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dc2198af

DEMO MANUAL DC2198A

COMMON DEMO BOARD OPERATIONS

MARGIN ALL RAILS

The LTC2980 power system manager not only monitors

eachofthesixteenoutputsbutalsocanmargintheoutputs

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

theuseofexternalhardwareorresources.TheGUIprovides

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

withoutcreatingafaultevenifthefaultlimitsareexceeded.

A look at the telemetry window shows the effect of the

marginhighormarginlowoperation.Thefollowingscreen

shotshowsallrailsgoingfromnominalsetpointstomargin

high, margin low, and back to nominal voltages.

Each LTC2977 inside the LTC2980 has a multiplexed ADC

that is used to provide voltage, current, and temperature

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

amulti-channeloscilloscopewhichiscapableofdisplaying

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

thedevice’sconfiguration.RefertotheLTC2977datasheet

for complete ADC timing specifications.

Creating a Fault

There is a pushbutton on the DC2198A 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 pushbutton creates a fault on chan-

nel 10, the 2.5V output (GUI channel U1:2). The user

shouldseealloutputspoweroff,thefaultLEDmomentarily

illuminate, 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.

The LTC2980 has a feature, which allows it to sequence its

channels off in a controlled manner, as opposed to turning

all rails off immediately. The SequenceOffOnFault bit in the

MFR_CONFIG_LTC2977registersetsthisbehavioroneach

channel. The DC2198A demo board has been configured

to sequence off all channels when a fault occurs. Pressing

the “CREATE FAULT” pushbutton causes the Fault pin to

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