The **MAX1663** is a specialized integrated circuit (IC) primarily designed as a **SMBus-Controlled, Single-Output, Constant-Current/Constant-Voltage (CC/CV) Battery Charger Controller**. It was developed by Maxim Integrated (now part of Analog Devices) to manage the charging of Lithium-Ion (Li+) or Nickel-based batteries. --- ## 1. Core Technical Specifications The MAX1663 acts as a "brain" for a switching power supply, regulating the flow of electricity into a battery pack based on commands received via a digital interface. | Feature | Specification | | :--- | :--- | | **Interface** | SMBus (System Management Bus) | | **Chemistry Support** | Li+, NiCd, NiMH | | **Input Voltage Range** | 8V to 28V | | **Output Voltage Range** | 0V to 18.4V | | **Voltage Accuracy** | ±0.5% | | **Package Type** | 20-pin QSOP | --- ## 2. Key Internal Components To understand how the MAX1663 works, it is essential to look at its functional blocks: ### A. The SMBus Interface The MAX1663 is a "slave" device. A host microcontroller (or the Smart Battery itself) sends digital commands to set the **Charge Voltage** and **Charge Current**. This removes the need for manual resistor-tuning of the output. ### B. High-Resolution DACs The chip contains internal Digital-to-Analog Converters (DACs): * **Voltage DAC:** Provides 11-bit resolution for precise voltage control (essential for Li-Ion safety). * **Current DAC:** Provides 6-bit resolution to set the charging rate. ### C. PWM Controller It utilizes a Synchronous Buck (step-down) topology. It drives external N-channel MOSFETs to efficiently convert a high input voltage (like a laptop power brick) down to the specific battery voltage. --- ## 3. Typical Application Circuit In a real-world circuit, the MAX1663 does not work alone. It requires several external electronic parts: 1. **External MOSFETs:** Two N-channel MOSFETs are used for the switching power conversion. 2. **Inductor:** Stores energy during the switching cycle to provide a smooth DC current. 3. **Sense Resistor:** A low-resistance shunt used by the MAX1663 to measure the actual current flowing into the battery for feedback loops. 4. **Capacitors:** Decoupling and filter capacitors to reduce electrical noise. --- ## 4. Operational Modes * **Constant Current (CC):** Used when the battery is low. The controller maintains a steady flow of current while the voltage rises. * **Constant Voltage (CV):** Used when the battery is nearly full. The controller fixes the voltage and allows the current to taper off to prevent overcharging. ---