4.2 Additional Tests
4.2.1 SYSREF Example
The SROUT of LMX2820 can be used to generate or duplicate SYSREF signal. The output of SROUT can be a
single pulse, series of pulse, or a continuous stream of pulses. These pulses are synchronous with the RFOUT
signal with an adjustable delay. To use the SYSREF capability, the PLL must be in phase SYNC mode with
PHASE_SYNC_EN = 1. Here is an example of Pulsed mode.
Figure 4-3. SYSREF Pulsed Mode Setting
4.2.2 Offset Mixing With PFDIN Pin
The LMX2820 supports offset mxing with PFDIN pin. In this mode, the internal N divider is bypassed.
When using offset mixing with PFDIN pin, the phase detector must operate with a single PFD. As a result, the
charge pump current is equal to half the current setting made in register CPG.
Figure 4-4. Offset Mixing With PFDIN Pin Setting
Typical Measurement
8
LMX2820EVM Evaluation Module
SNAU246A – JUNE 2020 – REVISED JANUARY 2021
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