(

)

J(MAX)

A

(MAX)

JA

T

T

PD

-

=

q

N

D

OLi

Li

i 1

P

V

I

=

=

´

å

14

TPL7407L

SLRS066D – JANUARY 2014 – REVISED MARCH 2016

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Copyright © 2014–2016, Texas Instruments Incorporated

10.3 Thermal Considerations

The number of coils driven is dependent on the coil current and on-chip power dissipation. The number of coils

driven can be determined by Figure 3, Figure 4, Figure 5, Figure 6, Figure 7, or Figure 8.

For a more accurate determination of number of coils possible, use the below equation to calculate TPL7407L

on-chip power dissipation PD:

Where:

N is the number of channels active together.

VOLi is the OUTi pin voltage for the load current ILi. This is the same as VCE(SAT)

(2)

In order to guarantee reliability of TPL7407L and the system, the on-chip power dissipation must be lower than or

equal to the maximum allowable power dissipation (PD(MAX)) dictated by below equation Equation 3.

Where:

TJ(MAX) is the target maximum junction temperature.

TA is the operating ambient temperature.

θJA is the package junction to ambient thermal resistance.

(3)

It is recommended to limit TPL7407L IC’s die junction temperature to less than 125°C. The IC junction

temperature is directly proportional to the on-chip power dissipation.

10.3.1 Improving Package Thermal Performance

θJA value depends on the PC board layout. An external heat sink and/or a cooling mechanism, like a cold air fan,

can help reduce

θJA and thus improve device thermal capabilities. Refer to TI’s design support web page at

www.ti.com/thermal for a general guidance on improving device thermal performance.