DATA SHEET
HAL855
Table 4–1: Temperature compensation, continued
4.5. Ambient Temperature
Due to the internal power dissipation, the temperature
on the silicon chip (junction temperature TJ) is higher
than the temperature outside the package (ambient
temperature TA).
Typ. Temperature Coefficient TC
of Magnet (ppm/K)
TCSQ
−1080
−1150
−1180
−1270
−1290
−1360
−1430
−1460
−1540
−1600
−1670
−1740
−1810
−1880
−1950
−2020
−2100
−17
−16
−15
−14
−13
−12
−11
−10
−9
10
11
11
12
12
13
14
14
15
16
17
18
19
20
21
22
23
TJ = TA + ΔT
At static conditions and continuous operation, the fol-
lowing equation applies:
ΔT = IDD × VDD × Rthjx + IOut × VOutLow × Rthjx
For typical values, use the typical parameters. For
worst case calculation, use the max. parameters for
IDD and Rth, and the max. value for VDD from the
application.
−8
Example with typical given values:
−7
I
DD = 0.007 A
DD = 5 V
thja = 235 K/W
jmax = 170
−6
V
−5
R
−4
T
−3
The current through the output is calculated as follows:
Pull-up = 5 V
−2
V
R
R
Pull-up = 470 Ω
DS,on = 50 Ω
−1
VPull – up
5V
--------------------------------------------- -------------
=
IOut
=
0.01A
RPull – up + RDS, on 520Ω
VOutLow = IOut × RDS, on = 0.01A × 50Ω = 0.5V
ΔT is calculated as follows:
K
W
K
W
----
----
ΔT = 0.007A × 5V × 235 + 0.01A × 0.5V × 235 = 9.4
The maximum ambient temperature TAmax can be
calculated as:
TAmax = TJmax – ΔT
Micronas
Nov. 26, 2008; DSH000149_003EN
29
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