The LMX2581 is a low noise wideband frequency synthesizer that integrates a delta-sigma
fractional N PLL, multiple core VCO, programmable output divider, and two differential output
buffers. The VCO frequency range is from 1880 to 3760 MHz and can be sent directly to the output
buffers or divided down by even values from 2 to 38. Each buffer is capable of output power from 3
to +12 dBm at 2700 MHz. Integrated low noise LDOs are used for superior noise immunity and
This synthesizer is a highly programmable device and it enables the user to optimize its
performance. In fractional mode, the denominator and the modulator order are programmable and can
be configured with dithering as well. The user also has the ability to directly specify a VCO core
or entirely bypass the internal VCO. Finally, many convenient features are included such as power
down, Fastlock, auto mute, and lock detection. All registers can be programmed through a simple 3
wire interface and a read back feature is also available.
The LMX2581 operates on a single 3.3 V supply and comes in a 32 pin 5.0 mm × 5.0
mm WQFN package.
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