STMicroelectronics EFL700A39

Overview

EFL700A39 from STMicroelectronics is a solid-state rechargeable lithium thin-film microbattery with 0.7 mAh nominal capacity, 3.9 V nominal voltage, and 25.7 × 25.7 mm footprint. It features LiCoO₂ cathode, LiPON ceramic electrolyte, and lithium anode, enabling ultra-thin (220 µm) form factor and fast recharge for energy-constrained IoT sensor nodes.

For engineers reviewing the EFL700A39 datasheet, EFL700A39 pinout, EFL700A39 application, or EFL700A39 equivalent, key selection criteria include its 100 Ω internal resistance, 4000-cycle life to 80% capacity, -20 °C to +60 °C operating range, pulsed discharge capability up to 10 mA, and compliance with IEC 62133 and UN 38.3 safety standards.

Technical Context

The EFL700A39 operates within a 3.0–4.2 V voltage window and delivers up to 5 mA continuous discharge current. Its LiPON solid electrolyte eliminates liquid leakage risk and enables stable performance under mechanical flexing per ISO/IEC 10373 smartcard standards.

Charge completes at 4.2 V ±0.05 V constant voltage; >90% capacity is restored when charge current drops below 0.1 mA. Discharge cut-off is 3.0 V for DC loads but may be lowered to 2.0 V during 100 ms pulses at 10 mA, validated at 30 °C.

Key Specifications

Pinout & Package

EnFilm™ EFL700A39 is a two-terminal solid-state battery with no active pins. Interconnection is via top-side (+) and bottom-side (–) metallized contacts defined in Figure 4 and Table 4 of ST DocID17370 Rev 5. The device uses a monolithic planar construction: anode and cathode layers are deposited on a rigid substrate with edge-exposed terminals for surface-mount soldering or conductive adhesive bonding.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar thin-film microbattery applications.

Compared with Cymbet CC1002 and Infinite Power THINERGY® MEC225, the EFL700A39 uniquely balances 0.7 mAh capacity, 220 µm thickness, and 10 mA pulse capability-making it optimal for space-limited, intermittently active IoT endpoints requiring reliable rechargeable backup.

Availability

EFL700A39 is available at Aetrix Electronics and suitable for IoT sensor nodes, smart card backup systems, and wearable health patches requiring stable component supply across multi-year production programs.

Supply support for EFL700A39 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

STMicroelectronics is a global semiconductor leader headquartered in Geneva, Switzerland, designing and manufacturing microcontrollers, power management ICs, sensors, and analog/mixed-signal products for industrial, automotive, and consumer markets.

The EnFilm™ microbattery product line targets ultra-thin, solid-state energy storage for constrained-edge electronics-including RFID, smart cards, and energy-harvesting sensor platforms-where safety, longevity, and mechanical robustness are critical.

FAQ

What is the recommended charging method for EFL700A39?

Charge using a constant-voltage source set to 4.2 V ±0.05 V, with or without current limiting. Termination occurs when charge current falls below 0.1 mA, restoring >90% of full capacity in ≤20 minutes. Avoid constant-current charging above 10 mA to prevent accelerated degradation.

Can EFL700A39 be soldered directly to a PCB?

Yes-ST provides validated manual and automated assembly guidelines (AN4046 and AN4351). Use lead-free solder paste with peak temperature ≤235 °C and dwell time <60 seconds. Avoid thermal shock; ensure uniform heating across the 25.7 × 25.7 mm area to prevent delamination.

Is EFL700A39 suitable for implantable medical devices?

No. ST explicitly prohibits use in implantable medical devices (e.g., pacemakers, neurostimulators), US government custom applications, or wafer test equipment. It is approved only for non-implantable medical wearables, such as external ECG patches or glucose monitors.

How does temperature affect EFL700A39 cycle life?

Operating at 60 °C reduces cycle life versus 30 °C due to accelerated electrolyte aging. At -20 °C, discharge capacity drops to ~33% of room-temperature value under 1/30 C load. Full 4000-cycle rating applies only at 30 °C with 1C cycling between 75% and 0% SoC.