BGS3 Hardware Interface Description
3.5 Charging Control
63
BGS3_HD_v01.000d
Page 41 of 109
2010-03-26
Confidential / Released
3.5.5
Charger Requirements
For using the implemented charging algorithm and the reference charging circuit recommend-
ed in
, the charger has to meet the following requirements:
Output voltage: up to 7.0V (stabilized voltage)
Output current: 500mA
Chargers with a higher output current are acceptable too, but please consider
that only 500mA will be applied when a 0.3Ohms shunt resistor is connected
between VSENSE and ISENSE. See
for further details.
3.5.6
Implemented Charging Technique
If all requirements listed above are met (appropriate external charging circuit of application, bat-
tery 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 bat-
tery is deeply discharged or has undervoltage.
- If deeply discharged (Deep Discharge Lockout at V
BATT+
= 0…2.5V) the battery is charged
at 30mA.
- In case of undervoltage (Undervoltage Lockout at V
BATT+
= 2.5…3.0V) the battery is
charged at 60mA.
- If V
BATT+
= 3.0V... 3.2V the battery is charged at 100mA.
Software controlled charging:
•
Controlled over 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 reduc-
ing charge current until full battery capacity is reached.
Duration of charging:
•
BGS3 provides a software controlled timer set to 4 hours as a safety feature to prevent per-
manent charging of defective batteries. 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.
If the software timer expires a charging error occurs, i.e., the AT^SBC’s battery connecting
status (<bcs>) is 4. To prevent this time out the charge current should be adjusted to the
battery capacity.
