MIC2582_09 Datasheet, PDF (22/25 Pages) Micrel Semiconductor – Single Channel Hot Swap Controllers

Micrel, Inc.
PCB Layout Considerations
Because of the low values of the sense resistors used
with the MIC2582/83 controllers, special attention to the
layout must be used in order for the device’s circuit
breaker function to operate properly. Specifically, the
use of a 4-wire Kelvin connection to accurately measure
the voltage across R_SENSE is highly recommended. Kelvin
sensing is simply a means of making sure that any
voltage drops in the power traces connecting to the
resistors does not get picked up by the traces
themselves. Additionally, these Kelvin connections
should be isolated from all other signal traces to avoid
introducing noise onto these sensitive nodes. Figure 11
illustrates a recommended, single layer layout for the
R_SENSE, Power MOSFET, timer(s), and feedback network
connections. The feedback network resistor values are
selected for a 12V application. Many hot swap
applications will require load currents of several
amperes. Therefore, the power (V_CC and Return) trace
.
MIC2582/MIC2583
widths (W) need to be wide enough to allow the current
to flow while the rise in temperature for a given copper
plate (e.g., 1oz. or 2oz.) is kept to a maximum of
10ºC~25ºC. Also, these traces should be as short as
possible in order to minimize the IR drops between the
input and the load.
Finally, the use of plated-through vias will be needed to
make circuit connections to power and ground planes
when utilizing multi-layer PC boards.
MOSFET and Sense Resistor Vendors
Device types and manufacturer contact information for
power MOSFETs and sense resistors are provided in
Table 4. Some of the recommended MOSFETs include a
metal heat sink on the bottom side of the package. The
recommended trace for the MOSFET Gate of Figure 11
must be redirected when using MOSFETs packaged in
this style. Contact the device manufacturer for package
information.
Figure 11. Recommended PCB Layout for Sense Resistor,
Power MOSFET, and Feedback Network
April 2009
22
M9999-043009-C