BD9E151NUX Datasheet, PDF (16/22 Pages) Rohm – 1ch Step-Down Switching Regulator

BD9E151NUX
Datasheet
Power Dissipation
It is shown below reducing characteristics of power dissipation to mount 70mm×70mm×1.6mm^t PCB
Junction temperature must be designed not to exceed 150℃.
2.5
②
2
VSON008X2030 Package
On 70mm×70mm×1.6mm^t glass epoxy PCB
①1-layer board (Backside copper foil area 15mm×15mm)
②4-layer board (Backside copper foil area 70mm×70mm)
1.5
1
0.5
①
0.412
0
0
25
50
75
100
125
Ambient Temperature [℃]
Figure 29. Power Dissipation ( 70mm×70mm×1.6mm^t 1layer PCB)
Power Dissipation Estimate
The following formulas show how to estimate the device power dissipation under continuous mode operations. They should not
be used if the device is working in the discontinuous conduction mode.
The device power dissipation includes:
1) Conduction loss： Pcon = IOUT² × RonH × VOUT/VIN
2) Switching loss: Psw = 0.25 × 10^–9 × VIN² × IOUT × fsw
3) Gate charge loss： Pgc = 22.8 × 10^–9 × fsw
4) Quiescent current loss： Pq = 0.7 × 10^–3 × VIN
Where:
IOUT is the output current (A）, RonH is the on-resistance of the high-side MOSFET（Ω）, VOUT is the output voltage (V).
VIN is the input voltage (V), fsw is the switching frequency (Hz).
Therefore
Power dissipation of IC is the sum of above dissipation.
Pd = Pcon + Psw + Pgc + Pq
For given Tj, Tj =Ta + θja × Pd
Where:
Pd is the total device power dissipation (W), Ta is the ambient temperature (℃)
Tj is the junction temperature (℃), θja is the thermal resistance of the package (℃)
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TSZ22111・15・001
16/19
TSZ02210-0Q3Q0AZ00160-1-2
2013.07.17 Rev.001