Using the LL pin, the user can
configure the power level at which the UCC25660x
family enters
the HF pulse skip and LF Burst mode. The two thresholds that can be set are the
HFBurstEntry and LFBursttEntry. More details on how this
configuration is done is shown in Section 7.5.3.3.
Figure 7-19describes the entry and exit behavior of UCC25660X in burst
mode.
- The HFBurstEntry,
corresponds to the FBReplica voltage at desired power level where the
system enters HF Pulse skip.
- The LFBurstEntry
corresponds to a modified FBReplica voltage at which the system enters LF
Burst.
- When FBreplica is higher
than HFBurstEntry, UCC25660x
family operates in normal
switching.
- When FBreplica is less
than HFBurstEntry but greater than LFBurstEntry, UCC25660x
family operates in HF pulse skip mode. In the HF
pulse skip mode, the energy in each packet is still controlled by the control
signal FBReplica.
- When FBreplica is less
than LFBurstEntry, UCC25660X operates in LF burst mode. In the LF Burst
mode, the energy in each packet is fixed at LFBurstEntry threshold.
- While operating in LF Burst mode,
a new LF Burst segment is started when the FBReplica rises above the
LFBurstEntry threshold. The segment is terminated when the desired
number of packets are delivered and the FBReplica is below the
PacketStop threshold.
- The desired number of packets in
a LF Burst segment is computed to regulate the LF Burst operating frequency
within 200Hz to 400Hz.
- In case of a sudden load drop,
the LF Burst segment is immedialtelly terminated to avoid output over voltage
condition.