BD90640HFP-CTR Datasheet, PDF (32/44 Pages) Rohm – 1ch Step-Down Switching Regulator

BD906xx-C series
Power Dissipation
For thermal design, be sure to operate the IC within the following conditions.
(Since the temperatures described hereunder are all guaranteed temperatures, take margin into account.)
1. The ambient temperature Ta is to be 125 °C or less.
2. The chip junction temperature Tj is to be 150 °C or less.
The chip junction temperature Tj can be considered in the following two patterns:
① To obtain Tj from the package surface center temperature Tt in actual use
𝑇𝑗 = 𝑇𝑡 + 𝜓_{𝐽𝑇} × 𝑊
② To obtain Tj from the ambient temperature Ta
𝑇𝑗 = 𝑇𝑎 + 𝜃𝑗𝑎 × 𝑊
＜Reference Value＞
HRP7
＜Reference Value＞
θjc
Top : 22 °C / W
Bottom : 2 °C / W
θja
95.3 °C / W 1-layer PCB
17.9 °C / W 4-layer PCB
ψJT
5 °C / W 1-layer PCB
1 °C / W 4-layer PCB
PCB Size 114.3 mm x 76.2 mm x 1.60 mmt
HTSOP-J8
θjc
Top : 44 °C / W
Bottom : 14 °C / W
θja
189.4 °C / W 1-layer PCB
40.3 °C / W 4-layer PCB
ψJT
21°C / W 1-layer PCB
5°C / W 4-layer PCB
PCB Size 114.3 mmx76.2 mm x 1.60 mmt
The heat loss W of the IC can be obtained by the formula shown below:
𝑊
=
𝑅_ON
×
𝐼_𝑂 ²
×
𝑉_𝑂
𝑉_{𝐼𝑁}
+
𝑉_{𝐼𝑁}
×
𝐼_{𝐼𝑁}
+
1
2
×
(𝑇𝑟
+
𝑇𝑓)
×
𝑉_{𝐼𝑁}
×
𝐼_𝑂
×
𝑓𝑠𝑤
Where:
RON is the ON Resistance of IC (Refer to page 7) [Ω]
IO is the Load Current [A]
VO is the Output Voltage [V]
VIN is the Input Voltage [V]
IIN is the Circuit Current (Refer to page 7) [A]
Tr is the Switching Rise Time [s] (Typ:17ns)
Tf is the Switching Fall Time [s] (Typ:17ns)
fsw is the Switching Frequency [Hz]
Tr
(17 ns)
Tf
(17 ns)
①
V_IN
SW wave form
GND
T=
1
fsw
②
①𝑅_{𝑂𝑁} × 𝐼_{𝑂2}
1
1
② ₂ × (𝑇𝑟 + 𝑇𝑓) × 𝑉_{𝐼𝑁} × 𝐼_𝑂 × _𝑇
= 𝑇𝑟 × 𝑉_{𝐼𝑁} × 𝐼_𝑂 × 𝑓𝑠𝑤
SW Wave Form
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TSZ22111・15・001
32/40
TSZ02201-0T1T0AL00130-1-2
15.Sep.2015 Rev.005