UQQ-24/4-Q12PB-C Murata Power Solutions Inc, UQQ-24/4-Q12PB-C Datasheet - Page 16

• Manufacturer Part Number: UQQ-24/4-Q12PB-C
• Description: CONV DC/DC 96W 4A 24V T/H
• Manufacturer: Murata Power Solutions Inc
• Series: UQQr
• Type: Isolatedr

Specifications of UQQ-24/4-Q12PB-C

• Number Of Outputs: 1
• Output: 24V
• Power (watts): 96W
• Mounting Type: Through Hole
• Voltage - Input: 10 ~ 36V
• Package / Case: 8-DIP Module, 1/4 Brick
• 1st Output: 24 VDC @ 4A
• Size / Dimension: 2.22" L x 1.45" W x 0.50" H (56.4mm x 36.8mm x 12.7mm)
• Power (watts) - Rated: 96W
• Operating Temperature: -40°C ~ 85°C
• Efficiency: 89%
• Approvals: CSA, cUL, EN, UL
• Output Power: 96 W
• Input Voltage Range: 9 V to 36 V
• Output Voltage (channel 1): 24 V
• Output Current (channel 1): 4 A
• Isolation Voltage: 2 KV
• Package / Case Size: Quarter Brick
• Output Type: Isolated Single
• Product: Isolated
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• 3rd Output: -
• 2nd Output: -
• 4th Output: -
• Lead Free Status / Rohs Status: Lead free / RoHS Compliant
• Other names: 811-1889-5

UQQ Series Aluminum Heatsink
Please note – The UQQ series shares the same heatsink kits as the UVQ
series. Therefore, when ordering these heat sinks, use the model numbers
below which end with the ‘UVQ’ suffi x. The UQQ series converter baseplate
can be attached either to an enclosure wall or a heatsink to remove heat from
internal power dissipation. The discussion below concerns only the heatsink
alternative. The UQQ’s are available with a low-profi le extruded aluminum
heatsink kit, models HS-QB25-UVQ, HS-QB50-UVQ, and HS-QB100-UVQ.
This kit includes the heatsink, thermal mounting pad, screws and mounting
hardware. See the assembly diagram below. Do not overtighten the screws in
the tapped holes in the converter. This kit adds excellent thermal performance
without sacrifi cing too much component height. See the Mechanical Outline
Drawings for assembled dimensions. If the thermal pad is fi rmly attached, no
thermal compound (“thermal grease”) is required.
When assembling these kits onto the converter, include ALL kit hardware to
assure adequate mechanical capture and proper clearances. Thread relief is
0.090" (2.3mm).
Figure 7. Model UQQ Heatsink Assembly Diagram
www.murata-ps.com
Thermal Performance
The HS-QB25-UVQ heatsink has a thermal resistance of 12 degrees Celsius
per Watt of internal heat dissipation with “natural convection” airfl ow (no
fans or other mechanical airfl ow) at sea level altitude. This thermal resistance
assumes that the heatsink is fi rmly attached using the supplied thermal pad
and that there is no nearby wall or enclosure surface to inhibit the airfl ow. The
thermal pad adds a negligible series resistance of approximately 0.5°C/Watt so
that the total assembled resistance is 12.5°C/Watt.
Be aware that we need to handle only the internal heat dissipation, not the full
power output of the converter. This internal heat dissipation is related to the
effi ciency as follows:
Effi ciency of course varies with input voltage and the total output power. Please
refer to the Performance Curves.
Since many applications do include fans, here is an approximate equation to
calculate the net thermal resistance:
Where,
R4 [at airfl ow] is the net thermal resistance (in °C/W) with the amount of
airfl ow available and,
R4 [natural convection] is the still air total path thermal resistance or in this
case 12.5°C/Watt and,
“Airfl ow in LFM” is the net air movement fl ow rate immediately at the converter.
This equation simplifi es an otherwise complex aerodynamic model but is a
useful starting point. The “Airfl ow Constant” is dependent on the fan and enclo-
sure geometry. For example, if 200 LFM of airfl ow reduces the effective natural
convection thermal resistance by one half, the airfl ow constant would be
0.005. There is no practical way to publish a “one size fi ts all” airfl ow constant
because of variations in airfl ow direction, heatsink orientation, adjacent walls,
enclosure geometry, etc. Each application must be determined empirically and
the equation is primarily a way to help understand the cooling arithmetic.
This equation basically says that small amounts of forced airfl ow are quite
effective removing the heat. But very high airfl ows give diminishing returns.
Conversely, no forced airfl ow causes considerable heat buildup. At zero airfl ow,
cooling occurs only because of natural convection over the heatsink. Natural
convection is often well below 50 LFM, not much of a breeze.
While these equations are useful as a conceptual aid, most users fi nd it very
diffi cult to measure actual airfl ow rates at the converter. Even if you know
the velocity specifi cations of the fan, this does not usually relate directly to
the enclosure geometry. Be sure to use a considerable safety margin doing
thermal analysis. If in doubt, measure the actual heat sink temperature with
a calibrated thermocouple, RTD or thermistor. Safe operation should keep the
heat sink below 100°C.
Power Dissipation [Pd] = Power In – Power Out [1]
Power Out / Power In = Effi ciency [in %] / 100 [2]
Power Dissipation [Pd] = Power In x (1 –Effi ciency%/100) [3]
Power Dissipation [Pd] = Power Out x (1 / (Effi ciency%/100) - 1) [4]
R4 [at airfl ow] = R4 [natural convection] / (1 + (Airfl ow in LFM) x
[Airfl ow Constant]) [5]
Wide Input Range Single Output DC/DC Converters
25 Mar 2011 MDC_UQQ.B01 Page 16 of 18
email: [e-mail]
UQQ Series