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ILC7080AIM5-50 Datasheet(PDF) 7 Page - Impala Linear Corporation |
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ILC7080AIM5-50 Datasheet(HTML) 7 Page - Impala Linear Corporation |
7 / 16 page 50/100mA SOT-23 CMOS RF LDO™ Regulators Impala Linear Corporation 7 (408) 574-3939 www.impalalinear.com Sept. 1998 ILC7080/81 1.1 Maximum Output Current The maximum output current available from the ILC7080/81 is limited by the maximum package power dissipation as well as the device’s internal current limit. For a given ambi- ent temperature, TA, the maximum package power dissipa- tion is given by: PD(max) = (TJ(max) - TA) / θJA where TJ(max) = 150°C is the maximum junction temperature and θ JA = 333°C/W is the package thermal resistance. For example at TA = 85°C ambient temperature, the maximum package power dissipation is; PD(max) = 195mW. The maximum output current can be calculated from the fol- lowing equation: IOUT(max) < PD(max) / (VIN - VOUT) For example at VIN = 6V, VOUT = 5V and TA = 85°C, the maximum output current is IOUT(max) < 195mA. At higher output current, the die temperature will rise and cause the thermal protection circuit to be enabled. APPLICATION HINTS Figure 4 shows the typical application circuit for the ILC7080/81. Input Capacitor An input capacitor CIN of value 1mF or larger should be con- nected from VIN to the main ground plane. This will help to filter supply noise from entering the LDO. The input capac- itor 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 power supply ripple rejection. A ceramic or tantalum capac- itor 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 regulator’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, CIN, will hold VIN higher than VOUT 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 COUT and CNOISE. The ILC7080/81 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 capaci- tor may be used at the output. Use of ceramic chip capacitors offer significant advantages over tantalum capacitors. A ceramic capacitor is typically considerably cheaper than a tantalum capacitor, it usually has a smaller footprint, lower height, and lighter weight than a tantalum capacitor. Furthermore, unlike tantalum capaci- tors which are polarized and can be damaged if connected incorrectly, ceramic capacitors are non-polarized. Low value ceramic chip capacitors with X7R dielectric are avail- able in the 100pF to 4.7µF range, while high value capaci- tors with Y5V dielectric are available in the 2200pF to 22µF range. Evaluate carefully before using capacitors with Y5V dielectric because their ESR increases significantly at cold temperatures. Figure 10 shows a list of recommended ceramic capacitors for use at the output of ILC7080/81. Note: If a tantalum output capacitor is used then for stable opera- tion Impala recommends a low ESR tantalum capacitor with max- imum rated ESR at or below 0.4 Ω. 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 expected, use a high value but low ESR output capacitor for superior load transient response. The ILC7080/81 is stable with no load. Noise Bypass Capacitor In low noise applications, the self noise of the ILC7080/81 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 0.01µF or larger, ceramic chip capacitor. Note that the turn on and turn off response of the ILC7080/81 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 applications were exceptionally low output noise is not required, consider omitting the noise bypass capacitor altogether. ILC7080 ILC7081 V OUT V IN C OUT C NOISE SOT23-5 12 3 4 5 ON OFF Figure 4: Basic application circuit for fixed output voltage versions |
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