LMH2110 Datasheet, PDF (24/33 Pages) National Semiconductor (TI) – 8 GHz Logarithmic RMS Power Detector with 45 dB Dynamic Range

LMH2110
SNWS022C – JANUARY 2010 – REVISED MARCH 2013
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2.4
3
2.0
2
1.6
-40°C _25°C
1
1.2
0
0.8
-1
85°C
0.4
-2
0.0
-40
-30 -20 -10
0
RF INPUT POWER (dBm)
-3
10
Figure 53. V_OUT and E_LC vs. RF input Power at 1900 MHz
Variation over Temperature Error
In contrast to the log conformance error, the variation over temperature error (E_VOT) purely measures the error
due to temperature variation. The measured output voltage at 25°C is subtracted from the output voltage at
another temperature. Subsequently, it is translated into an input referred error by dividing it by K_SLOPE at 25°C.
The equation for variation over temperature is given by:
E_VOT = (V_{OUT_TEMP} – V_{OUT 25°C}) / K_{SLOPE 25°C}
(14)
The variation over temperature is shown in Figure 54, where a dynamic range of 41 dB is obtained (from P_MIN = -
36 dBm) for E_VOT = ±0.5 dB.
2.0
1.5
1.0
-40°C
0.5
0.0
-0.5
85°C
-1.0
-1.5
-2.0
-40 -30 -20 -10
0
10
RF INPUT POWER (dBm)
Figure 54. E_VOT vs. RF Input Power at 1900 MHz
1 dB step error
This parameter is a measure for the error for an 1 dB power step. According to a 3GPP specification, the error
should be less than ±0.3 dB. Often, this condition is used to define a useful dynamic range of the detector.
The 1 dB step error is calculated in 3 steps:
1. Determine the maximum sensitivity.
2. Determine average sensitivity.
3. Calculate the 1 dB step error.
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