Microchip Technology MCP73838-FCI/UN

Overview

MCP73838-FCI/UN from Microchip Technology is a fully integrated linear Li-Ion/Li-Polymer battery charge management controller with autonomous AC adapter or USB port source selection, ±0.5% voltage regulation accuracy, 4.20V fixed charge voltage, 1000 mA max AC charge current, and Timer Enable (TE) pin for safety timer control. It operates in portable medical devices and ultra-mobile systems requiring dual-source charging with thermal regulation.

For engineers reviewing the MCP73838-FCI/UN datasheet, MCP73838-FCI/UN pinout, MCP73838-FCI/UN application, or MCP73838-FCI/UN equivalent, key selection criteria include USB/AC source arbitration logic, programmable AC charge current via PROG1, TE pin-driven safety timer enable/disable, thermistor-based temperature monitoring, and DFN-10 package thermal performance.

Technical Context

The MCP73838-FCI/UN implements a CC/CV charge algorithm with factory-set 4.20V regulation, selectable preconditioning and termination thresholds, and thermal regulation that dynamically reduces charge current above 150°C junction temperature. Its autonomous power source selection prioritizes VAC over VUSB when both are present.

It integrates pass transistors (350 mΩ typical R_DS(on)), current sense (G = 0.001), reverse discharge protection, and LDO-mode operation. The TE pin (Pin 8) enables/disables the safety timer - Low activates 4/6/8-hour options; High disables timing - distinguishing it from MCP73837.

Key Specifications

Pinout & Package

Package: 10-Lead 3 mm × 3 mm DFN with exposed thermal pad (EP), internally connected to VSS. Requires PCB thermal pad connection for optimal thermal performance.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar Li-ion linear charge management applications.

Compared with MCP73837-FCI/UN, MCP73838-FCI/UN trades PG output for TE control - enabling host-directed timer disable - while retaining identical charge accuracy, thermal regulation, and dual-source architecture. BQ24075RGTR offers higher current but sacrifices AC input support and autonomous arbitration.

Availability

MCP73838-FCI/UN is available at Aetrix Electronics and suitable for smartphones, portable medical devices, ultra-mobile devices, and digital cameras requiring stable component supply, long-term lifecycle support, and RoHS-compliant packaging.

Supply support for MCP73838-FCI/UN 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

Microchip Technology Inc. is a leading provider of microcontrollers, analog components, and battery management ICs, serving automotive, industrial, and consumer markets since 1989.

The MCP7383x family delivers highly integrated, autonomous linear Li-ion chargers optimized for space-constrained portable electronics with dual-input power sources and stringent safety requirements.

FAQ

What is the function of the TE pin on the MCP73838-FCI/UN?

The TE (Timer Enable) pin on the MCP73838-FCI/UN is an active-low input that enables or disables the internal safety timer. When pulled Low, the timer operates in one of three factory-configured durations (4/6/8 hours); when pulled High, the timer is disabled entirely. This distinguishes MCP73838-FCI/UN from MCP73837-FCI/UN, which lacks TE and has a permanently enabled timer. The TE pin allows host MCU control over charge timeout behavior in the MCP73838-FCI/UN.

Does the MCP73838-FCI/UN support 4.35V battery chemistry?

No, the MCP73838-FCI/UN does not support 4.35V battery chemistry. It is factory-configured for 4.20V ±0.5% constant-voltage regulation, as indicated by the "FCI" suffix in the part number per Microchip's Product Identification System. Other variants such as MCP73838-PCI/UN (4.35V) or MCP73838-RCI/UN (4.40V) support higher voltages, but MCP73838-FCI/UN is strictly 4.20V-rated and must not be used with 4.35V cells without risking overcharge and safety violation.

How does the MCP73838-FCI/UN handle simultaneous VAC and VUSB presence?

The MCP73838-FCI/UN implements autonomous power source selection with fixed priority: VAC input dominates over VUSB. When both are present, the device draws power exclusively from VAC and ignores VUSB for charging. This prevents backfeed and ensures maximum charge current (up to 1000 mA) is delivered without host MCU involvement. The VUSB path remains inactive but monitored - if VAC is removed, VUSB automatically engages within milliseconds, maintaining uninterrupted charging in the MCP73838-FCI/UN.

What is the minimum bypass capacitance required at VBAT for the MCP73838-FCI/UN?

The MCP73838-FCI/UN requires a minimum 1 µF ceramic capacitor between VBAT and VSS to ensure loop stability, especially when the battery is disconnected or under light-load conditions. This value is specified in Section 3.11 of the datasheet. For applications with output currents exceeding 250 mA, Microchip recommends increasing the capacitance to 4.7 µF to maintain regulation accuracy and transient response - a requirement directly tied to the internal compensation network of the MCP73838-FCI/UN.

Can the MCP73838-FCI/UN be used without a thermistor?

Yes, the MCP73838-FCI/UN can operate without a thermistor. The THERM pin defaults to a high-impedance state when unconnected, and the device proceeds with normal charging. However, temperature-based safety features - including overtemperature shutdown and cold-charge inhibition - are disabled. Microchip specifies that full safety compliance (e.g., JEITA) requires a properly biased NTC thermistor (2–50 kΩ) connected to THERM. For non-temperature-critical applications like consumer audio players, omitting the thermistor is permissible but removes a critical layer of battery protection in the MCP73838-FCI/UN.