Specifications

Smart Battery Charger Specification
SBS Implementers Forum -Page 11- Revision 1.1
5.1.2. ChargingVoltage() (0x15)
Description:
The Battery, System Host or other master device sends the desired charging voltage to the Smart Battery
Charger (mV).
Purpose:
The ChargingVoltage() function sets the maximum voltage that a Smart Battery Charger may deliver to the
Smart Battery. In combination with the ChargingCurrent() function and the battery's internal impedance,
this function determines the Smart Battery Charger's desired operating point. Together, these functions
permit a Smart Battery Charger to dynamically adjust its charging profile (current/voltage) for optimal
charge. The Smart Battery can effectively turn off the Smart Battery Charger by returning a value of 0 for
this function. Smart Battery Chargers may be operated as a constant current source above their maximum
regulated voltage range by returning a ChargingVoltage() value of 65535.
SMBus Protocol: Write Word
Output: unsigned int -- charger output voltage in mV
Units: mV
Range: data range is 0 to 65,534 mV
output range is defined by the specific implementation, but not less
than 8 bits within the 16 bit field
Granularity: 0.4% (8 bits) or better, monotonic
Minimum Accuracy: +1/-9% of the programmatic maximum voltage while
operating in constant voltage mode with sufficient input power to
regulate to the ChargingVoltage() value. If VOLTAGE_NOTREG or
VOLTAGE_OR bits in ChargerStatus() are set, the charge voltage may
be less than (programmatic maximum – 9%). See Appendix E for a
discussion on system design alternatives for improved charging
accuracy.
Invalid Data Indication: 65,535 indicates the battery needs a constant current at the
ChargingCurrent() value.
Note1: This is the same value as that listed in 5.2.2. In the case shown, the Smart Battery or other master
device writes the value to the Smart Battery Charger.
Note2: The Smart Battery Charger responds to voltage requests in one of three ways:
• supply the voltage requested
• supply the programmatic maximum voltage if the request is greater than its programmatic
maximum and less than 65535
• supply its maximum safe voltage if the request is 65535
Note3: The SBS specifications allow a Smart Battery to adjust its ChargingCurrent() and
ChargingVoltage() values in response to the Smart Battery Charger’s output. This technique
allows the Smart Battery to fine tune the Smart Battery Charger’s output, thus reducing the
accuracy requirements of the Smart Battery Charger. The Smart Battery’s algorithm must safely
control the Smart Battery Charger’s output under all conditions.
5.1.3. AlarmWarning() (0x16)
Description:
The Smart Battery, acting as a bus master device, sends the AlarmWarning() message to the Smart Battery
Charger and/or the System Host, to notify them that the one or more alarm conditions exist. Alarm
indications are encoded as bit fields in the Battery's Status register, which is then sent to the System Host
and/or Smart Battery Charger by this function. The battery AlarmWarning() message sets the
corresponding bits in the charger's AlarmWarning(). Note that the SMBus specification requires that the
command code for this function be the same as the Smart Battery's address. This allows the Smart Battery