Specifications

Smart Battery Charger Specification
SBS Implementers Forum -Page 9- Revision 1.1
The functions are described as follows:
FunctionName() 0xnn (command code)
Description:
A brief description of the function.
Purpose:
The purpose of the function, and an example where appropriate.
Supported by:
This function must be supported by the charger level specified.
SMBus Protocol:
Describes the data protocol used by the function
Input, Output or Input/Output: A description of the data supplied to or returned by the function.
The data is described as follows:
data type: The type of data the function conveys (See Appendix B)
Units: The units the data is presented in
Range: The range of valid data
Granularity: See next paragraph
Accuracy: How "good" is the data.
Integral to the Smart Battery/Smart Battery Charger concept is that the “measured” values, that is, those
provided by the battery, exceed the accuracy of the “regulated” values provided by the charger. In this
way, the cost of the system is kept to a minimum because there is no need to duplicate the costs associated
with highly accurate analog components at both the charger and the battery.
A Smart Battery Charger's granularity is generally defined by the resolution of its D-A. For example, a
Smart Battery Charger that has a designed maximum regulated charge current of 4 Amps will have a
ChargingCurrent() granularity of 0.4% (15.6mA) for an 8-bit D-A, 0.2% (7.8mA) for a 9-bit D-A, 0.1%
(3.9mA) for a 10 bit D-A and 0.05% (1.9mA) for an 11 bit D-A.
This specification requires that a monotonic D-A converter with at least 8-bits of resolution be used to meet
the minimum granularity requirements for charger “regulated” values. Although the granularity and
accuracy values specified represent a minimum standard of performance, better performance is encouraged.