AD9662

Rev. C | Page 11 of 16

Using the preceding method, actual data was taken to

Immediately after power-up, V1 was measured to be 593 mV.

The supply current was 27 mA. The AD9662 was adjusted to

deliver 200 mA into a 10 Ω load. This resulted in a total supply

current of 244 mA. After allowing the part to reach thermal

equilibrium, V2 measured 412 mV. The voltage drop across the

120 mΩ internal resistor due to the change in supply current

was then calculated.

The change in junction temperature can then be determined.

5V

–

+

10V

ENR

V1, V2

AD9662

1M

Ω

(244 mA – 27 mA) × 120 mΩ = 26 mV

This 26 mV internal voltage drop was then added to the

The die temperature change measured 82.4°C. The output of

the AD9662 was at a voltage of 2 V. The part dissipated an

AD9962 mounted on its 2-layer board was calculated to be:

600 mW/82.4°C = 137°C/W.

Figure 15. Junction Temperature Measurement Circuit

This 2-point measurement allows the rise in die temperature to

system can be calculated using the power dissipation of the LDD.

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

40

20

60

80

100

120

140

160

TEMPERATURE (

°C)

Figure 16 shows a graph of the measured voltage between ENR

constructed using a 2-layer evaluation board for the AD9662

(see Figure 17).