UR5HCSPI-06-FN View Datasheet(PDF) - Semtech Corporation
Part Name
Description
MFG CO.
'UR5HCSPI-06-FN' PDF : 20 Pages View PDF
IMPLEMENTATION NOTES FOR THE UR5HCSPI-06
The following notes pertain to the suggested schematic found on the
previous page.
The Built-in Oscillator on the UR5HCSPI-06 requires the attachment of the
2.00 MHz Ceramic Resonators with built-in Load Capacitors.. You can use
either an AVX, part number PBRC-2.00 BR; or a Murata part number
CSTCC2.00MG ceramic resonator.
It may also be possible to operate with the 2.00 MHz Crystal, albeit with
reduced performance. Due to their high Q, the Crystal oscillator circuits
start-up slowly. Since the SPICoderTM constantly switches the clock on and
off, it is important that the Ceramic Resonator is used (it starts up much
quicker than the Crystal). Resonators are also less expensive than Crystals.
Also, if Crystal is attached, two Load Capacitors (33pF to 47pF) should be
added, a Capacitor between each side of the Crystal and ground.
In both cases, using Ceramic Resonator with built-in Load Capacitors, or
Crystal with external Load Capacitors, a feedback Resistor of 1 Meg should
be connected between OSCIN and OSCOUT.
Troubleshoot the circuit by looking at the Output pin of the Oscillator. If the
voltage is half-way between Supply and Ground (while the Oscillator should
be running) --- the problem is with the Load Caps / Crystal. If the voltage is
all the way at Supply or Ground (while the Oscillator should be running) ---
there are shorts on the PCB.
Note: When the Oscillator is intentionally turned OFF, the voltage on the
Output pin of the Oscillator is High (at the Supply rail).
Copyright Semtech 1997-2001
16
DOC5-SPI-06-DS-103
www.semtech.com
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