SMBus / PMBus Device Connection
Power Management Bus
The Power Management Bus PMBus is a two wire interface which is based on the SMBus bus.
In fact the specification refers to the SMBus standard for physical layer information, although does specify 100kHz or 400kHz operation.
The PMBus is a protocol that defines communication between power conversion devices, using SMBus as the physical layer.
Unfortunately this particular web site only covers the electrical and physical layers of an interface.
The PMBus specification does define some timing parameters and an operating frequency between 10 to 400kHz.
Although the timing data seems to be identical to SMbus, or nearly identical.
No other signals are define, additions pins on an IC are permitted [which would not be part of the PMBus].
Editor note; Some block diagrams show two additional signal lines in a PMBus system;
The two signal lines; CNTL and SMBALRT are included in some block diagrams, but are not found in either the SMBus or PMBus specifications.
It appears that the additional lines are used in addition to the PMBus, but are not part of the specification.
But at the same time used by the PMBus host in the system.
The Intermediate Bus Architecture [IBA] describes a possible interconnect.
Also refer to the I2C Bus or AccessBus page.
PMBus Power System Management Protocol Specification; Version 1.2 is the current version in 2 parts:
Part I - General Requirements, Transport and Electrical Interface
Part II - Command Language
Release dates: Revision 1.0 2005, Revision 1.1 2007 & Revision 1.2 2010
Cadex Electronics Inc.
{Smart Battery Charges}
Linear Technology
{Digital DC/DC Controller with PMBus Interface}
Maxim Integrated Products
{PMBus Compliant Digital Controller/Monitor IC, PMICs}
PMIC: Power Management IC
It could be that because the PMBus is based on the SMBus, any change made to that spec may be followed in the PMBus spec.
However IC using additional pins for programming or control will be listed as PMBus compatible and not SMBus compatible.
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