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Section 1. Power Management Tutorials
PART 1 Power Management
Section 1 Power Management Tutorials Ceramic input capacitors can cause overvoltage transients (1) When it comes to input filtering, ceramic capacitors are a great choice. They offer high ripple current rating and low ESR and ESL. Also, ceramic capacitors are not very sensitive to overvoltage and can be used without derating the operating voltage. However, designers must be aware of a potential overvoltage condition that is generated when input voltage is applied abruptly. After applying an input voltage step, typical input filter circuits with ceramic capacitors can generate voltage transients twice as high as the input voltage. This note describes how to efficiently use ceramic capacitors for input filters and how to avoid potential problems due to input voltage transients.
Minimizing switching regulator residue in linear regulator outputs (2) 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, submillivolt signals.
Power conditioning for notebook and palmtop systems (3) Notebook and palmtop systems need a number of voltages developed from a battery. Competitive solutions require small size, high efficiency and light weight. This publication includes circuits for high efficiency 5V and 3.3V switching and linear regulators, backlight display drivers and battery chargers. All the circuits are specifically tailored for the requirements outlined above.
Two wire virtual remote sensing for voltage regulators (4) Wires and connectors have resistance. This simple, unavoidable truth dictates that a power source’s remote load voltage will be less than the source’s output voltage. The classical approach to mitigating this utilizes ‘‘4-wire’’ remote sensing to eliminate line drop effects. The power supply’s high impedance sense inputs are fed from separate, load-referred sense wires. This scheme works well, but requires dedicated sense wires, a significant disadvantage in many applications. A new approach, utilizing carrier modulation techniques, eliminates sense wires while maintaining load regulation.
Section 1 Power Management Tutorials Ceramic input capacitors can cause overvoltage transients (1) When it comes to input filtering, ceramic capacitors are a great choice. They offer high ripple current rating and low ESR and ESL. Also, ceramic capacitors are not very sensitive to overvoltage and can be used without derating the operating voltage. However, designers must be aware of a potential overvoltage condition that is generated when input voltage is applied abruptly. After applying an input voltage step, typical input filter circuits with ceramic capacitors can generate voltage transients twice as high as the input voltage. This note describes how to efficiently use ceramic capacitors for input filters and how to avoid potential problems due to input voltage transients.
Minimizing switching regulator residue in linear regulator outputs (2) 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, submillivolt signals.
Power conditioning for notebook and palmtop systems (3) Notebook and palmtop systems need a number of voltages developed from a battery. Competitive solutions require small size, high efficiency and light weight. This publication includes circuits for high efficiency 5V and 3.3V switching and linear regulators, backlight display drivers and battery chargers. All the circuits are specifically tailored for the requirements outlined above.
Two wire virtual remote sensing for voltage regulators (4) Wires and connectors have resistance. This simple, unavoidable truth dictates that a power source’s remote load voltage will be less than the source’s output voltage. The classical approach to mitigating this utilizes ‘‘4-wire’’ remote sensing to eliminate line drop effects. The power supply’s high impedance sense inputs are fed from separate, load-referred sense wires. This scheme works well, but requires dedicated sense wires, a significant disadvantage in many applications. A new approach, utilizing carrier modulation techniques, eliminates sense wires while maintaining load regulation.