SLUAAP9 October   2023 TPS568215 , TPS568230

 

  1.   1
  2.   Abstract
  3.   Trademarks
  4. 1Introduction
  5. 2Features Description
    1. 2.1 Light Load Operation
    2. 2.2 Large Duty Operation
  6. 3Control Modes Description
    1. 3.1 PCM and ACM
    2. 3.2 D-CAP2 and D-CAP3
    3. 3.3 Control Modes Comparison
  7. 4Specifications Comparison
  8. 5Summary
  9. 6References

2.1 Light Load Operation

Three operation modes of light load are mentioned in this application note.

Power Save Mode (PSM) can decrease the device switching frequency to improve efficiency at light load.

Out-of-Audio (OOA) mode is a unique control feature that keeps the switching frequency above audible frequency (20 Hz-20 KHz) with minimum reduction in efficiency, which prevents audio noise generation from the output capacitors and inductor. The Understanding OOA Operation application note describes the OOA details.

Forced Continuous Conduction Mode (FCCM) allows the inductor current to become negative in light load, the switching frequency is maintained, achieve small ripple at light load.

Table 2-1 lists the comparison between PSM, OOA and FCCM mode.

Table 2-1 Comparison Between PSM, OOA, and FCCM Mode
Light Load ModePSMOOAFCCM
fswLowMiddleHigh
Vout RippleLargeMiddleSmall
Light Load EfficiencyHighMiddleLow
Designed for ApplicationsRequire high light-load efficiencyRequire high efficiency without audible noise in light loadRequire almost fixed fsw and small Vout ripple across whole loading range

There is an ultra-low quiescent current (ULQ™) mode which enhances PSM mode efficiencies at very light load. ULQ™ mode is useful for prolong battery life in system standby mode.