Two-Wire Chopper-Stabilized Hall Effect Latch
A1242
9
Allegro MicroSystems, Inc.
115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
1.508.853.5000; www.allegromicro.com
Power Derating
Power Derating
The device must be operated below the maximum junction
temperature of the device, T
J(max)
. Under certain combinations of
peak conditions, reliable operation may require derating sup-
plied power or improving the heat dissipation properties of the
application. This section presents a procedure for correlating
factors affecting operating T
J
. (Thermal data is also available on
the Allegro MicroSystems Web site.)
The Package Thermal Resistance, R
qJA
, is a figure of merit sum-
marizing the ability of the application and the device to dissipate
heat from the junction (die), through all paths to the ambient air.
Its primary component is the Effective Thermal Conductivity,
K, of the printed circuit board, including adjacent devices and
traces. Radiation from the die through the device case, R
qJC
, is
relatively small component of R
qJA
. Ambient air temperature,
T
A
, and air motion are significant external factors, damped by
overmolding.
The effect of varying power levels (Power Dissipation, P
D
), can
be estimated. The following formulas represent the fundamental
relationships used to estimate T
J
, at P
D
.
P
D
= V
IN
?/DIV>
I
IN
(1)
DT = P
D
?/DIV>
R
qJA
(2)
T
J
= T
A
+ 擳
(3)
For example, given common conditions such as: T
A
= 25癈,
V
CC
= 12 V, I
CC
= 6 mA, and R
qJA
= 165 癈/W, then:
P
D
= V
CC
?/DIV>
I
CC
= 12 V
?/DIV>
6 mA = 72 mW
DT = P
D
?/DIV>
R
qJA
= 72 mW
?/DIV>
165 癈/W = 12癈
T
J
= T
A
+ DT = 25癈 + 12癈 = 37癈
A worst-case estimate, P
D(max)
, represents the maximum allow-
able power level (V
CC(max)
, I
CC(max)
), without exceeding T
J(max)
,
at a selected R
qJA
and T
A
.
Example: Reliability for V
CC
at T
A
=
150癈, package LH, using
minimum-K PCB.
Observe the worst-case ratings for the device, specifically:
R
qJA
=
228癈/W, T
J(max)
=
165癈, V
CC(max)
=
24 V, and
I
CC(max)
=
17
mA.
Calculate the maximum allowable power level, P
D(max)
. First,
invert equation 3:
DT
max
= T
J(max)
T
A
= 165
癈
150
癈 = 15
癈
This provides the allowable increase to T
J
resulting from internal
power dissipation. Then, invert equation 2:
P
D(max)
= DT
max
?R
qJA
= 15癈 ?228 癈/W = 66 mW
Finally, invert equation 1 with respect to voltage:
V
CC(est)
= P
D(max)
? I
CC(max)
= 66 mW ?17 mA = 3.9 V
The result indicates that, at T
A
, the application and device can
dissipate adequate amounts of heat at voltages dV
CC(est)
.
Compare V
CC(est)
to V
CC(max)
. If V
CC(est)
d V
CC(max)
, then reli-
able operation between V
CC(est)
and V
CC(max)
requires enhanced
R
qJA
. If V
CC(est)
e V
CC(max)
, then operation between V
CC(est)
and
V
CC(max)
is reliable under these conditions.
发布紧急采购，3分钟左右您将得到回复。
相关PDF资料
A1244LUA-I2-T
IC HALL EFFECT LATCH SIP-3
A1302KUA-T
IC SENSOR HALL EFFECT 3-SIP
A1323LLHLT-T
IC SENSOR HALL EFFECT SOT23W
A1351LKTTN-T
IC SENSOR HALL EFFECT 4-SIP
A1354KKT-T
IC SENSOR HALL EFFECT 4-SIP
A1356LKB-T
IC SENSOR HALL EFFECT 3 SIP
A1361LKTTN-T
IC HALL EFFECT SENSOR LN 4-SIP
A1374EKB-T
IC SENSOR HALL EFFECT PREC 3-SIP
相关代理商/技术参数
A1243
制造商:Hakko 功能描述:Tip,0.8D,929 -2/939,903 Used With Soldering Stations
A1243LLHLX-I1-T
功能描述:IC HALL EFFECT LTCH DGTL SOT23W 制造商:allegro microsystems, llc 系列:* 零件状态:在售 标准包装:10,000
A1243LLHLX-I2-T
功能描述:IC HALL EFFECT LTCH DGTL SOT23W 制造商:allegro microsystems, llc 系列:- 包装:- 零件状态:有效 功能:- 技术:- 极化:- 感应范围:- 测试条件:- 电压 - 电源:- 电流 - 电源（最大值）:- 电流 - 输出（最大值）:- 输出类型:- 特性:- 工作温度:- 封装/外壳:- 供应商器件封装:- 标准包装:10,000
A1244
制造商:ALLEGRO 制造商全称:Allegro MicroSystems 功能描述:Chopper-Stabilized, Two Wire Hall-Effect Latch
A-1244
制造商:TE Connectivity 功能描述:
A12441/2
制造商:TITEX 功能描述:TITEX A1244 HSCO JOBBER DRILL 1/2"
A12442.0
制造商:TITEX 功能描述:TITEX A1244 HSCO JOBBER DRILL 2.00MM
A12442.5
制造商:TITEX 功能描述:TITEX A1244 HSCO JOBBER DRILL 2.50MM