MIC2593-2BTQ TR Micrel Inc, MIC2593-2BTQ TR Datasheet - Page 25

• Manufacturer Part Number: MIC2593-2BTQ TR
• Description: IC PCI HOT PLUG CTLR DUAL 48TQFP
• Manufacturer: Micrel Inc
• Type: Hot-Swap Controllerr

Specifications of MIC2593-2BTQ TR

• Applications: PCI, PCI-X
• Internal Switch(s): No
• Voltage - Supply: 3.3V, 5V, ±12V
• Operating Temperature: 0°C ~ 70°C
• Mounting Type: Surface Mount
• Package / Case: 48-TQFP
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant
• Other names: MIC2593-2BTQTR; MIC2593-2BTQTR

–12V Input Clamp Diode
The –12V input to the MIC2593 is the most negative
potential on the part and is therefore connected to the
chip’s substrate (as described in “Power Supply
Decoupling,” above). Although no particular sequencing of
the –12V supply relative to the other MIC2593 supplies is
required for normal operation, this substrate connection
does mean that the –12V input must never exceed the
voltage on the GROUND pin of the IC by more than 0.3
volts. Small amounts of internal leakage current can
cause this to happen when the VSTBY pins are energized
and the 12MVIN pins are not energized. In addition,
power supply output ringing or L(di/dt) effects in the wiring
and on the PCB itself will cause brief transient voltages in
excess of +0.3V to appear at the –12V input. For this
reason, it is required to clamp the –12V input to ground
with a Schottky diode. A diode rated at 1 amp and 20V to
40V as shown in our application schematic diagram is
suggested. The diode’s anode should be physically
placed directly at the –12V input to the MIC2593, and its
cathode should have as short a path as possible back to
the part’s ground. A good SMT part for this application is a
type MBRS140T3 (1A, 40V).
Micrel, Inc.
September 2008
25
Gate Resistor Guidelines
The MIC2593 controls four external power MOSFETs,
that handle the high currents for each of the two 3.3V and
5V outputs. A capacitor is connected in the application
circuit from each GATE pin of the MIC2593 to ground.
However, an external capacitor, C
operation of the MIC2593. Each C
up rate of its respective power output (e.g., 5VOUTB).
These capacitors, which are typically in the 10nF range,
cause the GATE outputs of the MIC2593 to have very low
AC impedances to ground at any significant frequency. It
is therefore necessary to place a modest value of gate
damping resistance (R
gate of its associated MOSFET as shown in Figure 15.
These resistances prevent high-frequency MOSFET
source-follower oscillations from occurring. The exact
value of the resistors used is not critical; 10Ω to 33Ω is
usually a sufficient choice. Each R
physically located directly adjacent to the MOSFET gate
lead to which it connects.
MIC2593
Figure 15. C
GATE
GATE
GATE
C
10nF
and R
) between each C
GATE
R
GATE
GATE
GATE
GATE
Connection
, is not required for
controls the ramp-
GATE
External
MOSFET
M9999-092208
GATE
should be
MIC2593
and the