GS6150 Datasheet, PDF (20/64 Pages) Gennum Corporation – Automatic or Manual Rate Selection

The method of strength detection is measurement of the average rectified differential
voltage on the input pins. The strength detection method is therefore inherently
dependent on the input signal's eye shape, particularly the rise/fall times of the input
signal relative to the data rate. Additionally, the circuit has a lower bandwidth limit of
operation (20Mb/s) below which it is recommended that the edge detection method is
used. The absolute value of the threshold can be determined for any input swings
according to Equation 4-1 below:
Threshold = ^1----.-9---m------^V-----^×---₍-⁽-_D--^D--_E--^D-_V---^II-^[-_C-⁰--_E-^.-^.-_{_}-³--_S-^]-^_-_P--^L-_E--^O-_C---^S-_I-_F-^_--_I-^T-_C--^H-_{_}---_LR---_OE---^S-_S--^H-_{_}---_TO---_H-^L---_RD---_E-^_--_S-^C--_H--^O--_O--^N--_L--^T-_D--^R--₎-^O----^L----⁾----^×----5---3--
where DEVICE_SPECIFIC_LOS_THRESHOLD specifies the LOS threshold value for a
100mV input swing at SD-rate specific to each device. The other rates scale according to
the fractional relationship given in Figure 4-1 and Figure 4-2 below.
60
Equation 4-1
55
50
45
40
35
30
0
20
40
60
80
100
120
Frequency (Mb/s)
Figure 4-1: LOS Threshold at 100mV Input Swing vs. Low Frequency Rates for a Nominal
DEVICE_SPECIFIC_LOS_THRESHOLD of 53
Note: Edge detection method is recommended for signals in shaded areas.
GS6150
Final Data Sheet
PDS-060127
Rev.2
March 2015
www.semtech.com
20 of 64
Proprietary & Confidential