LTC2928IG datasheet(21/32 Pages) LINER

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LTC2928

2928f

Forcing Supplies Off or Disabling Unused Channels

The most convenient way to mask an unused channel is

to tie its respective RT input to ground. After sequenc-

ing begins, any enable output (EN) may be pulled low

permanently by driving the respective RT input to ground

(asynchronous OFF command). An asynchronously OFF

channel cannot be re-enabled until a new sequence-up

procedure is started. Any channel that is asynchronously

OFF is removed from participation in the sequencing and

supply monitoring processes, allowing the LTC2928 to

operate normally on the remaining operating channels.

When experiencing a fault in the “No Shutdown Debug

Mode”, the asynchronous OFF feature may be used to

conveniently pull down the enable outputs. Alternatively,

VCC may be turned off and on again. Clearing a fault con-

dition requires the ON input to be low while the supplies

are below their sequence-down thresholds.

Forcing Supplies On Prior to Sequencing

Prior to sequencing, any or all enable pins may be forced

high by pulling the respective RT pin to VCC. In this man-

ner, supplies may be tested individually or together in any

combination.WithanyRTpinatVCC,therespectivevoltage

monitorinputsandcomparatoroutputsbecomeactivewith

thresholds parked at the conﬁgured sequence-up thresh-

old. Outside of sequencing, RST (with 100% thresholds

selected) and OV are always functional, regardless of

RT pin state. If all four RT pins are at VCC, the LTC2928

can be used as a stand-alone quad voltage monitor with

under- and overvoltage indication as shown in Figure 11

(100% thresholds). With ON low in the RT forcing mode,

sequence,commandandresetfaultsdonotoccur.External

faultshowever,maybedetected(overvoltage,forexample).

Any previously logged faults remain in memory and their

reporting will return upon exiting the forcing mode.

EN1

LTC2928

EN2

EN3

EN4

RT1

HVCC

3.32k

SUPPLY

BANK

0.047 F

VCC

0.1 F

RT4

CMP1

CMP2

CMP3

CMP4

SQT2

SQT1

MS1

MS2

RT2

RT3

VSEL

GND

RTMR

PTMR

STMR

VCC

REF

OVA

DONE

FLT

RDIS

CAS

RST

10k

52.3k

3.3V

1.8V

1.5V

2.5V

23.7k

17.8k

36.5k

10k

2928 TA05

SYSTEM

LOGIC

Figure 11. Quad Supervisor (No Sequencing)

APPLICATIO S I FOR ATIO

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