Timing and electrical characteristics of the PMBus protocol can be found in the PMB Power Management Protocol Specification, Part 1, revision 1.1 available at http://pmbus.org. The TPS4022 device supports both the 100 kHz and 400 kHz bus timing requirements. The device does not stretch pulses on the PMBus interface when communicating with the master device.

Communication over the PMBus interface can either support the Packet Error Checking (PEC) scheme or not. If the master supplies CLK pulses for the PEC byte, it is used. If the CLK pulses are not present before a STOP, the PEC is not used.

The TPS4022 device supports a subset of the commands in the PMBus 1.1 specification. Most controller parameters can be programmed using the PMBus interface and stored as defaults for later use. All commands that require data input or output use the linear format. The exponent of the data words is fixed at a reasonable value for the command and altering the exponent is not supported. Direct format data input or output is not supported by the device. See the Section 8.6.1 section for specific details.

The TPS4022 device also supports the SMBALERT response protocol. The SMBALERT response protocol is a mechanism by which a slave (the TPS4022 device) can alert the bus master that it wants to talk. The master processes this event and simultaneously accesses all slaves on the bus (that support the protocol) through the alert response address. Only the slave that caused the alert acknowledges this request. The host performs a modified receive byte operation to get the slave’s address. At this point, the master can use the PMBus status commands to query the slave that caused the alert. For more information on the SMBus alert response protocol, see the System Management Bus (SMBus) specification.

The device uses non-volatile memory to store configuration settings and scale factors. However, the device does not automatically save the programmed settings into this non-volatile memory. The STORE_USER_ALL command must be used to commit the current settings to non-volatile memory as device defaults. The detailed description of each setting notes if it is able to be stored in non-volatile memory.