MIC2342 Datasheet, PDF (24/32 Pages) Micrel Semiconductor – Dual-Slot PCI Express® Hot-Plug Controller

Micrel, Inc.
/PWRGD[A/B] and /DLY_PWRGD Digital Outputs
The MIC2342 has two /PWRGD outputs and two
/DLY_PWRGD outputs, one for each slot. These are
open-drain, active-low outputs that are activated after
power-on-reset and are normally connected by an
external 10kΩ resistor to V_STBY or a local logic supply.
Each /PWRGD[A/B] output is asserted when a slot has
been enabled and has successfully begun delivering
power to its respective +12V, +3.3V, and VAUX outputs.
The /DLY_PWRGD[A/B] outputs are asserted 164ms
after its corresponding /PWRGD[A/B] output. An
equivalent logic diagram for /PWRGD[A/B] is shown in
Figure 8 with their corresponding state diagrams.
MIC2342/2342R
SYSPWRGD Digital Output
SYSPWRGD is an open-drain, asserted active-HIGH
digital output provided by the MIC2342 for additional slot
status information to the service or system processor.
This output is normally connected by an external 10kΩ
resistor to V_STBY or a local logic supply. There is one
SYSPWRGD output for each MIC2342 and this signal
becomes activated after power-on-reset. This signal is
asserted unless at least one PCIe slot is occupied, either
ON[A/B] and/or AUXEN[A/B] of the slot in question is
asserted, either /FORCE_ON[A/B] inputs are not
asserted, and the output voltages at the load are lower
than respective Power-is-Good output threshold
voltages. Functionality of the SYSPWRGD output signal
has been designed to accommodate single- and dual-
slot applications as well as applications where the
MAIN[A/B] outputs are used, but the VAUX[A/B] outputs
are not. In multiple MIC2342 applications where one or
more PCIe slots are unused and one or multiple ON[A/B]
and AUXEN[A/B] input signals are not asserted, each
SYSPWRGD digital output will appear asserted
facilitating an “OR-tying” of all SYSPWRGD output
signals, thereby ensuring correct logic functionality
across the entire system. See Table 1 for the
SYSPWRGD truth table.
Figure 8. State Diagrams for /PWRGD[A/B] and
/DLY_PWRGD[A/B]
June 2008
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M9999-062008-B