FEATURE DESCRIPTIONS (CON.
)
Ratio-Metric
Ratio–metric (Figure 37) is implemented by placing the
voltage divider on the TRACK pin that comprises R1 and
R2, to create a proportional voltage with Vo
PS1
to the
Track pin of PS2.
For Ratio-Metric applications that need the outputs of
PS1 and PS2 reach the regulation set point at the same
time
The following equation can be used to calculate the value
of R1 and R2.
The suggested value of R2 is 10kΩ.
V
o
,
PS
2
V
o
,
PS
1
=
R
2
R
1
+
R
2
PS1
Vin
Vo
PS1
R1
TRACK
R2
On/Off
On/Off
Vin
Vo
PS2
THERMAL CONSIDERATIONS
Thermal management is an important part of the system
design. To ensure proper, reliable operation, sufficient
cooling of the power module is needed over the entire
temperature range of the module. Convection cooling is
usually the dominant mode of heat transfer.
Hence, the choice of equipment to characterize the
thermal performance of the power module is a wind
tunnel.
Thermal Testing Setup
Delta’s DC/DC power modules are characterized in
heated vertical wind tunnels that simulate the thermal
environments encountered in most electronics
equipment. This type of equipment commonly uses
vertically mounted circuit cards in cabinet racks in which
the power modules are mounted.
The following figure shows the wind tunnel
characterization setup. The power module is mounted
on a test PWB and is vertically positioned within the
wind tunnel. The height of this fan duct is constantly kept
at 25.4mm (1’’).
PS2
Thermal Derating
Heat can be removed by increasing airflow over the
module. To enhance system reliability, the power
module should always be operated below the maximum
operating temperature. If the temperature exceeds the
maximum module temperature, reliability of the unit may
be affected.
FANCING PWB
PWB
MODULE
The high for positive logic
The low for negative logic
AIR F LOW
Note: Wind Tunnel Test Setup Figure Dimensions are in millimeters and (Inches)
Figure 38:
Wind tunnel test setup
DS_DNL10SMD_07182012
50.8(2.00")
AIR VELOCITY
AND AMBIENT
TEMPERATURE
SURED BELOW
THE MODULE
12
DELTA [ DELTA ELECTRONICS, INC. ]
