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AC75 Hardware Interface Description
Strictly confidential / Preliminary
3.5.5 Charger Requirements
For using the implemented charging algorithm and the reference charging circuit
recommended in [4] and in Figure 46, the charger has to meet the following requirements:
Output voltage:
Output current:
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 discharged or has undervoltage. If deeply discharged (Deep Discharge
Lockout at V
BATT+
(Undervoltage Lockout at V
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
) the software adjusts the maximum charge current for charging the
BATT+
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:
•
AC75 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.
AC75_HD_V00.202
5.2Volts ±0.2V (stabilized voltage)
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 [4] for
further details.
= 0...2.5V) the battery is charged with 5mA, in case of undervoltage
= 2.5...3.2V) it is charged with 30mA
BATT+
Page 44 of 120
s
27.04.2006
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