XRP9710 Datasheet, PDF (34/36 Pages) Exar Corporation – Dual 6A Programmable Power Module

XRP9710 and XRP9711
Dual 6A Programmable Power Module
APPLICATION INFORMATION
THERMAL DESIGN
Proper thermal design is critical in controlling
device temperatures and in achieving robust
designs. There are a number of factors that
affect the thermal performance. One key
factor is the temperature rise of the devices
in the package, which is a function of the
thermal resistances of the devices inside the
package and the power being dissipated
(P_DISS).
The thermal resistance of the XRP9710/1 is
shown in the “Operating Ratings” section of
this datasheet. The JEDEC θJA thermal
resistance provided is based on tests that
comply with the JESD51-2A “Integrated
Circuit Thermal Test Method Environmental
Conditions – Natural Convection” standard.
JESD51-xx are a group of standards whose
intent is to provide comparative data based
on a standard test condition which includes a
defined board construction. Since the actual
board design in the final application will be
different from the board defined in the
standard, the thermal resistances in the final
design may be different from those shown.
The package thermal derating curve is shown
in Figure 18. The total package power
dissipation (P_PKG) is dependent on the final
application design for channels three and
four, and is the sum of the losses for the two
channels. The power losses for a channel will
depend mainly on the input voltage, output
voltage, and output current. Figure 19 and
Figure 20 show the power losses for input
voltages of 5V and 12V respectively.
First, determine the package power derating
for a maximum ambient temperature (T_AMB)
using Figure 18. Then, based on the design
input voltage, use Figures 19 or 20
accordingly.
For example:
Consider a two channel design that has a
T_AMB= 50°C, V_IN = 12V, V_OUT3 = 1V, V_OUT4 =
3.3V. Figure 18 shows P_PKG max is 4.1 Watts
at 50°C. The result is that the sum of the
power dissipation for both channels must be
less than the 4.1W.
Figure 20 shows the power dissipation for V_IN
= 12V designs. If the 1V output current is 6A,
then its P_DISS is 2.1W. This leaves 2W for the
3.3V channel. The graph shows that at 2W
the maximum 3.3V output current would be
4.7A.
EMI EMISSIONS
The XRP9711 has been tested on the
evaluation board and passes CISPR22 Level B
radiated emissions.
LAYOUT GUIDELINES
Refer to application note ANP-32 “Practical
Layout Guidelines for Power^XR Designs”.
These apply primarily to the two external
power stages available on the XRP9711.
Also refer to the XRP9710 or XRP9711
Evaluation Board Manual for specifics in
grounding and heat sinking.
BOARD ASSEMBLY
Detailed boards assembly information
specifically to address the unique package
requirement is available in ANP-45, LGA
Module Assembly Application Note.
© 2014 Exar Corporation
34/36
Rev. 1.0.1