1. Device Overview & Functionality

️· What it is: The ISL9301 is a linear Li-ion battery charger IC designed for systems needing both battery charging and regulated system power.
️· Primary Roles:
- Charges a Li-ion battery.
- Provides regulated 4.5V power to the system (VOUT).
- Allows for battery disconnection (BATON pin).
️· Charging Stages: It operates with a typical Li-ion charging profile:
- Trickle Charge: For batteries initially at low voltage.
- Constant Current (CC): Charges at a programmed current.
- Constant Voltage (CV): Maintains voltage at 4.2V to complete charging.

2. Key Features & Programming

️· Programmable Charge Current (IREF): Controlled by an external resistor (R IREF). Equation: `I REF = R3886 / RIREF (mA)`
️· Programmable End-of-Charge Current (IMIN): Controlled by an external resistor (R IMIN). Equation: `I MIN = R3151 / RIMIN (mA)`
️· Timeout Feature: Maintains output voltage even after EOC is reached. CHG signal remains high until VBAT falls below 4.05V.
️· Battery Disconnect (BATON): Allows disabling battery charging and preventing battery drain.
️· Thermal Foldback: Automatically reduces charge current if the internal temperature reaches approximately 115°C, protecting the device from overheating.

3. Pin Descriptions (Most Important)

️· VIN: Input power supply.
️· VBAT: Battery connection.
️· VOUT: Regulated 4.5V output for system power.
️· IREF: Charge current program and monitoring.
️· IMIN: End-of-charge current program.
️· CHG: Charge completion indication (logic LOW during charging, logic HIGH after EOC).
️· TIME: Clock signal.
️· PPR: Power Present.
️· BATON: Battery disconnect control.

4. Operation Details

️· System Power Priority: VOUT is regulated first. Battery charging occurs afterward, but can be interrupted if system power demands exceed the charger’s capabilities.
️· CHG Signal: Indicates charging state. Latches HIGH after EOC. Resets to LOW when VBAT falls below 4.05V.
️· Thermal Protection: Automatically limits charge current to prevent overheating.

5. Typical Application Circuit (Important for Implementation)

️· Shows key external components: resistors, capacitors, diodes for programming, and connections to the battery and system.
️· Highlights the use of resistors (RTIME, RIMIN, RIREF) for crucial settings.

Important Notes from the Datasheet

️· External Components: Careful selection of external components (resistors, capacitors) is crucial for proper operation.
️· Thermal Management: Adequate PCB layout and thermal management are necessary, especially to prevent overheating.
️· Press and Hold: It states that pressing and holding the button for 2 seconds will turn the device on.