Datasheet

LPC185X_3X_2X_1X All information provided in this document is subject to legal disclaimers. © NXP Semiconductors N.V. 2014. All rights reserved.
Product data sheet Rev. 4.1 — 6 May 2014 86 of 148
NXP Semiconductors
LPC185x/3x/2x/1x
32-bit ARM Cortex-M3 microcontroller
9. Thermal characteristics
The average chip junction temperature, T
j
(C), can be calculated using the following
equation:
(1)
• T
amb
= ambient temperature (C),
• R
th(j-a)
= the package junction-to-ambient thermal resistance (C/W)
• P
D
= sum of internal and I/O power dissipation
The internal power dissipation is the product of I
DD(REG)(3V3)
and V
DD(REG)(3V3)
. The I/O
power dissipation of the I/O pins is often small and many times can be negligible. However
it can be significant in some applications.
Table 8. Thermal characteristics
Symbol Parameter Min Typ Max Unit
T
j(max)
maximum junction
temperature
--125 C
Table 9. Thermal resistance (LQFP packages)
Symbol Parameter Conditions Thermal resistance in C/W ±15 %
LQFP144 LQFP208
R
th(j-a)
thermal resistance
from junction to
ambient
JEDEC (4.5 in  4 in); still
air
38 31
Single-layer (4.5 in  3 in);
still air
50 39
R
th(j-c)
thermal resistance
from junction to case
11 10
Table 10. Thermal resistance value (BGA packages)
Symbol Parameter Conditions Thermal resistance in C/W ±15 %
LBGA256 TFBGA100
R
th(j-a)
thermal resistance from
junction to ambient
JEDEC (4.5 in  4 in);
still air
29 46
8-layer (4.5 in  3 in);
still air
24 37
R
th(j-c)
thermal resistance from
junction to case
14 11
T
j
T
amb
P
D
R
th j a–
+=