting, CC/CV charging, and MPPT-regulated input voltage to sustain operation during low-light periods. Use Value: Enables >90% average power extraction from solar panels across varying irradiance and temperature, extending deployment interval by 3× vs non-MPPT solutions. | Use Scenario: Portable multimeter or data logger powered by Li-ion battery and charged via USB or wall adapter. IC Role / Device Role / Timing Role: Single-chip charger providing programmable 400mA charge current, precise 2.400V feedback, and NTC-qualified charging for field reliability. Use Value: Eliminates need for external microcontroller-based charging logic while meeting IEC 62368-1 battery safety requirements through integrated timer and fault detection. |
| Military-Grade Telemetry Units | Asset Tracking Beacons |
Use Scenario: Ruggedized GPS tracker operating in extreme ambient temperatures (–40°C to +85°C) with solar-assisted charging. IC Role / Device Role / Timing Role: High-temp-rated charger IC delivering robust CC/CV regulation, low-battery preconditioning, and thermal fault response across full military temperature range. Use Value: Guarantees safe charging initiation below 0°C and automatic suspension above 60°C using NTC interface, preventing battery degradation in harsh deployments. | Use Scenario: Low-power cellular IoT beacon with long-life Li-ion battery recharged intermittently via small solar cell or docking station. IC Role / Device Role / Timing Role: Efficient step-down charger supporting wide-input (5–36V) sources and auto-restart when battery drops 2.2% post-termination. Use Value: Reduces standby current to ≤110µA in sleep mode and enables maintenance-free operation over 5+ years in duty-cycled tracking applications. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar battery charger applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| LTC4125IUF#PBF | Integrated 500mA buck charger with adaptive MPPT, but fixed 4.2V float voltage and no programmable FB divider. | Designed for Li-ion only; lacks adjustable float voltage for multi-chemistry support. | Select LTC4121IUD#PBF when flexible chemistry support (e.g., LiFePO₄ at 3.6V) or custom float voltage is required. |
| BQ24650RGER | 4A buck charger with 4.2V/8.4V/12.6V fixed float options, no MPPT, and higher current capability. | Targets high-current applications (e.g., power tools); lacks solar-optimized input regulation. | Select LTC4121IUD#PBF for solar-harvesting systems needing MPPT and sub-1A precision charging in compact QFN. |
Compared with LTC4125IUF#PBF and BQ24650RGER, the LTC4121IUD#PBF uniquely combines programmable float voltage, true MPPT for solar, and industrial temperature rating in a 3mm×3mm footprint-making it optimal for space-constrained, multi-chemistry, energy-harvesting designs.
Availability
LTC4121IUD#PBF is available at Aetrix Electronics and suitable for solar-powered remote sensors, industrial handheld instruments, and military telemetry units requiring stable component supply across extended temperature ranges and long production lifecycles.
Supply support for LTC4121IUD#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 LTC4121 belongs to Linear's Power Management product line, engineered for high-efficiency, feature-rich battery charging in energy-constrained and environmentally demanding applications-including solar harvesting, portable instrumentation, and ruggedized IoT.
FAQ
What is the exact float voltage range supported by the LTC4121IUD#PBF?
The LTC4121IUD#PBF supports a programmable float voltage range of 3.5V to 18V, set via an external resistive divider from BAT to FB to FBG. This is confirmed in the Electrical Characteristics table (page 3) and Applications section, distinguishing it from the fixed 4.2V LTC4121-4.2 variant. The feedback regulation voltage is precisely 2.400V ±1%, enabling accurate scaling across the full range.
Does the LTC4121IUD#PBF require external MOSFETs for operation?
No, the LTC4121IUD#PBF integrates both high-side and low-side synchronous MOSFETs (RDSON = 0.8Ω and 0.5Ω respectively) within the 16-lead QFN package. No external power switches are needed - only an external inductor, input/output capacitors, PROG resistor, and FB/FBG divider are required for basic operation per the Typical Application schematic (page 1).
How does MPPT work on the LTC4121IUD#PBF, and what external components are needed?
The LTC4121IUD#PBF implements autonomous MPPT by pausing charging every ~28 seconds, measuring open-circuit input voltage (VOC) for 36ms, storing it digitally, and regulating input voltage to a user-defined percentage (e.g., 90% VOC) via the MPPT pin. An external resistive divider from IN to MPPT to GND sets the target percentage; no MCU or external ADC is required.
What is the purpose of the FBG pin on the LTC4121IUD#PBF?
The FBG (Feedback Ground) pin on the LTC4121IUD#PBF disconnects the FB resistive divider from the battery during shutdown or disabled modes, reducing battery leakage current. During active regulation, FBG presents low impedance (~1000–2000Ω) to GND; in shutdown, it becomes high-impedance - a key feature enabling ultra-low sleep current (<110µA) in battery-backed systems.
Can the LTC4121IUD#PBF charge batteries below 0°C or above 60°C?
The LTC4121IUD#PBF suspends charging outside safe temperature limits using its NTC interface: cold fault triggers below ~73% of INTVCC (≈1.8V at 25°C), hot fault above ~36.5% of INTVCC (≈1.5V). With proper NTC thermistor selection and biasing, it enforces charging halt below 0°C and above 60°C - verified in Typical Performance Characteristics (page 6, G02/G08) and Pin Functions (page 9).
LTC4121IUD#PBF Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc.
- Series:
- -
- Package/Case:
- 16-WFQFN Exposed Pad
- Packaging:
- Tube
- Product Status:
- Active
- Battery Chemistry:
- Multi-Chemistry
- Number of Cells:
- -
- Current - Charging:
- Constant - Programmable
- Programmable Features:
- -
- Fault Protection:
- -
- Charge Current - Max:
- 400mA
- Battery Pack Voltage:
- 18V (Max)
- Voltage - Supply (Max):
- 40V
- Interface:
- -
- Operating Temperature:
- -40°C ~ 125°C (TJ)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 16-QFN (3x3)
LTC4121IUD#PBF FAQ
1.How can I place an order for LTC4121IUD#PBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LTC4121IUD#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 LTC4121IUD#PBF reliable?
The price and inventory of LTC4121IUD#PBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LTC4121IUD#PBF is usually 5 days.
3.What payment methods are accepted for LTC4121IUD#PBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LTC4121IUD#PBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LTC4121IUD#PBF?
LTC4121IUD#PBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LTC4121IUD#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 LTC4121IUD#PBF?
For technical support, including LTC4121IUD#PBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LTC4121IUD#PBF requirements.
6.How does Aetrix verify that LTC4121IUD#PBF is sourced from the original manufacturer or authorized distributors?
All LTC4121IUD#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 LTC4121IUD#PBF meets industry standards.
7.What is the process for return or replacement of LTC4121IUD#PBF?
All LTC4121IUD#PBF units undergo pre-shipment inspection (PSI). If there is an issue with LTC4121IUD#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 LTC4121IUD#PBF part is unused and in its original packaging.
Return procedure for LTC4121IUD#PBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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