Rev 1.5

Page 32 of 41

03/2018

PI352x-00

θ

INT-TOP

the thermal impedance from the hottest component inside the SiP to the top side

θ

INT-PCB

the thermal impedance from the hottest component inside the SiP to the customer PCB, assuming all pins are

at one temperature.

θ

INT-VIN

the thermal impedance from the hottest component inside the SiP to the circuit board VIN pads.

θ

INT-VS1

the thermal impedance from the hottest component inside the SiP to the circuit board VS1 pads.

θ

INT-PGND1

the thermal impedance from the hottest component inside the SiP to the circuit board at the PGND1 pads.

PGND1 is pins 12A-K.

θ

INT-PGND2

the thermal impedance from the hottest component inside the SiP to the circuit board at the PGND2 pads .

PGND2 is pins 2F-J, 3F-J, 4C-J, 5B-J and 6C-K.

θ

INT-SGND

the thermal impedance from the hottest component inside the SiP to the circuit board at the SGND pads.

The following equation can predict the junction temperature

based on the heat load applied to the SiP and the known ambient

conditions with the simplified thermal circuit model:

+

+

1

θ

INT-TOP

1

θ

INT-PCB

T

TOP

θ

INT-TOP

T

PCB

θ

INT-PCB

PD +

(1)

T

Product

System

Simplified SiP

Thermal Impedances

Detailed SiP Thermal Impedances

θ

INT-TOP

(°C / W)

θ

INT-PCB

(°C / W)

θ

INT-TOP

(°C / W)

θ

INT-VIN

(°C / W)

θ

INT-VS1

(°C / W)

θ

INT-PGND1

(°C / W)

θ

INT-PGND2

(°C / W)

θ

INT-SGND

(°C / W)

PI3523

69.9

0.98

69.9

3.43

1.74

9.81

27.45

86.72

PI3525

68.7

1.477

68.7

3.34

3.76

22.61

19.78

58.78

PI3526

108

1.79

108.25

3.40

5.75

23.80

26.65

86.44

Table 2 — PI352x-00 SiP Thermal Impedance

Where the symbol in Figure 89(a) and (b) is defined as the following:

θ

INT-TOP

the thermal impedance from the hot spot to the top surface of the core.

θ

INT-BOT

the thermal impedance from the hot spot to the bottom surface of the core.

θ

INT-TAB

the thermal impedance from the hot spot to the metal mounting tab on the core body, if applicable.

θ

INT-LEAD1

the thermal impedance from the hot spot to one of the mounting leads.

Since the leads are the same thermal impedance, there is no need to specify by explicit pin number.

θ

INT-LEAD2

the thermal impedance from the hot spot to the other mounting lead.

Where the symbol in Figure 89(c) is defined as the following:

Table 3 — Inductor effective thermal model parameters

Product

System

Inductor Part

Number

Effective Thermal Impedances

θ

INT-TOP

(°C / W)

θ

(°C / W)

θ

INT-BOTTOM

(°C / W)

θ

INT-TAB

(°C / W)

PI3523

FP2207R1-R230-R

11.01

9.42

6.87

n/a

PI3525

FP2207R1-R230-R

8.75

9.54

5.99

n/a

PI3526

HCV1707R1-R48-R

65.41

17.74

20.46

703