> 3.5.6 | Implemented Charging Technique

> If all requirements listed above are met (appropriate external charging circuit of application, battery pack, r, AT^SBC settings) 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. If deeply discharged (Deep Discharge Lockout at VBATT+= <2.5 V) the battery is charged with 5 mA, in case of undervoltage (Undervoltage Lockout at VBATT+= 2.5…3.2 V) it is charged with 30 mA 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. 500 mA) until the battery voltage reaches 4.2 V (approx. 80% of the battery capacity).

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

> Duration of charging:

> • | TC65 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 timer 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.