ADM1087 Analog Devices, ADM1087 Datasheet - Page 11

• Manufacturer Part Number: ADM1087
• Description: Voltage Sequencer with Active Low, Open-Drain Enable Output
• Manufacturer: Analog Devices

Specifications of ADM1087

• # Supplies Monitored: 1
• Volt Monitoring Accuracy: 7%
• # Output Drivers: 1
• Fet Drive/enable Output: Enable
• Sequencing: Up
• Package: 6 ld SC70

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.
12V
CONTROL
ENABLE
EN
DC/DC
IN
OUT
3.3V
V
ENIN
IN
ADM1085
3.3V
V
CC
ENOUT
CEXT
3.3V
2.5V
1.8V
1.2V
12V
3.3V
EN
t
EN1
DC/DC
Figure 23. Typical ADM1085 Application Circuit
IN
t
EN2
OUT
t
Rev. A | Page 11 of 16
EN3
2.5V
V
ENIN
IN
ADM1085
3.3V
V
CC
ENOUT
CEXT
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-to-dc converters and
ADM1085s are connected in a 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-to-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.
ADM1085/ADM1086/ADM1087/ADM1088
3.3V
EN
DC/DC
IN
EXTERNAL
DISABLE
OUT
1.8V
V
ENIN
IN
ADM1085
3.3V
V
CC
ENOUT
CEXT
3.3V
EN
DC/DC
IN
OUT
1.2V