Linear Technology DC2518A Guida rapida alla configurazione

dc2518af

DEMO MANUAL DC2518A

DESCRIPTION

LTC2975

4-Channel PMBus Power System Manager

with ±12V and ±48V Power Supply Rails

The DC2518A is a demonstration system for the LT C

2975

Power System Manager that interfaces to various regula-

tors. The board contains all the circuitry needed to use

the LTC2975 in a power system and control four power

supplies. The four power supplies include linear and

switching regulators for the purpose of demonstrating a

variety of methods to sense voltage and current. The demo

board provides a sophisticated, digitally programmable

4-channel power supply system.

The LTC2975 is a 4-channel I2C/SMBus/PMBus Power

System Manager that features accurate input current and

energy measurement. The device monitors input current

and input voltage to calculate input power and energy.

The DC2518A demonstrates the ability of the LTC2975

to sequence, trim, margin, supervise, monitor, and log

faults for four power supplies. The LTC2975 monitors

each channel’s output voltage and output current and also

monitors each channel’s external temperature sensor and

its own internal die temperature.

TheDC2518Aboardcontainsfourindependentpowersup-

plyrails.The+12V/–12Vrailsarebased on LDO regulators,

and the +48V/–48V rails are based on DC/DC switching

regulators. The board is pre-configured with these volt-

ages and may be re-configured with feedback resistors.

The LTpowerPlay

graphical user interface (GUI) supports

thisdemonstrationsystemandenablescompletecontrolof

all the features of the LTC2975. Together, the LTpowerPlay

software and DC2518A hardware system create a power-

ful development environment for designing and testing

configurationsettingsoftheLTC2975.LTpowerPlay stores

these settings in the LTC2975’s internal EEPROM or in a

project file. The software displays all of the configuration

settings and real time measurements from the Power

System Management IC. Telemetry allows easy access

and decoding of the fault log created by the LTC2975.

The board comes pre-programmed with the EEPROM

values appropriate for the four power supply rails on the

DC2518A. Just plug and play!

L, LT, LTC, LTM, Linear Technology and the Linear logo, Linear Express and LTpowerPlay are

registered trademarks of Linear Technology Corporation. All other trademarks are the property

of their respective owners.

Order pre-programmed devices from Linear Express

using LTpowerPlay.

The following items are required:

•+12VDC Power Supply

•USB-to-I2C/SMBus/PMBus Controller (DC1613)

• LTpowerPlay Software

•PC

DC2518A Features

•Sequence, Trim, Margin, and Supervise Four Power

Supplies

• Manage Faults, Monitor Telemetry, Create Fault Logs

• PMBus Compliant Command Set

• Supported by LTpowerPlay GUI

• Margin or Trim Supplies to 0.25% Accuracy

• Four IOUT and One IIN Monitor

• Input Power Measurement and Energy Accumulation

• Fast OV/UV Supervisors Per Channel

• Multi-Channel Fault Management

• Automatic Fault Logging to Internal EEPROM

• Operates Autonomously without Additional Software

•Monitors: Voltage, Current, Power, Temperature

• 4-Channel Time-Based Output Sequencer

•I2C/SMBus Serial Interface

• Powered from 9V to 14V

Design files for this circuit board are available at

http://www.linear.com/demo/DC2518A

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DEMO MANUAL DC2518A

PERFORMANCE SUMMARY

Specifications are at TA= 25°C

PARAMETER CONDITIONS VALUE

VPWR Supply Input Operating Range 9V to 15V

VDD33 Supply Input Operating Range 3.13V to 3.47V

ADC Total Unadjusted Error VIN ≥ 1V ±0.25%

ADC Voltage Sensing Input Range –0.1V to 6V

ADC Current Sensing Input Range Differential Current Sense Voltage –170mV to 170mV

ADC Voltage Sensing Resolution 0V ≤ VIN_ADC ≤ 6V 122µV/LSB

ADC Current Sense Resolution 0mV < |VIN_ADC| < 16mV

16mV < |VIN_ADC| < 32mV

32mV < |VIN_ADC| < 63.9mV

63.9mV < |VIN_ADC| < 127.9mV

127.9mV < |VIN_ADC|

15.6µV/LSB

31.25µV/LSB

62.5µV/LSB

125µV/LSB

250µV/LSB

DAC Resolution 10 Bits

DAC Full Scale Output Voltage Buffer Gain Setting 0

Buffer Gain Setting 1

1.38V Typ.

2.65V Typ.

Temperature Sensor TUE ±1°C

Voltage Supervisor Input Voltage

Range (Programmable)

VSENSEP[n] 0V to 6V (Low Resolution)

0V to 3.8V (High Resolution)

Voltage Supervisor Sensing Resolution 0V to 3.8V Range: 4.096/1024

0V to 6V Range: 8.192/1024

4mV/LSB

8mV/LSB

Voltage Supervisor

Total Unadjusted Error (TUE)

2V < VIN_VS < 6V, Low Resolution Mode

1.5V < VIN_VS < 3.8V, High Resolution Mode

0.8V < VIN_VS < 1.5V, High Resolution Mode

±1.25 %

±1.0 %

±1.5 %

I2C Serial Clock Frequency 10kHz to 400kHz

NOMINAL

UNTRIMMED VOUT

REGULATOR

PART #

RESISTORS THAT SET

UNTRIMMED VOUT RDAC MARGIN RANGE

CH0 +12V ±1% LT3081 R3, R4 ±10%

CH1 –12V ±1% LT3090 R17, R18 R31, R32 ±10%

CH2 +48V ±1% LT8330 R34, R35 R40 ±5%

CH3 –48V ±1% LT8580 R52 R58, R59 ±5%

Notes:

– Keep load currents < 100mA on ±48V channels and < 250mA on ±12V channels.

–Output voltages can be margined by ±10% from nominal with the default resistor values. These values can be eas-

ily changed. See section Changing Nominal Output Voltages. Use the LTC2975 Resistor Selection Tool which is

accessed from LTpowerPlay.

DEMO BOARD SYSTEM SPECIFICATIONS

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DEMO MANUAL DC2518A

GLOSSARY OF TERMS

Figure 1. DC2518A Demo Setup

The following list contain terms used throughout the

document.

Channel –The collection of functions that monitor, su-

pervise, and trim a given power supply rail.

EEPROM – Nonvolatile memory (NVM) storage used to

retain data after power is removed.

Margin – Term used typically in board level testing that

increases/decreases the output voltage to look for sensi-

tivity/marginality problems.

Monitor –The act of measuring voltage, current, and

temperature readings.

NVM – Nonvolatile memory, see EEPROM.

OV – Overvoltage, the result of a voltage comparison that

a pin voltage is above a programmable threshold voltage.

PMBus – An industry standard power management proto-

col with a fully defined command language that facilitates

communication with power converters and other devices

in a power system.

Rail

–Thefinal output voltagethattheLTC2975 supervises.

Supervise – The act of quickly responding to a voltage

andcurrent condition that is compared to pre-programmed

values.

Trim – The act of adjusting the final output voltage. A servo

loop is typically used to trim the voltage.

UV – Undervoltage, the result of a voltage comparison that

a pin voltage is below a programmable threshold voltage.

•Prototype your system by modifying:nominal output

voltages, range and resolution of margining, sequenc-

ing, OV/UV limits, and OC limits.

•Create your own configuration:store in the LTC2975

EEPROMor save toaprojectfile. Order pre-programmed

parts.

•Test fault scenarios. Short outputs to ground, and

observe system response and faults.

WHAT THIS DEMO SYSTEM CAN DO

Demo System Hardware

Hardware Required:

1. DC2518A

2. PC + USB Cable

3. 12V, >1A Power Supply

4. USB to I2C/SMBus/PMBus Controller (DC1613)

dc2518a F01

USB to I2C/SMBus/

PMBus Controller

(DC1613)

LTC2975 PSM &

4-Ch HV/Neg Demo

Board (DC2518A)

+12V Power

Supply

USB

CH0: +12V

CH1: –12V

CH2: +48V

CH3: –48V

dc2518af

DEMO MANUAL DC2518A

LTpowerPlay is a powerful Windows-based development

environmentthatsupportsLinearTechnology powersystem

management ICs with EEPROM, including the LTC2975

4-channel Power System Manager. The software supports

a variety of different tasks. You can use LTpowerPlay to

evaluate Linear Technology ICs by connecting to a demo

boardsystem.LTpowerPlayfeaturesanoffline modetobuild

a multi-chip configuration file for later use with hardware.

LTpowerPlay provides unprecedented system level diag-

nosticand debug features. It becomes a valuablediagnostic

tool during board bring-up to program or tweak the power

management scheme in a system or to diagnose power

LTpowerPlay GUI SOFTWARE

issues when bringing up rails. LTpowerPlay utilizes the

DC1613I2C/SMBus/PMBusControllertocommunicatewith

oneof manypotentialtargets,includingthe DC2518A demo

system or a customer board. The software also provides

an automatic update feature to keep the software current

with the latest set of device drivers and documentation.

Download the software from:

www.linear.com/ltpowerplay

Select “Help, View Online Help”from the LTpowerPlay

menu to access technical documents.

Figure 2. Screen Shot of the LTpowerPlay GUI

SYSTEM TREE OF

ALL DEVICES

CONFIGURATION SETTINGS

FOR ALL DEVICES IN

SYSTEM TREE

REAL-TIME

TELEMETRY

DATA

CHIP DASHBOARD

AND ENERGY

METER

DISPLAY OF SELECTED

PARAMETER (CONFIG

OR TELEMETRY)

ACROSS SYSTEM

IDEALIZED ON/OFF

SUPPLY WAVEFORMS SCOPE-LIKE

TELEMETRY WINDOW

dc2518af

DEMO MANUAL DC2518A

QUICK START PROCEDURE

Thefollowing proceduredescribeshow tosetup aDC2518A

demo system.

1. Download and install the LTpowerPlay GUI:

www.linear.com/ltpowerplay

2. Remove the board from the ESD protective bag and

place it on a level surface. Connect the DC1613 I2C/

SMBus/PMBus controller to the DC2518A board using

the 12-pin ribbon cable.

3. Confirm that the RUN switch is set to its OFF position.

4. Plugthe DC1613 USB-to-I2C/SMBus/PMBus controller

into a USB port on your PC. The board should power up

with the LED labeled “LTC2975 ON”illuminated green.

5. Connect a +12VDC power supply with > 1A capacity to

the VIN input jack of the DC2518A board. The blue LEDs

will illuminate indicating that DC jack power and input

power to the LDOs is applied. Move the RUN switch to

the ON position. The four outputs will power up and

the green LEDs will illuminate.

6. Launch the LTpowerPlay GUI.

a. The GUI automatically identifies the DC2518A and

builds a system tree for each I2C device. The system

tree on the left hand side will look like this:

Figure 3. Connecting DC2518A and the DC1613 USB to I2C/SMBus/PMBus Controller

b. A green message box will be displayed momentarily

in the lower left hand corner confirming that the

DC2518A is communicating.

dc2518af

DEMO MANUAL DC2518A

c. You may make configuration changes. When you

update registers in the GUI by using either function

key F12 to write an individual register or use the

Write All icon to write all registers, you may need

these settings for future use. Save the demo board

configuration to a (*.proj) file by clicking the “Save”

icon. This creates a backup file on your C:drive.

Name it whatever you like.

QUICK START PROCEDURE

Ifyou need to load the originalboard default configu-

ration,select theGUI menupull-down itemDEMO →

DC2518A_Defaults. This writes the board defaults

into the LTC2975’s RAM and automatically to NVM

as well.

7. The LTC2975 is configured to use the RUN switch to

sequence on/off the four channels. Slide the switch to

RUN to enable, OFF to disable all channels.

Loading a Configuration (*.proj) File with the GUI

To load a previously saved proj file:

1. In the upper left hand corner of the GUI, File →Open

→browse to your *.proj file. This will load the file into

the GUI.

2. Click on the “Go Online”icon, then click on the “PC→

RAM” icon to write all registers. This

loadstheconfigurationintotheworking

RAM of the LTC2975.

3. To store the configuration to NVM (EEPROM), click on

the “RAM → NVM” icon.

dc2518af

DEMO MANUAL DC2518A

DC2518A DETAILS

DC1613

CONNECTOR

RUN

SWITCH

CH2 AND CH3

OUTPUTS

CASCADING

CONNECTOR

LTC2975 PSM

CH0 AND CH1

OUTPUTS

PUSHBUTTON

TO FORCE

A RESET AND

A FAULT

I2C PORTS

CASCADING

CONNECTOR

DC JACK

(+12V)

Figure 4. DC2518A Details

dc2518af

DEMO MANUAL DC2518A

Overview

A simplified block diagram of the DC2518A is shown

in Figure 5. The LTC2975 measures input current with

a 10mΩ sense resistor. It also controls, monitors, and

supervises all four outputs.

Powering the Board

The DC2518A board is powered from a wall-powered 12V

supply. The supply must be capable of delivering > 1A. If

the four channels are loaded with the maximum allowable

current, the input current will be greater than 1A. The

LTC2975 device is powered either from the DC1613’s

3.3V power or jack power if VIN is applied.

DC2518A LEDs

There are three blue LEDs near the power jack. These

indicate that the DC jack has voltage and ±15V switching

regulator outputs are up and running. The LED labeled

VDD33 illuminates when the LTC2975 is powered from

either the USB controller or the external VIN power. Each

channel has its own green LED which indicates that the

channel is enabled. The red LEDs on ALERTB and FAULTB

indicate a warning or fault has occurred.

COMMON BOARD OPERATIONS

Reset the LTC2975

To reset the LTC2975 and reload the EEPROM contents into

operating memory (RAM), press the pushbutton switch

SW2 labeled RESET.

Preload the Outputs

Each of the outputs has preload resistors that provide

10mA of load. This ensures that the output voltage decays

to GND quickly when the channel is disabled. This is useful

when sequencing off then on quickly.

Controlling/Sequencing Channels

By default all four channels on the DC2518A board are

controlled by a single RUN switch.

TheLTC2975 is pre-configured with different TON_DELAY

values for each channel. The TON_DELAY parameter is

applied to each of the channels relative to the CONTROL

pin or Group operation command toturn all channels “on”.

Figure 6 shows an oscilloscope screen capture of the four

output rails sequencing up.

The same applies to TOFF_DELAY values. When the Run

switch is set to the OFF position, all rails will power down

sequentially based on the TOFF_DELAY values.

PMBus

LDO

+12V

LDO

–12V

DC/DC

+48V

DC/DC

–48V

+3.3V

CH0

CH1

CH2

CH3

DC/DC

±15V

+VIN

VIN

dc2518a F05

VPWR

CONTROL

IIN_SNSM

VIN_SNS IIN_SNSP

LTC2975

4-CH POWER

SYSTEM MANAGER

DC1613

USB DONGLE HEADER

RUN

SWITCH

INPUT

CURRENT SENSE

Figure 5. Simplified Block Diagram of the DC2518A

dc2518af

DEMO MANUAL DC2518A

COMMON BOARD OPERATIONS

Each channel has an LED which visually indicates if the

channel has power. When the CONTROL pin is switched

on and off, you will observe the relative on/off timing of

the four channels. The timings are intentionally skewed

to show the rails ramp times more clearly.

For the LTC2975, the TON_DELAY and TOFF_DELAY

values extend to 655ms, providing a reasonable range

for sequencing power supply rails on and off.

Figure 6. Sequencing Output Channels On/Off

Figure 7. TON_DELAY and TOFF_DELAY Settings

Margin All Rails

The LTC2975 Power System Manageron the DC2518A

not only monitors each of the four outputs but can margin

the outputs either high or low. Margining is the operation

that moves a rail up or down for testing purposes. It al-

lows a system to be fully characterized over supply limits

without the use of external hardware or resources. The

GUI provides an easy way to margin all rails high or all low

by clicking one of four buttons. To invoke the margining

dialog, click the GroupOp icon in the toolbar. The buttons

labeled “ignore faults”will margin without creating a fault

even if the fault limits are exceeded.

A look at the telemetry window shows the effect of the

margin high and margin low operations. This screen shot

is a telemetry plot of READ_VOUT_PERCENT showing all

railsgoing from nominal set-points to margin high, margin

low, and back to nominal voltages.

dc2518af

DEMO MANUAL DC2518A

The LTC2975 has a multiplexed ADC that is used to pro-

vide voltage, current, and temperature readback values.

The telemetry plot in the GUI is similar to a multi-channel

oscilloscope which is capable of displaying any parameter

that is displayed in the telemetry window. Due to the nature

of a multiplexed ADC converter, it has an associated ADC

loop time of approximately 160ms.

Creating a Fault

There is a pushbutton on the DC2518A board that is used

to force a fault and demonstrate the demo board’s ability

to detect it and respond according to the configuration.

When depressed, the Fault pushbutton creates a fault

(shorts VSENSE node to ground) on CH0, the +12V output

(GUI channel U0:0). When faulted, all channels power

down immediately and the GUI’s system tree indicates

the color red for the status portion of that channel. You

shouldseealloutputspoweroff,the fault LED momentarily

illuminate, the alert LED illuminate continuously, and all

rails sequence back on after a retry period. You may also

hold the FAULT pushbutton indefinitely to demonstrate

the fault behavior and retry timing.

COMMON BOARD OPERATIONS

Clearing a Fault

To clear a fault, you can click the CF icon in the GUI or

simplypush theRESET pushbutton(SW2) onthe DC2518A

demo board. In both cases, the red (+) on the CF icon and

alert LED on the board are both cleared. Notice that all

rails are automatically re-enabled after a programmable

retry period. A dialog box may pop up after clicking the

Clear Faults (CF) icon. If a fault log is present, a dialog will

ask if you would like to clear the fault log as well as clear

system faults. After clearing faults, the system tree will

return to “green” and fault logs are re-armed. For further

information, see the ‘Working with the Fault Log’section.

“Why Am I Off?” Tool

Use the “Why am I Off”tool in the LTpowerPlay GUI to

diagnose the cause for a power supply channel being in

an off state. The tool is located in the top right corner of

the GUI, above the “Register Information”tab. Hover your

cursor over the tab to show the tool.

First select an output channel in the system tree. The

tool collects various status information and provides a

diagnosis.

Figure 8. “Why Am I Off” tool in the LTpowerPlay GUI

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