ADM1085AKS-REEL7 View Datasheet(PDF) - Analog Devices
Part Name
Description
Manufacturer
ADM1085AKS-REEL7 Datasheet PDF : 16 Pages
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ADM1085/ADM1086/ADM1087/ADM1088
APPLICATION INFORMATION
SEQUENCING CIRCUITS
The ADM1085/ADM1086/ADM1087/ADM1088 are
compatible with voltage regulators and dc-to-dc converters that
have active-high or active-low enable or shutdown inputs, with
a choice of open-drain or push-pull output stages. Figure 23 to
Figure 25 illustrate how each of the ADM1085/ADM1086/
ADM1087/ADM1088 simple sequencers can be used in
multiple-supply systems, depending on which regulators are
used and which output stage is preferred.
In Figure 23, three ADM1085s are used to sequence four
supplies on power-up. Separate capacitors on the CEXT pins
determine the time delays between enabling of the 3.3 V, 2.5 V,
1.8 V, and 1.2 V supplies. Because the dc/dc converters and
ADM1085s are connected in cascade, and the output of any
converter is dependent on that of the previous one, an external
controller can disable all four supplies simultaneously by
disabling the first dc/dc converter in the chain.
For power-down sequencing, an external controller dictates
when the supplies are switched off by accessing the ENIN
inputs individually.
12V
3.3V
3.3V
3.3V
IN
EN DC/DC OUT
3.3V
3.3V
IN
EN DC/DC OUT
2.5V
3.3V
IN
EN DC/DC OUT
1.8V
3.3V
IN
EN DC/DC OUT 1.2V
ENABLE
CONTROL
VCC
VIN
ENOUT
ADM1085
ENIN CEXT
VCC
VIN
ENOUT
ADM1085
ENIN CEXT
VCC
VIN
ENOUT
ADM1085
ENIN CEXT
12V
3.3V
2.5V
1.8V
1.2V
tEN1
tEN2
tEN3
EXTERNAL
DISABLE
Figure 23. Typical ADM1085 Application Circuit
Rev. 0 | Page 11 of 16
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