UQQ-5/20-Q48P-C Murata Power Solutions Inc, UQQ-5/20-Q48P-C Datasheet - Page 10

• Manufacturer Part Number: UQQ-5/20-Q48P-C
• Description: CONVERTER, DC/DC, WI, 100W, 5V
• Manufacturer: Murata Power Solutions Inc
• Series: UQQr

Specifications of UQQ-5/20-Q48P-C

• Output Type: Single
• No. Of Output Channels: 1
• Input Voltage: 18V To 75V
• Power Rating: 100W
• Output Voltage: 5V
• Output Current: 20A
• Supply Voltage: 48V
• Dc / Dc Converter Case Style: Quarter Brick
• Dc / Dc Converter O/p Type: Single
• No. Of Outputs: 1
• Approval Bodies: EN / IEC / UL
• Rohs Compliant: Yes
• Product: Isolated
• Output Power: 100 W
• Input Voltage Range: 18 V to 75 V
• Input Voltage (nominal): 48 V
• Number Of Outputs: 1
• Output Voltage (channel 1): 5 V
• Output Current (channel 1): 20 A
• Isolation Voltage: 2.25 KV
• Package / Case Size: Quarter Brick
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

Calculating Maximum Power Dissipation
To determine the maximum amount of internal power dissipation, find the
ambient temperature inside the enclosure and the airflow (in Linear Feet per
Minute – LFM) at the converter. Determine the expected heat dissipation
using the Efficiency curves and the converter Input Voltage. You should also
compensate for lower atmospheric pressure if your application altitude is
considerably above sea level.
The general proceedure is to compute the expected temperature rise of the
heatsink. If the heatsink exceeds +00°C. either increase the airflow and/or
reduce the power output. Start with this equation:
where “Ta” is the enclosure ambient air temperature and,
where “Ts” is the heatsink temperature and,
where “RQ [at airflow]” is a specific heat transfer thermal resistance (in
degrees Celsius per Watt) for a particular heat sink at a set airflow rate. We
have already estimated RQ [at airflow] in the equations above.
Note particularly that Ta is the air temperature inside the enclosure at the
heatsink, not the outside air temperature. Most enclosures have higher
internal temperatures, especially if the converter is “downwind” from other
heat-producing circuits. Note also that this “Pd” term is only the internal heat
dissipated inside the converter and not the total power output of the converter.
We can rearrange this equation to give an estimated temperature rise of the
heatsink as follows:
These model numbers are correct for the UQQ series.
www.cd4power.com
P O W E R E L E C T R O N I C S D I V I S I O N
Heatsink Kit *
Model Number
HS-QB25-UVQ
HS-QB50-UVQ
HS-QB00-UVQ
* Kit includes heatsink, thermal pad and mounting hardware.
Internal Heat Dissipation [Pd in Watts] = (Ts – Ta)/RQ [at airflow] [6]
Ts = (Pd x RQ [at airflow]) + Ta [7]
Still Air (Natural convection)
thermal resistance
0.6°C/Watt
2°C/Watt
8°C/Watt
Heatsink height
0.25" (6.35mm)
0.50" (2.7mm)
.00" (25.4mm)
(see drawing)
Heat Sink Example
Assume an efficiency of 92% and power output of 00 Watts. Using equation
[4], Pd is about 8.7 Watts at an input voltage of 48 Volts. Using +30°C ambient
temperature inside the enclosure, we wish to limit the heat sink temperature
to +90°C maximum baseplate temperature to stay well away from thermal
shutdown. The +90°C. figure also allows some margin in case the ambient
climbs above +30°C or the input voltage varies, giving us less than 92%
efficiency. The heat sink and airflow combination must have the following
characteristics:
Since the ambient thermal resistance of the heatsink and pad is 2.5°C/W, we
need additional forced cooling to get us down to 6.9°C/W. Using a hypothetical
airflow constant of 0.005, we can rearrange equation [5] as follows:
or,
and, rearranging again,
62 LFM is the minumum airflow to keep the heatsink below +90°C. Increase
the airflow to several hundred LFM to reduce the heatsink temperature further
and improve life and reliability.
(2.54)
(Required Airflow, LFM) x (Airflow Constant) = RQ[Nat.Convection] /
RQ[at airflow] –
(Required Airflow, LFM) x (Airflow Constant) = 2.5/6.9 – = 0.8
8.7 W = (90-30) / RQ[airflow] or,
RQ[airflow] = 60/8.7 = 6.9°C/W
(Required Airflow, LFM) = 0.8/0.005 = 62 LFM
0.10
* UQQ SERIES HEATSINKS ARE AVAILABLE IN 3 HEIGHTS:
0.140 DIA. (3.56) (4 PLACES)
Wide Input Range Single Output DC/DC Converters
MATERIAL: BLACK ANODIZED ALUMINUM
0.25 (6.35), 0.50 (12.70) AND 1.00 (25.4)
Dimensions in inches (mm)
Optional Heatsink
(57.91)
(47.24)
1.860
2.28
D C / D C C O N V E R T E R S
UQQ Series
MDC_UQQ_A02
(26.16)
1.03
*
Page 0 of 4
(36.83)
1.45