Simple Sequencers
®
in 6-Lead SC70
ADM1085/ADM1086/ADM1087/ADM1088
FEATURES
Provide programmable time delays between enable
signals
Can be cascaded with power modules for multiple
supply sequencing
Power supply monitoring from 0.6 V
Output stages
High voltage (up to 22 V) open-drain output
(ADM1085/ADM1087)
Push-pull output (ADM1086/ADM1088)
Capacitor-adjustable time delays
High voltage (up to 22 V) enable and V
IN
inputs
Low power consumption (15 μA)
Specified over –40°C to +125°C temperature range
6-lead SC70 package
FUNCTIONAL BLOCK DIAGRAMS
V
CC
ADM1085/ADM1086
V
IN
0.6V
CAPACITOR
ADJUSTABLE
DELAY
ENOUT
GND
CEXT
ENIN
V
CC
ADM1087/ADM1088
V
IN
0.6V
CAPACITOR
ADJUSTABLE
DELAY
APPLICATIONS
Desktop/notebook computers, servers
Low power portable equipment
Routers
Base stations
Line cards
Graphics cards
ENOUT
GND
CEXT
ENIN
Figure 1.
GENERAL DESCRIPTION
The ADM1085/ADM1086/ADM1087/ADM1088 are simple
sequencing circuits that provide a time delay between the
enabling of voltage regulators and/or dc-dc converters at power-
up in multiple supply systems. When the output voltage of the
first power module reaches a preset threshold, a time delay is
initiated before an enable signal allows subsequent regulators to
power up. Any number of these devices can be cascaded with
regulators to allow sequencing of multiple power supplies.
Threshold levels can be set with a pair of external resistors in a
voltage divider configuration. With appropriate resistor values,
the threshold can be adjusted to monitor voltages as low as 0.6 V.
The ADM1086 and ADM1088 have push-pull output stages,
with active high (ENOUT) and active low (ENOUT) logic
outputs, respectively. The ADM1085 has an active-high
(ENOUT) logic output; the ADM1087 has an active-low
(ENOUT) output. Both the ADM1085 and ADM1087 have
open-drain output stages that can be pulled up to voltage levels
as high as 22 V through an external resistor. This level-shifting
property ensures compatibility with enable input logic levels of
different regulators and converters.
Rev. A
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All four models have a dedicated enable input pin that allows
the output signal to the regulator to be controlled externally.
This is an active high input (ENIN) for the ADM1085 and
ADM1086, and an active low input (ENIN) for the ADM1087
and ADM1088.
The Simple Sequencers are specified over the extended
−40°C to +125°C temperature range. With low current
consumption of 15 μA (typical) and 6-lead SC70 packaging,
the parts are suitable for low-power portable applications.
Table 1. Selection Table
Part No.
ADM1085
ADM1086
ADM1087
ADM1088
Enable Input
ENIN
ENIN
ENIN
ENIN
Open-drain
Push-pull
Output Stage
ENOUT
ENOUT
Open-drain
Push-pull
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