Datenblatt-Suchmaschine für elektronische Bauteile |
|
LM2575-12IKTT Datenblatt(PDF) 8 Page - Texas Instruments |
|
LM2575-12IKTT Datenblatt(HTML) 8 Page - Texas Instruments |
8 / 12 page www.ti.com Input Capacitor (C IN) I C,RMS u 1.2( ton T ) I LOAD, where: ton T + V OUT V IN {buck regulator}, and ton T + |V OUT| (|V OUT| ) VIN) {buck−boost regulator} Output Capacitor (C OUT) Catch Diode Inductor LM2575 1-A SIMPLE STEP-DOWN SWITCHING VOLTAGE REGULATOR SLVS569D – JANUARY 2005 – REVISED JULY 2005 APPLICATION INFORMATION (continued) For stability concerns, an input bypass capacitor (electrolytic, CIN ≥ 47 µF) needs to be located as close as possible to the regulator. For operating temperatures below –25 °C, C IN may need to be larger in value. In addition, since most electrolytic capacitors have decreasing capacitances and increasing ESR as temperature drops, adding a ceramic or solid tantalum capacitor in parallel increases the stability in cold temperatures. To extend the capacitor operating lifetime, the capacitor RMS ripple current rating should be: For both loop stability and filtering of ripple voltage, an output capacitor also is required, again in close proximity to the regulator. For best performance, low-ESR aluminum electrolytics are recommended, although standard aluminum electrolytics may be adequate for some applications. Based on the following equation: Output Ripple Voltage = (ESR of COUT) × (inductor ripple current) Output ripple of 50 mV to 150 mV typically can be achieved with capacitor values of 220 µF to 680 µF. Larger COUT can reduce the ripple 20 mV to 50 mV peak-to-peak. To improve further on output ripple, paralleling of standard electrolytic capacitors may be used. Alternatively, higher-grade capacitors such as “high frequency”, “low inductance”, or “low ESR” can be used. The following should be taken into account when selecting COUT: • At cold temperatures, the ESR of the electrolytic capacitors can rise dramatically (typically 3 × nominal value at –25 °C). Because solid tantalum capacitors have significantly better ESR specifications at cold temperatures, they should be used at operating temperature lower than –25 °C. As an alternative, tantalums also can be paralleled to aluminum electrolytics and should contribute 10% to 20% to the total capacitance. • Low ESR for COUT is desirable for low output ripple. However, the ESR should be greater than 0.05 Ω to avoid the possibility of regulator instability. Hence, a sole tantalum capacitor used for COUT is most susceptible to this occurrence. • The capacitor’s ripple current rating of 52 kHz should be at least 50% higher than the peak-to-peak inductor ripple current. As with other external components, the catch diode should be placed close to the output to minimize unwanted noise. Schottky diodes have fast switching speeds and low forward voltage drops and, thus, offer the best performance, especially for switching regulators with low output voltages (VOUT < 5 V). If a high-efficiency, fast-recovery, or ultra-fast-recovery diode is used in place of a Schottky, it should have a soft recovery (versus abrupt turn-off characteristics) to avoid the chance of causing instability and EMI. Standard 50-/60-Hz diodes, such as the 1N4001 or 1N5400 series, are NOT suitable. Proper inductor selection is key to the performance-switching power-supply designs. One important factor to consider is whether the regulator will be used in continuous (inductor current flows continuously and never drops to zero) or in discontinuous mode (inductor current goes to zero during the normal switching cycle). Each mode has distinctively different operating characteristics and, therefore, can affect the regulator performance and requirements. In many applications, the continuous mode is the preferred mode of operation, since it offers greater output power with lower peak currents, and also can result in lower output ripple voltage. The advantages of continuous mode of operation come at the expense of a larger inductor required to keep inductor current continuous, especially at low output currents and/or high input voltages. 8 |
Ähnliche Teilenummer - LM2575-12IKTT |
|
Ähnliche Beschreibung - LM2575-12IKTT |
|
|
Link URL |
Privatsphäre und Datenschutz |
ALLDATASHEETDE.COM |
War ALLDATASHEET hilfreich? [ DONATE ] |
Über Alldatasheet | Werbung | Kontakt | Privatsphäre und Datenschutz | Linktausch | Hersteller All Rights Reserved©Alldatasheet.com |
Russian : Alldatasheetru.com | Korean : Alldatasheet.co.kr | Spanish : Alldatasheet.es | French : Alldatasheet.fr | Italian : Alldatasheetit.com Portuguese : Alldatasheetpt.com | Polish : Alldatasheet.pl | Vietnamese : Alldatasheet.vn Indian : Alldatasheet.in | Mexican : Alldatasheet.com.mx | British : Alldatasheet.co.uk | New Zealand : Alldatasheet.co.nz |
Family Site : ic2ic.com |
icmetro.com |