The **MIC79110-4.2YML** is a high-accuracy, single-cell Li-Ion battery charger IC developed by Microchip (formerly Micrel). It is designed specifically for portable applications where space is limited and charging precision is critical. --- ## 1. Key Technical Specifications | Parameter | Specification | | :--- | :--- | | **Input Voltage Range** | 4.5V to 16V | | **Output Voltage (Fixed)** | 4.2V | | **Charge Current** | Up to 1.2A (Adjustable) | | **Regulation Accuracy** | ±0.75% over temperature | | **Package** | 10-Pin 3mm x 3mm MLF® (QFN) | | **Operating Temperature** | -40°C to +125°C | --- ## 2. Core Functional Blocks The internal architecture of the MIC79110 consists of several critical stages to ensure safe and efficient charging: ### A. The Control Loop The device employs a **Constant Current (CC) / Constant Voltage (CV)** algorithm. 1. **Pre-charge:** If the battery is below 2.8V, it applies a trickle charge. 2. **Constant Current:** Once above 2.8V, it charges at the user-defined maximum current. 3. **Constant Voltage:** As the battery nears 4.2V, the current tapers off while maintaining a precise voltage. ### B. Safety Features * **Thermal Regulation:** Reduces charge current if the internal die temperature exceeds a threshold (typically 125°C). * **Reverse Current Protection:** Prevents the battery from discharging back into the IC when the input power is removed. * **Charge Termination:** Automatically shuts off charging when the current drops below a specific threshold (C/10). --- ## 3. Pin Configuration and Components The typical application circuit requires minimal external components. | Pin Name | Function | Description | | :--- | :--- | :--- | | **VIN** | Input Supply | Connect to a 5V or 12V source (decoupled with 1µF - 10µF). | | **BATT** | Battery Connect | Output pin connected to the positive terminal of the Li-Ion cell. | | **ISET** | Current Set | A resistor connected from this pin to GND sets the charging current. | | **EN** | Enable | High = On, Low = Shutdown. | | **/CHG** | Status Indicator | Open-drain output that pulls low during charging. | --- ## 4. Design Considerations ### Current Setting Formula To program the fast-charge current ($I_{CHG}$), a resistor ($R_{SET}$) is used on the ISET pin. The relationship is generally governed by: ```text I_CHG = (V_REF / R_SET) * Ratio ``` *(Consult the datasheet for the specific constant ratio assigned to the 79110 model).* ### Thermal Management Since the MIC79110 is a **linear charger**, it dissipates heat based on the formula: `Power Dissipation = (VIN - VBATT) * I_CHG` Ensure the PCB has adequate copper pours connected to the MLF thermal pad to prevent premature thermal throttling. ---