LTC2928

14

2928f

OPERATIO

Table 3. Sequence Time Position Resistors (1%)

Position Number

RT (kΩ)

1

95.3

2

42.2

3

24.3

4

15.0

5

9.53

6

6.04

7

3.40

8

1.50

Table 4. Sequencing Threshold Selection

(% of 0.5V for ADJ, % of REF for –ADJ)

Sequence-Up (%)

Sequence-Down (%)

SQT1

SQT2

100

100

100

67

Open

100

33

Open

Open

100

10

Open

GND

67

100

Open

67

67

GND

67

33

GND

Open

67

10

GND

GND

33

100

GND

* No shutdown debug mode. In this mode, any internal or external fault will halt the system with full fault reporting but all enabled supplies remain enabled.

Table 2. Master/Slave Configuration Pins

Master

Slave

First

Cascade Position

Not First

Cascade Position



RST Pulls FLT



RST Does not

Pull FLT

No Shutdown

Debug Mode*

MS1

MS2

●

●

●

GND

GND

●

●

●

GND

Open

●

●

●

GND

●

●

●

Open

GND

●

●

●

Open

Open

●

●

●

Open

●

●

●

●

GND

●

●

●

●

Open

●

●

●

●

Table 1. Input Polarity Selection

V1

V2

V3

V4

VSEL

+ ADJ (0.5V)

+ ADJ (0.5V)

+ ADJ (0.5V)

+ ADJ (0.5V)

GND

– ADJ (0V)

+ ADJ (0.5V)

+ ADJ (0.5V)

+ ADJ (0.5V)

good timer starts with the first enable output pulling low

and is cleared when the last supply monitor input crosses

itssequence-downthreshold.Asequence-downfaultpulls



FLT and all enable outputs low. Use a single capacitor from

PTMR to ground to select the power good time. To disable

the power good timer, tie PTMR to ground.

All comparator outputs pull low at the start of the

sequence-down phase (ON low). If a sequence-down fault

occurs, use the fault report capability to determine which

supply failed to meet threshold (or other source of fault).

Force all supplies down in an un-sequenced manner by

pulling FLT low (external fault). For more details refer to

the Applications Information and discussion on system

faults later in this document.

After the system has clocked through “time position

1”, the last LTC2928 (defined by a 2.4k to 5.1k pull-up

resistor on DONE) releases the pull down on DONE and



DONE pulls high.