LTC2972 datasheet(103/112 Pages) LINER

103 / 112 page

LTC2972

103

2972fa

For more information www.linear.com/LTC2972

APPLICATIONS INFORMATION

Connecting the DC1613 USB to I2C/SMBus/PMBus

Controller to the LTC2972 in System

The DC1613 USB to I2C/SMBus/PMBus Controller can

be interfaced to the LTC2972s on the user’s board for

programming, telemetry and system debug. The control-

ler, when used in conjunction with LTpowerPlay software,

provides a powerful way to debug an entire power system.

Failuresarequicklydiagnosedusingtelemetry,faultstatus

registers and the fault log. The final configuration can be

quickly developed and stored to the LTC2972’s EEPROM.

Figure 42 and Figure 43 illustrate application schematics

for powering, programming and communicating with

one or more LTC2972’s via the ADI I2C/SMBus/PMBus

controller regardless of whether or not system power

is present.

Figure42showstherecommendedschematictousewhen

the LTC2972 is powered by the system intermediate bus

through its VPWR pin.

Figure43showstherecommendedschematictousewhen

the LTC2972 is powered by the system 3.3V through its

VDD33 and VPWR pins. The LTC4412 ideal OR’ing circuit

allowseitherthecontrollerorsystemtopowertheLTC2972.

Becauseofthecontroller’slimitedcurrentsourcingcapabil-

ity, only the LTC2972s, their associated pull-up resistors

and the I2C/SMBus pull-up resistors should be powered

from the ORed 3.3V supply. In addition, any device sharing

I2C/SMBus bus connections with the LTC2972 should not

have body diodes between the SDA/SCL pins and its VDD

node because this will interfere with bus communication

in the absence of system power.

The ADI controller’s I2C/SMBus connections are opto-

isolated from the PC’s USB. The 3.3V from the controller

and the LTC2972’s VDD33 pin can be paralleled because

the ADI LDOs that generate these voltages can be back

driven and draw <10μA. The controller’s 3.3V current

limit is 100mA.

Figure 42. ADI Controller Connections When VPWR Is Used

2972 F42

VPWR

VDD33

LTC2972*

WP GND

*PIN CONNECTIONS

OMITTED FOR CLARITY

REPEAT OUTLINED CIRCUIT FOR EVERY LTC2972

TO/FROM OTHER LTC

POWER SYSTEM MANAGERS

0.1µF

5.49k

10k

VDD33

0.1µF

VDD25

0.1µF

49.9k

150k

SCL

SDA

SHARE_CLK

TO LTC USB TO

I2C/SMBUS/PMBUS

CONTROLLER

ISOLATED 3.3V

NTS4173P

4.5V TO 15V

SCL

GND

SDA

LTC2972 Datasheet(PDF) 103 Page - Linear Technology

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