AD9148BPCZ datasheet(65/73 Pages) AD

65 / 73 page

Preliminary Technical Data

AD9148

Rev. PrA | Page 65 of 73

TEMPERATURE SENSOR

The AD9148 has a diode-based temperature sensor for measuring

the temperature of the die. The temperature reading is accessed

by Register 0x5E and Register 0x5F. The temperature of the die

can be calculated as

126

)

46875

]

[

(

−

= DieTemp

DIE

where TDIE is the die temperature in degrees Celsius. The

temperature accuracy is ±5°C typical over TBD range.

Estimates of the ambient temperature can be made if the power

dissipation of the device is known. For example, if the device power

dissipation is 800 mW and the measured die temperature is 50°C,

then the ambient temperature can be calculated as

TA = TDIE – PD × TJA = 50 – 0.8 × 19.1 = 34.7°C

where:

TA is the ambient temperature in degrees Celsius.

TJA is the thermal resistance from junction to ambient of the

AD9148 as shown in Table 7.

To use the temperature sensor, it must be enabled by setting

Bit 0, Register 0x5C to 0. Before the temperature sensor data can

be readback, it must be latched by toggling Bit 1, Register 0x5C

from 0 to 1. In addition, to get accurate readings, the range

control register (Register 0x5D) should be set to 0x02.

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