MCP73842-820I/UN: A Comprehensive Guide to Microchip's Linear Li-Ion/Li-Polymer Charge Management Controller

In the realm of portable electronics, efficient and reliable battery charging is paramount. The MCP73842-820I/UN from Microchip Technology stands as a pivotal solution, offering a highly integrated and sophisticated approach to managing the charging process for single-cell Lithium-Ion (Li-Ion) and Lithium-Polymer (Li-Polymer) batteries. This comprehensive guide delves into the features, operation, and application of this versatile charge management controller.

Understanding the MCP73842-820I/UN

The MCP73842-820I/UN is a fully integrated linear charge management controller housed in a compact 10-lead, 3x3 mm DFN package. Its primary function is to regulate the voltage and current delivered to a single-cell Li-Ion or Li-Polymer battery from an external power source, typically a USB port or an AC-DC wall adapter. The "820" in its part number signifies its key preset regulation voltage of 4.20V, the standard termination voltage for most common Li-Ion chemistries.

Key Features and Operational Modes

The device integrates a pass transistor (MOSFET) and current sense resistor, significantly reducing external component count and simplifying board design. Its operation is defined by three distinct charging phases:

1. Preconditioning/Trickle Charge: If the battery voltage is below a pre-set threshold (typically ~2.8V), the IC initiates a trickle charge mode. This safeguards deeply discharged cells by applying a reduced current (10% of the programmed full-scale current) until the voltage rises to a safe level.

2. Constant Current (CC) Regulation: Once the battery voltage is above the trickle charge threshold, the charger enters the constant current mode. Here, it delivers the programmable fast charge current to the battery. This current is set using a single external resistor (`R_PROG`), allowing designers to tailor the charge rate to the battery's capacity, up to 500mA.

3. Constant Voltage (CV) Regulation: When the battery voltage approaches the preset 4.20V regulation voltage, the controller seamlessly transitions to constant voltage mode. The voltage is held steady while the charge current gradually tapers down as the battery reaches full capacity.

Advanced Functionality and Protection

The MCP73842-820I/UN is more than just a linear regulator; it is a complete management system. It features an integrated precision voltage regulation circuit with an accuracy of ±0.75%, ensuring the battery is charged to the exact voltage required for safety and longevity.

A critical feature is its automatic charge termination. The controller monitors the charge current during the CV phase. Once this current tapers down to a pre-set fraction (typically 10%) of the programmed fast charge current, the internal timer begins. After the timer elapses, the charge cycle is terminated, the pass transistor is turned off, and the STAT (status) output is driven high to indicate a charge complete condition.

The device also includes comprehensive protection features:

Thermal Regulation: If the junction temperature exceeds ~110°C, the IC automatically reduces the charge current. This built-in thermal management prevents damage to the controller and the surrounding components under high power dissipation or ambient temperature conditions.

Reverse Blocking Protection: This feature prevents current from flowing from the battery back to the input source if it is removed or shorted.

Typical Applications

The MCP73842-820I/UN is ideal for space-constrained, portable applications where a USB port is the primary power source, including:

Bluetooth Headsets and Speakers

Portable Medical Devices

Handheld Instruments and scanners

Wearable Technology

Various consumer electronics

ICGOOODFIND: The MCP73842-820I/UN from Microchip Technology is an exemplary linear charge management controller that combines high integration, precision, and robust protection features in a minuscule package. Its ability to simplify design, ensure safe charging cycles, and maximize battery life makes it an exceptional choice for modern, portable electronic products powered by single-cell Li-Ion or Li-Polymer batteries.

Keywords:

1. Li-Ion Battery Charger

2. Linear Charge Management

3. Programmable Charge Current

4. Automatic Charge Termination

5. Thermal Regulation