LTP8800-4AIPVPBF datasheet(13/21 Pages) AD

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LTP8800-4A

Rev. A

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PMBus COMMUNICATION AND COMMAND

PROCESSING

The LTP8800-4A series communicate through PMBus

with other compliant devices. The LTP8800-4A is always

configured as a subordinate device in the overall system,

requiring a two-wire interface with one data pin (SDA) and

one clock pin (SCL). As subordinate devices, LTP8800-4A

power μModule ICs decode the command sent from the

main device and respond accordingly. Data transfer of

the PMBus subordinate is based on PMBus commands.

According to the PMBus/SMBus/I2C communication

protocol, all PMBus commands start with a subordinate

address with the R/W bit cleared (set to 0), followed by

the command code, with mostly the stop bit as the last

bit in a complete data transfer.

Commands can be categorized as send, read, or write

types. For read or write commands, data is transferred

between devices in a byte wide format. For send com-

mands, the subordinate device execute the commands

upon receiving the stop bit. To ensure robust communica-

tion, the main and subordinate devices send acknowledge

(ACK) or no acknowledge (NACK) bits as a method of

handshaking, eliminating the busy errors between devices.

Manufacturer-specific extended commands are also sup-

ported by LTP8800-4A. These commands follow the same

protocol as the standard PMBus commands. However, the

command code consists of two bytes: Command code

extension (0xFE) and Extended command code (0x00

to 0xFF). By use of the manufacturer-specific extended

commands, the PMBus command set is greatly extended.

The detailed information of standard PMBus and manu-

facturer-specific commands can be found in the ADP1055

data sheet.

PMBus ADDRESS SELECTION

The PMBus address is set by connecting an external resis-

tor from the ADD pin to AGND. Table 2 lists the recom-

mended resistor values and associated PMBus addresses.

Table 2. Recommended Resistor Values and Associated PMBus

Addresses

PMBus ADDRESS

1% RESISTOR ON ADD PIN (Ω)

0x40

210 (or Connect to GND)

0x41

750

0x42

1330

0x43

2050

0x44

2670

0x45

3570

0x46

4420

0x47

5360

0x48

6340

0x49

7320

0x4A

8450

0x4B

9530

0x4C

10,700

0x4D

12,100

0x4E

13,700

0x4F

15,000 (or Connect to 3V3)

APPLICATIONS INFORMATION

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