Lavry DA2002 Operation Manual - page 10
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the jitter content is random, much is due to coupling of the data itself into the receiver circuitry.
rejection of low frequency jitter content (typically hundreds of Hz of zero rejection bandwidth). While some of
signal. The need to keep enough bandwidth for locking to and tracking the incoming data translates to zero
incoming clock. The same circuits perform very poorly in the removal of low frequency jitter from the clock
Ordinary phase lock loops circuits (PLLs) do a reasonable job at removing high frequency jitter from the
Jitter removal
feeding the deglitcher circuit a precise jitter free on / off drive signal.
be somewhat sloppy, as long as the signals are well settled prior to turn on. Fighting the jitter wars means
deglitcher turn on and turn off are critical for good results. In fact switching during deglitcher blocking time can
timing point is all at the deglitcher circuit. Each sample value must exist over the same time period thus precise
The main reason for using DMOS transistors is their sub nanosecond switching capabilities. The jitter critical
resistance variations is neutralized by use of the strong feedback of the deglitcher amplifier.
technology thus providing extremely low resistance during the on state. The remaining problems due to on state
(switch two and four) are shorted to allow the signal path to the output. The deglither circuit utilizes DMOS
During the deglitcher on state, the shunt switches (switch one and three) are opened and the series switches
third switch. The remaining tiny energy is further blocked by the fourth opened series switch.
connected to the second switch that is in open state. Whatever comes through gets shunted to ground be the
The deglitcher utilizes four switches: the first switch shunt (shorts) the signal to ground. The remaining signal is
values should feed forward less than one microvolt. A single switch can not yield such blocking performance.
The blocking requirement is very demanding because a transition of many volts between two adjacent sample
the transitions from feeding forwards to the output filter.
output filter with minimum disturbance. The deglitcher off time settling requires the circuit to block as much of
critical time and no digital activity takes place anywhere near the analog circuits. The settled signals are fed to the
The deglitcher circuit is in off state about half a sample time, and on for the rest of the time. The on time is the
disappear, and for each new analog sample to accurately settle to its final value.
from feeding to the output for long enough time after each transition, thus allowing the glitches enough time to
and can not be removed by filtering. The purpose of the deglitcher circuit (see diagram) is to block the signal
Such switching causes unwanted glitch energy to come into play. The glitch energy is code and signal dependent
corresponding setting of analog switches and multiplexers to tap the appropriate voltage from the analog nodes.
The conversion from a digital sample value to an analog voltage consists of translating a digital code to a
Timing and deglitcher
minutes typically.
conditions (ovenized components). The remaining calibration at each subsequent power on takes less then 2
already, and each new calibration needs to deal only with component drift under the same given temperature
adjustments are initialized to the last settings. Therefore the initial tolerance of the components is pre calibrated
calibrated, the settings are stored in non volatile ram for future startup point of reference, thus all future
solution by design. Calibrating a DA2002 for the first time (at the factory) often exceeds 25 minutes. Once
nodes interaction exist during the adjustment process, the overall network is guaranteed to converge on a
nodes. The processor repeats the calibration cycle numerous times until all the nodes are set properly. Though
some misadjustment at all the other nodes). A single calibration cycle consists of reading and adjusting of all the
The calibration process takes a long time because the node adjustment is interactive (adjusting a node causes
DA2002
Operations Manual