SLVSAF1E October   2010  – May 2019

PRODUCTION DATA.

1. Features
2. Applications
3. Description
1.     Device Images
4. Revision History
5. Pin Configuration and Functions
6. Specifications
7. Detailed Description
1. 7.1 Overview
2. 7.2 Functional Block Diagram
3. 7.3 Feature Description
4. 7.4 Device Functional Modes
8. Application and Implementation
1. 8.1 Application Information
2. 8.2 Typical Application
1. 8.2.1 Design Requirements
2. 8.2.2 Detailed Design Procedure
3. 8.2.3 Application Curves
9. Power Supply Recommendations
10. 10Layout
11. 11Device and Documentation Support
12. 12Mechanical, Packaging, and Orderable Information

• RTE|16
• RTE|16

7.4.15 Small-Signal Model for Frequency Compensation

The TPS54388-Q1 device uses a transconductance amplifier for the error amplifier and readily supports two of the commonly used frequency-compensation circuits. Figure 33 shows the compensation circuits. The most-likely implementation of Type 2B circuits is in high-bandwidth power-supply designs using low-ESR output capacitors. Type 2A contains one additional high-frequency pole to attenuate high-frequency noise. Figure 33. Types of Frequency Compensation

The design guidelines for TPS54388-Q1 loop compensation are as follows:

1. Calculate the modulator pole, f(p,mod), and the ESR zero, f(z,mod), using Equation 14 and Equation 15. The output capacitor (C(OUT)) may require derating if the output voltage is a high percentage of the capacitor rating. Use the manufacturer information for the capacitor to derate the capacitor value. Use Equation 16 and Equation 17 to estimate a starting point for the crossover frequency, f(c). Equation 16 is the geometric mean of the modulator pole and the ESR zero, and Equation 17 is the mean of the modulator pole and the switching frequency. Use the lower value of Equation 16 or Equation 17 as the maximum crossover frequency.
2. Equation 14. Equation 15. Equation 16. Equation 17. 3. Determine R3 using Equation 18.
4. Equation 18. where

• gm(ea) is the amplifier gain (245 μS)
• gm(ps) is the power-stage gain (25 S)
5. Place a compensation zero at the dominant pole:
6. Equation 19. 7. Determine C1 using Equation 20.
8. Equation 20. vertical spacer

9. C2 is optional. Use it, if necessary, to cancel the zero from the ESR of C(OUT).
10. Equation 21. 