Datenblatt-Suchmaschine für elektronische Bauteile |
|
ILC7082 Datenblatt(PDF) 7 Page - Impala Linear Corporation |
|
ILC7082 Datenblatt(HTML) 7 Page - Impala Linear Corporation |
7 / 16 page 150mA SOT-23 Ultra Low Noise CMOS RF-LDO™ Regulator Impala Linear Corporation 7 (408) 574-3939 www.impalalinear.com April 1999 ILC7082 1.3 Input Capacitor An input capacitor C IN of value 1 µF or larger should be con- nected from V IN to the main ground plane. This will help to filter supply noise from entering the LDO. The input capaci- tor should be connected as close to the LDO regulator input pin as is practical. Using a high-value input capacitor will offer superior line transient response as well as better pow- er supply ripple rejection. A ceramic or tantalum capacitor may be used at the input of the LDO regulator. Note that there is a parasitic diode from the LDO regulator output to the input. If the input voltage swings below the reg- ulator’s output voltage by a couple of hundred milivolts then the regulator may be damaged. This condition must be avoided. In many applications a large value input capacitor, C IN, will hold VIN higher than V OUT and decay slower than VOUT when the LDO is powered off. Output Capacitor Selection Impala strongly recommends the use of low ESR (equiva- lent series resistance) ceramic capacitors for C OUT and C NOISE The ILC7082 is stable with low ESR capacitor (as low as zero Ω). The value of the output capacitor should be 1µF or higher. Either ceramic chip or a tantalum capacitor may be used at the output. Use of ceramic chip capacitors offer significant advantages over tantalum capacitors. A ceramic capacitor is typically cheaper than a tantalum capacitor, it usually has a smaller footprint, lower height, and lighter weight than a tantalum capacitor. Furthermore, unlike tantalum capacitors which are polarized and can be damaged if connected incorrectly, ceramic capacitors are non-polarized. Low value ceramic chip capacitors with X5R or X7R dielectric are available in the 100pF to 4.7mF range. Beware of using ceramic capaci- tors with Y5V dielectric since their ESR increases significant- ly at cold temperatures. Figure 12 shows a list of recom- mended ceramic capacitors for use at the output of ILC7082. Note: If a tantalum output capacitor is used then for stable operation Impala recommends a low ESR tantalum capaci- tor with maximum rated ESR at or below 0.4W. Low ESR tantalum capacitors, such as the TPS series from AVX Corporation (www.avxcorp.com) or the T495 series from Kemet (www.kemet.com) may be used. In applications where a high output surge current can be expect- ed, use a high value but low ESR output capacitor for superior load transient response. The ILC7082 is stable with no load. Noise Bypass Capacitor In low noise applications, the self noise of the ILC7082 can be decreased further by connecting a capacitor from the noise bypass pin (pin 4) to ground (pin 2). The noise bypass pin is a high impedance node as such care should be taken in printed circuit board layout to avoid noise pick-up from external sources. Moreover, the noise bypass capacitor should have low leakage. Noise bypass capacitors with a value as low as 470pF may be used. However, for optimum performance, use a 0.01mF or larger, ceramic chip capacitor. Note that the turn on and turn off response of the ILC7082 is inversely proportional to the value of the noise bypass capacitor. For fast turn on and turn off, use a small value noise bypass capacitor. In appli- cations were exceptionally low output noise is not required, consider omitting the noise bypass capacitor altogether. The Effects of ESR (Equivalent Series Resistance) The ESR of a capacitor is a measure of the resistance due to the leads and the internal connections of the component. Typically measured in m Ω (milli-ohms) it can increase to ohms in some cases. Wherever there is a combination of resistance and current, voltages will be present. The control functions of LDOs use two voltages in order to maintain the output precisely; V OUT and V REF. With reference to the block diagram in figure 4, V OUT is fed back to the error amplifier and is used as the supply voltage for the internal components of the ILC7082. So any change in V OUT will cause the error amplifier to try to compensate to maintain V OUT at the set level and noise on V OUT will be reflected into the supply of each internal components of the ILC7082. So any change in V OUT will cause the error ampli- fier to try to compensate to maintain V OUT at the set level and noise on V OUT will be reflected into the supply of each inter- nal circuit. The reference voltage, V REF, is influenced by the C NOISE pin. Noise into this pin will add to the reference volt- age and be fed through the circuit. These factors will not cause a problem if some simple steps are taken. Figure 5 shows where these added ESR resistances are present in the typical LDO circuit. With this in mind low ESR components will offer better per- formance where the LDO may be subjected to large load transients current. ESR is less of a problem with C IN as the voltage fluctuations at the input will be filtered by the LDO. ILC7082 V IN SOT-23-5 C IN ON OFF 12 3 4 5 C NOISE RF LDOTM Regulator R* R* R C V OUT C OUT I C I OUT Figure 5: ESR present in COUT and CNOISE |
Ähnliche Teilenummer - ILC7082 |
|
Ähnliche Beschreibung - ILC7082 |
|
|
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 |