LMH2120 Datasheet, PDF (25/34 Pages) National Semiconductor (TI) – Linear RMS power detector particularly suited for accurate

LMH2120
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SNWS021C – JULY 2010 – REVISED FEBRUARY 2013
1.5
1.2
0.9
0.6
0.3
0.0
-0.3
-0.6
-0.9
-1.2
-1.5
-50
85°C
25°C
-40°C
-40 -30 -20 -10 0 10
RF INPUT POWER (dBm)
Figure 63. 1 dB Step Error vs. RF Input Power at 1900 MHz
10 dB step error
This error is defined in a different manner than the 1 dB step error. This parameter shows the input power error
over temperature for a 10 dB power step. The 10 dB step at 25°C is taken as a reference.
To determine the 10 dB step error first the output voltage levels (V1 and V2) for power levels “P” and “P+10dB”
at the 25°C are determined (Figure 64). Subsequently these 2 output voltages are used to determine the
corresponding power levels at temperature T (P_T and P_T+X). The difference between those two power levels
minus 10 results in the 10 dB step error.
25°C response
V2
Temp (T)
response
V1
P P+10 dB
RF_IN (dBm)
P_T
P_T+X
Figure 64. Graphical Representation of 10 dB Step Error Calculations
Figure 65 shows the typical 10 dB step error at 1900 MHz, where a dynamic range of 35 dB is obtained for E_10dB
= ±1dB.
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