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ADM1085 View Datasheet(PDF) - Analog Devices

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ADM1085 Datasheet PDF : 16 Pages
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Simple Sequencersin 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 VIN inputs
Low power consumption (15 µA)
Specified over –40°C to +125°C temperature range
6-lead SC70 package
APPLICATIONS
Desktop/notebook computers, servers
Low power portable equipment
Routers
Base stations
Line cards
Graphics cards
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. By choosing 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
Rev. 0
Information furnished by Analog Devices is believed to be accurate and reliable.
However, no responsibility is assumed by Analog Devices for its use, nor for any
infringements of patents or other rights of third parties that may result from its use.
Specifications subject to change without notice. No license is granted by implication
or otherwise under any patent or patent rights of Analog Devices. Trademarks and
registered trademarks are the property of their respective owners.
FUNCTIONAL BLOCK DIAGRAMS
VCC
ADM1085/ADM1086
VIN
0.6V
CAPACITOR
ADJUSTABLE
DELAY
ENOUT
GND
CEXT
ENIN
VCC
ADM1087/ADM1088
VIN
0.6V
CAPACITOR
ADJUSTABLE
DELAY
ENOUT
GND
CEXT
ENIN
Figure 1.
property ensures compatibility with enable input logic levels of
different regulators and converters.
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 (typ) 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
Output Stage
ENOUT
ENOUT
Open-Drain
Push-Pull
Open-Drain
Push-Pull
One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A.
Tel: 781.329.4700
www.analog.com
Fax: 781.326.8703 © 2004 Analog Devices, Inc. All rights reserved.
 

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