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
ENOUT
Desktop/notebook computers, servers
Low power portable equipment
Routers
Base stations
Line cards
Graphics cards
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. 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.
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
Output Stage
Part No.
ADM1085
ADM1086
ADM1087
ADM1088
Enable Input
ENIN
ENIN
ENIN
ENIN
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.
04591-PrG-001
APPLICATIONS
ADM1085/ADM1086/ADM1087/ADM1088
TABLE OF CONTENTS
Specifications..................................................................................... 3
Absolute Maximum Ratings............................................................ 4
ESD Caution.................................................................................. 4
Pin Configuration and Function Descriptions............................. 5
Typical Performance Characteristics ............................................. 6
Circuit Information .......................................................................... 9
Timing Characteristics and Truth Tables.................................. 9
Capacitor-Adjustable Delay Circuit........................................... 9
Open-Drain and Push-Pull Outputs ....................................... 10
Application Information................................................................ 11
Sequencing Circuits ................................................................... 11
Dual LOFO Sequencing ............................................................ 13
Simultaneous Enabling.............................................................. 13
Power Good Signal Delays........................................................ 13
Quad-Supply Power Good Indicator....................................... 14
Sequencing with FET Switches................................................. 14
Outline Dimensions ....................................................................... 15
Ordering Guide .......................................................................... 15
REVISION HISTORY
7/04—Revision 0: Initial Version
Rev. 0 | Page 2 of 16
ADM1085/ADM1086/ADM1087/ADM1088
SPECIFICATIONS
V
CC
= full operating range, T
A
= −40°C to +125°C, unless otherwise noted.
Table 2.
Parameter
SUPPLY
V
CC
Operating Voltage Range
V
IN
Operating Voltage Range
Supply Current
V
IN
Rising Threshold, V
TH_RISING
V
IN
Falling Threshold, V
TH_FALLING
V
IN
Hysteresis
V
IN
to ENOUT/ENOUT Delay
V
IN
Rising
V
IN
Falling
V
IN
Leakage Current
CEXT Charge Current
Threshold Temperature Coefficient
ENIN/ENIN TO ENOUT/ENOUT Propagation
Delay
ENIN/ENIN Voltage Low
ENIN/ENIN Voltage High
ENIN/ENIN Leakage Current
ENOUT/ENOUT Voltage Low
Min
2.25
0
0.56
0.545
10
0.6
0.585
15
35
2
20
170
250
30
0.5
Typ
Max
3.6
22
15
0.64
0.625
Unit
V
V
µA
V
V
mV
µs
ms
µs
µA
nA
ppm/°C
µs
V
V
µA
V
Test Conditions/Comments
V
CC
= 3.3 V
V
CC
= 3.3 V
CEXT floating, C = 20 pF
CEXT = 470 pF
V
IN
= V
TH_FALLING
to (V
TH_FALLING
–
100 mV)
V
IN
= 22 V
125
375
V
IN
> V
TH_RISING
0.3 V
CC
− 0.2
0.3 V
CC
+ 0.2
170
0.4
ENOUT/ENOUT Voltage High
(ADM1086/ADM1088)
ENOUT/ENOUT Open-Drain Output Leakage
Current (ADM1085/ADM1087)
0.8 V
CC
V
0.4
µA
ENIN/ENIN = 22 V
V
IN
< V
TH_FALLING
(ENOUT),
V
IN
> V
TH_RISING
(ENOUT),
I
SINK
= 1.2 mA
V
IN
> V
TH_RISING
(ENOUT),
V
IN
< V
TH_FALLING
(ENOUT),
I
SOURCE
= 500 µA
ENOUT/ENOUT = 22 V
Rev. 0 | Page 3 of 16
ADM1085/ADM1086/ADM1087/ADM1088
ABSOLUTE MAXIMUM RATINGS
T
A
= 25°C, unless otherwise noted.
Table 3.
Parameter
V
CC
V
IN
CEXT
ENIN, ENIN
ENOUT, ENOUT (ADM1085, ADM1087)
ENOUT, ENOUT (ADM1086, ADM1088)
Operating Temperature Range
Storage Temperature Range
θ
JA
Thermal Impedance, SC70
Lead Temperature
Soldering (10 s)
Vapor Phase (60 s)
Infrared (15 s)
Rating
−0.3
V to +6 V
−0.3
V to +25 V
−0.3
V to +6 V
−0.3
V to +25 V
−0.3
V to +25 V
−0.3
V to +6 V
−40°C
to +125°C
−65°C
to +150°C
146°C/W
300°C
215°C
220°C
Stresses above those listed under Absolute Maximum Ratings
may cause permanent damage to the device. This is a stress
rating only and functional operation of the device at these or
any other conditions above those indicated in the operational
section of this specification is not implied. Exposure to absolute
maximum rating conditions for extended periods may affect
device reliability.
ESD CAUTION
ESD (electrostatic discharge) sensitive device. Electrostatic charges as high as 4000 V readily accumulate on
the human body and test equipment and can discharge without detection. Although this product features
proprietary ESD protection circuitry, permanent damage may occur on devices subjected to high energy
electrostatic discharges. Therefore, proper ESD precautions are recommended to avoid performance
degradation or loss of functionality.
Rev. 0 | Page 4 of 16
ADM1085/ADM1086/ADM1087/ADM1088
PIN CONFIGURATION AND FUNCTION DESCRIPTIONS
ENIN/ENIN
1
GND
2
V
IN 3
04591-PrG-002
ADM1085/
ADM1086/
ADM1087/
ADM1088
6
5
V
CC
CEXT
4
ENOUT/ENOUT
TOP VIEW
(Not to Scale)
Figure 2. Pin Configuration
Table 4. Pin Function Descriptions
Pin No.
1
2
3
Mnemonic
ENIN, ENIN
GND
V
IN
Description
Enable Input. Controls the status of the enable output. Active high for ADM1085/ADM1086. Active low for
ADM1087/ADM1088.
Ground.
Input for the Monitored Voltage Signal. Can be biased via a voltage divider resistor network to customize the
effective input threshold. Can precisely monitor an analog power supply output signal and detect when it has
powered up. The voltage applied at this pin is compared with a 0.6 V on-chip reference. With this reference,
digital signals with various logic-level thresholds can also be detected.
Enable Output. Asserted when the voltage at V
IN
is above V
TH_RISING
and the time delay has elapsed, provided
that the enable input is asserted. Active high for the ADM1085/ADM1086. Active low for the
ADM1087/ADM1088.
External Capacitor Pin. The capacitance on this pin determines the time delay on the enable output. The delay
is seen only when the voltage at V
IN
rises past V
TH_RISING
, and not when it falls below V
TH_FALLING
.
Power Supply.
4
ENOUT, ENOUT
5
6
CEXT
V
CC
Rev. 0 | Page 5 of 16
