ADP1053ACPZ-R7 datasheet(34/84 Pages) AD

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ADP1053

Data Sheet

Rev. A | Page 34 of 84

PMBus/I2C COMMUNICATION

The PMBus slave allows a device to interface to a PMBus-

compliant master device, as specified by the PMBus Power

System Management Protocol Specification (Revision 1.1,

February 5, 2007). The PMBus slave is a 2-wire interface that

can be used to communicate with other PMBus-compliant

devices and is compatible in a multimaster, multislave bus

configuration.

FEATURES

The function of the PMBus slave is to decode the command sent

from the master device and respond as requested. Communi-

cation is established using an I2C-like 2-wire interface with

a clock line (SCL) and data line (SDA). The PMBus slave is

designed to externally move chunks of 8-bit data (bytes) while

maintaining compliance with the PMBus protocol. The PMBus

protocol is based on the SMBus Specification (Version 2.0,

August 2000). The SMBus specification is, in turn, based on

the Philips I2C Bus Specification (Version 2.1, January 2000).

The PMBus incorporates the following features:

•

Slave operation on multiple device systems

•

7-bit addressing

•

100 kHz and 400 kHz data rates

•

General call address support

•

Support for clock low extension (clock stretching)

•

Separate multibyte receive and transmit FIFO

•

Extensive fault monitoring

OVERVIEW

The PMBus slave module is a 2-wire interface that can be used

to communicate with other PMBus-compliant devices. Its trans-

fer protocol is based on the Philips I2C transfer mechanism. The

ADP1053 is always configured as a slave device in the overall

system. The ADP1053 communicates with the master device

using one data pin (SDA) and one clock pin (SCL). Because the

ADP1053 is a slave device, it cannot generate the clock signal.

However, it is capable of clock-stretching the SCL line to put the

master device in a wait state when it is not ready to respond to

the master’s request.

Communication is initiated when the master device sends a

command to the PMBus slave device. Commands can be read

or write commands, in which case data is transferred between

the devices in a byte wide format. Commands can also be send

commands, in which case the command is executed by the slave

device upon receiving the stop bit. The stop bit is the last bit in a

complete data transfer, as defined in the PMBus/I2C communi-

cation protocol. During communication, the master and slave

devices send acknowledge (A) or not-acknowledge (A) bits as a

method of handshaking between devices. See the PMBus speci-

fication for a more detailed description of the communication

protocol.

When communicating with the master device, it is possible

for illegal or corrupted data to be received by the PMBus slave

device. In this case, the PMBus slave device should respond to

the invalid command or data, as defined by the PMBus specifi-

cation, and indicate to the master device that an error or fault

condition has occurred. This method of handshaking can be used

as a first level of defense against inadvertent programming of

the slave device that can potentially damage the chip or system.

The PMBus specification defines a set of generic PMBus

commands that is recommended for a power management

system. However, each PMBus device manufacturer can choose

to implement and support certain commands as it deems fit for

its system. In addition, the PMBus device manufacturer can

choose to implement manufacturer-specific commands whose

functions are not included in the generic PMBus command set.

The list of standard PMBus and manufacturer-specific commands

can be found in the PMBUS Command Set (Supported by the

ADP1053) section and the Manufacturer-Specific Extended

Command List section.

PMBus/I2C ADDRESS

The PMBus address of the ADP1053 is set by connecting an

external resistor from the ADD pin to AGND. Table 11 lists the

recommended resistor values and associated PMBus addresses.

Seven different addresses can be used.

Table 11. PMBus Address Settings and Resistor Values

PMBus Address

ADD Pin Resistor Value (kΩ)

0x60

10 (or connect directly to AGND)

0x61

28.7

0x62

48.7

0x63

68.1

0x64

88.7

0x65

109

0x67

200 (or connect directly to VDD)

The recommended resistor values in Table 11 can vary by ±2 kΩ.

Therefore, it is recommended that 1% tolerance resistors be used

on the ADD pin.

The part responds to the standard PMBus broadcast address

(general call) of 0x00. However, it is not recommended that the

general call address be used when more than one ADP1053 is

connected to the master device because the data returned by

multiple slave devices will be corrupted.

For more information, see the General Call Support section.

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