LTC2928CUHF View Datasheet(PDF) - Linear Technology

Part Name

Description

MFG CO.

LTC2928CUHF

Multichannel Power Supply Sequencer and Supervisor

Linear Technology 

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LTC2928

Applications Information

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. With any RT pin at VCC, the respective voltage

monitor inputs and comparator outputs become active with

thresholds parked at the configured sequence-up thresh-

old. Outside of sequencing, RST (with 100% thresholds

selected) and OV 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, command and reset faults do not occur. External

faults however, may be detected (overvoltage, for example).

Any previously logged faults remain in memory and their

reporting will return upon exiting the forcing mode.

22

VCC

SUPPLY

BANK

LTC2928

2.5V

1.5V

1.8V

3.3V

52.3k

23.7k

17.8k

36.5k

EN1

V1

EN2

V2

EN3

V3

EN4

V4

RT1

HVCC

RT2

MS1

10k

10k

RT3

MS2

10k

10k

RT4

VSEL

CMP1

CMP2

GND

RTMR

0.047µF

CMP3

PTMR

CMP4

STMR

0.1µF

VCC

REF

SQT2

OVA

SQT1

RST

CAS

OV

RDIS

FLT

SYSTEM

LOGIC

ON

DONE

3.32k 10k 10k

2928 TA05

Figure 11. Quad Supervisor (No Sequencing)

For more information www.linear.com/LTC2928

2928fa

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