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Due to part-to-part variations in log-slope and log-intercept, a system-level calibration is recommended to satisfy

absolute accuracy requirements. When performing this calibration, choose at least two test points: near the top-end

and bottom-end of the measurement range. It is best to measure the calibration points in the regions (of frequency and

amplitude) where accuracy is most important. Derive the log-slope and log-intercept, and store them in non-volatile

memory. Calibrate iPAR scaling by measuring the peak-to-average ratio of a known signal.

For example if the following two calibration points were measured at 2.35 GHz:

With Vrms = 2.34V at Pin= -7dBm,

and Vrms=1.84V at Pin= -16dBm

Slope Calibration Constant = SCC

SCC = (-16+7)/(1.84-2.34) = 18 dB/V

Intercept Calibration Constant = ICC

ICC = Pin – SCC*Vrms = -7 – 18.0 * 2.34 = -49.12dBm

Now performing a power measurement:

Vrms measures 2.13V

[Measured Pin] = [Measured Vrms]*SCC + ICC

[Measured Pin] = 2.13*18.0 – 49.12 = -10.78dBm

An error of only 0.22dB

Factory system calibration measurements should be made using an input signal representative of the application. If

the power detector will operate over a wide range of frequencies, choose a central frequency for calibration.

Layout Considerations

• Mount RF input coupling capacitors close to the IN+ and IN- pins.

• Solder the heat slug on the package underside to a grounded island which can draw heat away from the die

with low thermal impedance. The grounded island should be at RF ground potential.

• Connect power detector ground to the RF ground plane, and mount the supply decoupling capacitors close

to the supply pins.

Definitions:

• Input Dynamic Range: the range of average input power for which there is a corresponding RMS output

voltage with “RMS Output Error” falling within a specific error tolerance.

• Crest Factor: Peak power to average power ratio for time-varying signals.

System Calibration

HMC714LP5 / 714LP5E

v05.0309

DUAL RMS POWER DETECTOR

0.1 - 3.9 GHz