LTC3889 datasheet(34/118 Pages) AD

34 / 118 page

LTC3888/LTC3888-1/

LTC3888-2

Rev. B

For more information www.analog.com

OPERATION

The BUSY bit in STATUS_BYTE also asserts ALERT and

cannot be masked. This bit can be set as a result of inter-

action between internal operations and PMBus communi-

cation. This fault occurs when a command is received that

cannot be safely executed with one or both master chan-

nels enabled. As discussed in Application Information,

BUSY faults can be avoided by polling MFR_COMMON

before executing some commands.

Status information contained in MFR_COMMON and

MFR_PADS_LTC3888 can be used to clarify the con-

tents of STATUS_BYTE or STATUS_WORD as shown,

but the contents of these registers do not affect the state

of the ALERT pin and may not directly influence bits in

STATUS_BYTE or STATUS_WORD.

FAULT PIN I/O

The LTC3888 can map various fault indicators to their

respective FAULT pin using the MFR_FAULT_PROPAGATE

command.

Channel-to-channel fault dependencies and communica-

tion can be created by connecting FAULT pins together. In

the event of an internal fault, one or more of the channels

is configured to pull the bussed FAULT pins low. All chan-

nels are then configured to shut down when the bussed

FAULT pins are pulled low (MFR_FAULT_RESPONSE set

to 0xC0). If latch off is the programmed response on the

faulted channel, the FAULT pin remains low until one of

the following occurs:

• A CLEAR_FAULTS, RESTORE_USER_ALL or MFR_

RESET Command Is Issued

• The Related Status Bit Is Written to a One

• The Faulted Channel Is Properly Commanded Off and

Back On

• IC Supply Power Is Cycled

For autonomous group retry, the faulted channel is con-

figured to release the FAULT pin(s) after a retry interval,

assuming the original fault has cleared. All the channels

in the group then begin a soft-start sequence.

As noted above, FAULT pins can also find use as inputs

to detect faults external to the controller that require an

immediate response. External faults propagated into the

chip using FAULT pins are not deglitched.

Refer to MFR_FAULT_PROPAGATE for additional details.

FAULT LOG OPERATION

The LTC3888 supports fault logging to provide telemetry

recording capability. A conceptual diagram of the fault

log is shown in Figure 3. During normal operation the

contents of primary status registers and all ADC readings,

including peak voltage and current results, are stored in

a continuously updated RAM buffer if enabled by bit 7

of MFR_CONFIG_ALL. The operation is similar to a strip

recorder. When a fault occurs that disables either master

channel, recording to internal memory is halted (locked)

and the fault log information is made available from RAM

via the MFR_FAULT_LOG command. Some contents of

the locked RAM fault log are also copied into EEPROM for

nonvolatile storage. See Fault Log Details below.

Figure 3. Fault Log Conceptual Diagram

388812 F03

LOCK RAM

AND TRANSFER

TO EEPROM

AT TIME OF FAULT

TRANSFER FROM

EEPROM AFTER

RESET

ADC READINGS

CONTINUOUSLY

FILL BUFFER

UNTIL FAULT

RAM BYTES

EEPROM BYTES

•

PMBus READ

OF FAULT

LOG

LATEST 6

RECORDS

LATEST 4

RECORDS

LTC3889 Datasheet(PDF) 34 Page - Analog Devices

LTC3889 Datasheet(HTML) 34 Page - Analog Devices

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 ...More

Datasheet Download

Link URL