The **MIC79110-4.2BML** is a high-accuracy, full-featured linear battery charger IC developed by Micrel (now part of Microchip Technology). It is specifically designed for single-cell Lithium-Ion (Li-Ion) batteries. --- ## 1. Core Technical Specifications The following table summarizes the key electrical characteristics of the MIC79110-4.2BML: | Parameter | Specification | | :--- | :--- | | **Battery Chemistry** | Lithium-Ion / Lithium-Polymer | | **Fixed Output Voltage** | 4.2V (±0.75% accuracy) | | **Input Voltage Range** | 4.5V to 16V | | **Charge Current** | Programmable up to 1.2A | | **Package Type** | 10-Pin MLF® (3mm x 3mm) | | **Operating Temp** | -40°C to +125°C | --- ## 2. Key Internal Components & Features The MIC79110 integrates several electronic stages to ensure safe and efficient charging: ### A. Precision Voltage Reference The "4.2" in the part number indicates a fixed 4.2V termination voltage. The internal reference is highly stable, ensuring the battery is not overcharged, which is critical for Li-Ion safety. ### B. Current Sense & Programming * **ISET Pin:** This allows the user to set the maximum charging current using an external resistor. * **Constant Current (CC) / Constant Voltage (CV):** The IC automatically transitions between these two modes as the battery reaches its capacity. ### C. Safety Mechanisms * **Thermal Regulation:** Unlike simple chargers, this IC includes on-chip thermal limiting. If the die temperature rises too high, it automatically reduces the charge current to prevent damage. * **Under-Voltage Lockout (UVLO):** Prevents the device from operating if the input voltage is too low to guarantee stable charging. ### D. Status Indicators The chip features a **Charge Status Pin** (typically an open-collector output) that can drive an LED or interface with a microcontroller to indicate whether the battery is currently charging or if the cycle is complete. --- ## 3. Typical Application Circuit To utilize the MIC79110, minimal external components are required: ```mermaid graph LR Vin[Input Voltage 5V-16V] --> MIC[MIC79110] MIC --> Batt[Single Cell Li-Ion 4.2V] Res[ISET Resistor] --- MIC Cap1[Input Cap] --- Vin Cap2[Output Cap] --- Batt ``` 1. **Input Capacitor:** Usually a 1µF–10µF ceramic capacitor for stability. 2. **Output Capacitor:** Required to maintain the control loop stability. 3. **ISET Resistor:** Determines the charging speed (e.g., 500mA vs 1A). --- ## 4. Common Use Cases * Handheld GPS units. * Digital cameras and portable media players. * Low-noise medical instrumentation. * Industrial data loggers.