A1184 Allegro MicroSystems, A1184 Datasheet - Page 10

• Manufacturer Part Number: A1184
• Description: (A1180 - A1184) Unipolar Hall-Effect Switch
• Manufacturer: Allegro MicroSystems

Due
temperature of the IC, Tj, is higher than the ambient
environment temperature, Ta. To ensure that the device
does not operate above the maximum rated junction
temperature use the following calculations:
Where: P
Where T denotes the temperature rise resulting from the
IC’s power dissipation.
For the sensor :
Typical Tj calculation:
7
The “LH”
TWO-WIRE, PROGRAMMABLE, UNIPOLAR HALL-EFFECT SWITCH FAMILY
to
Tj = Ta + T
Tj(max) = 170°C
R ja (UA Pkg) = 206°C/W
Ta = 25 °C
Vcc = 12 V
Icc = Icc
P
Tj = Ta + T = 25 °C + 35.8 °C = 60.8 °C
Rev. 1.8 25 April 2003
T = P
T = P
D
D
PPD is based on a 0.062" thick FR4, single-sided board using 2 oz. copper, with a 0.55 mm
internal
= Vcc * Icc = 12 V * 14.5 mA = 174 mW
= Vcc * Icc
T=Vcc * Icc * R ja
D
D
Page 10
* R ja
* R ja = 174 mW * 206°C/W = 35.8 °C
ONtyp
(PRELIMINARY INFORMATION – SUBJECT TO CHANGE)
power
= 14.5 mA
consumption,
the
POWER DE-RATING
junction
Maximum
Calculation for A118X Family
Assume:
If:
Then:
If:
Then:
If:
Then the maximum Vcc at 150°C is therefore:
30
25
20
15
10
Ta = Ta
Tj(max) = 170°C
Icc = I
Tj = Ta + T
P
mW
P
Vccmax = P
5
0
T
T = P
Dmax
D
0
max
Maximum Supply Voltage vs Ambient Temperature
= Vcc * Icc
= T
ONmax
= Tj
D
max
* R ja
Allowable
UA (ROJA = 206°C/W)
LH (ROJA = 228°C/W)
25
max
max
= 150 °C
= 17 mA
Dmax
115 Northeast Cutoff, Box 15036
Worcester, Massachus etts 01615-0036 [phone]
Copyright © 1993, 1995 Allegro MicroSystems, Inc.
– Ta
2
/ R ja = 20 °C / 206 °C/W = 97.1
area of copper attached to the ground lead.
50
max
Temperature (°C)
/ Icc = 97.1 mW / 17 mA = 5.7 V
= 170 °C - 150 °C = 20 °C
75
Power
7
:
100
Dissipation
125
150