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APPLICATION INFORMATIONALLEGRO CURRENT SENSOR ICS CAN TAKE THE HEAT!
UNIQUE PACKAGING OPTIONS FOR EVERY THERMAL BUDGET
By Kasey Hampton, Ryan Dunn, and Evan Shorman
Allegro MicroSystems

INTRODUCTION
Allegro MicroSystems offers current sensor IC solutions
that satisfy a wide array of applications, from smart
homes and car audio speakers to on-board chargers,
electric vehicles, and DC/DC converters. For applications with typical operating currents up to 50 A, Allegrooffers current sensor ICs in several standard packages,including SOIC-8 (LC), SOICW-16 (MA/LA), and QFN(EX). These packages have a typical maximum continuous current rating of up to 60 A. For applications withnormal operating currents from 50 A to 250 A, Allegro
offers current sensor ICs in the MC, LR, and CB packages. The maximum continuous current ratings of thesepackages are 100 A, 120 A, and 250 A, respectively.
Due to the small resistance of the integrated conductor,
these current sensor ICs feature high power densitywith little loss when placed in series with the current
being measured.
The data contained within this application note allows
the user to effectively choose an Allegro current sensor
package based on their system’s specifications. Using
the system’s ambient temperature, the user can predict
the sensor’s maximum operating temperature and continuous current value. In addition, data here can be used
to predict the IC’s worst-case overcurrent conditions interms of how long it will take the package to fail and at
what current. These packages have transient current
capability for overcurrent survival; Allegro has options
that meet the various DC operating requirements andovercurrent demands of many different applications.

BACKGROUND
Each package evaluated in this article is depicted inTable 1 through Table 3. Allegro offers several devices ineach package, consequently providing a viable solution
for the majority of current sensing applications. Clickthe package name in each table to be directed to thedevice web page of a popular product in that package.

THERMAL TESTING PERFORMED
Lab testing was conducted on Allegro’s current sensor
packages. Tests included:• Time to reach the maximum junction temperature, TJ(max), of 165°C vs. current• Time to fuse the current conductor open vs.
current• Die temperature vs. steady state current andambient temperature
Note that tests were conducted using the standard
Allegro demonstration board.

SAFE OPERATING RANGE
The current values in Table 1 represent the greatest DC
current value that can be supplied for the corresponding
duration before the maximum junction temperature isexceeded or the conductor has fused open. Currents
under these values are within the safe operating regionof the sensor. To ensure functionality and trustworthy
results, every application should stay within the safe
operating range of the sensor or the die may become
damaged, and the specifications of the device are nolonger guaranteed.

DC/RMS CURRENT CAPABILITY
Table 2 summarizes the package’s maximum continuous current at varying ambient operating temperatures.
Ambient temperature largely impact’s the device’s current capability. Table 3 summarizes the rise in die temperature at corresponding continuous currents. Thesetables provide the user a method of determining the best
package based on their system’s thermal constraints.

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APPLICATION INFORMATIONCONCLUSION
Understanding thermal capabilities is crucial for dependable operation in any current sensing application. Allegro
current sensors are built with reliability and lifetime performance in mind, and with Allegro’s large portfolio, there is afully integrated sensing solutions for a broad range of demanding, high-current applications.

Table 1: Safe Operating Area, Fuse and Overtemperature Time vs. Current [1]DC or RMS Current
QFN (EX)

SOIC-8 (LC)SOICW-16 (MA)SOICW-16 (MC)7-pin PSOF
(LR)

5-pin CB

Area: 9 mm2

Area: 29.4 mm2

Area: 106.09 mm2

Area: 146.77 mm2

Area: 40.96 mm2

Area: 311.92 mm2Height: 0.75 mm

Height: 1.75 mm

Height: 2.65 mm

Height: 3.01 mm

Height: 1.5 mm

Height: 10.5 mm

Time(ms)

10210 A

217 A

>400 A>600 A>700A>700 A

100120 A

137 A

350 A

>600 A

700 A>700 A

1000

75 A

91 A

128 A

320 A

350 A

>700 A

Note: ‘>’ indicates testing was not done to failure for these devices.

Table 2: Maximum Continuous Current of Allegro Current Sensor Packages at Various Ambient Temperatures [1]Continuous Current
QFN (EX)

SOIC-8 (LC)SOICW-16 (MA)SOICW-16 (MC)7-pin PSOF
(LR)

5-pin CB

2560 A

55 A

60 A

100 A

120 A

250 A

65

53 A

49 A

53 A

87 A

104 A

220 A

85

48 A

45 A

48 A

79 A

95 A

200 A

12536 A

35 A

35 A

59 A

69 A

150 A

AmbientTemperature(°C)[1] More detailed results and analysis for current capability and fuse characteristic data for these packages can be found on the Allegro web-site. For the EX, LC, MA, and MC packages, data can be found here. For the LR and CB packages, data can be found here.

955 PERIMETER ROAD • MANCHESTER, NH 03103 • USA+1-603-626-2300 • FAX: +1-603-641-5336 • ALLEGROMICRO.COM

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APPLICATION INFORMATION

Table 3: Change in Die Temperature of Allegro Current Sensor Packages at Various Continuous Currents [1]Change in Steady-State Die Temperature (°C)
QFN (EX)

SOIC-8 (LC)SOICW-16 (MA)SOICW-16 (MC)7-pin PSOF(LR)5-pin CB1043312<12012111244<130

2728

28

108240

54

54

53

18

14

350

93

99

87

30

21

560

––

132

44

30

670

–––

63

40

880

–––

86

55

1090

–––

121

68

14100

–––

147

88

18110

––––

113

21120

––––

139

25

150

–

––––

42

200

–

––––

83

225

–––––

106

250

––––

–

138

ContinuousCurrent (A)Note: ‘–’ indicates the maximum junction temperature, TJ(max) = 165°C, was exceeded at the corresponding continuous current value.

[1] More detailed results and analysis for current capability and fuse characteristic data for these packages can be found on the Allegro web-site. For the EX, LC, MA, and MC packages, data can be found here. For the LR and CB packages, data can be found here.

955 PERIMETER ROAD • MANCHESTER, NH 03103 • USA+1-603-626-2300 • FAX: +1-603-641-5336 • ALLEGROMICRO.COM

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Revision History
NumberDate

Description

Responsibility–July 9, 2020

Initial release

Kasey Hampton

Copyright 2020, Allegro MicroSystems.
The information contained in this document does not constitute any representation, warranty, assurance, guaranty,
or inducement by Allegro to the customer with respect to the subject matter of this document. The information being
provided does not guarantee that a process based on this information will be reliable, or that Allegro has explored
all of the possible failure modes. It is the customer’s responsibility to do sufficient qualification testing of the final
product to ensure that it is reliable and meets all design requirements.
Copies of this document are considered uncontrolled documents.

955 PERIMETER ROAD • MANCHESTER, NH 03103 • USA+1-603-626-2300 • FAX: +1-603-641-5336 • ALLEGROMICRO.COM