LTC2928I データシートの表示（PDF） - Linear Technology

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LTC2928I

Multichannel Power Supply Sequencer and Supervisor

Linear Technology 

LTC2928

Applications Information

Fault Detection

The LTC2928 has sophisticated fault detection circuitry

which can detect:

• Stalled supplies (with power good timer enabled)

during sequencing

• Under or overvoltage supplies

• System controller command errors

• Externally commanded faults

If any of the above faults are detected, the LTC2928

immediately pulls the EN1 through EN4 outputs low,

turning off all enabled supplies.

In order to clear the fault condition within the LTC2928,

the following conditions must exist:

• All sequenced supplies must be below their sequence-

down thresholds

• The ON input must be below 0.97V

• The FLT pin must be externally released

Sequencing Faults

The LTC2928 keeps track of power supplies that need to

exceed their sequencing thresholds within the configured

power good time during the sequence-up and sequence-

down phases. Should any supply fail this test a sequence

fault is generated. All enable outputs and FLT are pulled low.

System Controller Command Faults

After the sequence-up phase has begun (ON input high),

the ON input must remain above 1V until DONE pulls

low (sequence-up complete). Pulling ON low before the

sequence-up process is complete is considered a com-

mand fault. All enable outputs and FLT are pulled low.

Similarly, after the sequence-down phase has begun (ON

input low), the ON input must remain below 0.97V until

DONE pulls high (sequence-down complete). Pulling ON

high before the sequence-down process is complete is

considered a command fault. All enable outputs and FLT

are pulled low.

Reset Faults

Use the MS1 and MS2 configuration pins to select whether

or not the system should fault if any monitored input falls

below its undervoltage threshold. A reset fault may only

occur after the LTC2928 comes out of reset for the first

time after sequencing. All enable outputs and FLT are

pulled low.

External Faults

An external fault is generated by pulling the FLT pin low.

Tie the OV pin to FLT to generate overvoltage faults. In

applications using multiple LTC2928s, tie all the FLT pins

together to ensure proper re-sequencing. Upon detecting

an external fault, all enable outputs are pulled low.

Fault Reporting Map

For diagnostic purposes, fault information is latched to

the comparator outputs after a fault. The table below

provides a map to the available fault information. The fault

information remains latched until the LTC2928 completes

the next sequence-up operation.

Table 5. Fault Reporting

Fault Type

Sequence Fault

Reset Fault

Command Fault

External Fault

Fault Codes

CMP1

Low

Low

High

High

CMP2

Low

High

Low

High

Fault Channel

1

2

3

4

CMP3

Low

Low

High

High

CMP4

Low

High

Low

High

Should multiple faults occur simultaneously, the reported

fault is given priority according to the following order:

1) Sequence Fault

2) External Fault

3) Reset Fault

4) Command Fault (channel code is meaningless)

2928fa

16

For more information www.linear.com/LTC2928

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