Minimizing Switching Regulator Residue in Linear Regulator Outputs (Linear Technology) - 7
| Authors | Jim Williams |
| Manufacturer | Linear Technology |
| Description | Application Note 101. Linear regulators are commonly employed to post-regulate switching regulator outputs. Benefits include improved stability, accuracy, transient response and lowered output impedance. Ideally, these performance gains would be accompanied by markedly reduced switching regulator generated ripple and spikes. In practice, all linear regulators encounter some difficulty with ripple and spikes, particularly as frequency rises. This publication explains the causes of linear regulators' dynamic limitations and presents board level techniques for improving ripple and spike rejection. A hardware based ripple/spike simulator is presented, enabling rapid breadboard testing under various conditions. Three appendices review ferrite beads, inductor based filters and probing practice for wideband, sub-millivolt signals. |
| Pages / Page | 12 / 7 — Figure 10. Adding Ferrite Bead to Regulator Input Increases High |
| File Format / Size | PDF / 358 Kb |
| Document Language | English |
Figure 10. Adding Ferrite Bead to Regulator Input Increases High
Text Version of Document
Application Note 101 0.005V/DIV 0.005V/DIV AC COUPLED ON 3V AC COUPLED ON 3V DC DC 200ns/DIV 200ns/DIV
Figure 10. Adding Ferrite Bead to Regulator Input Increases High Figure 11. Ferrite Bead in Regulator Output Further Reduces Frequency Losses, Dramaticlly Attenuating Spikes Spike Amplitude
200μV/DIV A = 200μV/DIV AC COUPLED ON 3VDC 200ns/DIV 200ns/DIV
Figure 12. Higher Gain Version of Previous Figure Measures Figure 13. Grounding Oscilloscope Input Near Measurement 900
μ
V Spike Amplitude–Almost 20
×
Lower Than Without Ferrite Point Verifi es Figure 12’s Results Are Nearly Free of Common Beads. Instrumentation Noise Floor Causes Trace Baseline Mode Corruption Thickening
an101f AN101-7
Figure 10. Adding Ferrite Bead to Regulator Input Increases High Figure 11. Ferrite Bead in Regulator Output Further Reduces Frequency Losses, Dramaticlly Attenuating Spikes Spike Amplitude
200μV/DIV A = 200μV/DIV AC COUPLED ON 3VDC 200ns/DIV 200ns/DIV
Figure 12. Higher Gain Version of Previous Figure Measures Figure 13. Grounding Oscilloscope Input Near Measurement 900
μ
V Spike Amplitude–Almost 20
×
Lower Than Without Ferrite Point Verifi es Figure 12’s Results Are Nearly Free of Common Beads. Instrumentation Noise Floor Causes Trace Baseline Mode Corruption Thickening
an101f AN101-7
