ATS612LSG datasheet(6/15 Pages) ALLEGRO

6 / 15 page

ATS612LSG

DYNAMIC, SELF-CALIBRATING, PEAK-DETECTING,

DIFFERENTIAL HALL-EFFECT GEAR TOOTH SENSOR

Page 6 of 15

115 Northeast Cutoff, Box 15036

Worcester, Massachusetts 01615-0036 (508) 853-5000

POWER DE-RATING

Due to internal power consumption, the temperature of

the IC (junction temperature, 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:

∆T = P

D × R

θJA

Where: PD = VCC × ICC

∴ ∆T=V

CC × ICC × R

θJA

Where

∆T denotes the temperature rise resulting from

the IC’s power dissipation.

TJ = TA + ∆T

For the sensor :

TJ(max) = 165°C

RθJA = 126°C/W

Typical TJ calculation:

TA = 25 °C

VCC = 5 V

ICC = (ICC(ON)typ + ICC(OFF)typ) / 2 = (10.7 mA +

8.7 mA) / 2 = 9.7 mA

PD = VCC × ICC = 5 V × 9.7 mA = 48.5 mW

∆T = P

D × R

θJA = 48.5 mW × 165°C/W = 8.0°C

TJ = TA + ∆T = 25°C + 8.0°C = 33.0°C

Maximum Allowable Power Dissipation Calculation

for ATS612LSG:

Assume:

TA = TA(max) = 150 °C

TJ(max) = 165°C

Icc = (ION(max) + IOFF(max)) / 2

= (15 mA + 13 mA) / 2 = 14 mA

If:

TJ = TA + ∆T

Then:

∆T

(max) = TJ(max) – TA(max) = 165°C - 150°C = 15°C

If:

∆T = P

D × R

θJA

then:

PD(max) = ∆T(max) / RθJA = 15°C / 126°C/W = 119 mW

If:

PD = VCC × ICC

then the maximum VCC at 150°C is therefore:

VCC(max) = PD(max) / ICC = 119 mW / 15 mA = 7.9 V

This value applies only to the voltage drop across the

ATS612 chip. If a protective series diode or resistor is

used, the effective maximum supply voltage is

increased.

For example, when a standard diode with a 0.7 V drop is

used:

VS(max) = 7.9 V + 0.7 V = 8.6 V

SG Package Power De-Rating Curve

Thermal Resistance = 126°C/Watt, Tjmax = 165°C

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Ambient Temperature [°C]

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