LTC2978A(RevA) View Datasheet(PDF) - Linear Technology

Part Name

Description

MFG CO.

LTC2978A
(Rev.:RevA)

8-Channel PMBus Power System Manager Featuring Accurate Output Voltage Measurement

Linear Technology 

LTC2978A

APPLICATIONS INFORMATION

OVERVIEW

The LTC2978A is a power management IC that is capable

of sequencing, margining, trimming, supervising output

voltage for OV/UV conditions, providing fault management,

and voltage read back for eight DC/DC converters. Input

voltage and LTC2978A junction temperature read back are

also available. Odd numbered channels can be configured

to read back sense resistor voltages to provide current

measurements for those channels. Linear Technology

Power System Managers can coordinate operation among

multiple devices using common SHARE_CLK, FAULTB and

CONTROL pins. The LTC2978A utilizes a PMBus compliant

interface and command set.

POWERING THE LTC2978A

The LTC2978A can be powered two ways. The first method

requires that a voltage between 4.5V and 15V be applied

to the VPWR pin. See Figure 14. An internal linear regula-

tor converts VPWR down to 3.3V which drives all of the

internal circuitry of the LTC2978A.

Alternatively, power from an external 3.3V supply may

be applied directly to the VDD33 pins 16 and 17 using a

voltage between 3.13V and 3.47V. Tie VPWR to VDD33 pins.

See Figure 15. All functionality is available when using

this alternate power method. The higher voltages needed

for the VOUT_EN[3:0] pins and bias for the VSENSE pins are

charge-pumped from VDD33.

SETTING COMMAND REGISTER VALUES

The command register settings described herein are in-

tended as a reference and for the purpose of understanding

the registers in a software development environment. In

actual practice, the LTC2978A can be completely config-

ured for standalone operation with the LTC USB to I2C/

SMBus/PMBus controller (DC1613) and software GUI

using intuitive menu driven objects.

SEQUENCE, SERVO, MARGIN AND RESTART

OPERATIONS

Command Units On or Off

Three control parameters determine how a particular

channel is turned on and off. The CONTROL pins, the

OPERATION command and the value of the input voltage

measured at the VIN_SNS pin (VIN). In all cases, VIN must

exceed VIN_ON in order to enable the device to respond

to the CONTROL pin or OPERATION command. When VIN

drops below VIN_OFF an immediate OFF of all channels

will result. Refer to the OPERATION section in the data

sheet for a detailed description of the ON_OFF_CONFIG

command.

4.5V < VPWR < 15V

0.1µF 0.1µF

0.1µF

VPWR

VIN_SNS

VDD33

VDD33

VDD25

LTC2978A

GND

*SOME DETAILS

OMITTED FOR CLARITY

2978a F14

Figure 14. Powering LTC2978A Directly from an Intermediate Bus

EXTERNAL 3.3V

0.1µF

0.1µF

VPWR

VDD33

VDD33

VDD25

LTC2978A

GND

*SOME DETAILS

OMITTED FOR CLARITY

2978a F15

Figure 15. Powering LTC2978A from External 3.3V Supply

For more information www.linear.com/LTC2978A

2978afa

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