Linear Technology LTC3880 Guida rapida alla configurazione

dc1962cf

DEMO MANUAL DC1962C

Description

14-Channel Power Supply

System Employing LTC3880/LTC2974/LTC2977

Power System Managers with EEPROM

The DC1962C is a demonstration system that showcases three

different Linear Technology devices—the LT C

3880, LTC2974,

and LTC2977. The LTC2974 and LTC2977 devices are I2C/

SMBus/PMBus power system managers with EEPROM. The

LTC3880 isadualoutput PolyPhase

step-downDC/DCcontrol-

ler with digital power system management. The LTC3880 moni-

tors and controls 2 power supply rails, the LTC2974 monitors

and controls 4 power supply rails, and the LTC2977 monitors

and controls 8 power supply rails. The DC1962C demonstrates

theabilityof thesedevicesto sequence,trim,margin,supervise,

monitor, and log faults for fourteen power supplies. Each power

supply channel’s output voltage is monitored and each device

monitors its own internal die temperature. Six channels have

current and external temperature sensing.

The DC1962C is a single circuit board that contains fourteen

independent power supply rails. The board employs twelve

LTC3405A 300mA switch-mode regulators, which are config-

ured to be controlled by the LTC2974 (4) and LTC2977 (8). The

LTC3880’s two channels have much of the switching regulator

integrated, only requiring the external power stage (power

MOSFETs), inductor, and other passives. This board provides

a sophisticated fourteen channel digitally programmable power

supply system. The rail voltages are programmable within the

trim range shown in Table 1.

This demonstration system is supported by the LTpowerPlay™

graphical user interface (GUI) enabling complete control of the

featuresonallthreedevices.Together,the LTpowerPlay software

and DC1962C hardware system create a powerful development

environment for designing and testing configuration settings

of the LTC3880, LTC2974, and LTC2977. These settings can

be stored in each of the devices’ internal EEPROM or in a file.

This file can later be used to order pre-programmed devices or

to program devices in a production environment. The software

displays all of the configuration settings and real time measure-

ments from the three digital power ICs. Telemetry allows easy

access and decoding of the fault log created by each device.

The board comes pre-programmed with the EEPROM values

appropriate for the fourteen power supply rails on the DC1962C.

Just plug and play!

Multiple DC1962C boards can be cascaded together to form a

high channel count power supply (see the Multi-Board Arrays

section). This allows for the formation of a single, coherent

L, LT, LTC, LTM, Linear Technology, the Linear logo and PolyPhase are registered trademarks

and LTpowerPlay is a trademark of Linear Technology Corporation. All other trademarks are the

property of their respective owners.

power supply system. The user configures up to eight DC1962C

boards, thereby controlling up to 112 separate power supply

rails. This cascaded configuration demonstrates features of the

LT power system management ICs which enable timing and

fault information to be shared across multiple ICs.

The DC1962C demo board can be powered by an external power

supply, such as a +12VDC supply. Communication with the

software is provided through the DC1613 USB-to-I2C/SMBus/

PMBus Controller. The following is a checklist of items which

can be obtained from the LT C website or LT C Field Sales.

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

• LTpowerPlay Software

DC1962C Features

• I2C/SMBus Serial Interface

• PMBus Compliant Command Set

• Configuration EEPROM with CRC

• Black Box Fault Logging to Internal EEPROM

• Differential Input, 16-Bit Δ∑ ADC with less than ±0.25% of

Total Unadjusted Error (±0.5% for LTC3880)

• Voltage Servos Precisely Adjust Supply Voltages

• LTC2974 and LTC2977 Utilize 10-Bit trim DACs with

Soft-Connect

• Telemetry Reads Back VIN, IIN, VOUT, IOUT, Temperature (Int.

and Ext.)

• Output Sequencer-Time Based orTracking(Tracking support

on LTC2974 Only)

• Supports Multichannel Fault Management

• Operates Autonomously without Additional SW

• Powered from 6V to 14V

• Packaging:

– LTC2974/LTC2977 in 64-lead QFN

– LTC3880 in 40-lead QFN

Design files for this circuit board are available at

http://www.linear.com/demo

dc1962cf

DEMO MANUAL DC1962C

performance summary

Specifications are at TA= 25°C

POWER SUPPLY CHANNEL CH(0:1) CH(2:5) CH(6:13)

Manager/Controller LTC3880 LTC2974 LTC2977

Nominal Untrimmed Output Voltages 0.85V, 1.1V

(Defined by Config)

1.5V, 1.8V, 2.0V, 2.2V 0.9V, 1.0V, 1.1V, 1.2V,

2.5V, 2.7V, 3.0V, 3.3V

Rated Output Current 0.3A

Default Margin Range ± 5%

Output Trim Range (VFS_VDAC = 1.38V) Each Channel Is Adjustable

from 0.5V to 4.5V (Note 1)

15%/–11% 15%/–11%

Temperature 1 Internal, 2 Ext. 1 Internal, 4 Ext. 1 Internal

Common Characteristics. Specifications Valid Over Full Operating Temperature Range

PARAMETER CONDITIONS

VALUE

MIN TYP MAX UNITS

VPWR Supply Input Voltage Range 6 14 V

ADC Total Unadjusted Error VIN_ADC ≥ 1V, Applies to LTC2974/LTC2977 ±0.25 %

VIN_ADC ≥ 1V, Applies to LTC3880 ±0.5 %

ADC Voltage Sensing Input Range Differential Voltage: VIN_ADC = (VSENSEPn– VSENSEMn) 0 6 V

Note 1: Note that VOUT_MAX limit is set to 2.5V by default. VOUT_MAX clamps the voltage setpoint to 2.5V. It is recommended that you change the VOUT_MAX

The following list contain terms used throughout the document.

Channel – The collection of functions that monitor, supervise, and trim a given power supply rail.

EEPROM – Non-volatile 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 sensitivity/

marginality problems

NVM – Non-volatile memory, see EEPROM.

Monitor – The act of measuring voltage, current, and temperature readings.

PMBus – An industry standard power-management protocol 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 power supply controller manages.

Supervise – The act of quickly responding (warning or faulting) to a voltage, current, temperature 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.

Glossary of terms

dc1962cf

DEMO MANUAL DC1962C

ltpowerplay Gui software

LTpowerPlay is a powerful Windows-based development environment that supports Linear Technology power system

management ICs with EEPROM, including the LTC2974 and LTC2977 4-channel and 8-channel PMBus power system

managers, and the LTC3880 dual output PolyPhase step-down DC/DC controller with digital power system manage-

ment. The software supports a variety of different tasks. You can use LTpowerPlay to evaluate Linear Technology ICs

by connecting to a demo board system. LTpowerPlay can also be used in an offline mode (with no hardware present)

in order to build a multi-chip configuration file that can be saved and re-loaded at a later time. LTpowerPlay provides

unprecedented system level diagnostic and debug features. It becomes a valuable diagnostic tool during board bring-up

to program or tweak the power management scheme in a system or to diagnose power issues when bringing up rails.

LTpowerPlay utilizes the DC1613 I2C/SMBus/PMBus Controller to communicate with one of many potential targets,

including the DC1962C 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. The LTpowerPlay software can

be downloaded from:

http://www.linear.com/ltpowerplay

Figure 1. Screenshot of the LTpowerPlay GUI

dc1962cf

DEMO MANUAL DC1962C

Quick start proceDure

To access technical support documents for LT C Digital Power Products visit “Help, View Online help” on the LTpow-

erPlay menu.

The following are examples of content available in the online help:

1. Demonstration and Tutorial Videos

• An updated Quick Start Demonstration video of LTpowerPlay and this demo board

• Product/Feature-specific demonstration and tutorial videos

2. Detailed Technical Documentation

• Schematic Checklists

• Device Programming Options

• Firmware ‘Getting Started’ guides with sample code (margining, reading telemetry, etc.)

The following procedure describes how to set up a DC1962C 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 DC1962C board using the 12-pin ribbon cable.

Figure 2. Connecting DC1962C Board and the DC1613 I2C/SMBus/PMBus Controller

dc1962cf

DEMO MANUAL DC1962C

3. Confirm that the CONTROL switch is set to the RUN

position.

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

USB port on your PC. The board should power up with

all power good LEDs and 5V LED illuminated green. The

USB-to-I2C/SMBus/PMBusControllersupplies~100mA

of current which should be sufficient for a single demo

board.

5. Connect a 12VDC power supply with > 0.5A capacity to

the VIN input jack of any DC1962C, if multiple boards

are being powered.

6. Launch the LTpowerPlay GUI.

a. The GUI automatically identifies the DC1962C and

builds asystem tree for each power system manager.

The system tree on the left hand side will look as

below:

Note:For multiple boardarrays, the GUIautomatically

ensures each device has a unique address. In this

scenario, it is recommended at this point to store

these addresses to NVM (EEPROM) by clicking the

“RAM to NVM” icon in the toolbar.

b. A green message box will be displayed momentarily

in the lower left hand corner confirming that the

DC1962C is communicating.

Quick start proceDure

c. Save the demo board configuration to a (*.proj) file

by clicking the “Save” icon. This creates a backup

file. Name it whatever you want.

7. The CONTROL switch is configured to control all 14

channels. Slide the switch to RUN to enable, OFF to

disable all channels. For multiple board arrays, the

CONTROL switch is wired to a signal that is common

across all boards. All CONTROL switches must be set

to the RUN position to enable all boards.

dc1962cf

DEMO MANUAL DC1962C

Quick start proceDure

Loading a DC1962C Configuration (*.proj) File with the GUI

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. This loads the configuration

into the working RAM of the devices.

3. To store the configuration to NVM (EEPROM), click on the “RAM →NVM” icon as shown below.

Dc1962c Details - top siDe

Figure 3. DC1962C Top Side Details

dc1962cf

DEMO MANUAL DC1962C

common Demo BoarD operations

Margin All Rails

The digital power products on the DC1962C not only

monitor each of their respective outputs but can margin

the outputs either high or low. Margining is the operation

that moves a rail either 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

(LTC2974 and LTC2977 only).

A look at the telemetry window shows the effect of the

margin high or margin low operation. The following screen

shot shows all rails going from nominal set points to

margin high, margin low, and back to nominal voltages.

Each of the power management ICs has a multiplexed ADC

that is used to provide voltage, current, and temperature

readback values. The telemetry plot in the GUI is similar to

a multichannel 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. The total ADC loop time

(~100ms to 160ms) for a given channel is dependent on

the device’s configuration. See corresponding data sheet.

dc1962cf

DEMO MANUAL DC1962C

Creating a Fault

There is a pushbutton on the DC1962C board that is used

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

detectit and respond according to the configuration. When

depressed, the pushbutton creates a fault on channel 2,

the 1.5V output (GUI channel U1:0). The user should

see all outputs power off, the fault LED momentarily il-

luminate, the alert LED illuminate continuously, and all

rails sequence back on after a retry period. The user may

also short any power supply output indefinitely. This is a

good way to induce UV faults and shows that a shorted

channel will not be damaged. Use a jumper wire or a coin

to short any output.

common Demo BoarD operations

Clearing a Fault

To clear a fault, the user may click the CF icon in the

GUI or simply push the RESET pushbutton on the demo

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

LED on the board will be cleared. You will notice that all

rails are automatically re-enabled after a programmable

retry period. The alert LED may be cleared by clicking the

Clear Faults (CF) icon in the GUI. After clearing faults, the

system tree may remain “yellow” if any non-volatile fault

logs are present. For further information, see the Working

with the Fault Log section.

Reset the DC1962C

A reset pushbutton is provided on the board. To reset all

devices on the DC1962C board and reload the EEPROM

contents into operating memory (RAM), press RESET

(SW2) on the DC1962C. Note that the “RESET” icon in

the GUI tool bar issues a software reset for any LTC3880

device in the system. It is recommended that you use the

reset pushbutton on the board to provide a reset condition

to the entire system.

DC1962C LEDs

Each individual channel on DC1962C also has its own

green power good LED (RUN_CH0 through RUN_CH13).

When USB power (DC1613 Controller) or external power

(6V to 14V jack) is applied, the +5V green LED will illu-

minate, indicating that the power system managers are

powered. The red LEDs will illuminate when an alert or a

fault has occurred.

dc1962cf

DEMO MANUAL DC1962C

Figure 4. Sequencing Output Channels with DC1962C Using TON_DELAY

common Demo BoarD operations

Figure 5. TON_DELAY Configuration Figure 6. TOFF_DELAY Configuration

Sequencing Output Channels

The LTC3880, LTC2974, and LTC2977 have been pre-

configured with different TON_DELAY values for each

channel. The TON_DELAY parameter is applied to each

device relative to the respective CONTROL pin (RUN on

the LTC3880). On this demo board, all CONTROL/RUN

pins are wire OR’d. Therefore the TON and TOFF delays

are enforced relative to one edge. Figure 4 shows an oscil-

loscope screen capture of four output rails sequencing up.

The same applies to TOFF_DELAY values. When the

CONTROL switch is set to the OFF position, all rails will

power down sequentially based on each of the device’s

TOFF_DELAY values. 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 14 channels. Figures 5 and 6

show TON and TOFF delays for all channels at once. You

will notice in Figure 1 that the GUI shows idealized on/off

waveforms.Thisgraphical view shows therelative TON and

TOFF delays in response to an on/off command, whether

it comes from the CONTROL switch or PMBus command.

Once a new timing value is entered, the timing change will

be reflected in the idealized waveforms.

dc1962cf

DEMO MANUAL DC1962C

"Why Am I Off?” Tool

Use the “Why am I Off?” tool in the LTpowerPlay GUI to diagnose the reason a power supply channel is turned off.

The tool can be located in the top right corner of the GUI, above the Register Information tab. Hover your cursor over

this tab to show the tool.

common Demo BoarD operations

Figure 7. "Why Am I Off” Tool in the LTpowerPlay GUI

What Is a Fault Log?

A fault log is a non-volatile record of the power system

leading up to the time of fault. It holds the most recent

monitored values (uptime, voltage, current, temperature)

that can be analyzed to help determine the cause of the

fault. It is a powerful diagnostic feature of each of the

digital power managers on the DC1962C demo board.

Create a Fault and Fault Log

To create a fault log, you must create a fault, as described

in the Creating a Fault on page 8. Select the appropriate

device in the system tree by clicking on the U1 LTC2974

chip. We will proceed to work with the LTC2974 fault log.

aDvanceD Demo BoarD operations

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