SPRUI30H November 2015 – May 2024 DRA745 , DRA746 , DRA750 , DRA756
DPLL supports several power modes for type A and only one power mode for type B. Each mode results in a tradeoff between power savings and relock time. The PRCM module allows only a few modes for each DPLL, depending on the use of the DPLL.
Table 3-45 lists the DPLL power modes.
Power Mode | CLKOUT State | Logic Current (mA) | Analog Current (mA) | Freq Lock Time | Phase Lock Time |
---|---|---|---|---|---|
Low-power stop | Clock stopped | 0.065 (leakage) | 0.009 (leakage) | 2.5 µs + (70 × (N+1) / Fref) | 2.5 µs + (120 × (N+1) / Fref) |
Fast-relock stop | Clock stopped | 0.065 (leakage) | 0.009 (leakage) | 2.5 µs + (70 × (N+1) / Fref) | 2.5 µs + (120 × (N+1) / Fref) |
Low-power bypass | Bypass clock/clock stopped | 0.065 (leakage) | 0.009 (leakage) | 2.5 μs + (70 × (N+1) / Fref) | 2.5 μs + (120 × (N+1) / Fref) |
Fast-relock bypass | Bypass clock/clock stopped | 0.065 (leakage) | 0.5 (leakage) | 0.05 μs + (70 × (N+1) / Fref) | 0.05 μs + (120 × (N+1) / Fref) |
Lock | Synthesized clock | 0.95 (active) | 3 (active) | N/A | N/A |
Where:
A DPLL power mode can be achieved on a software request (manual) and/or automatically (automatic), depending on the specific hardware conditions.
A DPLL can switch from one mode to another as a result of the following:
With Tref = 1 / Fref = (N + 1) / CLKINP; (Fref = CLKINP / (N + 1)):
Trefis the REF_CLK period.
This formula indicates that a smaller N divider value provides a smaller time for switching the clock after an M2 post-divider change.
A compromise is necessary between the clock switching latency and power consumption. Having a smaller N value:
When the DPLL is in Low-Power bypass mode, Auto-idle mode is disabled and no clock is requested, the DPLL makes a transition to Low-power stop mode.