TDK-Lambda PAQ100S48-1R2 Instruction Manual Download Page 22

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PAQ

B-246

・All specifications are subject to change without notice.

PAQ100S48-*/B**Instruction Manual

1. Output Derating

There  is  no  restriction  on  mounting  direction  but  there
should  be  enough  consideration  for  airflow  so  that  heat
does not accumulate around the power module vicinity.De-
termine external components configuration and mounting
direction on PCB such that air could flow through power
module  at  forced  air  cooling  or  convection  cooling.  By
maintaining baseplate temperature below 100℃, operation
is possible. But according to the models, output derating
is needed as shown in figure 1-1. Measure baseplate tem-
perature at center of baseplate as indicated in fig.1-2. For
better improvement of power module reliability, more derat-
ing of baseplate temperature when using is recommended.

100

−40

−20

100

1.2V,1.8V model

2.5V,3.3V,5V model

Baseplate Temperature (℃)

Load (%)

Fig.1-1 PAQ100S48/B Output Derating

Temperature

Measuring Point of

Baseplate

Fig.1-2 Temperature Measuring Point of Baseplate

Forced cooling to power module improve radiation capa-
bility more than convection cooling. Figure 1-3 indicates
thermal resistance value between baseplate and air at
standard vertical mounting. For details on standard vertical
mounting, refer to “PAQ-S48 Series Instruction Manual”
Figure 1-4 to 1-8 indicates power dissipation (Pd) of each
models at following condition.

Output Voltage:

Nominal value

Ambient Temperature: 60℃

An example of thermal design using these condition is
shown as follows.

1 Example of Thermal design

Calculate minimum necessary air velocity at following con-
dition.

Use Model:

PAQ100S48-5/B

Input Voltage:

48V

Maximum Output Current:

15A

Maximum Ambient Temperature: 65℃
Mounting Method:

Standard Vertical Mounting

Power dissipation is as shown in Fig.1-8

　　　　　Pd=9.0 (W)

Maximum baseplate temperature (Tbp) at output current
15A is as shown in Fig. 1-1

　　　　　Tbp=95 (℃ )

Therefore

　　　　Tbp=Ta+θbp−a × Pd
　　　　　 Ta：　 Ambient temperature (℃ )
　　　　　 θbp−a：Thermal Resistance (℃ /W)
　　　　　　 (Baseplate - Air)

Equation is as follows.

　　　　　θbp−a=

Tbp−Ta

=3.33

（℃ /W）

Air Velocity is as shown in Fig.1-3.

　　　　　Air Velocity=0.8 (m/s)　

This is minimum necessary air velocity at above condition.
Measure actual baseplate temperature and verify it is
same as the design. If there are discrepancy, re-check
each condition and re-design.

Note
1） Data shown in Fig.1-3 to 1-8 is the typical value and

it changes depending on measurement condition.
Recommend to design with sufficient margin against
calculation value.

2） When the condition of input voltage and output volt-

age are different and it is impossible to determine
power dissipation (Pd) from Fig.1-4 to 1-8, calculate
power dissipation as follows.

　　　　　Pd=Pin−Pout= 100−η ×Pout

　　　　　Pin:

Input Power (W)

　　　　　Pout: Output Power (W)
　　　　　η:

Efficiency (%)

Note

● This instruction manual describes only changed items from

the standard model’