EV9900 Datasheet, PDF (24/27 Pages) CML Microcircuits – Evaluation Kit

Evaluation Kit for CMX990
EV9900
6.7.2 Transmitter Operation
Error Observed
Transmitter loop does not lock
Transmitter loop does not lock
Poor modulation spectrum in
transmit.
Possible Cause
No modulation is present.
The PA is not turned on.
An incorrect filter has
been chosen for the
selected Tx IF.
Remedy
Ensure the transmitter is
outputting data. The TSO
command can be used to
continuously send data for
testing. Note also the modem
needs to be in transmit mode
and main DAC enable (register
$03)
The Tx loop in the engineering
silicon of the CMX990 requires
a reasonable level of feedback
for the loop to lock. The PA
ramping register (0x09) should
be set to at least 0x39 to ensure
lock.
Select the correct filter using
bits 5 and 6 of the Aux PLL M
div MSB register ($26).
© 2005 CML Microsystems Plc
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UM9900/1