Diodes ZXLD1370 - Manual (Page 24)

ZXLD1370
Document number: DS32165 Rev. 5 - 2
24 of 39
www.diodes.com
September 2012
© Diodes Incorporated
ZXLD1370
A Product Line of
Diodes Incorporated
Application Information
(cont.)
Junction Temperature Estimation
Finally, the ZXLD1370 junction temperature can be estimated using the following equations:
Total supply current of ZXLD1370:
I
QTOT
≈ I
Q
+ f • Q
G
Where I
Q
= total quiescent current I
Q-IN
+ I
Q-AUX
Power consumed by ZXLD1370
P
IC
= V
IN
• (I
Q
+ f • Qg)
Or in case of separate voltage supply, with V
AUX
< 15V
P
IC
= V
IN
• I
Q-IN
+ V
aux
• (I
Q-AUX
+ f • Qg)
T
J
= T
A
+ P
IC
• θ
JA
= T
A
+ P
IC
• ( θ
JC
+ θ
CA)
Where the total quiescent current IQ
TOT
consists of the static supply current (IQ) and the current required to charge and discharge the gate of the
power MOSFET. Moreover the part of thermal resistance between case and ambient depends on the PCB characteristics.
0
0.5
1
1.5
2
2.5
-40 -25 -10 5 20 35 50 65 80 95 110 125
Ambient temperature (°C)
P
o
w
er
di
ss
ipa
ti
on
(m
W
)
Figure 27 Power Derating Curve for ZXLD1370 Mounted on Test Board According to JESD51