RT8251GSP Richtek USA Inc, RT8251GSP Datasheet - Page 12

• Manufacturer Part Number: RT8251GSP
• Description: IC DCDC CTRLR STP-DN 8SOP
• Manufacturer: Richtek USA Inc
• Type: Step-Down (Buck)r

Specifications of RT8251GSP

• Internal Switch(s): Yes
• Synchronous Rectifier: Yes
• Number Of Outputs: 1
• Voltage - Output: 0.8 V ~ 15 V
• Current - Output: 5A
• Frequency - Switching: 570kHz
• Voltage - Input: 4.75 V ~ 24 V
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: 8-SOIC (0.154", 3.90mm Width) Exposed Pad
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

RT8251
SOP-8 (Exposed Pad) pad (Figure 6a),
Adding copper area of pad under the SOP-8 (Exposed
Pad) (Figure 6.b) reduces the
increasing the copper area of pad to 70mm
reduces the
The maximum power dissipation depends on operating
ambient temperature for fixed T
resistance
in Figure 7 and Figure 8 allow the designer to see the
effect of rising ambient temperature on the maximum power
dissipation allowed.
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12
2.2
2.0
1.8
1.6
1.4
1.2
1.0
0.8
0.6
0.4
0.2
0.0
1.6
1.4
1.2
1.0
0.8
0.6
0.4
0.2
0.0
Figure 7. Derating Curves for PSOP-8 Package
Figure 8. Derating Curves for WQFN Package
0
0
JA
15
. For RT8251 packages, the derating curves
JA
to 49 C/W.
25
30
Ambient Temperature (°C)
Ambient Temperature
45
50
60
JA
75
to 64 C/W. Even further,
WQFN-16L 3x3
75
J(MAX)
90
Four Layer PCB
Four Layer PCB
105
( C)
JA
Copper Area
and thermal
70mm
50mm
30mm
10mm
2
Min.Layout
100
(Figure 6.e)
is 75 C/W.
120 135
2
2
2
2
125
Figure 6. Themal Resistance vs. Copper Area Layout
(a) Copper Area = (2.3 x 2.3) mm
(c) Copper Area = 30mm
(d) Copper Area = 50mm
(e) Copper Area = 70mm
(b) Copper Area = 10mm
Design
2
2
2
2
DS8251-01 March 2011
,
,
,
,
JA
JA
JA
JA
2
,
= 64 C/W
= 54 C/W
= 51 C/W
= 49 C/W
JA
= 75 C/W