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CDB5378 Datasheet, PDF (28/72 Pages) Cirrus Logic – Single-channel Seismic Evaluation System | |||
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CDB5378
Telemetry signals enter CDB5378 through RS-485 transceivers, which are differential current mode trans-
ceivers that can reliably drive long distance communication. Data passes through the RS-485 transceiv-
ers to the microcontroller I2C interface and the clock and synchronization inputs.
Specification
RS-485 Transceiver - Linear Tech
Surface Mount Package Type
Supply Voltage, Quiescent Current
Maximum Data Rate
Transmitter Delay, Receiver Delay
Transmitter Current, Full Termination (60 â¦)
Transmitter Current, Half Termination (120 â¦)
Value
LTC1480IS8
SOIC-8, 5mm x 6mm
3.3V, 600 µA
2.5 Mbps
25 - 80 ns, 30 - 200 ns
25 mA
13 mA
2.3.5.1 CLK, SYNC
Clock and synchronization telemetry signals into CDB5378 are received through RS-485 twisted pairs.
These signals are required to be distributed through the external system with minimal jitter and timing
skew, and so are normally driven through high-speed bus connections.
Specification
Synchronous Inputs, 2 wires each
Specification
Distributed SYNC Signal Synchronization
Distributed Clock Synchronization
Analog Sampling Synchronization Accuracy
Value
CLK±, SYNC±
Value
± 240 ns
± 240 ns
± 480 ns
Synchronization of the measurement channel is critical to ensure simultaneous analog sampling across
a network. Several options are available for connecting a SYNC signal through the RS-485 telemetry to
the digital filter.
A direct connection is made when the SYNC_IO signal is received over the dedicated RS-485 twisted pair
and sent directly to the digital filter SYNC pin through jumper J56. The incoming SYNC_IO signal must be
synchronized to the network at the transmitter since no local timing adjustment is available.
A microcontroller hardware connection is made when the SYNC_IO signal is received over the dedicated
RS-485 twisted pair and detected by a microcontroller interrupt. The microcontroller can then use an in-
ternal counter to re-time the SYNC_MC signal output to the digital filter SYNC input as required.
A microcontroller software connection is made when the SYNC_MC signal output is created by the micro-
controller on command from the system telemetry. The microcontroller can use an internal counter to re-
time the SYNC_MC signal output to the digital filter SYNC input as required.
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DS639DB3
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