LTC2928CUHF View Datasheet(PDF) - Linear Technology
Part Name
Description
MFG CO.
'LTC2928CUHF' PDF : 34 Pages View PDF
LTC2928
Operation
good timer starts with the first enable output pulling low
and is cleared when the last supply monitor input crosses
its sequence-down threshold. A sequence-down fault pulls
FLT 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 FLT 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 resis-
tor on DONE) releases the pull down on DONE and DONE
pulls high.
Table 1. Input Polarity Selection
V1
+ ADJ (0.5V)
V2
+ ADJ (0.5V)
V3
+ ADJ (0.5V)
V4
+ ADJ (0.5V)
VSEL
GND
– ADJ (0V)
+ ADJ (0.5V)
+ ADJ (0.5V)
+ ADJ (0.5V)
VCC
Table 2. Master/Slave Configuration Pins
Master
Slave
First
Not First
RST Pulls FLT
Cascade Position Cascade Position
RST Does not
Pull FLT
No Shutdown
Debug Mode*
MS1
MS2
l
l
l
GND
GND
l
l
l
GND
Open
l
l
l
GND
VCC
l
l
l
Open
GND
l
l
l
Open
Open
l
l
l
l
l
l
l
l
l
Open
VCC
l
VCC
GND
l
VCC
Open
l
l
l
l
VCC
VCC
* 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 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 (%)
100
100
100
67
100
33
100
10
67
100
67
67
67
33
67
10
33
100
SQT1
VCC
Open
Open
Open
VCC
GND
GND
GND
VCC
SQT2
VCC
VCC
Open
GND
Open
VCC
Open
GND
GND
For more information www.linear.com/LTC2928
2928fa
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