SNAS835 September 2022 LMK5B33414
PRODUCTION DATA
The reference inputs (IN0, IN1, IN2 and IN3) 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 provided they 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_DC_COUPLED_EN, REFx_TYPE | INPUT TYPES | INTERNAL SWITCH SETTINGS | |||
---|---|---|---|---|---|
INTERNAL SINGLE-END TERM. (S1)(2) | INTERNAL DIFFERENTIAL TERM. (S2) (2) | INTERNAL BIAS (S3)(3) | LVCMOS/DIFF INTERNAL AC CAPACITOR BYPASS MODE (S4)(1) | ||
0x00, 0x00 | DC-Differential (external termination) | OFF | OFF | OFF | OFF |
0x00, 0x01 | AC-Differential (external termination) | OFF | OFF | ON (1.3 V) | OFF |
0x00, 0x02 | DC-Differential (internal termination) | OFF | 100 Ω | OFF | OFF |
0x00, 0x03 | LVDS / HSDS, AC-Differential (internal termination) | OFF | 100 Ω | ON (1.3 V) | OFF |
0x00, 0x04 | HCSL,DC-Differential (internal termination 50-Ω) | 50 Ω | OFF | OFF | OFF |
0x00, 0x05 | LVPECL,AC-Differential (internal termination 50-Ω) | 50 Ω | OFF | ON (1.3 V) | OFF |
0x00, 0x08 | LVCMOS(External DC-coupling, internal AC coupling) | OFF | OFF | OFF | OFF |
0x01, 0x08 | LVCMOS (External DC-coupling, internal DC coupling) | OFF | OFF | OFF | ON |
0x01, 0x0C | LVCMOS(External DC-coupling, internal DC coupling, internal termination 50-Ω) | 50 Ω | OFF | OFF | ON |