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Analog Devices Inc. LTC1731EMS8-8.4#PBF
- Part No.:
- LTC1731EMS8-8.4#PBF
- Manufacturer:
- Analog Devices Inc.
- Category:
- Battery Chargers
- Package:
- 8-TSSOP, 8-MSOP (0.118", 3.00mm Width)
- Datasheet:
-
LTC1731EMS8-8.4#PBF.pdf
- Description:
- IC BATT CHG MULT-CHEM 2CEL 8MSOP
- Quantity:
- Payment:
- Shipping:
Inventory:2,245
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Product details
Overview
LTC1731EMS8-8.4#PBF from Analog Devices (formerly Linear Technology) is a complete constant-current/constant-voltage linear charger controller for 2-cell lithium-ion batteries, delivering ±1% float voltage accuracy at 8.4V, supporting up to 500mA charge current with 7% sense resistor–based current setting, and featuring automatic trickle charge below 4.95V battery voltage - used in handheld computing and charging cradles.
For engineers reviewing the LTC1731EMS8-8.4#PBF datasheet, LTC1731EMS8-8.4#PBF pinout, LTC1731EMS8-8.4#PBF application, or LTC1731EMS8-8.4#PBF equivalent, key selection concerns include C/10 end-of-charge detection, programmable timer termination via external capacitor, sleep-mode battery drain of 15µA, and compatibility with P-channel MOSFET or high-gain PNP pass devices.
Technical Context
The LTC1731EMS8-8.4#PBF implements dual-loop control: a current amplifier servoing the DRV pin to maintain precise IBAT via RSENSE and RPROG, and a voltage amplifier regulating BAT to 8.4V using an internal 2.457V reference and precision resistive divider. It integrates a 30-hour/µF programmable timer, C/10 comparator with 320ms latch delay, and automatic transition from trickle (10% IBAT) to constant-current mode above 4.95V.
It operates only when VCC ≥ 8.8V and (VCC – VBAT) ≥ 54mV; undervoltage lockout activates at 8.2V with 200mV hysteresis. Sleep mode engages when input is removed, reducing ICC to 15µA typical and disconnecting the BAT divider to minimize battery drain.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Float Voltage | 8.4V ±1% (LTC1731EMS8-8.4#PBF variant; enables accurate 2-cell Li-Ion termination without external feedback) |
| Charge Current Accuracy | ±7% (set by external RSENSE; determines absolute current tolerance in production designs) |
| Trickle Threshold | 4.95V (battery voltage below which 10% full-scale current is applied; prevents damage to deeply discharged cells) |
| Sleep Mode Drain | 15µA typical (reduces standby battery loss in portable systems during AC adapter removal) |
| Timer Range | 30 hours/µF (CTIMER = 0.1µF yields ~3-hour timeout; supports safe NiMH/NiCd charge termination) |
| C/10 Detection | 10% of programmed IBAT (latched after 320ms; provides reliable near-full-charge signal for host MCU monitoring) |
| UVLO Threshold | 8.2V rising (prevents unstable operation during brownout; 200mV hysteresis avoids oscillation) |
Pinout & Package
Package: 8-lead MSOP (3.0mm × 3.0mm, 0.65mm pitch), RoHS-compliant, moisture sensitivity level 1.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| BAT (1) | Battery voltage sense input | Connects to battery positive; internal 720Ω/100kΩ divider sets 8.4V regulation point; bypass with ≥10µF capacitor for stability |
| CHRG (2) | Open-drain charge status output | Pulled low during fast charge; switches to 100µA sink at C/10; goes high-Z after timer expiry or shutdown |
| TIMER (3) | Timer capacitor and CV-disable input | CTIMER to GND sets total charge time; tied to VCC disables voltage regulation and timer for CC-only NiMH/NiCd use |
| GND (4) | Analog and power ground reference | Common return for all internal amplifiers and comparators; must be low-impedance connection to system ground plane |
| PROG (5) | Charge current programming and shutdown input | RPROG to GND sets IBAT; floating PROG pulls pin to 2.457V via 2.5µA source, forcing shutdown (ICC ≈ 1mA) |
| DRV (6) | External pass device drive output | Drives gate of P-MOSFET or base of high-gain PNP; clamped to VCC – 6.5V to protect low-VGS devices |
| VCC (7) | Main input supply (8.8V–12V) | Power source for internal circuitry; requires 1µF bypass capacitor; UVLO active below 8.2V |
| SENSE (8) | Current sense amplifier input | Connected to low-side of RSENSE; senses voltage drop to regulate IBAT; polarity matches P-channel configuration |
Key Features
| Feature | Design Value |
|---|---|
| ±1% float voltage regulation | Enables compliant 2-cell Li-Ion charging without trimming or calibration; meets JEITA voltage limits for safety |
| Automatic trickle-to-CC transition | Activates 10% IBAT below 4.95V and exits when battery reaches threshold - prevents overcurrent stress on depleted cells |
| Programmable C/10 detection with latch | 320ms delay prevents false triggering from transient load spikes; provides clean digital signal for MCU state machines |
| Dual-mode operation (CV+CC or CC-only) | TIMER pin logic selects between Li-Ion (voltage-regulated) and NiMH/NiCd (current-source-only) modes - one IC supports two chemistries |
| Low-power sleep mode | 15µA battery drain extends shelf life and runtime in always-connected portable devices during AC adapter disconnection |
Applications
| Handheld Computers | Charging Docks and Cradles |
|---|---|
Use Scenario: Recharging enterprise-grade rugged tablets with removable 2-cell Li-Ion packs via USB-C PD or proprietary dock interface. IC Role / Device Role / Timing Role: Linear charger controller managing constant-current ramp and 8.4V float regulation while interfacing with host MCU via CHRG pin states. Use Value: Eliminates need for external voltage references or op-amps; ±1% regulation ensures cell longevity and compliance with IEC 62133. |
Use Scenario: Multi-bay desktop cradle simultaneously charging four handheld scanners using shared 9V/12V DC input. IC Role / Device Role / Timing Role: Independent charge controller per bay, using TIMER pin to set fixed 2.5-hour timeout and CHRG pin for LED status indication. Use Value: Programmable timer prevents overcharge across varying battery capacities; sleep mode avoids parasitic drain when bays are empty. |
| Cellular Phones (Legacy 2-Cell Designs) | Programmable Current Sources |
Use Scenario: Feature phones with dual 3.7V Li-Ion cells in series, charged from wall adapter with limited thermal headroom. IC Role / Device Role / Timing Role: Linear controller providing low-noise, thermally predictable charging without switching EMI - critical for RF-sensitive layouts. Use Value: 15µA sleep current preserves battery charge during storage; DRV clamp protects 8V-rated P-MOSFETs in compact PCB footprints. |
Use Scenario: Precision lab equipment requiring stable 100mA–500mA current sources for sensor biasing or electrochemical testing. IC Role / Device Role / Timing Role: Configured in constant-current-only mode (TIMER = VCC) with external termination, leveraging RPROG/RSENSE accuracy and low drift. Use Value: 7% current accuracy and <100ppm/°C drift enable repeatable measurements; PROG pin allows dynamic current scaling via DAC. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar linear battery charger controller applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| LTC1731ES8-8.4 | Same electrical specs and pinout; SO-8 package instead of MSOP-8; θJA = 125°C/W vs 200°C/W | Preferred for through-hole prototyping or higher-power dissipation scenarios where board space allows larger footprint | Select LTC1731ES8-8.4 when thermal margin >25°C is required or when legacy SO-8 layout reuse is prioritized |
| LTC1732EMS8 | Integrated FET (no external pass device); fixed 4.2V or 8.4V variants; no PROG pin; automatic recharge on voltage drop | Reduces BOM count but sacrifices programmability and thermal design flexibility; lacks C/10 output and timer disable | Choose LTC1732EMS8 only when simplified design, lower component count, and automatic top-off outweigh need for current programming and CC-only mode |
Compared with LTC1731EMS8-8.4#PBF, LTC1731ES8-8.4 offers identical functionality in a larger SO-8 package with better thermal performance, while LTC1732EMS8 trades external pass-device control and programmability for integration and automatic recharging - making LTC1731EMS8-8.4#PBF optimal for thermally constrained, multi-chemistry, or precision-current applications.
Availability
LTC1731EMS8-8.4#PBF is available at Aetrix Electronics and suitable for handheld computers, charging docks and cradles, and legacy cellular phone designs requiring stable component supply, long-lifecycle support, and guaranteed RoHS-compliant sourcing.
Supply support for LTC1731EMS8-8.4#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 full technical and manufacturing continuity for all Linear ICs, including precision analog power management products.
The LTC1731EMS8-8.4#PBF belongs to Linear's legacy linear battery charger controller family, designed specifically for space-constrained, low-EMI, 2-cell Li-Ion and multi-chemistry portable systems where external pass-device control and accurate voltage regulation are essential.
FAQ
What is the exact float voltage setpoint for LTC1731EMS8-8.4#PBF?
The LTC1731EMS8-8.4#PBF is factory-trimmed to deliver a nominal 8.4V regulated float voltage at the BAT pin, with guaranteed accuracy of ±1% (8.316V to 8.484V) over the full –40°C to +85°C operating temperature range. This value is fixed and not user-adjustable - it corresponds to the 4.2V-per-cell standard for 2-series Li-Ion configurations.
Can LTC1731EMS8-8.4#PBF charge NiMH or NiCd batteries?
Yes, the LTC1731EMS8-8.4#PBF can charge NiMH or NiCd batteries by configuring it in constant-current-only mode: tie the TIMER pin to VCC to disable voltage regulation and timer functions. In this mode, external termination (e.g., –ΔV detection or temperature cutoff) must be implemented, as the IC no longer regulates voltage or auto-terminates based on C/10.
What is the minimum recommended RSENSE value for LTC1731EMS8-8.4#PBF?
The minimum recommended RSENSE for LTC1731EMS8-8.4#PBF is 0.1Ω, based on stability and noise considerations. At 500mA full-scale current, this yields 50mV across RSENSE - sufficient for robust sensing while minimizing power loss and thermal drift. Values below 0.1Ω increase susceptibility to PCB trace resistance errors and noise coupling.
How does the CHRG pin indicate charge status for LTC1731EMS8-8.4#PBF?
The CHRG pin on LTC1731EMS8-8.4#PBF operates in three distinct states: (1) actively pulled low (<0.6V at 5mA) during constant-current charging; (2) weakly pulled to ~1V via 100µA current source at C/10; (3) high-impedance (>10MΩ) after timer expiry or shutdown. These states allow unambiguous detection of charge phase using a single GPIO with two pull-up resistors.
Does LTC1731EMS8-8.4#PBF require external compensation components?
No, the LTC1731EMS8-8.4#PBF is internally compensated and stable with a P-channel MOSFET pass device without external compensation. However, a ≥10µF capacitor is required at the BAT pin for loop stability when the battery is disconnected, and a 1nF capacitor from DRV to VCC is mandatory when using a PNP transistor to prevent oscillation in the voltage loop.
LTC1731EMS8-8.4#PBF Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc.
- Series:
- -
- Package/Case:
- 8-TSSOP, 8-MSOP (0.118", 3.00mm Width)
- Packaging:
- Tube
- Product Status:
- Active
- Battery Chemistry:
- Multi-Chemistry
- Number of Cells:
- 2
- Current - Charging:
- Constant - Programmable
- Programmable Features:
- Timer
- Fault Protection:
- -
- Charge Current - Max:
- 500mA
- Battery Pack Voltage:
- 8.4V
- Voltage - Supply (Max):
- 12V
- Interface:
- -
- Operating Temperature:
- -40°C ~ 85°C (TA)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 8-MSOP
LTC1731EMS8-8.4#PBF FAQ
1.How can I place an order for LTC1731EMS8-8.4#PBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LTC1731EMS8-8.4#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 LTC1731EMS8-8.4#PBF reliable?
The price and inventory of LTC1731EMS8-8.4#PBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LTC1731EMS8-8.4#PBF is usually 5 days.
3.What payment methods are accepted for LTC1731EMS8-8.4#PBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LTC1731EMS8-8.4#PBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LTC1731EMS8-8.4#PBF?
LTC1731EMS8-8.4#PBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LTC1731EMS8-8.4#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 LTC1731EMS8-8.4#PBF?
For technical support, including LTC1731EMS8-8.4#PBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LTC1731EMS8-8.4#PBF requirements.
6.How does Aetrix verify that LTC1731EMS8-8.4#PBF is sourced from the original manufacturer or authorized distributors?
All LTC1731EMS8-8.4#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 LTC1731EMS8-8.4#PBF meets industry standards.
7.What is the process for return or replacement of LTC1731EMS8-8.4#PBF?
All LTC1731EMS8-8.4#PBF units undergo pre-shipment inspection (PSI). If there is an issue with LTC1731EMS8-8.4#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 LTC1731EMS8-8.4#PBF part is unused and in its original packaging.
Return procedure for LTC1731EMS8-8.4#PBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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