lowESR

LowESR refers to capacitors with a minimized equivalent series resistance (ESR). ESR is the internal resistance of a capacitor, and lowering it improves the device’s ability to handle ripple current, reduces voltage drop during transients, and generally enhances efficiency in power conversion circuits. Products marketed as lowESR are often chosen for high-current, high-frequency applications.

ESR is an intrinsic property arising from the capacitor’s construction, including electrodes, electrolyte or dielectric, and interconnections. LowESR designs are achieved through technologies such as solid polymer electrolytes, certain ceramic capacitors, and specialized aluminum electrolytic formulations. ESR is typically specified at a given frequency (often around 100 kHz) and varies with temperature.

LowESR capacitors are widely used in decoupling and filtering for switching power supplies, voltage regulator modules, and other high-current circuits. They help suppress voltage ripple, improve transient response, and enable more compact power stages by allowing higher ripple currents and smaller capacitance values for the same performance.

Designers must consider trade-offs. Very low ESR can reduce damping in power converters, potentially causing ringing with the circuit’s inductance and stability issues in some regulators. Inrush currents may be higher, and ESR can change with temperature and age. Practical designs often combine capacitors with different ESR and ESL values to achieve stable, broadband filtering.

When selecting, consult datasheets for ESR vs. frequency, ripple current rating, and voltage rating. Consider the operating temperature range and whether a mix of capacitor types is needed to achieve the desired impedance profile across frequency.