ADMV1455BBCZ-R7 datasheet(83/141 Pages) AD

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Data Sheet

ADMV1455

THEORY OF OPERATION

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Rev. 0 | 83 of 141

POWER DETECTOR

The ADMV1455 contains a power detector after the RF signal

chains (RF_C) and before the I/Q mixer that allows for estimating

of the RF input power level. The power detector output can be

sampled by using the on-chip ADC, and the value can then be read

back via the SPI.

The internal termination resistor on the power detector can shift the

RF input power level vs. the ADC code response. Refer to Figure

96 for an example response curve.

Use Register 0x178 (DETECTOR_RES_CTRL) to set the internal

termination resistor. It is recommended to maintain a value of 7

for most applications, particularly when the chip is configured for

maximum gain. If there is a requirement for lower gain (more

attenuation), then it may be beneficial to use a lower value for the

internal termination resistor.

It is useful to perform a factory calibration, where known RF input

power levels are applied to RF_IN or DSA_IN, and then the corre-

sponding ADC codes are read back via the SPI. Create a table in

the system microcontroller for storing the factory calibration values.

Follow the instructions in the Automatic ADC Configuration section

for information on setting up the ADC and reading back the power

detector value.

TEMPERATURE SENSOR

The ADMV1455 contains an on-chip temperature sensor that allows

monitoring of the chip temperature. The temperature sensor output

can be sampled using the on-chip ADC, and the value can then be

read back via the SPI.

Follow the instructions in the Automatic ADC Configuration section

for information on setting up the ADC and reading back the temper-

ature sensor value.

To estimate the TC of the ADMV1455 use the following equation:

TC=−56×ADC_CODE+177

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