SNAS739D June 2018 – May 2020 LMX2615-SP
PRODUCTION DATA.
The LMX2615 can generate a SYSREF output signal that is synchronized to fOUT with a programmable delay. This output can be a single pulse, series of pulses, or a continuous stream of pulses. To use the SYSREF capability, the PLL must first be placed in SYNC mode with VCO_PHASE_SYNC = 1.
As Figure 27 shows, the SYSREF feature uses IncludedDivide and SYSREF_DIV_PRE divider to generate fINTERPOLATOR. This frequency is used for re-clocking of the rising and falling edges at the SysRefReq pin. In master mode, the fINTERPOLATOR is further divided by 2×SYSREF_DIV to generate finite series or continuous stream of pulses.
PARAMETER | MIN | TYP | MAX | UNIT |
---|---|---|---|---|
fVCO | 7600 | 15200 | MHz | |
fINTERPOLATOR | 0.8 | 1.5 | GHz | |
IncludedDivide | 4 or 6 | |||
SYSREF_DIV_PRE | 1, 2, or 4 | |||
SYSREF_DIV | 4,6,8, ..., 4098 | |||
fINTERPOLATOR | fPRESYSREF = fVCO /(IncludedDivide × SYSREF_DIV_PRE) | |||
fSYSREF | fSYSREF = fINTERPOLATOR / (2 × SYSREF_DIV) | |||
Delay step size | 9 | ps | ||
Pulses for pulsed mode (SYSREF_PULSE_CNT) | 0 | 15 | n/a |
The delay can be programmed using the JESD_DAC1_CTRL, JESD_DAC2_CTRL, JESD_DAC3_CTRL, and JESD_DAC4_CTRL words. By concatenating these words into a larger word called "SYSREFPHASESHIFT", the relative delay can be found. The sum of these words must always be 63.
SYSREFPHASESHIFT | DELAY | JESD_DAC1 | JESD_DAC2 | JESD_DAC3 | JESD_DAC4 |
---|---|---|---|---|---|
0 | Minimum | 36 | 27 | 0 | 0 |
... | 0 | 0 | |||
36 | 0 | 63 | 0 | 0 | |
37 | 62 | 1 | 0 | 0 | |
... | |||||
99 | 0 | 0 | 63 | 0 | |
100 | 0 | 0 | 62 | 1 | |
... | |||||
161 | 0 | 0 | 1 | 62 | |
162 | 0 | 0 | 0 | 63 | |
163 | 1 | 0 | 0 | 62 | |
225 | 63 | 0 | 0 | 0 | |
226 | 62 | 1 | 0 | 0 | |
247 | Maximum | 41 | 22 | 0 | 0 |
> 247 | Invalid | Invalid | Invalid | Invalid | Invalid |