SLVS719H June 2008 – June 2026 TL1963A
PRODUCTION DATA
The design of the TL1963A-xx regulators establish stability with a wide range of output capacitors. The ESR of the output capacitor affects stability, most notably with small capacitors. TI recommends a minimum output capacitor of 10μF with an ESR of 3Ω or less to prevent oscillations. Larger values of output capacitance can decrease the peak deviations and provide improved transient response for larger load current changes. Bypass capacitors, used to decouple individual components powered by the TL1963A-xx, increase the effective output capacitor value.
Give extra consideration when using ceramic capacitors. Ceramic capacitors are manufactured with a variety of dielectrics, each with different behavior overtemperature and applied voltage. The most common dielectrics used are Z5U, Y5V, X5R and X7R. The Z5U and Y5V dielectrics are good for providing high capacitances in a small package, but exhibit strong voltage and temperature coefficients. When used with a 5V regulator, a 10μF Y5V capacitor can exhibit an effective value as low as 1μF to 2μF over the operating temperature range. The X5R and X7R dielectrics result in more stable characteristics and are more appropriate for use as the output capacitor. The X7R type has better stability across temperature, while the X5R is less expensive and is available in higher values.
Voltage and temperature coefficients are not the only sources of problems. Some ceramic capacitors have a piezoelectric response. A piezoelectric device generates voltage across its terminals due to mechanical stress, similar to the way a piezoelectric accelerometer or microphone works. For a ceramic capacitor, the stress can be induced by vibrations in the system or thermal transients.
Although an input capacitor is not required for stability, good analog design practice is to connect a capacitor from IN to GND. Some input supplies have a high impedance, thus placing the input capacitor on the input supply helps reduce the input impedance. This capacitor counteracts reactive input sources and improves transient response, input ripple, and PSRR. If the input supply has a high impedance over a large range of frequencies, several input capacitors can be used in parallel to lower the impedance over frequency. Use a higher-value capacitor if large, fast, rise-time load transients are anticipated, or if the device is located several inches from the input power source.