MIC2582_14 Datasheet, PDF (23/27 Pages) Micrel Semiconductor – Single-Channel Hot Swap Controllers

Micrel, Inc.
MIC2582/MIC5283
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 10 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
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 10
must be redirected when using MOSFETs packaged in this
style. Contact the device manufacturer for package
information.
Figure 10. Recommended PCB Layout for Sense Resistor,
Power MOSFET, and Feedback Network
May 23, 2014
23
Revision 5.0