JAJSLQ6A April 2021 – December 2021 DAC53004 , DAC63004
PRODUCTION DATA
The PMBus protocol is an I2C-based communication standard for power-supply management. PMBus contains standard command codes tailored to power supply applications. The DACx3004 implement some PMBus commands such as Turn Off, Turn On, Margin Low, Margin High, Communication Failure Alert Bit (CML), as well as PMBUS revision. Figure 7-11 shows typical PMBus connections. The EN-PMBUS bit in the INTERFACE-CONFIG register must be set to 1 to enable the PMBus protocol.
Similar to I2C, PMBus is a variable length packet of 8-bit data bytes, each with a receiver acknowledge, wrapped between a start and stop bit. The first byte is always a 7-bit target address followed by a write bit, sometimes called the even address that identifies the intended receiver of the packet. The second byte is an 8-bit command byte, identifying the PMBus command being transmitted using the respective command code. After the command byte, the transmitter either sends data associated with the command to write to the receiver command register (from least significant byte to most significant byte, as shown in Table 7-7), or sends a new start bit indicating the desire to read the data associated with the command register from the receiver. Then the receiver transmits the data following the same least significant byte first format (see Table 7-8).
MSB | .... | LSB | ACK | MSB | ... | LSB | ACK | MSB | ... | LSB | ACK | MSB | ... | LSB | ACK |
---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
Address (A) byte Section 7.5.2.2.1 |
Command byte Section 7.5.2.2.2 |
Data byte - LSDB | Data byte - MSDB (Optional) | ||||||||||||
DB [31:24] | DB [23:16] | DB [15:8] | DB [7:0] |
S | MSB | … | R/W (0) | ACK | MSB | … | LSB | ACK | Sr | MSB | … | R/W (1) | ACK | MSB | … | LSB | ACK | MSB | … | LSB | ACK |
---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
ADDRESS BYTE Section 7.5.2.2.1 |
COMMAND BYTE Section 7.5.2.2.2 |
Sr | ADDRESS
BYTE Section 7.5.2.2.1 |
LSDB | MSDB (Optional) | ||||||||||||||||
From Controller | Target | From Controller | Target | From Controller | Target | From Target | Controller | From Target | Controller |
The DACx3004 I2C interface implements some of the PMBus commands. Table 7-9 shows the supported PMBus commands that are implemented in DACx3004.The DAC uses DAC-X-MARGIN-LOW, DAC-X-MARGIN-HIGH bits, SLEW-RATE-X, and CODE-STEP-X bits for PMBUS-OPERATION-CMD-X. To access multiple channels, write the PMBus page address as specified in Table 7-21 to the PMBUS-PAGE register first, followed by a write to the channel-specific register.
REGISTER | PMBUS-OPERATION-CMD-X[15:8] | DESCRIPTION |
---|---|---|
PMBUS-OP-CMD-X | 00h | Turn off |
80h | Turn on | |
94h | Margin low | |
A4h | Margin high |
The DACx3004 also implement PMBus features such as group command protocol and communication time-out failure. The CML bit in the PMBUS-CML register indicates a communication fault in the PMBus. This bit is reset by writing 1.
To get the PMBus version, read the PMBUS-VERSION register.