Specifications

XT65/XT75 Hardware Interface Description
3.5 Charging Control
s
XT65_XT75_HD_v01.001 Page 44 of 133 2007-1-8
Confidential / Released
3.5.5 Charger Requirements
For using the implemented charging algorithm and the reference charging circuit recommended in [5] and in Fig-
ure 54, the charger has to meet the following requirements:
Output voltage: 5.2Volts ±0.2V (stabilized voltage)
Output current: 500mA
Chargers with a higher output current are acceptable, but please consider that only 500mA
will be applied when a 0.3Ohms shunt resistor is connected between VSENSE and ISENSE.
See [5] for further details.
3.5.6 Implemented Charging Technique
If all requirements listed above are met (appropriate external charging circuit of application, battery pack,
charger, 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 dis-
charged or has undervoltage. If deeply discharged (Deep Discharge Lockout at V
BATT+
= <2.5V) the battery is
charged with 5mA, in case of undervoltage (Undervoltage Lockout at V
BATT+
= 2.5…3.2V) it is charged with
30mA
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 V
BATT+
)
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).
- 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:
• XT65/XT75 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.