M02040-15 Datasheet, PDF (24/31 Pages) M/A-COM Technology Solutions, Inc. – 3.3 5V Limiting Amplifier for Applications to 2.125 Gbps

M02040-15
3.3/5V Limiting Amplifier for Applications to 2.125 Gbps
Rev V4
4.1.6
Setting the Signal Detect Level
Using Figure 4-3, the value for R_ST is chosen to set the LOS threshold at the desired value. The resulting hystere-
sis is also shown in Figure 4-3.
From Figure 4-3, it is apparent that small variations in R_ST cause significant variation in the LOS threshold level,
particularly for low input signal levels. This is because of the logarithmic relationship between the RSSI voltage and
the input signal level. It is recommended that a 1% resistor be used for R_ST and that allowance is provided for LOS
variation, particularly when the LOS threshold is near the sensitivity limit of the M02040-15.
Example R_ST resistor values are given in Table 4-1.
Table 4-1. Typical LOS Assert and De-assert Levels for Various 1% R_ST Resistor Values
R_ST (kΩ)
VIN (mV pp) differential
LOS Assert
LOS De-Assert
7.50
4.9
7.8
6.81
11.7
17.0
6.19
23.2
33.4
5.49
55.0
77.3
Figure 4-3. Typical Loss of Signal Characteristic (Full Input Signal Range)
80
70
Conditions:
60
1.25 Gbps, 2³¹ - 1
50
Vcc = 3.3V, Temp = 25C
De-assert
40
Optical Hysteresis
30
= 10*log₁₀(De-assert/Assert)
20
Assert
10
0
5.5 5.7 5.9 6.1 6.3 6.5 6.7 6.9 7.1 7.3 7.5
R_ST (kΩ)
24
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