Datasheet

ADM1085/ADM1086/ADM1087/ADM1088
Rev. A | Page 14 of 16
QUAD-SUPPLY POWER GOOD INDICATOR
The enable output of the Simple Sequencers is equivalent to an
AND function of V
IN
and ENIN. ENOUT is high only when
the voltage at V
IN
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-AND’ed together to make a quad-
supply power good indicator.
ADM1085
ENOUT
3.3V
3.3
V
ENIN
V
IN
9V
5V
ADM1085
ENOUT
3.3V
ENIN
V
IN
2.5V
1.8V
POWER_GOOD
04591-035
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 that 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.
ADM1085
ENOUT
3.3V
12
V
ENIN CEXT
V
IN
2.5V
04591-036
Figure 31. Sequencing with a FET Switch