SNAS816C March 2022 – February 2025 LMK5B33216
PRODUCTION DATA
The reference inputs (IN0 and IN1) can accept differential or single-ended clocks. Each input has programmable input type, termination, and DC-coupled or AC-coupled input biasing configurations as shown in Figure 8-9. Each input buffer drives the reference input mux of the DPLL block. The DPLL input mux can select from any of the reference inputs. The DPLL can switch between inputs with different frequencies if the frequencies can be divided-down to a common frequency by DPLL R dividers. The reference input paths also drive the various detector blocks for reference input monitoring and validation. DC-path switch can bypass internal AC-coupling capacitors to make low frequency input work robustly.
Table 8-2 lists the reference input buffer configurations for common clock interface types.
REFx_ITYPE, R68/R67 | INPUT TYPE | INTERNAL REGISTER AND SWITCH SETTINGS | |||||
---|---|---|---|---|---|---|---|
HYSTERESIS, R68[5] | AC CAPACITOR BYPASS, R68[4], S4(1) | SINGLE-ENDED SELECT, R68[3] | SINGLE-ENDED TERM., R68[2], S1(2) | DIFFERENTIAL TERM., R68[1], S2(2) | WEAK BIAS (1.3V) R68[0], S3(3) | ||
0x00 | Differential, ext. DC-coupled, ext. term. | 0 | 0 | 0 | 0 | 0 | 0 |
0x01 | Differential, ext. AC-coupled, ext. term. | 0 | 0 | 0 | 0 | 0 | 1 |
0x02 | Differential, ext. DC-coupled, int. 100Ω diff. term., LVDS/HSDS | 0 | 0 | 0 | 0 | 1 | 0 |
0x03 | Differential, ext. AC-coupled, int. 100Ω diff. term., LVDS/HSDS | 0 | 0 | 0 | 0 | 1 | 1 |
0x04 | Differential, ext. DC-coupled, int. 50Ω to GND HCSL | 0 | 0 | 0 | 1 | 0 | 0 |
0x05 | Differential, ext. AC-coupled, int. 50Ω to GND, HCSL | 0 | 0 | 0 | 1 | 0 | 1 |
0x08 | Single-ended, ext. DC-coupled, int. AC-coupled 70mV threshold, LVCMOS | 0 | 0 | 1 | 0 | 0 | 0 |
0x0C | Single-ended, ext. DC-coupled, int. AC-coupled, int. 50Ω to GND, 70mV threshold | 0 | 0 | 1 | 1 | 0 | 0 |
0x18 | Single-ended, ext. DC-coupled, int. DC-coupled 150mV hysteresis, LVCMOS | 0 | 1 | 1 | 0 | 0 | 0 |
0x28 | Single-ended, ext. DC-coupled, int. AC-coupled 210mV hysteresis, LVCMOS | 1 | 0 | 1 | 0 | 0 | 0 |
0x38 | Single-ended, ext. DC-coupled, int. DC-coupled 0mV hysteresis, LVCMOS | 1 | 1 | 1 | 0 | 0 | 0 |