ADM1087 View Datasheet(PDF) - Analog Devices
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ADM1087 Datasheet PDF : 16 Pages
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ADM1085/ADM1086/ADM1087/ADM1088
QUAD-SUPPLY POWER GOOD INDICATOR
The enable output of the simple sequencers is equivalent to an
AND function of VIN and ENIN. ENOUT is high only when the
voltage at VIN is above the threshold and the enable input
(ENIN) is high as well. Although ENIN is a digital input, it can
tolerate voltages as high as 22 V and can detect if a supply is
present. Therefore, a simple sequencer can monitor two supplies
and assert what can be interpreted as a Power Good signal
when both supplies are present. The outputs of two ADM1085s
can be wire-ANDed together to make a quad-supply Power
Good indicator.
3.3V
3.3V
9V
VIN
ENOUT
POWER_GOOD
ADM1085
5V
ENIN
3.3V
2.5V
VIN
ENOUT
ADM1085
1.8V
ENIN
Figure 30. Quad-Supply Power Good Indicator
SEQUENCING WITH FET SWITCHES
The open-drain outputs of the ADM1085 and ADM1087 can
drive external FET transistors, which can switch on power-
supply rails. All that is needed is a pull-up resistor to a voltage
source that is high enough to turn on the FET.
12V
3.3V
VIN
ENOUT
ADM1085
ENIN CEXT
2.5V
Figure 31. Sequencing with a FET Switch
Rev. 0 | Page 14 of 16
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