SLUAAN2 april   2023 TPS543620 , TPS54620 , TPS54J060 , TPS54J061 , TPS566231 , TPS566235 , TPS566238 , TPS566242 , TPS566247

 

  1.   Abstract
  2.   Trademarks
  3. 1Introduction
  4. 2Features Description
    1. 2.1 Light Load Operation
    2. 2.2 Large Duty Operation
    3. 2.3 BST Cap Integrated
    4. 2.4 Voltage Identification Control
    5. 2.5 Output-voltage Tracking
  5. 3Control Modes Description
    1. 3.1 PCM/ACM
    2. 3.2 D-CAP2™/D-CAP3™
    3. 3.3 Control Modes Comparison
  6. 4Specifications Comparison
  7. 5References

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 Mode PSM OOA FCCM
fsw Low Middle High
Vout Ripple Large Middle Small
Light Load Efficiency High Middle Low
Suitable Applications Require highlight load efficiency Require high efficiency without audible noise in light load Require almost fixed fsw and small Vout ripple across whole loading range

Besides, 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.