MIC2342 MICREL [Micrel Semiconductor], MIC2342 Datasheet - Page 25

• Manufacturer Part Number: MIC2342
• Manufacturer: MICREL [Micrel Semiconductor]

Hardware Interface
Once the input power supply voltages are above their
respective UVLO thresholds, the MIC2342/MIC2342R’s
hardware interface can be enabled for power control by
asserting
AUXEN[A/B], and ON[A/B]) appropriately for each slot.
The MIC2342/MIC2342R’s ON[A/B] and AUXEN[A/B]
signals are asserted active-HIGH, level-sensitive digital
inputs with internal pull-up 45kΩ resistors to VSTBY[A]
to save pc board area and external component costs. As
such, external hot-plug controllers connecting to these
pins should configure their respective output drivers to
OPEN-DRAIN and configure their firmware to de-assert
these signals to turn OFF either the MAIN[A/B] outputs
or the VAUX[A/B] outputs. As these input control signals
Micrel, Inc.
June 2008
where “1” = Logic HIGH
the
X
X
X
X
1
1
“0” = Logic LOW
“X” = Don’t care
control
X
X
X
X
X
1
X
X
X
0
0
0
input
1
1
1
X
X
X
pins
UV
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X
X
X
X
(/CRSW[A/B],
Table 1. SYSPWRGD Truth Table
UV
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X
X
UV
X
X
X
X
X
25
X
X
X
X
1
1
are already asserted after POR, the corresponding
/CRSW[A/B] control signal should be used to enable the
slot’s gate drive circuits to initiate a power-up sequence.
For example, in order for the MIC2342/MIC2342R to
switch on the VAUX supply for either slot, the
AUXEN[A/B] control can be enabled during or after the
power-on-reset operation (typically, t
timing response diagram of Figure 9 illustrates the
hardware interface operation where an overcurrent fault
is detected by the MIC2342/MIC2342R controller after
initiating a power-up sequence. The MAIN (+12V &
+3.3V) and VAUX[A/B] supply rails, /FAULT, /PWRGD
and /INT output responses for both AUX and MAIN are
shown in the figure.
X
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X
X
X
1
X
X
X
0
0
0
X
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X
1
1
1
UV
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X
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X
X
UV
X
X
X
X
X
UV
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X
X
X
POR
MIC2342/2342R
M9999-062008-B
= 160µs. The
0
0
0
0
0
0