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Thermal Consideration
General
The product is designed to operate in different thermal
environments and sufficient cooling must be provided to
ensure reliable operation.
Cooling is achieved mainly by conduction, from the pins to the
host board, and convection, which is dependent on the airflow
across the product. Increased airflow enhances the cooling of
the product.
The Output Current Derating graph found in the Output section
for each model provides the available output current vs.
ambient air temperature and air velocity at specified V
I
.
The product is tested on a 254 x 254 mm, 35 µm (1 oz), test
board mounted vertically in a wind tunnel with a cross-section
of 608 x 203 mm. The test board has 8 layers.
Proper cooling of the product can be verified by measuring the
temperature at positions P1 and P2. The temperature at these
positions should not exceed the max values provided in the
table below.
Note that the max value is the absolute maximum rating
(non destruction) and that the electrical Output data is
guaranteed up to T
P1
+95 °C.
See Design Note 019 for further information.
Definition of product operating temperature
The product operating temperatures are used to monitor the
temperature of the product, and proper thermal conditions can
be verified by measuring the temperature at positions P1 and
P2. The temperature at these positions (T
P1
, T
P2
) should not
exceed the maximum temperatures in the table below. The
number of measurement points may vary with different thermal
design and topology. Temperatures above maximum T
P1
,
measured at the reference point P1 are not allowed and may
cause permanent damage. It should also be noted that
depending on setting of the over temperature protection (OTP)
and operating conditions, the product may shut down before
the maximum allowed temperature at T
P1
is reached.
Position
Description
Max Temp.
P1
Reference point, L1,
inductor
125 °C *
P2
N1, control circuit
125 °C *
* A guard band of 5 °C is applied to the maximum recorded
component temperatures when calculating output current
derating curves.
Temperature positions and air flow direction.
SIP version
Temperature positions and air flow direction.
Definition of reference temperature T
P1
The reference temperature is used to monitor the temperature
limits of the product. Temperature above maximum T
P1
,
measured at the reference point P1 is not allowed and may
cause degradation or permanent damage to the product. T
P1
is
also used to define the temperature range for normal operating
conditions. T
P1
is defined by the design and used to guarantee
safety margins, proper operation and high reliability of the
product.
Top view
Bottom view
AIR FLOW
P1
P2
P1
P2
AIR FLOW
BMR4
6
series
PoL Regulators
Input 4.5-14 V, Output up to 50 A / 165 W
1/28701-BMR 464 Rev.B
July 2019
© Flex
Technical Specification
BMR4
6
series
PoL Regulators
Input
4.5-14
V, Output up to
50
A
/
165
W
1/28701-BMR 464 Rev.B
July 2019
©
Flex
Technical Specification
60