LTM4673 datasheet(65/132 Pages) AD

65 / 132 page

LTM4683

Rev. 0

For more information www.analog.com

APPLICATIONS INFORMATION

final configuration can be quickly developed and stored

in the LTM4683 EEPROM. Figure 30 illustrates the appli-

cation schematic for powering, programming and com-

munication with one or more LTM4683s via the ADI I2C/

SMBus/PMBus adapter regardless of whether or not sys-

tem power is present. If system power is not present, the

dongle will power the LTM4683 through the VDD33_nn

supply pin. To initialize the part when VINnn is not applied,

and the VDD33_nn pin is powered, use global address 0x5B

command 0xBD data 0x2B followed by address 0x5B

command 0xBD data 0xC4. The LTM4683 can now com-

municate with the internal EEPROM and read the project

file. To write the updated project file to the NVM, issue a

STORE_USER_ALL command. When VIN is applied, an

MFR_RESET must be issued to allow the PWM POWER

to be enabled and valid ADCs to be read.

Because of the adapter’s limited current sourcing capabil-

ity, only the LTM4683s, their associated pull-up resistors,

and the I2C pull-up resistors should be powered from the

VDD33 3.3V supply. In addition, any device sharing the I2C

bus connections with the LTM4683 should not have body

diodes between the SDA/SCL pins and their respective

VDD node because this will interfere with bus communica-

tion without system power. If VIN is applied, the DC1613A

will not supply the power to the LTM4683s on the board.

It is recommended that the RUNn pins be held low or no

voltage configuration resistors inserted to avoid providing

power to the load until the part is fully configured.

The LTM4683 is fully isolated from the host PC’s ground

by the DC1613A. The 3.3V from the adapter and the

LTM4683 VDD33_nn pin must be driven to each LTM4683

internal controller with a separate PFET. If both VIN and

VBIAS are not on, the VDD33_nn pins can be in parallel

because the on-chip LDO is off. The controller’s 3.3V

current limit is 100mA, but typical VDD33_nn currents are

under 15mA. The VDD33_nn does back drive the INTVCC/

VBIAS pin. Normally, this is not an issue if VIN is open.

LTpowerPlay: AN INTERACTIVE GUI FOR

DIGITAL POWER

The LTpowerPlay (see Figure 31) is a powerful Windows-

based development environment that supports Analog

Devices, Inc's digital power system management ICs,

including the LTM4683. The software supports a vari-

ety of different tasks. LTpowerPlay can evaluate Analog

Devices, Inc's ICs by connecting to a demo board or the

user application. LTpowerPlay can also be used in an

offline mode (with no hardware present) to build mul-

tiple IC configuration files that can be saved and reloaded

later. LTpowerPlay provides unprecedented diagnostic and

debug features. It becomes a valuable diagnostic tool

during board bring-up to program or tweak the power

system or to diagnose power issues when bring up rails.

LTpowerPlay utilizes Analog Devices, Inc's USB-to-I2C/

SMBus/PMBus adapter to communicate with one of the

many potential targets, including the DC2924A, DC3082A

demo boards, or a customer target system. The software

also provides an automatic update feature to keep the

revisions current with the latest set of device drivers

and documentation.

A great deal of context-sensitive help is available with

LTpowerPlay, along with several tutorial demos.

PMBus COMMUNICATION AND COMMAND

PROCESSING

The LTM4683 internal controllers have a one-deep buf-

fer to hold the last data written for each supported com-

mand before processing, as shown in Figure 32, write

command data processing. When the part receives a new

command from the bus, it copies the data into the write

command data buffer, indicates to the internal processor

that this command data needs to be fetched, and con-

verts the command to its internal format so that it can be

executed. Two distinct parallel blocks manage command

buffering and command processing (fetch, convert, and

execute) to ensure the last data written to any command

is never lost. Command data buffering handles incoming

PMBus writes by storing the command data in the write

command data buffer and marking these commands for

future processing. The internal processor runs in parallel

and handles the sometimes slower task of fetching, con-

verting and executing commands marked for processing.

Some computationally intensive commands (e.g., timing

parameters, temperatures, voltages and currents) have

internal processor execution times that may be long

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