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BD9876AEFJ Datasheet, PDF (16/24 Pages) Rohm – Flexible Step-down Switching Regulators with Built-in Power MOSFET | |||
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BD9876AEFJ
Datasheet
âPower Dissipation
It is shown below reducing characteristics of power dissipation to mount 70mmÃ70mmÃ1.6mmt PCB
Junction temperature must be designed not to exceed 150â.
4000
â£3760mW
3500
3000
HTSOP-J8 Package -
On 70mmÃ70mmÃ1.6mmt glass epoxy PCB
â 1-layer board ï¼Backside copper foil area 0mmÃ0mmï¼
â¡2-layer board ( Backside copper foil area 15mmÃ15mm)
â¢2-layer board ï¼Backside copper foil area 70mmÃ70mmï¼
â£4-layer board ï¼Backside copper foil area 70mmÃ70mmï¼
2500
2000
â¢2210mW
1500 â¡1100mW
1000 â 820mW
500
0
0
25
50
75
100
125
150
Ambient Temperature - â
Figure 45. Power Dissipation ( 70mmÃ70mmÃ1.6mmt 1layer PCB)
âPower 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 lossï¼ Pcon = IOUT2 Ã RonH Ã VOUT/VCC
2) Switching loss: Psw = 1.25 Ã 10â9 Ã VCC2 Ã IOUT Ã fsw
3) Gate charge lossï¼ Pgc = 22.8 Ã 10â9 Ã fsw
4) Quiescent current lossï¼ Pq = 1.0 Ã 10â3 Ã VCC
Where:
IOUT is the output current (Aï¼, RonH is the on-resistance of the high-side MOSFETï¼â¦ï¼, VOUT is the output voltage (V).
VCC 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 à Pd
Where:
Pd is the total device power dissipation (W), Ta is the ambient temperature (â)
Tj is the junction temperature (â), θja is the thermal resistance of the package (â)
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TSZ22111ã»15ã»001
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TSZ02201-0Q1Q0AJ00170-1-2
28.JAN.2014 Rev.003
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