A1190 ALLEGRO [Allegro MicroSystems], A1190 Datasheet - Page 15

• Manufacturer Part Number: A1190
• Description: Programmable, Chopper-Stabilized, Two Wire Hall-Effect Switches
• Manufacturer: ALLEGRO [Allegro MicroSystems]

A1190, A1192,
and A1193
The device must be operated below the maximum junction tem-
perature of the device, T
peak conditions, reliable operation may require derating supplied
power or improving the heat dissipation properties of the appli-
cation. This section presents a procedure for correlating factors
affecting operating T
Allegro MicroSystems Web site.)
The Package Thermal Resistance, R
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
small component of R
motion are significant external factors, damped by overmolding.
The effect of varying power levels (Power Dissipation, P
be estimated. The following formulas represent the fundamental
relationships used to estimate T

For example, given common conditions such as: T
V

A worst-case estimate, P
able power level (V
T
J
CC
(max), at a selected R
T = P
= 12 V, I
T = P
CC
P
D
= 4 mA, and R
= V
T
D
J
P
T
CC
= T
D
J
J
×
CC
. (Thermal data is also available on the
JA
= T
(max), I
= V
A
R
JA
J
×
D
(max). Under certain combinations of
. Ambient air temperature, T
A
JA
+ T = 25°C + 7°C = 32°C
D
(max), represents the maximum allow-
IN
I
+ ΔT
and T
×
CC
×
= 48 mW
CC
R
= 12 V
I
JA
J
JA
, at P
IN
(max)), without exceeding
A
.
= 140 °C/W, then:
JA
D
×
.
×
, is a figure of merit sum-
4 mA = 48 mW
140 °C/W = 7°C
JC
A
= 25°C,
, is relatively
A
, and air
Power Derating
D
), can
(1)
(2)
(3)
Programmable, Chopper-Stabilized,
Example: Reliability for V
low-K PCB.
Observe the worst-case ratings for the device, specifically:
R
I
Calculate the maximum allowable power level, P
invert equation 3:
This provides the allowable increase to T
power dissipation. Then, invert equation 2:
Finally, invert equation 1 with respect to voltage:
The result indicates that, at T
dissipate adequate amounts of heat at voltages ≤V
Compare V
able operation between V
R
and V
CC
JA
JA
V
T
(max) = 17 mA.
CC(est)
. If V
= 165 °C/W, T
P
Two Wire Hall-Effect Switches
CC
max
(max) is reliable under these conditions.
D
= T
= P
CC(est)
(max) = T
CC(est)
J
D
(max) – T
(max) ÷ I
≥ V
to V
J
(max) = 165°C, V
CC
max
CC
(max), then operation between V
A
CC
(max). If V
CC(est)
= 165 °C – 150 °C = 15 °C
÷ R
CC
(max) = 91 mW ÷ 17 mA = 5 V
115 Northeast Cutoff
1.508.853.5000; www.allegromicro.com
Allegro MicroSystems, Inc.
Worcester, Massachusetts 01615-0036 U.S.A.
A
JA
at T
, the application and device can
and V
= 15°C ÷ 165 °C/W = 91 mW
A
= 150°C, package UA, using a
CC(est)
CC
CC
(max) = 24 V, and
(max) requires enhanced
J
resulting from internal
≤ V
CC
(max), then reli-
D
CC(est)
(max). First,
.
CC(est)
15