M02040-15 Datasheet, PDF (29/31 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
Figure 4-9. Alternative PECL Termination
V_CC
PECLP ^Zo
M02040
PECLN ^Zo
V_CC
PECL
50 Ω
50 Ω
V_CC - 2V
10 nF
4.1.8
Using JAM
As shown in the typical applications circuit (Figure 1-2), the LOS output pin can optionally be connected to the Jam
input pin. When LOS asserts the Jam function sets the data outputs to a fixed “one” state (PECLP is held high and
PECLN is held low). This is normally used to allow data to propagate only when the signal is above the users' bit
error rate (BER) requirement. It prevents the outputs from toggling due to noise when no signal is present.
From the LOS assert and deassert figures above (Figure 4-2 - Figure 4-4), when an input signal is below the LOS
assert threshold, LOS asserts (LOS high) causing Jam to assert. When Jam asserts, the data outputs and the
internal servo loop of the M02040-15 are disabled. If the input signal reaches or exceeds the LOS deassert
threshold, LOS deasserts (LOS low) causing Jam to deassert, and hence enables the data outputs and the internal
servo loop. If, however, the input signal is slowly increasing to a level that does not exceed the LOS deassert
threshold (operating in the hysteresis region), the internal servo loop may not be fully established and this may
cause partial enabling of the data outputs. To avoid this the input signal needs to fully reach or exceed the LOS
deassert level to fully enable the data outputs.
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