SBVA102 august   2023 TPS56837

 

  1.   1
  2.   Abstract
  3.   Trademarks
  4. 1Introduction
  5. 2D-CAP3 Control Architecture
    1. 2.1 Adaptive On-Time Control
    2. 2.2 D-CAP3 Control
  6. 3Large Duty Cycle Operation
    1. 3.1 Min Off-Time Performance of Buck Converters
    2. 3.2 On-Time Extension Function
  7. 4Bench Test and Comparison
    1. 4.1 Comparison Between TPS56837 and TPS56637
    2. 4.2 Comparison of On-Time Extension between TPS56837 and TPS568230
    3. 4.3 Load Transient Improvement by On-Time Extension
  8. 5Summary
  9. 6References
  10. 7Also From TI

4.3 Load Transient Improvement by On-Time Extension

In addition to improving line dropout performance, the On-Time Extension function also improves load transient response. Figure 4-10 and Figure 4-11 indicate load transient test results of the comparison between TPS56837 and TPS56637. The setup is the same as previously indicated. The figures show the undershoot improvement during a light load to heavy load transient. The undershot for TPS56637 is 530mV while it's 224mV for TPS56837 with On-Time Extension.

When the load changes from 0 A to 8 A, the input voltage will drop about 1V, also the output voltage will drop and influence the loop response, both will allow the On-Time Extension to work. From Figure 4-11, the SW signal indicates the on-time is extended. With this longer HSFET ON, compared with non On-Time Extension in Figure 4-10, more energy is charged to the output to make the VOUT voltage drop less then when the load change happens.

GUID-20230823-SS0I-PD5F-RRPF-ZGCFZ1QFXDDX-low.svg
VIN = 8 V, VOUT = 5V, IOUT from 0A to 6A, Slew Rate = 2.5 A/us
Figure 4-10 TPS56637 Load Transient Without On-Time Extension Triggered
GUID-20230823-SS0I-QLWN-QNXZ-QGSD1WLMNQ8W-low.svg
VIN = 8 V, VOUT = 5V, IOUT from 0A to 6A, Slew Rate = 2.5 A/us
Figure 4-11 TPS56837 Load Transient With On-Time Extension Triggered