ATS665LSG

TRUE ZERO-SPEED GEAR TOOTH SENSOR

POWER DE-RATING

Due to internal power consumption, the junction

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:

∴ ∆T=Vcc * Icc * Rθja

Where

∆T denotes the temperature rise resulting from

the IC’s power dissipation.

Tj = Ta +

∆T

Final Version, Rev 1.0; DSD; 01Aug03

115 Northeast Cutoff, Box 15036

For the sensor :

Tj(max) = 165°C

R

θja = 126°C/W

Typical Tj calculation:

Ta = 25 °C

Vcc = 5 V

Icc = 7.0 mA

Tj = Ta +

∆T = 25 °C + 5.0°C = 30.0°C

Maximum Allowable Power Dissipation Calculation

for ATS665:

Assume:

Tj(max) = 165°C

Icc = 12.0 mA

4

If:

data

Tj = Ta +

∆T

Then, at Ta = 150 °C:

If:

Then, at Ta = 150°C:

If:

Then the maximum Vcc at 150°C is therefore:

This value applies only to the voltage drop across the

665 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:

Vsmax = 9.9 V + 0.7 V = 10.6 V

ATS665LSG Package Power De-Rating Curve

0.0

2.0

4.0

6.0

8.0

10.0

12.0

14.0

16.0

18.0

20.0

22.0

24.0

26.0

28.0

30.0

20

40

60

80

100

120

140

160

180

Ambient Temperature [°C]

c

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Copyright © 1993, 1995 Allegro MicroSystems, Inc.