Analog Devices DC2875A Guida rapida alla configurazione

DEMO MANUAL DC2875A

Rev. 0

DESCRIPTION

LTC2971

High Voltage Two 2-Channel PMBus Power System

Managers with Four Power Supply Rails

The DC2875A is a demonstration system for the LTC

2971

Power System Manager that interfaces to various regula-

tors. The board contains all the circuitry needed to demon-

strate a power system that utilizes two 2-channel LTC2971

devices that manage four power supplies. The four power

supplies include various switching regulators for the pur-

pose of demonstrating a variety of methods to sense volt-

age and current. The demo board provides a sophisticated

4-channel digitally programmable power supply system.

The LTC2971 is a 2-channel I2C/SMBus/PMBus Power

System Manager that features accurate input current

and energy measurement and is capable of managing

±60V supplies. The device monitors input current and

input voltage, and calculates input power and energy.

The DC2875A demonstrates the ability of the LTC2971

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

faults for four power supplies. The LTC2971 monitors

each channel’s output voltage and output current and also

monitors each channel’s external temperature sensor and

its own internal die temperature.

The DC2875A board contains four independent power

supply rails. All four rails are based on DC/DC switching

regulators. The +36V and +32V channels are managed by

an LTC2971 and the ±24V channels are managed by an

LTC2971-1. The board is pre-configured with these volt-

ages and may be re-configured with feedback resistors.

The LTpowerPlay

graphical user interface (GUI) sup-

ports this demonstration system and enables complete

control of all the features of the LTC2971. Together, the

LTpowerPlay software and DC2875A hardware system

create a powerful development environment for design-

ing and testing configuration settings of the LTC2971.

LTpowerPlay stores these settings in the LTC2971 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

LTC2971. The board comes preprogrammed with the

All registered trademarks and trademarks are the property of their respective owners. Protected

by U.S. patents, including 7382303, 7420359, and 7940091.

EEPROM values appropriate for the four power supply

rails on the DC2875A. Just plug and play!

Order preprogrammed devices from Analog Devices

Express (ADX) using LTpowerPlay: https://www.analog.

com/en/design-center/device-programming.html

The following items are required:

• +12VDC Power Supply

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

• LTpowerPlay Software

DC2875A 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 Two IIN Monitors

• 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

• 2-Channel Time-Based Output Sequencer

• I2C/SMBus Serial Interface

• Powered from 8V to 18V

Design files for this circuit board are available.

DEMO MANUAL DC2875A

Rev. 0

PARAMETER CONDITIONS VALUE

VPWR Supply Input Operating Range 4.5V to 60V*

VDD33 Supply Input Operating Range 3.13V to 3.47V

ADC VSENSE Total Unadjusted Error (TUE) 10V ≤ VSENSE ≤ 60V ±0.25%

ADC Voltage Sense Input Range LTC2971

LTC2971-1 (VOUT_SNS1)

0V to 60V

–60V to 0V

ADC Current Sense Input Range Differential Current Sense Voltage –100mV to 100mV

ADC Voltage Sensing Resolution 0V ≤ VIN_ADC ≤ 60V 4.5mV/LSB

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

16mV < |VIN_ADC| < 32mV

32mV < |VIN_ADC| < 63.9mV

63.9mV < |VIN_ADC| < 100mV

15.625μA/LSB

31.25μA/LSB

62.5μA/LSB

125μA/LSB

DAC Resolution 10 Bits

DAC Full-Scale Output Voltage Buffer Gain Setting 0

Buffer Gain Setting 1

1.38V Typ.

2.65V Typ.

Internal Temperature Sensor TUE

External Temperature Sensor TUE

±1°C

±3°C

Voltage Supervisor Input Voltage

Range (Programmable)

VOUT_SNS[n] 0 to 60V (Low Resolution)

0 to 34V (High Resolution)

Voltage Supervisor Sensing Resolution 0V to 60V Range (Low Resolution)

0V to 34V Range (High Resolution)

70.4mV/LSB

35.2mV/LSB

Voltage Supervisor TUE 9V < VIN_VS < 60V, Low Resolution Mode

4.5V < VIN_VS < 34V, High Resolution Mode

±1.5 %

±1.25 %

I2C Serial Clock Frequency 10kHz to 400kHz

* Powering the device from input voltages above 25V will create high power dissipation.

PERFORMANCE SUMMARY

Specifications are at TA= 25°C

DEMO BOARD SYSTEM SPECIFICATIONS

NOMINAL

UNTRIMMED VOUT

REGULATOR

PART NUMBER

RESISTORS THAT SET

UNTRIMMED VOUT RDAC MARGIN RANGE

CH0 +36V ±1% LT7101 R11, R12 R10 ±4%

CH1 +32V ±1% LT3991 R20, R21 R19 ±4%

CH2 +24V ±1% LT8630 R32, R33 R31 ±5%

CH3 –24V ±1% LT3758 R44, R45 R41, R42 ±5%

Notes:

1. Keep load currents < 300mA on +36V and +32V channels and < 400mA on ±24V channels.

2. Output voltages can be margined by ±4% or more from nominal with the default resistor values. These values can be easily changed. See section

Changing Nominal Output Voltages. Use the LTC2971 Resistor Selection Tool which is accessed from LTpowerPlay.

DEMO MANUAL DC2875A

Rev. 0

GLOSSARY OF TERMS

The following list contain terms used throughout the

document.

Channel – The collection of functions that monitor, super-

vise, 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 tem-

perature 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 –The final output voltage that the LTC2971

supervises.

Supervise – The act of quickly responding (compared to

a fault setting) to a voltage and current condition that is

compared to preprogrammed 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 out-

put voltages, range and resolution of margining,

sequencing, OV/UV limits, and OC limits.

• Create your own configuration:store in the LTC2971

EEPROM or save to a project file. Order prepro-

grammed 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. DC2875A

2. PC + USB Cable

3. 12V, >2A Power Supply

4. USB to I2C/SMBus/PMBus Controller

Figure1. DC2875A Demo Setup

USB TO

I2C/SMBus/PMBus

DONGLE (DC1613)

TWO LTC2971s

4-CH DEMO BOARD

(DC2875A)

+12V POWER

SUPPLY

USB

CH0: +36V

CH1: +32V

CH2: +24V

CH3: –24V

DC2875A F01

DEMO MANUAL DC2875A

Rev. 0

LTpowerPlay is a powerful Windows-based development

environment that supports Analog Devices Power System

Management ICs with EEPROM, including the LTC2971

2-Channel Power System Manager. The software supports

a variety of different tasks. You can use LTpowerPlay to

evaluate Analog Devices ICs by connecting to a demo

board system. LTpowerPlay features an offline mode to

build a multi-chip configuration file for later use with

hardware. LTpowerPlay provides unprecedented system

level diagnostic and debug features. It becomes a valu-

able diagnostic tool during board bring-up to program or

LTpowerPlay GUI SOFTWARE

tweak the power management scheme in a system or to

diagnose power issues when bringing up rails. LTpower-

Play utilizes the DC1613 I2C/SMBus/PMBus Controller to

communicate with one of many potential targets, includ-

ing the DC2875A 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:

LTpowerPlay

Select “Help, View Online Help”from the LTpowerPlay

menu to access technical documents.

Figure2. Screenshot 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

IDEALIZED ON/OFF SUPPLY WAVEFORMS SCOPE-LIKE TELEMETRY WINDOW

DISPLAY OF SELECTED

PARAMETER (CONFIG OR

TELEMETRY) ACROSS SYSTEM

DC2875A F02

DEMO MANUAL DC2875A

Rev. 0

QUICK START PROCEDURE

The following procedure describes how to set up a

DC2875A demo system.

1. Download and install the LTpowerPlay GUI.

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 DC2875A board

using the 12-pin ribbon cable.

6. Launch the LTpowerPlay GUI.

a. The GUI automatically identifies the DC2875A

and builds a system tree for each I

C device.

The system tree on the left hand side will look

like this:

b. A green message box will be displayed momen-

tarily in the lower left-hand corner confirming

that the DC2875A is communicating.

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.

If you need to load the original board default

configuration, select the GUI menu pull-down

item DEMO →DC2875A_Defaults. This writes

Figure3. Connecting DC2875A and the DC1613 USB to

I2C/SMBus/PMBus Controller

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

4. Plug the USB-to-I2C/SMBus/PMBus Controller into a

USB port on your PC. The DC1613’s ribbon cable will

power up the LTC2971 devices with the LED labeled

“VDD33" illuminated green next to each LTC2971. The

PG LEDs will illuminate red.

5. Connect a +12VDC power supply with >2A capacity

to the VIN input jack of the DC2875A board. The blue

LED will illuminate indicating that DC jack power is

applied. Move the RUN switch to the ON position. The

four outputs will power up and the green LEDs will

illuminate.

DEMO MANUAL DC2875A

Rev. 0

the board defaults into the RAM and NVM of

both LTC2971 devices.

7. The LTC2971 is configured to use the CONTROL

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.

QUICK START PROCEDURE

2. Click on the “Go Online” icon:

then click on the “PC →RAM” icon:

to write all registers. This loads the configuration into

the working RAM of the LTC2971 devices.

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

on the “RAM → NVM” icon.

DC2875A DETAILS

LTC2971

PSM

LTC2971-1

PSM

CH2 AND CH3 OUTPUTS

CASCADING

CONNECTOR

RUN/CONTROL

SWITCH

DC1613

CONNECTOR

DC JACK

(+12V)

CASCADING

CONNECTOR

CH0 AND CH1 OUTPUTS

I2C PORT

PUSHBUTTONS

TO FORCE A

RESET AND

A FAULT

Figure4. DC2875A Details

DEMO MANUAL DC2875A

Rev. 0

COMMON BOARD OPERATIONS

OVERVIEW

A simplified block diagram of the DC2875A is shown in Figure5. Each LTC2971 measures input current with a 50mΩ

sense resistor for their managed channels. Each device also controls, monitors, and supervises its two outputs.

Figure5. Simplified Block Diagram of the DC2875A

DEMO MANUAL DC2875A

Rev. 0

POWERING THE BOARD

The DC2875A board is powered from a wall-powered 12V

supply. The supply must be capable of delivering >2A.

If two channels are loaded with the maximum allowable

current, the input current may exceed 2A. The LTC2971

devices are powered either from the DC1613’s 3.3V power

or DC jack power if VIN is applied.

For your convenience, a 12V to 48V boost switch-

ing regulator has been designed into the board. The

48V supply acts as the input power supply to the four

channels. Each LTC2971 device measures 48V input

voltage and input current to the 2 power stages it man-

ages. A 12V wall transformer is much more common

than a 48V transformer.

DC2875A LEDs

The blue LED near the power jack indicates that the DC

jack has voltage. The green LEDs labeled VDD33 illumi-

nates when the LTC2971 is powered from either the USB

controller or the external V

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.

RESET THE LTC2971

To reset the LTC2971 and reload the EEPROM contents

into operating memory (RAM), press the pushbutton

switch SW1 labeled RESET.

PRE-LOAD THE OUTPUTS

Each of the outputs has pre-load resistors that provide

5mA of load current. 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 DC2875A board are

controlled by a single CONTROL switch S1.

To demonstrate time-based sequencing, let’s use the RUN

switch as the master enable. The LTC2971 devices are

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 opera-

tion command to turn all channels “on”. The same applies

to TOFF_DELAY values. When the CONTROL switch is

set to the OFF position, all rails will power down sequen-

tially based on the device’s TOFF_DELAY values. Figure6

shows an oscilloscope screen capture of the four output

rails sequencing up.

COMMON BOARD OPERATIONS

Figure6. Sequencing Output Channels On

Each channel has an LED that 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 LTC2971, the TON_DELAY and TOFF_DELAY val-

ues extend to 13.1 seconds, providing a reasonable range

for sequencing on and off the power supply rails.

Figure7. TON_DELAY and TOFF_DELAY Settings

DC2875A F06

DC2875A F07

DEMO MANUAL DC2875A

Rev. 0

MARGIN ALL RAILS

The LTC2971 power system manager not only monitors

output voltages and currents but can margin the outputs

either high or low. Margining is the operation that moves

a rail up or down for testing purposes. It allows 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 or margin low operation. This screen shot

is a telemetry plot of READ_VOUT_PERCENT showing

all rails going from nominal set-points to margin high,

margin low, and back to nominal voltages.

COMMON BOARD OPERATIONS

The LTC2971 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 param-

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

nature of a multiplexed ADC converter, it has an associ-

ated ADC loop time of approximately 135ms.

CREATING A FAULT

There is a pushbutton on the DC2875A 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 (SW2) creates

a fault (shorts VOUT_CH2 to ground) on CH2, the +24V

output. When faulted, all channels power down immedi-

ately and the GUI’s system tree indicates the color red for

the Status portion of that channel. You should see all out-

puts power off, 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.

CLEARING A FAULT

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

or simply push the RESET pushbutton (SW1) on the

DC2875A 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 program-

mable 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 re-armed. For further

information, see the Working with the Fault Log section.

DEMO MANUAL DC2875A

Rev. 0

COMMON BOARD OPERATIONS

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

WHAT IS A FAULT LOG?

A fault log is a nonvolatile record of the power system

leading up to the time of fault. Telemetry data is continu-

ously updated in a circular RAM buffer in the LTC2971.

When a fault occurs, the contents of the RAM buffer are

ADVANCED DEMO BOARD OPERATIONS

“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.

automatically written to NVM. The most recent monitored

values (uptime, voltage, current, temperature) provide

additional context preceding the fault. It is a power-

ful diagnostic feature of the LTC2971 on the DC2875A

demoboard.

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