Texas Instruments THS4012 manual ±9. Maximum Power Dissipation vs Free-Air Temperature

General PowerPAD Design Considerations

8)With these preparatory steps in place, the THS4012DGN IC is simply placed in position and run through the solder reflow operation as any standard surface-mount component. This results in a part that is properly installed.

The actual thermal performance achieved with the THS4012DGN in its PowerPAD package depends on the application. In the example above, if the size of the internal ground plane is approximately 3 inches ⋅3 inches, then the expected thermal coefficient, θJA, is about 58.4_C/W. For comparison, the non-PowerPAD version of the THS4012 IC (D-package in SOIC) is shown. For a given θJA, the maximum power dissipation is shown in Figure 1±9 and is calculated by the following formula:

PD	+ ￿	TMAX±TA	￿
		q
Where:		JA
PD	= Maximum power dissipation of THS4012 IC (watts)
TMAX = Absolute maximum junction temperature (150°C)
TA	= Free-ambient air temperature (°C)
θJA	= θJC + θCA
θJC	= Thermal coefficient from junction to case (4.7°C/W) for
θJC	THS4012DGN (PowerPAD)
	= Thermal coefficient from junction to case (38.3°C/W) for
θCA	THS4012D (SOIC)
	= Thermal coefficient from case to ambient air (°C/W)

Figure 1±9. Maximum Power Dissipation vs Free-Air Temperature

Maximum Power Dissipation ± W

3.5
	TJ = 150°C		No Air Flow
3
			DGN Package
2.5			θJA = 58.4°C/W
			2 oz Trace and
			Copper Pad
2			with Solder
		DGN Package
		θJA = 158°C/W
		2 oz Trace and

1.5Copper Pad

without Solder

1
.5	THS4012
	SOIC ± Package
	θJA = 166.7°C/W

0
±40	±20	0	20	40	60	80	100

TA ± Free-Air Temperature ± °C

Even though the THS4012 EVM PCB is smaller than the one in the example above, the results should give an idea of how much power can be dissipated by the PowerPAD IC package. The THS4012 EVM is a good example of proper thermal management when using PowerPAD-mounted devices.

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