SNAS783C June 2020 – February 2021 LMX2820
PRODUCTION DATA
An external VCO can also be used with the LMX2820, but note that the output buffers cannot be used while the SYSREF feature can. The charge pump voltage maximum output voltage is about 2.5 V, but this is not sufficient for most VCOs. For this reason, an active filter is recommended, which can keep the charge pump voltage biased around 1.2 V and provide the higher output voltage. If the VCO frequency is higher than 11.3 GHz, the EXTVCODIV bit must be enabled, otherwise, it should be zero.
When using the external VCO, the PFD_DLY word must be set manually as shown in Table 7-9. For the case of an integrated VCO, it is not necessary to program this word. PFD_DLY_MANUAL = 1 is required to manually set the PFD_DLY.
fRFIN/(RFIN Divider) | MASH_ORDER = 0 | MASH_ORDER = 1 | MASH_ORDER = 2 | MASH_ORDER = 3 |
---|---|---|---|---|
0.5 - 4 GHz | 1 | 1 | 2 | 4 |
4 - 5.5 GHz | 2 | 2 | 3 | 5 |
5.5 - 7 GHz | 3 | 3 | 4 | 6 |
7 - 8.5 GHz | 4 | 4 | 5 | 7 |
8.5 - 10 GHz | 5 | 5 | 6 | 8 |
> 10 GHz | 6 | 6 | 7 | 9 |