> 3.1 | Stages of Charging

> If the battery meets the requirements listed above and your application uses one the external charging circuits shown in Figure 4 or Section 6.2, then charging is enabled in various stages depending on the battery condition:
> Trickle charging:

> • | Trickle charge current flows over the VCHARGE line.

> • | Trickle charging is done when a charger is present (connected to VCHARGE) and the battery is deeply discharged or has undervoltage.

> • | Charging rate:

> - | If deeply discharged (Deep Discharge Lockout at VBATT+= 0…2.5V) the battery is charged at 30mA (AC75i, MC75i, TC63i, TC65i) resp. 5mA (all other supported modules).

> - | In case of undervoltage (Undervoltage Lockout at VBATT+= 2.5…3.2V) the battery is charged at 60mA (AC75i, MC75i, TC63i, TC65i) resp. 30mA (all other supported modules).

> Software controlled charging:

> • | Controlled over the CHARGEGATE.

> • | Temperature conditions: 0°C to 45°C

> • | Software controlled charging is done when the charger is present (connected to VCHARGE) and the battery voltage is at least above the undervoltage threshold. Software controlled charging passes the following stages:

> - | Power ramp: Depending on the discharge level of the battery (i.e. the measured battery voltage VBATT+) the software adjusts the maximum charge current for charging the battery. The duration of power ramp charging is very short (less than 30 seconds).

> - | Fast charging: Battery is charged with constant current (approx. 500mA) until the battery voltage reaches 4.2V (approx. 80% of the battery capacity). Options for applying a fast charging current higher than 500mA are described in Section 6.2.1.

> - | Top-up charging: The battery is charged with constant voltage of 4.2V at stepwise reducing charge current until full battery capacity is reached.

> Duration of charging:

> • | The module provides two charging timers: a software controlled timer set to 4 hours and a hardware controlled timer set to 4.66 hours.

> - | The duration of software controlled charging depends on the battery capacity and the level of discharge. Normally, charging stops when the battery is fully charged or, at the latest, when the software timer expires after 4 hours.

> - | The hardware timer1 is provided to prevent runaway charging and to stop charging if the software is not responding. The hardware timer will start each time the charger is plugged to the VCHARGE line.

> The stages of software controlled charging are illustrated in Figure 2.
> Figure 2: Stages of software controlled charging
> Figure 3: Charging details of power ramp phase

> 1
> Not supported by AC75i, MC75i, TC63i, TC65i