MIC2342R-2YTQ Micrel Inc, MIC2342R-2YTQ Datasheet - Page 20

• Manufacturer Part Number: MIC2342R-2YTQ
• Description: Dual -Slot PCI Express Hot-Plug Controller
• Manufacturer: Micrel Inc
• Type: Hot-Swap Controllerr

Specifications of MIC2342R-2YTQ

• Applications: General Purpose, PCI Express
• Internal Switch(s): No
• Current Limit: Adjustable
• Voltage - Supply: 3.3V, 12V
• Operating Temperature: 0°C ~ 70°C
• Mounting Type: Surface Mount
• Package / Case: 48-TQFP
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Other names: 576-2996

3VOUT[A/B], and when the internal 3VOUT[A/B] “Power
Good” flag is asserted is a simple matter of substituting
R
C
Even though individual internal “Power Good” flags may
be asserted, the conditions under which the MIC2342’s
external /PWRGD[A/B] and /DLY_PWRGD[A/B] digital
outputs are asserted is described in the section labeled
“/PWRGD[A/B] and /DLY_PWRGD[A/B] Digital Outputs.”
Power-Down Cycle
When a slot is turned off, resistors internal to the
MIC2342/MIC2342R are connected to each of the
outputs to provide a discharge path for capacitors
connected to the part’s outputs. The nominal output
discharge resistance values for each rail are found in the
“Electrical Characteristics” table.
Use of an External Gate Capacitor to Control Inrush
Current Profile
In PCI Express applications where the 12VOUT[A/B] and
the 3VOUT[A/B] maximum load capacitance is 1000 µF
(2000uF on the 12V rail for x16 modules), the PCI
Micrel, Inc.
June 2008
3VSENSE[A/B]
LOAD(12VOUT[A/B])
for
, and V
R
12VSENSE[A/B]
UVTH(3V)
for V
Figure 5. (Optional) External Gate Slew Control Components
,
UVTH(12V)
C
LOAD(3VOUT[A/B])
.
for
20
Express power control specification clearly states that
any inrush current rate-of-change shall not exceed
0.1A/µs. This situation is most likely to happen when the
controller is charging these large load capacitances in
current limit. Under these circumstances, it may be
preferable to modify the gate drive by using GATE
voltage control instead of active current regulation to
charge the load. As shown in Figure 5, an external
capacitor connected from each 3VGATE[A/B] to AGND
can be used. For the 12VGATE[A/B], an optional Miller
capacitor (Gate-Drain) can be used in conjunction with a
Gate-Source capacitor to form a Miller integrator to
control the output slew rate. The optimal capacitor value
is best determined empirically as the magnitude of the
inrush current slew rate is a function of the power
MOSFET’s
capacitance (C
the
R
gate voltage slew rate for large load capacitance may
affect the MIC2342/MIC2342R’s specified system turn-
on and turn-off time performance.
12VSENSE[A/B
current-limit
). Using an external capacitor to control the
input
LOAD(3VOUT[A/B])
sense
capacitance
resistor
and C
LOAD(12VOUT[A/B])
(C
(R
MIC2342/2342R
ISS
M9999-062008-B
3VSENSE[A/B]
),
the
), and
load
and