Simple Sequencers™
Preliminary Technical Data
ADM1085/ADM1086/ADM1087/ADM1088
FUNCTIONAL BLOCK DIAGRAMS
FEATURES
V
CC
Provide time delays between enabling of regulators
Can be cascaded with regulators for multiple supply
sequencing
ADM1085/ADM1086
V
Power supply monitoring from 0.6 V
Output stages
CAPACITOR
ADJUSTABLE
DELAY
IN
ENOUT
0.6V
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 input
Low power consumption (15 µA)
GND
CEXT
ENIN
V
CC
Specified over –40°C to +125°C temperature range
6-lead SC70 package
ADM1087/ADM1088
V
CAPACITOR
ADJUSTABLE
DELAY
IN
ENOUT
0.6V
APPLICATIONS
Desktop/notebook computers
Routers
GND
CEXT
ENIN
GSM basestations
Optical line cards
Figure 1.
GENERAL DESCRIPTION
The ADM1085/ADM1086/ADM1087/ADM1088 are simple
sequencing circuits that provide a time delay between the
enabling of voltage regulators at power-up in multiple supply
systems. When the output voltage of the first regulator 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.
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
ENIN
ADM1086, and an active low input (
and ADM1088.
) for the ADM1087
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.
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.
Table 1. Selection Table
Output Stage
Part No.
Enable Input
ENOUT
ENOUT
Open-Drain
Push-Pull
The ADM1086 and ADM1088 have push-pull output stages,
ADM1085
ADM1086
ADM1087
ADM1088
ENIN
ENIN
ENIN
ENIN
ENOUT
with active high (ENOUT) and active low (
) logic
outputs, respectively. Similarly, the ADM1085 has an active high
(ENOUT) logic output and the ADM1087 has an active low
Open-Drain
Push-Pull
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 of the ADM0185 and ADM1087 ensures compatibility
with enable input logic levels of different regulators and
converters.
Rev. PrG
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